Curator: Implementing purge routines on your Elasticsearch cluster

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Hi, dear readers! Welcome to my blog. On this post, we will learn how to use the Curator project to create purge routines on a Elasticsearch cluster.

When we have a cluster crunching logs and other data types from our systems, it is necessary to configure process that manages this data, doing actions like purges and backups. For this purpose, the Curator project comes in handy.

Curator is a Python tool, that allows several types of actions. On this post, we will focus on 2 actions, purge and backup. To install Curator, we can use pip, like the command bellow:

sudo pip install elasticsearch-curator

Once installed, let’s begin preparing our cluster to make the backups, by a backup repository. A backup repository is a Elasticsearch feature, that process backups and save them on a persistent store. On this case, we will configure the backups to be stored on a Amazon S3 bucket. First, let’s install AWS Cloud plugin for Elasticsearch, by running the following command on each of the cluster’s nodes:

bin/plugin install cloud-aws

And before we restart our nodes, we configure the AWS credentials for the cluster to connect to AWS, by configuring them on the elasticsearch.yml file:

cloud:
  aws:
    access_key: <access key>
    secret_key: <secret key>

Finally, let’s configure our backup repository, using Elasticsearch REST API:

PUT /_snapshot/elasticsearch_backups
{
 “type”: “s3”,
 “settings”: {
 “bucket”: “elastic-bckup”,
 “region”: “us-east-1”
 }
}

On the command above, we created a new backup repository, called “elasticsearch-backups”, also defining the bucket where the backups will be created. With our repository created, let’s create our YAMLs to configure Curator.

The first YAML is “curator-config.yml”, where we configure details such as the cluster address. A configuration example could be as follows:

client:
  hosts:
    — localhost
  port: 9200
  url_prefix:
  use_ssl: False
  certificate:
  client_cert:
  client_key:
  aws_key:
  aws_secret_key:
  aws_region:
  ssl_no_validate: False
  http_auth:
  timeout: 240
  master_only: False
logging:
  loglevel: INFO
  logfile:
  logformat: default
  blacklist: [‘elasticsearch’, ‘urllib3’]

The other YAML is “curator-action.yml”, where we configure a action list to be executed by Curator. On the example, we have indexes of data from Twitter, with the prefix “twitter”, where we first create a backup from indexes that are more then 2 days old and after the backup, we purge the data:

actions:
 1:
   action: snapshot
   description: >-
     Make backups of indices older then 2 days.
   options:
     repository: elasticsearch_backups
     name: twitter-%Y.%m.%d
     ignore_unavailable: False
     include_global_state: True
     partial: False
     wait_for_completion: True
     skip_repo_fs_check: False
     timeout_override:
     continue_if_exception: False
     disable_action: False
   filters:
   — filtertype: age
     source: creation_date
     direction: older
     unit: days
     unit_count: 2
     exclude:
  2:
    action: delete_indices
    description: >-
      Delete indices older than 2 days (based on index name).
    options:
      ignore_empty_list: True
      timeout_override:
      continue_if_exception: False
      disable_action: False
    filters:
    — filtertype: pattern
      kind: prefix
      value: twitter-
      exclude:
    — filtertype: age
      source: name
      direction: older
      timestring: ‘%Y.%m.%d’
      unit: days
      unit_count: 2
      exclude:

With the YAMLs configured, we can execute Curator, with the following command:

curator — config curator-config.yml curator-action.yml

The command will generate a log from the actions performed, showing that our configurations were a success:

2016–08–27 16:14:36,576 INFO Action #1: snapshot
2016–08–27 16:14:40,814 INFO Creating snapshot “twitter-2016.08.27” from indices: [u’twitter-2016.08.14', u’twitter-2016.08.25']
2016–08–27 16:15:34,725 INFO Snapshot twitter-2016.08.27 successfully completed.
2016–08–27 16:15:34,725 INFO Action #1: completed
2016–08–27 16:15:34,725 INFO Action #2: delete_indices
2016–08–27 16:15:34,769 INFO Deleting selected indices: [u’twitter-2016.08.14', u’twitter-2016.08.25']
2016–08–27 16:15:34,769 INFO — -deleting index twitter-2016.08.14
2016–08–27 16:15:34,769 INFO — -deleting index twitter-2016.08.25
2016–08–27 16:15:34,860 INFO Action #2: completed
2016–08–27 16:15:34,861 INFO Job completed.

That’s it! Now it is just schedule this script to execute from time to time – once per day, for example – and we will have automated backups and purges.

Thank you for following me on this post, until next time.

Elastalert: implementing rich monitoring with Elasticsearch

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Hi, dear readers! Welcome to my blog. On this post, we will take a tour on a open source project developed by Yelp, called Elastalert. Focused on enriching Elasticsearch’s role as a monitoring tool, it allow us to query Elasticsearch, sending alerts to different types of tools, such as e-mail boxes, Telegram chats, JIRA issues and more. So, without further delay, let’s go deep on the tool!

Set up

In order to set up Elastalert, we need to clone the project’s Git repository and install it with Python. If the reader doesn’t have Python or Git installed, I recommend following the instructions here for Python and here for Git. For this tutorial, I am using a Unix OS, but the instructions are similar for other environments such as Linux. Also, on this tutorial I am using virtulenv, in order to keep my Python interpreter “clean”. The reader can find instructions to install virtualenv here.

To display the alerts, we will use a Telegram channel, which will receive alerts sent by a Telegram bot. In order to prepare the bot, we need a Telegram account and use the Bot Father (@BotFather) to create the bot, then create a public channel on telegram and associate the bot on the channel’s admins. The instructions to make this configurations can be found here. In order to easy the steps for the reader, I leave the bot created for this lab (@elastalerthandson) published for anyone who wants to use this bot on his own telegram channels for testing!

With all the tools installed and ready, let’s begin by cloning the Elastalert Git repository. To do this, we run the following command, on the folder of our choice:

git clone https://github.com/Yelp/elastalert.git

After running the command, we will see that a folder called “elastalert” was created. Before we proceed, we will also create a virtualenv environment, where we will install Elastalert. We do this by running:

virtualenv virtualenvelastalert

After creating the virtual environment – which will create a folder called “virtualenvelastalert” -, we need to activate it before we proceed with the install. To do this, we run the following command, assuming the reader is on the same folder of the previous command:

source virtualenvelastalert/bin/activate

After activating, we will notice that the name of our virtual environment is now written as a prefix on the shell, meaning that it is activated. Now, to install elastalert, we navigate to the folder created previously by our git clone command and type the following:

python setup.py install
sudo pip install -r requirements.txt

That’s it! Now that we have Elastalert installed, let’s continue the setup by creating the Elasticsearch index that it will be used as a metadata repository by Elastalert.

Creating the metadata index

In order to create Elastalert’s index, we run the command:

elastalert-create-index

The command-line tool will ask us some settings such as the name we want for the index and the ip/port of our Elasticsearch’s cluster. After providing the settings, the tool will create the index, like we can see on the picture bellow:Creating the configuration files

All the configuration on Elastalert is made by YAML files. The main configuration file for the tool is called by default as “config.yaml” and is located on the same folder where we start Elastalert – which we will do in some moments. For our main configuration file, let’s create a file called “config.yaml” like the following:

rules_folder: rules_folder

run_every:
  seconds: 40

buffer_time:
  minutes: 15

es_host: 192.168.99.100

es_port: 9200

writeback_index: elastalert_status

alert_time_limit:
  days: 2

On the config above, we defined:

  • The rules_folder property which defines the folder where our rules will be (all YAML files on the folder will be processed);
  • The run_every property will make Elastalert to run all the rules on a 40 seconds frequency;
  • The buffer_time property will make Elastalert cache the last period of time defined by the range of the property. This approach is used when the queries made on Elasticsearch are not on real time data;
  • The host ip of the Elasticsearch’s node used to query the alerts;
  • The host port of the Elasticsearch’s node used to query the alerts;
  • The index used to store the metadata, that we created on the previous section;
  • The maximum period of time Elastalert will hold a alert that the delivery has failed, making retries during the period;

Now, let’s create the “rules_folder” folder and create 3 YAML files, which will hold our rules:

  • twitter_flatline.yaml
  • twitter_frequency.yaml
  • twitter-blacklist.yaml

On this rules, we will test 3 types of rules Elastalert can manage:

  • The flatline rule, which will alert when the number of documents find for a search drop bellow a threshold;
  • The frequency rule, which will alert when a number of documents for a certain period of time is reached;
  • The blacklist rule, which will alert when any document containing a list of words is found on the timeframe collected by the tool;

Of course, there’s other rule types alongside those that we will cover on this lab, like the spike rule that can detect abnormal grows or shrinks on data across a time period, or the whitelist rule, which alert on any documents that contain any words from a list. More information about rules and their types can be found at the references on the end of this post.

For this lab, we will use a elasticsearch index with twitter data. The reader can found more information about how to set up a ELK environment on my ELK series. The Logstash configuration file used on this lab is as follows:

input {
      twitter {
        consumer_key => "XXXXXXXXXXXXXXXXX"
        consumer_secret => "XXXXXXXXXXXXXXXX"
        keywords => ["coca cola","java","elasticsearch","amazon"]
        oauth_token => "XXXXXXXXXXXXXXX"
        oauth_token_secret => "XXXXXXXXXXXXXX"
    }
}



 output {
      stdout { codec => rubydebug }
      elasticsearch {
            hosts => [ "192.168.99.100:9200" ]
            index => "twitter-%{+YYYY.MM.dd}"
        }
}

With our ELK stack set up and running, let’s begin creating the rules. First, we create the frequency rule, by configuring the respective YAML file with the following code:

name: Twitter frequency rule

type: frequency

index: twitter-*

num_events: 3

timeframe:
  minutes: 15

realert:
  hours: 2

filter:
- query:
   query_string:
    query: "message:amazon"


alert:
- "telegram"

telegram_bot_token: 184186982:AAGpJRyWQ2Rb_RcFXncGrJrBrSK7BzoVFU8

telegram_room_id: "@elastalerthandson"

On the following file we configure a frequency rule. The rule is configured by setting the following properties:

  • name: This property defines the rule’s name. This property acts as the rule ID;
  • type: This property defines the type of rule we are creating;
  • index: This property defines the index on Elasticsearch where we want to make the searches;
  • num_events: The number of documents necessary to be found in order to fire the alert;
  • timeframe: The time period which will be queried to check the rule;
  • realert: This property defines the time period that Elastalert will stop realerting the rule after the first match, preventing the users to be flooded with alerts;
  • filter: This property is where we configure the query that will be send to Elasticsearch in order to check the rule;
  • alert: This property is a list of targets which we want our alerts to be send. On our case, we just defined the telegram target;
  • telegram_bot_token: On this property we set the access token from our bot, as received by the Botfather;
  • telegram_room_id: On this property we define the id of the channel we want the alerts to be sent;

As we can see, is a very straightforward and simple configuration file. For the flatline config, we configure our respective YAML as follows:

name: Twitter flatline rule

type: flatline

index: twitter-*

threshold: 30

timeframe: 
 minutes: 5

realert:
 minutes: 30

use_count_query: true

doc_type: logs

alert:
- "telegram"

telegram_bot_token: 184186982:AAGpJRyWQ2Rb_RcFXncGrJrBrSK7BzoVFU8

telegram_room_id: "@elastalerthandson"

The configuration is pretty much the same of the previous file, with the exception of 3 new properties:

  • threshold: This property defines the minimum amount of documents expected for the rule to receive in order that a alert is not needed to be sent;
  • use_count_query: This property defines that Elastalert must use the count API from Elasticsearch. This API returns just the number of documents for the rule to be validated, eliminating the need to process the query data;
  • doc_type: This property is needed by the count API aforementioned, in order to query the document count for a specific document type;

Finally, let’s configure our final rule, coding the final YAML as follows:

name: Twitter blacklist rule

type: blacklist

index: twitter-*

compare_key: message

blacklist:
- "android"
- "java"

realert:
  hours: 4

filter:
- query:
   query_string:
    query: "*"

alert:
- "telegram"

telegram_bot_token: 184186982:AAGpJRyWQ2Rb_RcFXncGrJrBrSK7BzoVFU8

telegram_room_id: "@elastalerthandson"

On this file, the new properties that we needed to configure are:

  • compare_key: This property defines the field on the documents that Elastalert will check the blacklist;
  • blacklist: This property is a list of words which Elastalert will compare against the documents in order to check if any document has a blacklisted word;

And that concludes our configuration. Now, let’s run Elastalert!

Running Elastalert

To run Elastalert, all we need to do is run a command like this, on the same folder of our YAML structure – where “config.yaml” is located:

elastalert --start NOW --verbose

On the command above, we set the flag “–start” to define that we want Elastalert to start the measurings from now up and the “–verbose” flag to print all the info log messages.

The simplest of the rules to test it out is the flatline rule. All we have to do is wait for about 5 minutes with Elasticsearch running and Logstash stopped – so no documents are streaming. After the wait, we can see on our channel that a alert is received on the channel:

And, as the time passes, we will receive other alerts as well, like the frequency alert:

Conclusion

And so we conclude our tutorial about Elastalert. With a simple usage, we can see that we can construct really powerful alerts for our Elasticsearch system, enforcing the rule of the search engine on a monitoring ecosystem. Thank you for following me on another post, until next time.

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Docker: using containers to implement a Microservices architecture

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Hello, dear readers! Welcome to another post from my blog. On this post, we will talk about the virtualization technology called Docker, which gained a ton of popularity this days, specially when we talk about Microservices architectures. But after all, what it is virtualization?

Virtualization

Virtualization, as the name implies, consists in the use of software to emulate any part of a environment, ranging from hardware components to a entire OS. In this world, there is several traditional technologies such as VMWare, Virtualbox, etc. This technologies, however, use hypervisors, which creates a intermediate layer responsible for isolating the virtual machine from the physical machine.

On containers, however, we don’t have this hypervisor layer. Instead, containers run directly on top of the kernel itself of the host machine they are running. This leads to a much more lightweight virtualization, allowing us to run a lot more VMs on a single host then we could do with a hypervisor.

Of course that using virtualization with hypervisors over containers has his benefits too, such as more flexibility – since you can’t for example run a windows container from a linux machine – and security, since this shared kernel approach leads to a scenario where if a attacker invades the kernel, he automatically get access to all the containers provided by that kernel, although we can say the same if the attacker invades the hypervisor of a machine running some VMs. This is a very heated debate, which we can find a lot of discussion by the Internet.

The fact is that containers are here to stay and his lightweight implementation provides a very good foundation for a lot of applications, such as a Microservices architecture. So, without further delay, let’s begin do dive in on Docker, one of the most popular container engines on the market today.

Docker Architecture

Docker was developed by Docker inc (formerly DotCloud inc) as a open-source engine for deployment of applications on containers. By providing a logical layer that manages the lifecycle of the containers, we can focus our development on the applications themselves, leaving the implementation of the container management to Docker.

The Docker architecture consists of a client-server model, where we have a Docker client, that could be the command line one provided by Docker, or a consumer of the RESTFul API also provided on the toolset, and the Docker server, also known as Docker daemon, which receives requests to create/start/stop containers, been responsible for the container management. The diagram bellow illustrates this architecture:

docker-architecture

On the image above we can see the Docker clients connecting to the daemon, making requests to start/stop/create containers etc. We can also see that the daemon is communicating with a image repository and using images while processing the requests. What are those images for? That’s what we will find out on the next section.

Containers & Images

When we talk about containers on Docker, we talk about processes running from instructions that were set on images. We can understand images as the building blocks from which containers are build, that way organizing the building of containers on a Docker environment.

This images are distributed on repositories, also known as a docker registry, which in turn are versioned using git. The main repository for the distribution of Docker images is, of course, the Docker Hub, managed by Docker itself.

A interesting thing is that the code behind the Docker Hub is open, so it is perfectly possible to host your own image repository. To know more about this, please visit:

github.com/docker/distribution

Docker Union File System

If the reader is familiar with traditional virtualization with hypervisors, he could be thinking: “How Docker manages the file system so the images didn’t get ‘dirt’ from the files generated on the executions of all the created containers?”. This could be even worse when we think that images can be inherited from other images, making a whole image tree.

The answer for this is how Docker utilizes the file system, with a file system called Union File System. On this system, each image is layered as a read-only layer. The layers are then overlapped on top of each other and finally on top of the chain a read-write layer is created, for the use of the container. This way, none of the image’s file systems are altered, making the images clean for use across multiple containers.

Using Docker in other OS

Docker is designed for use on Linux distributions. However, for use as a development environment, Docker inc released a Docker Toolbox that allows it to run Docker both on OSX and Windows environments as well.

In order to do this, the toolbox install virtualbox inside his distribution, as well as a micro linux VM, that only has the minimum kernel packages necessary for the launch of containers. This way, when we launch the terminal of the toolbox, the launcher starts the VM on virtualbox, starting Docker inside the VM.

One important thing to notice is that, when we launch Docker this way, we can’t use localhost anymore when we want to access Docker from the same host it is running, since it is binded to a specific ip. We can see the ip Docker is bind to by the initialization messages, as we can see on the image bellow, from a Docker installation on OSX:

Another thing to notice is that, when we use docker on OSX or Windows, we don’t need to use sudo to execute the commands, while on Linux we will need to execute the commands as root. Another way to use Docker that removes the need to use sudo is by having a group called ‘docker’ on the machine, which will make docker apply the permissions necessary to run docker without sudo to the group. Notice, however, that users from this group will have root permissions, so caution is required.

Docker commands

Well, now that we get the concepts out of the way, let’s start using Docker!

As said before, Docker uses image repositories to resolve the images it needs to run the containers. Let’s begin by running a simple container, to make a famous ‘hello world!’, Docker style.

To do this, let’s open a terminal – or the Docker QuickStart Terminal on other OS – and type:

docker run ubuntu echo 'hello, Docker!'

This is the run command, which creates a new container each time is called. On the command above,   we simply asked Docker to create a new container, using the image ubuntu – if it doesn’t have already, Docker will search Docker Hub for the latest version of the image and download it. If we wanted to use a specific version, we could specify like this: ‘ubuntu:14.04’ – from Docker Hub. At the end, we specify a command for the container to run, on this case, a simple “echo ‘hello world!’ “.

The image bellow show the command in action, downloading the image and executing:

To list the containers created, we run the command ‘docker ps’. If we run the command this way now, however, we won’t see anything, because the command by default only shows the active containers and on our case, our container simply stopped after running the command. If we run the command with the flag -a, we can then see the stopped containers, like the image bellow:

However, there’s a problem: our hello world container was just a test, so we didn’t want to keep with the container. Let’s correct this by removing the container, with the command:

docker rm 2f134296daa6

PS: The hash you can see on the command is part of the ID of the container, that you can see when you list the containers with docker ps.

Now, what about if we wanted to run again our hello world container, or any other container that we need just once, without the need to manually remove the container afterwards? We can do this using the –rm flag, running like this:

docker run --rm ubuntu echo 'hello, Docker!'

If we run docker ps -a again, after running the command above, we can see that there’s no containers  from our previous execution, proving that the flag worked correctly.

Let’s now do a little more complex example, starting a container with a Tomcat server. First, let’s search for the name of the image we want on Docker Hub. To do this, open a browser and type it:

https://hub.docker.com

Once inside the Docker Hub, let’s search for the image typing ‘tomcat’ on the search box on the top right corner of the site. We will be send to a screen like the one bellow. You can see the images with some classifiers like ‘official’ and ‘automated’.

Official means that the image is maintained by Docker itself, while automated means that the image is maintained by a CI workload.On the section ‘Publishing on Docker Hub’ we will understand more about the options to publish our own images to the Docker Hub.

From the Docker Hub we get that the name of the official image is ‘tomcat’, so let’s use this image. To use it, we simply run the following command, which will start a new container with the tomcat image:

docker run --name mytomcat -p 8888:8080 tomcat:8.0

You can see that we used some new flags on this command. First, we used the flag –name, which makes a name for our container, so we can refer to this name when running commands afterwards.

The -p flag is used to bind a port from the host machine to a port on the container. On the next sections, we will talk about creating our own images and we will see that we can expose ports from the container to be accessed by clients, like in this case that we exposed the port tomcat will serve on the container (8080) to the port 8888 of the host.

Lastly, when declaring the image we will use, we specified the version, 8.0, meaning that we want to use Tomcat 8.0. Note that we didn’t passed any command to the container, since the image is already configured to start the Tomcat server after the building. After running the command, we can see that tomcat is running inside our container:

The problem is that now our terminal is occupied by the tomcat process so we can’t issue more commands. Let’s press Crtl+C and type the docker ps command. The container is not active! the reason for this is that, by default, Docker don’t put the containers to run in background when we create a new container. To do this, we use the -d flagso on the previous command, all we had to do is include this flag to make the container start on background.

Let’s start the container again with the command docker start:

docker start mytomcat

After the start, we can see that the container is running, if we run docker ps:

Before we open the server on the browser, let’s just check if the container is exposed on the port we defined. To do this, we use the command:

docker port mytomcat

This command will return the following result:

8080/tcp -> 0.0.0.0:8888

Which means that the container is exposed on the port 8888, as defined. If we open the browser on localhost:8888 – or the ip binded by Docker on a non-linux environment – we will receive the following screen:

Excellent! Now we have our own dockerized Tomcat! However, by starting the container in background, we couldn’t see the logging of the server, to see if there wasn’t any problem on the startup of the web server. let’s see the last lines of the log of our container by entering the command:

docker logs mytomcat

This will show the last inputs of our container on the stdout. We could also use the command:

docker attach mytomcat

This command has the same effect of the tail command on a file, making it possible to watch the logs of the container. Take notice that after attaching to a container, pressing Ctrl+C will kill him!

Before ending our container, let’s see more detailed information about our container, such as the Java version, network mappings etc. To do this, we run the following command:

docker inspect mytomcat

This will produce a result like the following, in JSON format:

[

{

“Id”: “14598a44a3b4fe2a5b987ea365b2c83a0399f4fda476ad1754acee23c96fcc22”,

“Created”: “2016-01-03T17:59:49.632050403Z”,

“Path”: “catalina.sh”,

“Args”: [

“run”

],

“State”: {

“Status”: “running”,

“Running”: true,

“Paused”: false,

“Restarting”: false,

“OOMKilled”: false,

“Dead”: false,

“Pid”: 4811,

“ExitCode”: 0,

“Error”: “”,

“StartedAt”: “2016-01-03T17:59:49.728287604Z”,

“FinishedAt”: “0001-01-01T00:00:00Z”

},

“Image”: “af28fa31b54b2e45d53e80c5a7cbfd2693f198fdb8ba53d44d8a432832ad1012”,

“ResolvConfPath”: “/mnt/sda1/var/lib/docker/containers/14598a44a3b4fe2a5b987ea365b2c83a0399f4fda476ad1754acee23c96fcc22/resolv.conf”,

“HostnamePath”: “/mnt/sda1/var/lib/docker/containers/14598a44a3b4fe2a5b987ea365b2c83a0399f4fda476ad1754acee23c96fcc22/hostname”,

“HostsPath”: “/mnt/sda1/var/lib/docker/containers/14598a44a3b4fe2a5b987ea365b2c83a0399f4fda476ad1754acee23c96fcc22/hosts”,

“LogPath”: “/mnt/sda1/var/lib/docker/containers/14598a44a3b4fe2a5b987ea365b2c83a0399f4fda476ad1754acee23c96fcc22/14598a44a3b4fe2a5b987ea365b2c83a0399f4fda476ad1754acee23c96fcc22-json.log”,

“Name”: “/mytomcat”,

“RestartCount”: 0,

“Driver”: “aufs”,

“ExecDriver”: “native-0.2”,

“MountLabel”: “”,

“ProcessLabel”: “”,

“AppArmorProfile”: “”,

“ExecIDs”: null,

“HostConfig”: {

“Binds”: null,

“ContainerIDFile”: “”,

“LxcConf”: [],

“Memory”: 0,

“MemoryReservation”: 0,

“MemorySwap”: 0,

“KernelMemory”: 0,

“CpuShares”: 0,

“CpuPeriod”: 0,

“CpusetCpus”: “”,

“CpusetMems”: “”,

“CpuQuota”: 0,

“BlkioWeight”: 0,

“OomKillDisable”: false,

“MemorySwappiness”: -1,

“Privileged”: false,

“PortBindings”: {

“8080/tcp”: [

{

“HostIp”: “”,

“HostPort”: “8888”

}

]

},

“Links”: null,

“PublishAllPorts”: false,

“Dns”: [],

“DnsOptions”: [],

“DnsSearch”: [],

“ExtraHosts”: null,

“VolumesFrom”: null,

“Devices”: [],

“NetworkMode”: “default”,

“IpcMode”: “”,

“PidMode”: “”,

“UTSMode”: “”,

“CapAdd”: null,

“CapDrop”: null,

“GroupAdd”: null,

“RestartPolicy”: {

“Name”: “no”,

“MaximumRetryCount”: 0

},

“SecurityOpt”: null,

“ReadonlyRootfs”: false,

“Ulimits”: null,

“LogConfig”: {

“Type”: “json-file”,

“Config”: {}

},

“CgroupParent”: “”,

“ConsoleSize”: [

0,

0

],

“VolumeDriver”: “”

},

“GraphDriver”: {

“Name”: “aufs”,

“Data”: null

},

“Mounts”: [],

“Config”: {

“Hostname”: “14598a44a3b4”,

“Domainname”: “”,

“User”: “”,

“AttachStdin”: false,

“AttachStdout”: false,

“AttachStderr”: false,

“ExposedPorts”: {

“8080/tcp”: {}

},

“Tty”: false,

“OpenStdin”: false,

“StdinOnce”: false,

“Env”: [

“PATH=/usr/local/tomcat/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin”,

“LANG=C.UTF-8”,

“JAVA_VERSION=7u91”,

“JAVA_DEBIAN_VERSION=7u91-2.6.3-1~deb8u1”,

“CATALINA_HOME=/usr/local/tomcat”,

“TOMCAT_MAJOR=8”,

“TOMCAT_VERSION=8.0.30”,

“TOMCAT_TGZ_URL=https://www.apache.org/dist/tomcat/tomcat-8/v8.0.30/bin/apache-tomcat-8.0.30.tar.gz”

],

“Cmd”: [

“catalina.sh”,

“run”

],

“Image”: “tomcat:8.0”,

“Volumes”: null,

“WorkingDir”: “/usr/local/tomcat”,

“Entrypoint”: null,

“OnBuild”: null,

“Labels”: {},

“StopSignal”: “SIGTERM”

},

“NetworkSettings”: {

“Bridge”: “”,

“SandboxID”: “37fe977f6a45f4495eae95260a67f0e99a8168c73930151926ad521d211b4ac6”,

“HairpinMode”: false,

“LinkLocalIPv6Address”: “”,

“LinkLocalIPv6PrefixLen”: 0,

“Ports”: {

“8080/tcp”: [

{

“HostIp”: “0.0.0.0”,

“HostPort”: “8888”

}

]

},

“SandboxKey”: “/var/run/docker/netns/37fe977f6a45”,

“SecondaryIPAddresses”: null,

“SecondaryIPv6Addresses”: null,

“EndpointID”: “09477abf22e8019e2f8d3e0deeb18d9362136954a09e336f4a93286cb3b8b027”,

“Gateway”: “172.17.0.2”,

“GlobalIPv6Address”: “”,

“GlobalIPv6PrefixLen”: 0,

“IPAddress”: “172.17.0.3”,

“IPPrefixLen”: 16,

“IPv6Gateway”: “”,

“MacAddress”: “02:42:ac:11:00:03”,

“Networks”: {

“bridge”: {

“EndpointID”: “09477abf22e8019e2f8d3e0deeb18d9362136954a09e336f4a93286cb3b8b027”,

“Gateway”: “172.17.0.2”,

“IPAddress”: “172.17.0.3”,

“IPPrefixLen”: 16,

“IPv6Gateway”: “”,

“GlobalIPv6Address”: “”,

“GlobalIPv6PrefixLen”: 0,

“MacAddress”: “02:42:ac:11:00:03”

}

}

}

}

]

Now, let’s stop our container, by entering:

docker stop mytomcat

Finally, let’s remove the container, since we won’t use him anymore on this practice:

docker rm mytomcat

Let’s also remove the image, since we won’t use it either on our next steps:

docker rmi tomcat:8.0

And that concludes our breaking course on Docker’s commands! There are also other useful commands as well, of course, such as:

  • docker build: Used to build a image from a Dockerfile (see next sections);
  • docker commit: Creates a image from a container;
  • docker push: Pushes the image for a registry (Docker Hub by default);
  • docker exec: Submit a command for a running container;
  • docker export: Export the file system of a container as a tar file;
  • docker images: list the images inside Docker;
  • docker kill: force kill a running container;
  • docker restart: restart a container;
  • docker network: manages docker networks (see next sections);
  • docker volume: manages docker volumes (see next sections);

Creating your own images

On the previous section, we used a image from the Docker Hub, that creates a container with a Tomcat Web Server. This image is implemented by a script with building instructions called Dockerfile. On our lab we will create a Dockerfile, but for now, let’s just examine the Dockerfile from the tomcat’s image in order to learn some of the instructions available:

FROM java:7-jre
ENV CATALINA_HOME /usr/local/tomcat

ENV PATH $CATALINA_HOME/bin:$PATH

RUN mkdir -p “$CATALINA_HOME”

WORKDIR $CATALINA_HOME
# see https://www.apache.org/dist/tomcat/tomcat-8/KEYS

RUN gpg –keyserver pool.sks-keyservers.net –recv-keys \

05AB33110949707C93A279E3D3EFE6B686867BA6 \

07E48665A34DCAFAE522E5E6266191C37C037D42 \

47309207D818FFD8DCD3F83F1931D684307A10A5 \

541FBE7D8F78B25E055DDEE13C370389288584E7 \

61B832AC2F1C5A90F0F9B00A1C506407564C17A3 \

79F7026C690BAA50B92CD8B66A3AD3F4F22C4FED \

9BA44C2621385CB966EBA586F72C284D731FABEE \

A27677289986DB50844682F8ACB77FC2E86E29AC \

A9C5DF4D22E99998D9875A5110C01C5A2F6059E7 \

DCFD35E0BF8CA7344752DE8B6FB21E8933C60243 \

F3A04C595DB5B6A5F1ECA43E3B7BBB100D811BBE \

F7DA48BB64BCB84ECBA7EE6935CD23C10D498E23
ENV TOMCAT_MAJOR 8

ENV TOMCAT_VERSION 8.0.30

ENV TOMCAT_TGZ_URL https://www.apache.org/dist/tomcat/tomcat-$TOMCAT_MAJOR/v$TOMCAT_VERSION/bin/apache-tomcat-$TOMCAT_VERSION.tar.gz
RUN set -x \

&& curl -fSL “$TOMCAT_TGZ_URL” -o tomcat.tar.gz \

&& curl -fSL “$TOMCAT_TGZ_URL.asc” -o tomcat.tar.gz.asc \

&& gpg –verify tomcat.tar.gz.asc \

&& tar -xvf tomcat.tar.gz –strip-components=1 \

&& rm bin/*.bat \

&& rm tomcat.tar.gz*
EXPOSE 8080

CMD [“catalina.sh”, “run”]

As we can see, the first instruction is called FROM. This instruction delimits the base image upon the image will be constructed. On this case, the java:7-jre image will create a basic Linux environment, with Java 7 configured.

Then we see some ENV instructions. This commands set environment variables on the OS, as part of Tomcat’s configuration. We can also see a WORKDIR instruction, which defines the directory that, from that point, Docker will use to run the commands.

We also see some RUN instructions. This instructions, as the name implies, run commands on the container.On the case of our image, this instructions make tomcat’s installation process.

Finally we see the EXPOSE instruction, which exposes the 8080 port for the host. Finally, we see the CMD instruction, which defines the start of the server. One important distinction of the CMD command from the RUN ones is that, while the RUN instructions only executes on the build phase, the CMD instruction is executed on the container’s startup, making it the command to be executed on the creation and start of a container. For this reason, it is only allowed to have one CMD command per Dockerfile.

One important side note about the CMD command is that, when starting a container, it allows to override the command on the Dockerfile, so it could lead to security holes when used. For this reason, it is recommended to use the ENTRYPOINT instruction instead, that like the CMD instruction, it defines the command the container will run at startup, but on this case, it will not permit the command to be overridden, making it more secure.

We could also use ENTRYPOINT and CMD combined, making it possible to restrict the user to only pass flags and/or arguments to the running command.

Of course, that is not the only instructions we can use on a Dockerfile. Other instructions are:

  • MAINTAINER: Defines the author of the image;
  • LABEL: Adds metadata to a image, in a key=value format;
  • ADD: Adds a file, folder or remote file URL to a folder inside the container. The current directory from which this instruction point it out is the same directory of the Dockerfile;
  •  COPY: Analogous to ADD, this instruction also copies files and folders from the host to the container. The two major differences are that COPY doesn’t allow the use of URLs and COPY doesn’t uncompress known files, like ADD can;
  • VOLUME: Creates a volume. On the section “creating the base image” we will learn in more detail about what are volumes on Docker;
  • USER: Defines the name of the user used to run the RUN, CMD and ENTRYPOINT instructions;
  • ARG: Defines build-time variables, that could be used to pass parameters for the image’s buildings, using the build-arg flag;
  • ONBUILD: Defines a command to be triggered by other images, when the image is used as a base image for other images;
  • STOPSIGNAL: Defines the code for the container to stop, as a number or in the SIGNAME format, for instance SIGKILL.

Publishing on Docker Hub

As we saw on the previous section, in order to create our own images, all we have to do is create a “Dockerfile” file, with the instructions necessary for the building. However, in order to distribute our images, we need to register them on a image registry, like the Docker Hub, for example.

The simplest way to publish images are with the commit and push commands. For example, if we had  made changes to our Tomcat container and wanted to save those changes as a new image, we could do this with this command:

docker commit mytomcat alexandreesl/mytomcat

Where the second argument is the <repository ID>/<image name>. In order to push the images to Docker Hub, the repository ID must be equals to the username of our Docker Hub account.

After committing the changes, all we have to do is push the changes to the Hub, using the following command:

docker push alexandreesl/mytomcat

And that’s it! After the push, if we see our Docker Hub account, we can see that our image was successfully created:

NOTE: before pushing, you could have to run the command docker login to register your credentials from the Docker Hub

Another way of publishing is by linking our images with a git repository, this way the Docker Hub will rebuild the image each time a new version of the Dockerfile is pushed to the repository. Is this method of publishing that generates automated build images, since this way Docker can establish a CI Workload with the git repository. We will see this method in action on the next section, ‘Creating the base image’.

Practice: Using Docker to implement a microservices architecture

On our lab, we will take a step forward from my previous post about microservices with Spring Boot (haven’t see it? you can find it here, I am really grateful if you read that post as well!), by using a Service Registry called Eureka, designed by Netflix.

On the Service Registry pattern, we have a registry where microservices can register/unregister and also find the addresses of a service dynamically, this way decoupling the bounds between them. We will dockerize (run inside a container) the services of that lab and make them use Eureka, which will also run inside a container. In order to integrate with Eureka, we will modify our applications to use the Spring Cloud project, which according to the project’s description:

Spring Cloud provides tools for developers to quickly build some of the common patterns in distributed systems (e.g. configuration management, service discovery, circuit breakers, intelligent routing, micro-proxy, control bus, one-time tokens, global locks, leadership election, distributed sessions, cluster state). Coordination of distributed systems leads to boiler plate patterns, and using Spring Cloud developers can quickly stand up services and applications that implement those patterns. They will work well in any distributed environment, including the developer’s own laptop, bare metal data centres, and managed platforms such as Cloud Foundry.

Also, to “Springfy” even more our example, we will exchange our implementation from the previous post that uses pure jax-rs to the RestController implementation, present on the Spring Web project.

Creating the base image

Well, so let’s begin our practice! First, we will create a Docker Network to accommodate the containers.

If we see the network adapters from the host machine when the Docker Daemon is up, we will see that he creates a bridge adapter on the host, subsequently appending the containers on network interfaces inside the bridge adapter. This forms a subnet where the containers can see each other and also Docker facilitates the work for us, by mapping the container’s IPs with their names, on the /etc/hosts files inside.

On our scenario, we will use this feature so the microservices can easily find our Eureka registry, by mapping the address to the container’s name. Of course that on a real scenario we would have a cluster of Eurekas with a load balancer on separate hosts, but for simplicity’s sake of our lab, we will just use one Eureka instance.

So, in order to create a network to accommodate our architecture, first we create a network, by running the following command:

docker network create microservicesnet

After running the command we will see a hash’s ID indicating our network was created. We can see the details of our network by running the following command:

docker network inspect microservicesnet

Which will produce a result like the following:

[

{

“Name”: “microservicesnet”,

“Id”: “e8d401a00de26b74f4f2461c13dbf848c14f37127b3337a3e40465eff5897910”,

“Scope”: “local”,

“Driver”: “bridge”,

“IPAM”: {

“Driver”: “default”,

“Config”: [

{}

]

},

“Containers”: {},

“Options”: {}

}

]

Notice that, for now, the containers object is empty. This is why we didn’t add any containers to the network yet, but this will soon change.

Now we will create the Dockerfile. Create a folder in the directory of your choice and create a file called ‘Dockerfile’ (without any extension). On my case, I will push my Dockerfile to a Github repository, in order to create the image on Docker Hub as a automated build image. You can find the repositories with the source for this lab at the end of the post.

So, without further delay, let’s code the Dockerfile. The code for our image will be the following:

FROM java:8-jre

MAINTAINER Alexandre Lourenco <alexandreesl@example.com>

VOLUME [ "/data" ]

WORKDIR /data

EXPOSE 8080
ENTRYPOINT [ "java" ]
CMD ["-?"]

 

As we can see, it is a simple Dockerfile. We use Java’s 8 official image as the base,  define a volume and set his folder as our Workdir, expose the 8080 port which is the default for Spring Boot and finally we combine the entrypoint and cmd commands, meaning that anything we pass when we get up a container will be treated as parameters for the Java command. But what is this volume we have speaked of?

The reader must remember what we saw about the Union File System and how each image is layered as a read-only layer. The volumes on Docker is a technique that bypasses the Union File System, by defining a mount point on the Containers that points for a shared space on the host machine. The uses of this technique are in order to provide a place where the container can read/write information that needs to be persisted, alongside the need to share data between containers.

On our scenario, we will use the volume to point to a place where the jars of our microservices will be generated, so when a container runs a microservice, it runs the last version of the software. On a real-world scenario, this place could be a result of a CI workload, for example from a Jenkins job.

Now that we have our image, let’s build the image to test his correctness:

docker build -t alexandreesl/microservices-spring-boot-base .

At the end, we will see a message that our building was successful, validating the Dockerfile. Out of curiosity, if you see the building process, you will notice that Docker created several temporary containers for each instruction of our script, maintaining a status of the last successful instruction executed, so if we have to rebuild the image after a failure, we can restart from the failed point. We can disable this feature with the flag -no-cache if we want.

Now, let’s register the image on Docker Hub. I have created a Github repository here, so I will register the image directly on the site. To do this, we log in on our account and click on the “create automated build” menu item, as shown on the screen bellow:

After clicking, if we haven’t linked a github account yet, we will be prompted to do so. after making the linking, we will see a page with the list of our git repositories. We select the one with the Dockerfile and finally create the image, entering the name and a description for the image, as the screen bellow:

After clicking on the create button, we have completed our step, successfully registering our image on the Docker Hub! You can see my image on this link.

Lastly, just to test if our Docker Hub upload was really successful, we will remove the image from the local cache – that we added with our docker build command – and download using the docker pull command. First, let’s remove the image with the command:

docker rmi alexandreesl/microservices-spring-boot-base

And after, let’s pull the image with the command:

docker pull alexandreesl/microservices-spring-boot-base

After the download, we will have the image from the Docker Hub repository.

Preparing the service registry image

For the service registry image, we actually don’t have to do any coding, since we will use a already made image. We will start the image on the “Launching the containers” section, but the reader can see the image’s page to satisfy his curiosity here.

Preparing the services to use the registry

Now, Let’s prepare the services for the registering/deregistering of microservices, alongside service discovery when a service has dependencies.

To focus on the explanation, I will omit some details like the pom configuration, since the reader can easily get the configuration on the Github repository from the lab. On this lab, we have 3 microservices: a Customer service, a Product service and a Order service. The Order service has dependencies on the other 2 services, in order to mount a Order.

On the 3 projects we will have the same configuration for Spring Boot’s main class, called Application,  as follows:

@SpringBootApplication
@Configuration
@EnableAutoConfiguration
@EnableEurekaClient
public class Application {

public static void main(String[] args) {
 SpringApplication.run(Application.class, args);
 }
}

The key line here is the annotation @EnableEurekaClient, which configures the Spring Boot’s application to work with Eureka. Just with these annotation alone, we configure Spring Boot to connect to Eureka at startup and register itself with, send heartbeats during his lifecycle to keep the registration alive and finally make a unregistration when the process is terminated. Also, it instantiate a RestTemplate with a Ribbon load balancer, also made by Netflix, that can easily lookup service addresses from the registry. All of this with just one annotation!

In order to connect to Eureka, we have to provide the registry’s address. this is made by configuring a YAML file, called application.yml, that we put it on the resources source folder. We also configure a application name on this file, in order to inform Eureka about what Application’s ID we would like to use for the microservice.

So, in order to make this configuration, we create the files on our projects. seeing a example, for the Order’s service,  we have the following YAML configuration:

spring:
 application:
 name: OrderService
eureka:
 client:
 serviceUrl:
 defaultZone: http://eureka:8761/eureka/

Notice that when we configure Eureka’s address, we used “eureka” as the host name. This is the name of the container that we will use in order to deploy the Eureka server on our Docker Network, so on the /etc/hosts files of our containers, this name will be mapped to Eureka’s container IP, making it possible to point it out dynamically.

Now let’s see how our Microservices were implemented. For the Customer service, we have the following code:

@RestController
@RequestMapping("/")
public class CustomerRest {

private static List<Customer> clients = new ArrayList<Customer>();

static {
Customer customer1 = new Customer();
 customer1.setId(1);
 customer1.setName("Cliente 1");
 customer1.setEmail("customer1@gmail.com");

Customer customer2 = new Customer();
 customer2.setId(2);
 customer2.setName("Cliente 2");
 customer2.setEmail("customer2@gmail.com");

Customer customer3 = new Customer();
 customer3.setId(3);
 customer3.setName("Cliente 3");
 customer3.setEmail("customer3@gmail.com");

Customer customer4 = new Customer();
 customer4.setId(4);
 customer4.setName("Cliente 4");
 customer4.setEmail("customer4@gmail.com");

Customer customer5 = new Customer();
 customer5.setId(5);
 customer5.setName("Cliente 5");
 customer5.setEmail("customer5@gmail.com");

clients.add(customer1);
 clients.add(customer2);
 clients.add(customer3);
 clients.add(customer4);
 clients.add(customer5);
}

@RequestMapping(method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
 public List<Customer> getClientes() {
 return clients;
 }

@RequestMapping(value = "customer/{id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
 public Customer getCliente(@PathVariable long id) {

Customer cli = null;

for (Customer c : clients) {

if (c.getId() == id)
 cli = c;

}

return cli;
 }
}

As we can see, nothing out of normal, very simple usage of Spring’s REST Controllers. Now, on to the Product service:

@RestController
@RequestMapping("/")
public class ProductRest {

private static List<Product> products = new ArrayList<Product>();

static {

Product product1 = new Product();
 product1.setId(1);
 product1.setSku("abcd1");
 product1.setDescription("Produto1");

Product product2 = new Product();
 product2.setId(2);
 product2.setSku("abcd2");
 product2.setDescription("Produto2");

Product product3 = new Product();
 product3.setId(3);
 product3.setSku("abcd3");
 product3.setDescription("Produto3");

Product product4 = new Product();
 product4.setId(4);
 product4.setSku("abcd4");
 product4.setDescription("Produto4");

products.add(product1);
 products.add(product2);
 products.add(product3);
 products.add(product4);

}

@RequestMapping(method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
 public List<Product> getProdutos() {
 return products;
 }

@RequestMapping(value = "product/{id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
 public Product getProduto(@PathVariable long id) {

Product prod = null;

for (Product p : products) {

if (p.getId() == id)
 prod = p;

}

return prod;
 }

}

Again, nothing unusual on the code. Now, let’s see the Order service, where we will see the registry been used for consuming microservices:

@RestController
@RequestMapping("/")
public class OrderRest {

private static long id = 1;

// Created automatically by Spring Cloud
 @Autowired
 @LoadBalanced
 private RestTemplate restTemplate;

private Logger logger = Logger.getLogger(OrderRest.class);

@RequestMapping(value = "order/{idCustomer}/{idProduct}/{amount}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
 public Order submitOrder(@PathVariable long idCustomer, @PathVariable long idProduct, @PathVariable long amount) {

Order order = new Order();

 Map map = new HashMap();

 map.put("id", idCustomer);

ResponseEntity<Customer> customer = restTemplate.exchange("http://CUSTOMERSERVICE/customer/{id}",
 HttpMethod.GET, null, Customer.class, map);

 map = new HashMap();

 map.put("id", idProduct);

ResponseEntity<Product> product = restTemplate.exchange("http://PRODUCTSERVICE/product/{id}", HttpMethod.GET,
 null, Product.class, map);

order.setCustomer(customer.getBody());
order.setProduct(product.getBody());
order.setId(id);
order.setAmount(amount);
order.setOrderDate(new Date());

logger.warn("The order " + id + " for the client " + customer.getBody().getName() + " with the product "
 + product.getBody().getSku() + " with the amount " + amount + " was created!");

id++;

return order;
 }
}

The first thing we notice is the autowired RestTemplate, that also has a@LoadBalanced annotation. This RestTemplate is automatically instantiated by Spring Cloud, creating a interface which we could use to communicate with Eureka. The annotation informs that we want to use Ribbon to make the load balance, in case we have a cluster of instances of the same service.

The exchange method we use inside of the submitOrder method is where the magic happens. When we make our calls using this method, internally a lookup is made with the Eureka Server, the addresses of the service are passed to Ribbon in order to load balance the calls, and them the call is made. Notice that we used names like “CUSTOMERSERVICE” as the host address on our URIs. This pattern tells the framework the ID of the application we really want to call, been replaced at runtime with one of the IP addresses of the service we want to call.

And that concludes our quick explanation of the Java code involved on our lab. Again, if the reader want to get the full code, just head for the Github repositories at the end of this post. In order to run the lab, I recommend that you clone the whole repository and execute a mvn package command on each of the 3 projects. If you don’t have Maven, you can get it from here.

Launching the containers

Now that we are almost finished with the lab, it is time for the fun part: run our containers! To do this, we will use docker-compose. With docker-compose, we can start/stop/kill etc full stacks of containers, without having to instantiate everything by hand. In order to make our docker-compose stack, let’s create a YAML file called docker-compose.yml and include the following configuration:

eureka:
 image: springcloud/eureka
 container_name: eureka
 ports:
 - "8761:8761"
 net: "microservicesnet"
customer1:
 image: alexandreesl/microservices-spring-boot-base
 container_name: customer1
 hostname: customer1
 net: "microservicesnet"
 ports:
 - "8080:8080"
 volumes:
 - /Users/alexandrelourenco/Applications/git/docker-handson:/data
 command: -jar /data/Customer-backend/target/Customer-backend-1.0.jar
product1:
 image: alexandreesl/microservices-spring-boot-base
 container_name: product1
 hostname: product1
 net: "microservicesnet"
 ports:
 - "8081:8080"
 volumes:
 - /Users/alexandrelourenco/Applications/git/docker-handson:/data
 command: -jar /data/Product-backend/target/Product-backend-1.0.jar
order1:
 image: alexandreesl/microservices-spring-boot-base
 container_name: order1
 hostname: order1
 net: "microservicesnet"
 ports:
 - "8082:8080"
 volumes:
 - /Users/alexandrelourenco/Applications/git/docker-handson:/data
 command: -jar /data/Order-backend/target/Order-backend-1.0.jar

Some things to notice from our configuration:

  • In all the containers we configured our “microservicesnet” network, in order to use the Docker Network feature to resolve our needs;
  • On the MicroService’s containers, we also defined the hostname, to force Spring Cloud’s registration control to properly register the correct alias for the service’s addresses;
  • We have exposed Eureka’s port to the physical host at 8761, so we can see the web interface from outside the Docker environment;
  • On the volumes sections, I have mapped the base folder where my Maven projects from the microservices are placed, binding to the /data folder inside the container, which is defined as the workdir on the image we created previously. This way, on the command section, when we map the location of the microservice’s Spring Boot jar, we map the location from the /data folder;

Finally, after saving our file, we run the script by simply running the following command, at the same folder of the YAML file:

docker-compose up

We will see some information about our containers  getting up and at the end we will see some log information from all the containers mixed, with the name of the container as a prefix for identification:

After waiting some moments we will see our containers are up. Let’s see if the microservices are up? Let’s open a browser and point it to the port 8761, using localhost or the ip used by Docker in case you are in OSX/Windows:

Excellent! Not only has Eureka booted up successfully, but also all of our services have registered with it. Let’s now toy a little with our stack, to test it out.

Let’s begin by making a search for a customer of ID 1 on the Customer’s service:

curl -XGET 'http://<your ip>:8080/customer/1'

This will produce a JSON response like the following:

{"id":1,"name":"Cliente 1","email":"customer1@gmail.com"}

Next, let’s test out the Product service, with a call for the details of the Product of ID 4:

curl -XGET 'http://<your ip>:8081/product/4'

This time it will produce a response like the following:

{"id":4,"sku":"abcd4","description":"Produto4"}

Finally, the moment of true: let’s call the Order service, that utilises our other 2 services, to see if the service’s addresses are resolved with Eureka’s help. To test it, let’s make the following call:

curl -XGET 'http://<your ip>:8082/order/2/1/4'

If everything goes well, we will see a response like:

{"id":1,"amount":4,"orderDate":1452216090392,"customer":{"id":2,"name":"Cliente 2","email":"customer2@gmail.com"},"product":{"id":1,"sku":"abcd1","description":"Produto1"}}

Success! But can we have further proof? If we see the logs from the Order1 container, we can see some logs showing Ribbon in action, searching for the services we need on the call and initializing load balancers, in order to serve our needs:

Let’s make one last test before closing in: let’s add one more instance of the Product’s service, to see if the new instance is registered under the same application ID. To do this, let’s run the following command. Notice that we didn’t specify the port to expose the service, since we just want to add up the instance to load balance the internal calls from the Order service:

docker run --rm --name product2 --hostname=product2 --net=microservicesnet -v /Users/alexandrelourenco/Applications/git/docker-handson:/data alexandreesl/microservices-spring-boot-base -jar /data/Product-backend/target/Product-backend-1.0.jar

If we open the Eureka web interface again, we will see that the second address is mapped:

Finally, to test the balance, let’s make a call of the previous URL of the Order service. After the call, we will see that our service is aware of both addresses, proving that the balance is implemented, as we can see on the log’s fragment bellow:

[2016-01-08 14:14:09.703] boot – 1  INFO [http-nio-8080-exec-1] — ChainedDynamicProperty: Flipping property: PRODUCTSERVICE.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647

[2016-01-08 14:14:09.709] boot – 1  INFO [http-nio-8080-exec-1] — BaseLoadBalancer: Client:PRODUCTSERVICE instantiated a LoadBalancer:DynamicServerListLoadBalancer:{NFLoadBalancer:name=PRODUCTSERVICE,current list of Servers=[],Load balancer stats=Zone stats: {},Server stats: []}ServerList:null

[2016-01-08 14:14:09.714] boot – 1  INFO [http-nio-8080-exec-1] — ChainedDynamicProperty: Flipping property: PRODUCTSERVICE.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647

[2016-01-08 14:14:09.718] boot – 1  INFO [http-nio-8080-exec-1] — DynamicServerListLoadBalancer: DynamicServerListLoadBalancer for client PRODUCTSERVICE initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=PRODUCTSERVICE,current list of Servers=[product1:8080, product2:8080],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone; Instance count:2; Active connections count: 0; Circuit breaker tripped count: 0; Active connections per server: 0.0;]

},Server stats: [[Server:product2:8080; Zone:defaultZone; Total Requests:0; Successive connection failure:0; Total blackout seconds:0; Last connection made:Thu Jan 01 00:00:00 UTC 1970; First connection made: Thu Jan 01 00:00:00 UTC 1970; Active Connections:0; total failure count in last (1000) msecs:0; average resp time:0.0; 90 percentile resp time:0.0; 95 percentile resp time:0.0; min resp time:0.0; max resp time:0.0; stddev resp time:0.0]

, [Server:product1:8080; Zone:defaultZone; Total Requests:0; Successive connection failure:0; Total blackout seconds:0; Last connection made:Thu Jan 01 00:00:00 UTC 1970; First connection made: Thu Jan 01 00:00:00 UTC 1970; Active Connections:0; total failure count in last (1000) msecs:0; average resp time:0.0; 90 percentile resp time:0.0; 95 percentile resp time:0.0; min resp time:0.0; max resp time:0.0; stddev resp time:0.0]

]}ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@2561f098

[2016-01-08 14:14:09.738] boot – 1  INFO [http-nio-8080-exec-1] — ConnectionPoolCleaner: Initializing ConnectionPoolCleaner for NFHttpClient:PRODUCTSERVICE

And that concludes our lab. As we can see, we builded a robust stack to deploy our microservices with their dependencies, with little effort.

Clustering container hosts

In all of our examples, we are always working with a single Docker host, our own machine on the case. On a real production environment, we can have some dozens or even hundreds of Docker hosts. In order to make all the hosts to work together, it is necessary to implement some layer that manages the hosts, making them appear as a single cluster to the consumers.

This is the goal of Docker Swarm. With Docker Swarm, we can connect multiple Docker hosts across a network, using them as a single cluster by using Docker Swarm’s interface.

For further information about Docker Swarm alongside a good example of utilization, I suggest consulting the excellent “The Docker Book”, which I describe on the next section.

References

This post was inspired by my studies on Docker with The Docker Book, written by James Turnbull. It is a excellent source of information, that I highly recommend to buy it! You can find the book available to purchase online on:

www.dockerbook.com

Conclusion

And this concludes our tour on the world of Docker. With a simple interface, Docker allows us to use all the power of the container world, allowing us to quickly deploy and escalate our applications. Never it was so simple to deploy our applications! Thank you for following me on another post, until next time.

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ELK: using a centralized logging architecture – final part

ELK1
Standard

Welcome, dear reader! This is the last part of our series about the ELK stack, that provides a centralized architecture for gathering and analyse of application logs. On this last part, we will see how we can construct a rich front-end for our logging solution, using Kibana.

Kibana

Also developed by Elasticsearch, Kibana provides a way to explore the data and/or build rich dashboards of our data on the indexer. With a simple configuration, that consist of pointing Kibana to a ElasticSearch’s index – it also allows to point to multiple indexes at once, using a wildcard configuration -, it allow us to quickly set up a front-end for our stack.

So, without further delay, let’s begin our last step on the setup of our solution.

Hands-on

Installation

Beginning our lab, let’s download Kibana from the site. To do this, let’s open a terminal and type the following command:

curl https://download.elasticsearch.org/kibana/kibana/kibana-4.0.0-linux-x64.tar.gz | tar -zx

PS: this lab assumes the reader is using a linux 64-bit OS (I am using Ubuntu 14.10). If the reader is using another type of OS, the download page for Kibana is the following:

http://www.elasticsearch.org/overview/kibana/installation/

After running the command, we can see a folder called “kibana-4.0.0-linux-x64”. That’s all we need to do to install Kibana on our lab. Before we start running, however, we need to start both Logstash and ElasticSearch, to make our whole stack go live. If the reader didn’t have the stack set up, please refer to part 1 and part 2.

One configuration that the reader may take note is the elasticsearch_url property, inside the “kibana.yml” file, on the config folder. Since we didn’t change the default port from our elasticsearch’s cluster and we are running all the tools on the same machine, there is no need to change anything, but on a real world scenario, you may need to change this property to point to your elasticsearch’s cluster. The reader can made other configurations as well on this file, such as configuring a SSL connection between Kibana and Elasticsearch or configure the name of the index Kibana will use to store his metadata on elasticsearch.

After we start the rest of the stack, it is time to run Kibana.To run it, we navigate to the bin folder of Kibana’s installation folder, and type:

 ./kibana

After some seconds, we can see that Kibana has successfully booted:

Set up

Now, let’s start using Kibana. Let’s open a web browser and enter:

http://localhost:5601/

On our first run, we will be greeted with the following screen:

The reason because we are seeing this screen is because we dont have any index configured. It is on this screen that we can, for example, point to multiple indexes. If we think, for example, about the default naming pattern of logstash’s plugin, we can see that, for each new date we run, logstash will demand the creation of a new index with the pattern “logstash-%{+YYYY.MM.dd}”. So, if we want Kibana to use all the indexes created this way on a single dataset, we simply configure the field with the value “logstash-*”

On our case, we change the default naming of the index, to demonstrate the possible configurations of the tool, so we change the field to “log4jlogs”. One important thing to note on logstash’s plugin documentation, is that the idea behind the index pattern is to make more easy to do operations such as deleting old data, so in a real world scenario, it would be more wise to leave the default pattern enabled.

The other field we need to set is the Time-field name . This field is used by Kibana as a primary filter, allowing him to filter the data from the dashboards and data explorations on a timeline perspective. If we see our document type from the documents storing log information on elasticsearch, we can see it has a field called @timestamp. This field is perfectly fit to our time-field need, so we put “@timestamp” in the field.

After we click on the “create” button, we will be sent to a new page, where we can see all the fields from the index we pointed, proving that our configuration was a success:

Of course, there is other settings as well that we can configure, such as the precision on the numeric fields or the date mask when showing this kind of data on the interface, all available on the “advanced” menu. For our lab needs, however, the default options will suffice, so we leave this page by clicking on the “Discover” menu.

Discovering the data

When we enter the new page, if we didnt send any data to the cluster in the last 15 minutes, we will see a message of no data found (see bellow). The reason for this is because, by default, Kibana limits the results for the last 15 minutes only. To change this, we can either change the time limit by clicking on the value on the upper right corner of the page, or by running again the java program from the previous post, so we have more fresh data.

After we set some data to explore, we can see that the page changes to a data view, where we can dinamically change field filters, by changing the left menu, and drill down the data to the fields level, as we can see bellow. The reader can feel free to explore the page before we move on to our next part.

Dashboards

Now that we have all set, let’s begin by creating a simple dashboard. we will create a pie chart of the messages by the log level, a table view showing the count of messages by class and a line chart of the error messages across the time.

First, let’s begin with the pie chart. We will select, from the menu, “Visualize” , then follow this sequence of options on the next pages:

pie chart >> from a new search

We will enter a page like the one bellow:

In this page, we will make our log level pie chart. To do this, we leave the metrics area unchanged, with the “count” value as slice size. Then, we choose “split slices” on the buckets area and select a “terms” aggregation, by the field “priority”. The screen bellow show our pie chart born!

After we made our chart, before we leave this page, we click on the disk icon on the top menu, input a name for our chart – also called visualization by Kibana’s terminology – and save it, for later use.

Now it is time for our table view. From the same menu we used to save our pie chart, click on the most left icon, called “new visualization”, then select “data table” and “from a new search”. We will see a similar page from the pie chart one, with similar options of aggregations and metrics to configure. With the intent of not bothering the reader with much repetitive instructions, from now on I will keep the explanation the more graphical possible, by the screenshots.

So, our data table view is made by making the configurations we can see on the left menu:

Analogous with what we made on the previous visualization, let’s also save the table view and click on new visualization, selecting line chart this time. The configuration for this chart can be seen bellow:

That concludes our visualizations. Now, let’s conclude our lab by making a dashboard that will show all the visualizations we build on the same page. To do this, first we select the “dashboard” option on the top menu. We will be greeted with the screen bellow:

This is the dashboard page, where we can create, edit and load dashboards. To add visualizations, we simply click on the plus icon on the top right side and select the visualization we want to add, like we can see bellow:

After we add the visualizations, it is pretty simple to arrange them: all we have to do is to drag and drop the visualizations as we like. My final arrangement of the dashboard is bellow, but the reader can arrange the way he finds best:

Finally, to save the dashboard, we simply click on the disk icon and input a name for our dashboard.

Cons

Of course, we cant make a complete overview of a tool, if we dont mention any noticeable con of it. The most visible downside of Kibana, on my opinion, is the lack of a native support to authentication and authorization. The reader may notice, by our tour of the interface, that there is no user or permission CRUDs whatsoever. Indeed, Kibana doesnt come with this feature.

One common workaround for this is to configure basic authentication on the web server Kibana runs with it – if we were using Kibana 3 on our lab, we would have to install manually a web server and deploy Kibana on it. On Kibana 4, we dont have to do this, because Kibana comes with a embedded node.js – , so the authentication is made by URL patterns. This link to the official node.js documentation provides a path to set basic authentication on the embedded server Kibana comes with it. The file that starts the server and need to be edited is on /src/bin/kibana.js.

Very recently, Elasticsearch has released shield, a plugin that implements a versatile security layer on Elasticsearch and subsequently on Kibana. Evidently, is a much more elegant and complete solution then the previous one, but the reader has to keep it in mind that he has to acquire a license to use shield.

Conclusion

And that concludes our tour by the ELK stack. Of course, on a real world scenario, we have some more steps to do, like the aforementioned authentication configuration, the configuration of purge policies and so on.However, we still can see that the core features we need were implemented, with very little effort. Like we talked about on the beginning of our series, logging information is a very rich source of information, that it has to be better explored on the business world. Thanks to everyone that follows my blog, until next time.

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ELK: using a centralized logging architecture – part 2

ELK1
Standard

Welcome, dear reader, to another post of our series about the ELK stack for logging. On the last post, we talked about LogStash, a tool that allow us to integrate data from different sources to different destinations, using transformations along the way, in a stream-like form. On this post, we will talk about ElasticSearch, a indexer based on apache Lucene, which can allow us to organize our data and make textual searches on the data, in a scalable infrastructure. So, let’s begin by understanding how ElasticSearch is organized on the inside

Indexes, documents and shards

On ElasticSearch, we have the concept of indexes. A index is like a repository, where we can store our data in the format of documents. A document on ElasticSearch’s terminology consists of a structure for the data to be stored, analysed and classified, following a mapping definition, composed of a series of fields – a important thing to note, is that a field on ElasticSearch has the same type across the whole index, meaning that we cant have a field “phone” with the type int on a document and the type string on another.

In turn, we have our documents stored on shards, which divide the data on segments based on a rule – by default, the segmentation is made by hashing the data, but it can also be manually manipulated -, making the searches faster.

So, in a nutshell, we can say that the order of organization of ElasticSearch is as follows:

Index >> Document (mappings/type) >> shard

This organization is used by the user on the two basic operations of the cluster: indexing and searching.

One last thing to say about documents is that they can not only be stored as independent , but also be mounted on a tree-like hierarchy, with links between them. This is useful in scenarios that we can make use of hierarchical searches, such as product’s searches based on their categories.

Indexing

Indexing is the action of inputing the data from a external source to the cluster. ElasticSearch is a textual indexer, which means he can only analyse text on plain format, despite that we can use the cluster to store data in base64 format, using a plugin. Later on the post, we will see a example installation of a plugin, which are extensions we can aggregate to expand our cluster usability.

When we index our data,  we define which fields are to be analysed, which analyser to use, if the default ones does not suffice and which fields we want to store the data on the cluster, so we can use as the result of our searches. One important thing to note about the indexing operations is that, despite it has CRUD-like operations, the data is not really updated or deleted on the cluster, instead a new version is generated and the old version is marked as deleted.

This is a important thing to take note, because if not properly configured to make purges – which can be made with a configuration that break the shards into segments, and periodically make merges of the segments, phisically deleting the obsolet documents on the process -, the cluster will keep indefinitely expanding in size with the “deleted” older versions of our data, making specially the searches to became really slow.

All the operations can be made with a REST API provided by ElasticSearch, that we will see later on this post.

Searching

The other, and probably most important, action on ElasticSearch, is the searching of the data previously indexed. Like the indexing action, ElasticSearch also provide a REST API for the searches. The API provides a very rich range of possibilities of searching, from basic term searches to more complex searches such as hierarchical searches, searches by synonims, language detections, etc.

All the searching is based on a score system, where formulas are applied to confront the accuracy of the documents founded versus the query supplied. This score system can also be customized.

By default, the searching on the cluster occurs in 2 phases:

  • On the first phase, the master node sends the query for all the nodes, and subsequently shards , retrieving just the IDs and scores of the documents. Using a parameter called size which defines the maximum results from a query, the master selects the more meaningful documents, based on the score;
  • On the second phase, the master send requests for the nodes to retrieve the documents selected on the previous phase. After receiving the documents, the master finally sends the result for the client;

Alongside this search type, there’s also other modes, like the query_and_fetch. On this mode, the searching is made simultaneous on all shards, not only to retrieve the IDs and scores but also returning the data itself, limited only by the size parameter, which is applied per shard. In turn, on this mode, the maximum of results returned will be the size parameter plus the number of shards.

One interesting feature of ElasticSearch’s configuration options is the ability to make some nodes exclusive to query operations, and others to make the storage part, called data nodes. This way, when we query, our query dont need to run  across all the cluster to formulate the results, making the searches faster. On the next section we will see a little more about cluster configurations.

Cluster capabilities

When we talk about a cluster, we talk about scalability, but we also talk about availability. On ElasticSearch, we can configure the replication of shards, where the data is replicated by a given factor, so we dont lose our data if a node is lost. The replication if also maintained by the cluster, so if we lost a replica, the cluster itself will distribute a new replica for another node.

Other interesting feature of the cluster are the ability to discover itself. By the default configuration, when we start a node he will use a discovery mode called Zen, which uses unicast and multicast to search for another instances on all the ports of the OS. If it founds another instance, and the name of the cluster is the same – this is another one of the cluster’s configuration properties. All of this configurations can be made on the file elasticsearch.yml, on the config folder -, it will communicate with the instance and establish a new node for the already running cluster. There is another modes for this feature, including the discover of nodes from other servers.

Logging

The reader could be thinking: “Lol, do I need all of this to run a logging stack?”.

Of course that ElasticSearch is a very robust tool, that can be used on other solutions as well. However, on our case of making a centralized logging analysis solution, the core of ElasticSearch’s capabilities serve us well for this task, after all, we are talking about the textual analysis of log texts, for use on dashboards, reports, or simply for real-time exploration of the data.

Well, that concludes the conceptual part of our post. Now, let’s move on to the practice.

Hands-on

So, without further delay, let’s begin the hands-on. For this, we will use the previous Java program we used on our lab about LogStash. The code can be found on GitHub, on this link. On this program, we used the org.apache.log4j.net.SocketAppender from log4j to send all the logging we make to LogStash. However, on that point we just printed the messages on the console, instead of sending to ElasticSearch. Before we change this, let’s first start our cluster.

To do this, first we need to download the last version from the site and unzip the tar. Let’s open a terminal, and type the following command:

curl https://download.elasticsearch.org/elasticsearch/elasticsearch/elasticsearch-1.4.4.tar.gz | tar -zx

After running the command, we will find a new folder called “elasticsearch-1.4.4” created on the same folder we run our command. To our example, we will create 2 copies of this folder on a folder we call “elasticsearchcluster”, where each one will represent one node of the cluster. To do this, we run the following commands:

mkdir elasticsearchcluster

sudo cp -avr elasticsearch-1.4.4/ elasticsearchcluster/elasticsearch-1.4.4-node1/

sudo cp -avr elasticsearch-1.4.4/ elasticsearchcluster/elasticsearch-1.4.4-node2/

After we made our cluster structure, we dont need the original folder anymore, so we remove:

rm -R elasticsearch-1.4.4/

Now, let’s finally start our cluster! To do this, we open a terminal, navigate to the bin folder of our first node (elasticsearch-1.4.4-node1) and type:

./elasticsearch

After some seconds, we can see our first node is on:

For curiosity sake, we can see the name “Feral” on the node’s name on the log. All the names generated by the tool are based on Marvel Comic’s characters. IT world sure has some sense of humor, heh?

Now, let’s start our second node. On a new terminal window, let’s navigate to the folder of our second node (elasticsearch-1.4.4-node2) and type again the command “./elasticsearch”. After some seconds, we can see that the node is also started:

One interesting thing to notice is that our second node “Ooze”, has a mention of comunicating with our other node, “Feral”. That is the zen discover on the action, making the 2 nodes talk to each other and form a cluster. If we look again at the terminal of our first node, we can see another evidence of this bidirectional communication, as “Feral” has added “Ooze” to the cluster, as his role as a master node:

 Now that we have our cluster set up, let’s adjust our logstash script to send the messages to the cluster. To do this, let’s change the output part of the script, to the following:

input {
log4j {
port => 1500
type => “log4j”
tags => [ “technical”, “log”]
}
}

output {
stdout { codec => rubydebug }
elasticsearch_http {
host => “localhost”
port => 9200
index => “log4jlogs”
}
}

As we can see, we just included another output – we remained the console output just to check how logstash is receiving the data – including the ip and port where our ElasticSearch cluster will respond. We also defined the name of the index we want our logs to be stored. If this parameter is not defined, logstash will order elasticsearch to create a index with the pattern “logstash-%{+YYYY.MM.dd}”.

To execute this script, we do like we did on the previous post, we put the new script on a file called “configelasticsearch.conf” on the bin folder of logstash, and run with the command:

./logstash -f configelasticsearch.conf

PS1: On the GitHub repository, it is possible to find this config file, alongside a file containing all the commands we will send to ElasticSearch from now on.

PS2: For simplicity sake, we will use the default mappings logstash provide for us when sending messages to the cluster. It is also possible to pass a elasticsearch’s mapping structure, which consists of a JSON model, that logstash will use as a template. We will see the mapping from our log messages later on our lab, but for satisfying the reader curiosity for now, this is what a elasticsearch’s mapping structure look like, for example for a document type “product”:

“mappings” : {
“product”: {
“properties” : {

“variation” : { “type” : int }

“color”  : { “type” : “string” }

“code” : { “type” : int }

“quantity” : { “type” : int }

}
}
}

After some seconds, we can see that LogStash booted, so our configuration was a success. Now, let’s begin sending our logs!

To do this, we run the program from our previous post, running the class com.technology.alexandreesl.LogStashProvider . We can see on the console of logstash, after starting the program, that the messages are going through the stack:

Now that we have our cluster up and running, let’s start to use it. First, let’s see the mappings of the index that ElasticSearch created for us, based on the configuration we made on LogStash. Let’s open a terminal and run the following command:

curl -XGET ‘localhost:9200/log4jlogs/_mapping?pretty’

On the command above, we are using ElasticSearch’s REST API. The reader will notice that, after the ip and port, the URL contains the name of the index we configured. This pattern for calls of the API is applied to most of the actions, as we can see below:

<ip>:<port>/<index>/<doc type>/<action>?<attributes>

So, after this explanation, let’s see the result from our call:

{
“log4jlogs” : {
“mappings” : {
“log4j” : {
“properties” : {
“@timestamp” : {
“type” : “date”,
“format” : “dateOptionalTime”
},
“@version” : {
“type” : “string”
},
“class” : {
“type” : “string”
},
“file” : {
“type” : “string”
},
“host” : {
“type” : “string”
},
“logger_name” : {
“type” : “string”
},
“message” : {
“type” : “string”
},
“method” : {
“type” : “string”
},
“path” : {
“type” : “string”
},
“priority” : {
“type” : “string”
},
“stack_trace” : {
“type” : “string”
},
“tags” : {
“type” : “string”
},
“thread” : {
“type” : “string”
},
“type” : {
“type” : “string”
}
}
}
}
}
}

As we can see, the index “log4jlogs” was created, alongside the document type “log4j”. Also, a series of fields were created, representing information from the log messages, like the thread that generated the log, the class, the log level and the log message itself.

Now, let’s begin to make some searches.

Let’s begin by searching all log messages which the priority was “INFO”. We make this searching by running:
curl -XGET ‘localhost:9200/log4jlogs/log4j/_search?q=priority:info&pretty=true’
A fragment of the result of the query would be something like the following:

{
“took” : 12,
“timed_out” : false,
“_shards” : {
“total” : 5,
“successful” : 5,
“failed” : 0
},
“hits” : {
“total” : 18,
“max_score” : 1.1823215,
“hits” : [ {
“_index” : “log4jlogs”,
“_type” : “log4j”,
“_id” : “AUuxkDTk8qbJts0_16ph”,
“_score” : 1.1823215,
“_source”:{“message”:”STARTING DATA COLLECTION”,”@version”:”1″,”@timestamp”:”2015-02-22T13:53:12.907Z”,”type”:”log4j”,”tags”:[“technical”,”log”],”host”:”127.0.0.1:32942″,”path”:”com.technology.alexandreesl.LogStashProvider”,”priority”:”INFO”,”logger_name”:”com.technology.alexandreesl.LogStashProvider”,”thread”:”main”,”class”:”com.technology.alexandreesl.LogStashProvider”,”file”:”LogStashProvider.java:20″,”method”:”main”}
}

.

.

.

As we can see, the result is a JSON structure, with the documents that met our search. The beginning information of the result is not the documents themselves, but instead information about the search itself, such as the number of shards used, the seconds the search took to execute, etc. This kind of information is useful when we need to make a tuning of our searches, like manually defining the shards we which to use on the search, for example.

Let’s see another example. On our previous search, we received all the fields from the document on the result, which is not always the desired result, since we will not always use the whole information. To limit the fields we want to receive, we make our query like the following:
curl -XGET ‘localhost:9200/log4jlogs/log4j/_search?pretty=true’ -d ‘
{
“fields” : [ “priority”, “message”,”class” ],
“query” : {
“query_string” : { “query” : “priority:info” }
}
}’
On the query above, we asked ElasticSearch to limit the return to only return the priority, message and class fields. A fragment of the result can be seen bellow:

.

.

.

{
“_index” : “log4jlogs”,
“_type” : “log4j”,
“_id” : “AUuxkECZ8qbJts0_16pr”,
“_score” : 1.1823215,
“fields” : {
“priority” : [ “INFO” ],
“message” : [ “CLEANING UP!” ],
“class” : [ “com.technology.alexandreesl.LogStashProvider” ]
}
}

.

.

.

Now, let’s use the term search. On the term searches, we use ElasticSearch’s textual analysis to find a term inside the text of a field. Let’s run the following command:
curl -XGET ‘localhost:9200/log4jlogs/log4j/_search?pretty=true’ -d ‘
{
“fields” : [ “priority”, “message”,”class” ],
“query” : {
“term” : {
“message” : “up”
}
}
}’
If we see the result, it would be all the log messages that contains the word “up”. A fragment of the result can be seen bellow:

{
“_index” : “log4jlogs”,
“_type” : “log4j”,
“_id” : “AUuxkESc8qbJts0_16pv”,
“_score” : 1.1545612,
“fields” : {
“priority” : [ “INFO” ],
“message” : [ “CLEANING UP!” ],
“class” : [ “com.technology.alexandreesl.LogStashProvider” ]
}
}

Of course, there is a lot more of searching options on ElasticSearch, but the examples provided on this post are enough to make a good starting point for the reader. To make a final example, we will use the “prefix” search. On this type of search, ElasticSearch will search for terms that start with our given text, on a given field. For example, to search for log messages that have words starting with “clea”, part of the word “cleaning”, we run the following:
curl -XGET ‘localhost:9200/log4jlogs/log4j/_search?pretty=true’ -d ‘
{
“fields” : [ “priority”, “message”,”class” ],
“query” : {
“prefix” : {
“message” : “clea”
}
}
}’
If we see the results, we will see that are the same from the previous search, proving that our search worked correctly.

Kopf

The reader possibly could ask “Is there another way to send my queries without using the terminal?” or “Is there any graphical tool that I can use to monitor the status of my cluster?”. As a matter of fact, there is a answer for both of this questions, and the answer is the kopf plugin.

As we said before, plugins are extensions that we can install to improve the capacities of our cluster. In order to install the plugin, first let’s stop both the nodes of the cluster – press ctrl+c on both terminal windows to stop – then, navigate to the nodes root folder and type the following:

bin/plugin -install lmenezes/elasticsearch-kopf

If the plugin was installed correctly, we should see a message like the one bellow on the console:

.

.

.

-> Installing lmenezes/elasticsearch-kopf…
Trying https://github.com/lmenezes/elasticsearch-kopf/archive/master.zip&#8230;
Downloading …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..DONE
Installed lmenezes/elasticsearch-kopf into….

After installing on both nodes, we can start again the nodes, just as we did before. After the booting of the cluster, let’s open a browser and type the following URL:

http://localhost:9200/_plugin/kopf

We will see the following web page of the kopf plugin, showing the status of our cluster, such as the nodes, the indexes, shard information, etc

Now, let’s run our last example from the search queries on kopf. First, we select the “rest” option on the top menu. On the next screen, we select “POST” as the http method, include on the URL field the index and document type to narrow the results and on the textarea bellow we include our JSON query filters. The print bellow shows the query made on the interface:

 Conclusion

And so we conclude our post about ElasticSearch. A very powerful tool on the indexing and analysis of textual information, the central stone on our ELK stack for logging is a tool to be used, not only on a logging analysis system, but on other solutions that his features can be useful as well.

So, our stack is almost complete. We can gather our log information, and the information is indexed on our cluster. However, a final piece remains: we need a place where we can have a more friendly interface, that allow us not only to search the information, but also to make rich presentations of the data, such as dashboards. That’s when it enters our last part of our ELK series and the last tool we will see, Kibana. Thank you for following me on another post, until next time.

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ELK: using a centralized logging architecture – part 1

ELK1
Standard

Welcome, dear reader, to another post from my blog. On this new series, we will talk about a architecture specially designed to process data from log files coming from applications, with the junction of 3 tools, Logstash, ElasticSearch and Kibana. But after all, do we really need such a structure to process log files?

Stacks of log

On a company ecosystem, there is lots of systems, like the CRM, ERP, etc. On such environments, it is common for the systems to produce tons of logs, which provide not only a real-time analysis of the technical status of the software, but could also provide some business information too, like a log of a customer’s behavior  on a  shopping cart, for example. To dive into this useful source of information, enters the ELK architecture, which name came from the initials of the software involved: ElasticSearch, LogStash and Kibana. The picture below shows in a macro vision the flow between the tools:

As we can see, there’s a clear separation of concerns between the tools, where which one has his own individual part on the processing of the log data:

  • Logstash: Responsible for collect the data, make transformations like parsing – using regular expressions – adding fields, formatting as structures like JSON, etc and finally sending the data to various destinations, like a ElasticSearch cluster. Later on this post we will see more detail about this useful tool;
  •  ElasticSearch: RESTful data indexer, ElasticSearch provides a clustered solution to make searches and analysis on a set of data. On the second part of our series, we will see more about this tool;
  • Kibana: Web-based application, responsible for providing a light and easy-to-use dashboard tool. On the third and last part of our series, we will see more of this tool;

So, to begin our road in the ELK stack, let’s begin by talking about the tool responsible for integrating our data: LogStash.

LogStash installation

To install, all we need to do is unzip the file we get from LogStash’s site and run the binaries on the bin folder. The only pre-requisite for the tool is to have Java installed and configured in the environment. If the reader wants to follow my instructions with the same system then me, I am using Ubuntu 14.10 with Java 8, which can be downloaded from Oracle’s site here.

With Java installed and configured, we begin by downloading and unziping the file. To do this, we open a terminal and input:

curl https://download.elasticsearch.org/logstash/logstash/logstash-1.4.2.tar.gz | tar xz

After the download, we will have LogStash on a folder on the same place we run our ‘curl’ command. On the LogStash terminology, we have 4 types of configurations we can make for a stream, named:

  • input: On this configuration, we put the sources of our streams, that can range from polling files of a file system to more complex inputs such as a Amazon SQS queue and even Twitter;
  • codec: On this configuration we make transformations on the data, like turning into a JSON structure, or grouping together lines that are semantically related, like for example, a Java’s stack trace;
  • filter: On this configuration we make operations such as parsing data from/to different formats, removal of special characters and checksums for deduplication;
  • output: On this configuration we define the destinations for the processed data, such as a ElasticSearch cluster, AWS SQS, Nagios etc;

Now that we have established LogStash’s configuration structure, let’s begin with our first execution. In LogStash we have two ways to configure our execution, one way by providing the settings on the start command itself and the other one is by providing a configuration file for the command. The simplest way to boot a LogStash’s stream is by setting the input and output as the console itself, to make this execution, we open a terminal, navigate to the bin folder of our LogStash’s installation and execute the following command:

./logstash -e ‘input { stdin { } } output { stdout {} }’

As we can see after we run the command, we booted LogStash, setting the console as the input and the output, without any transformation or filtering. To test, we simply input anything on the console, seeing that our message is displayed back by the tool:

Now that we get the installation out of the way, let’s begin with the actual lab. Unfortunately -or not, depending on the point of view -, it would take us a lot of time to show all the features of what we can do with the tool, so to make a short but illustrative example, we will start 2 logstash streams, to do the following:

1st stream:

  • The input will be made by a java program, which will produce a log file with log4j, representing technical information;
  • For now, we will just print logstash’s events on the console, using the rubydebug codec. On our next part on the series, we will return to this configuration and change the output to send the events to elasticsearch;

2nd stream:

  • The input will be made by the same java program, which will produce a positional file, representing business information of costumers and orders;
  • We will then use the grok filter to parse the data of the positional file into separated fields, producing the data for the output step;
  • Finally, we use the mongodb output, to save our data – filtering to only persist the orders – on a  Mongodb collection;

With the streams defined, we can begin our coding. First, let’s create the java program which will generate the inputs for the streams. The code for the program can be seen bellow:

package com.technology.alexandreesl;

import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import org.apache.log4j.Logger;

public class LogStashProvider {

private static Logger logger = Logger.getLogger(LogStashProvider.class);

public static void main(String[] args) throws IOException {

try {

logger.info(“STARTING DATA COLLECTION”);

List<String> data = new ArrayList<String>();

Customer customer = new Customer();
customer.setName(“Alexandre”);
customer.setAge(32);
customer.setSex(‘M’);
customer.setIdentification(“4434554567”);

List<Order> orders = new ArrayList<Order>();

for (int counter = 1; counter < 10; counter++) {

Order order = new Order();

order.setOrderId(counter);
order.setProductId(counter);
order.setCustomerId(customer.getIdentification());
order.setQuantity(counter);

orders.add(order);

}

logger.info(“FETCHING RESULTS INTO DESTINATION”);

PrintWriter file = new PrintWriter(new FileWriter(
“/home/alexandreesl/logstashdataexample/data”
+ new Date().getTime() + “.txt”));

file.println(“1” + customer.getName() + customer.getSex()
+ customer.getAge() + customer.getIdentification());

for (Order order : orders) {
file.println(“2” + order.getOrderId() + order.getCustomerId()
+ order.getProductId() + order.getQuantity());
}

logger.info(“CLEANING UP!”);

file.flush();
file.close();

// forcing a error to simulate stack traces
PrintWriter fileError = new PrintWriter(new FileWriter(
“/etc/nopermission.txt”));

} catch (Exception e) {

logger.error(“ERROR!”, e);
}

}

}

As we can see, it is a very simple class, that uses log4j to generate some log and output a positional file representing data from customers and orders and at the end, try to create a file on a folder we don’t have permission to write by default, “forcing” a error to produce a stack trace. The complete code for the program can be found here. Now that we have made our data generator, let’s begin the configuration for logstash. The configuration for our first example is the following:

input {
log4j {
port => 1500
type => “log4j”
tags => [ “technical”, “log”]
}
}

output {
stdout { codec => rubydebug }
}

To run the script, let’s create a file called “config1.conf” and save the file with the script on the “bin” folder of logstash’s installation folder. Finally, we run the script with the following command:

 ./logstash -f config1.conf

This will start logstash process with the configurations we provided. To test, simply run the java program we coded earlier and we will see a sequence of message events in logstash’s console window, generated by the rubydebug codec, like the one bellow, for example:

{
“message” => “ERROR!”,
“@version” => “1”,
“@timestamp” => “2015-01-24T19:08:10.872Z”,
“type” => “log4j”,
“tags” => [
[0] “technical”,
[1] “log”
],
“host” => “127.0.0.1:34412”,
“path” => “com.technology.alexandreesl.LogStashProvider”,
“priority” => “ERROR”,
“logger_name” => “com.technology.alexandreesl.LogStashProvider”,
“thread” => “main”,
“class” => “com.technology.alexandreesl.LogStashProvider”,
“file” => “LogStashProvider.java:70”,
“method” => “main”,
“stack_trace” => “java.io.FileNotFoundException: /etc/nopermission.txt (Permission denied)\n\tat java.io.FileOutputStream.open(Native Method)\n\tat java.io.FileOutputStream.<init>(FileOutputStream.java:213)\n\tat java.io.FileOutputStream.<init>(FileOutputStream.java:101)\n\tat java.io.FileWriter.<init>(FileWriter.java:63)\n\tat com.technology.alexandreesl.LogStashProvider.main(LogStashProvider.java:66)”
}

Now, let’s move on to the next stream. First, we create another file, called “config2.conf”, on the same folder we created the first one. On this new file, we create the following configuration:

input {
file {
path => “/home/alexandreesl/logstashdataexample/data*.txt”
start_position => “beginning”
}
}

filter {
grok {
match => [ “message” , “(?<file_type>.{1})(?<name>.{9})(?<sex>.{1})(?<age>.{2})(?<identification>.{10})” , “message” , “(?<file_type>.{1})(?<order_id>.{1})(?<costumer_id>.{10})(?<product_id>.{1})(?<quantity>.{1})” ]
}
}

output {
stdout { codec => rubydebug }
if [file_type] == “2” {
mongodb {
collection => “testData”
database => “mydb”
uri => “mongodb://localhost”
}
}
}

With the configuration created, we can run our second example. Before we do that, however, let’s dive a little on the configuration we just made. First, we used the file input, which will make logstash keep monitoring the files on the folder and processing them as they appear on the input folder.

Next, we create a filter with the grok plugin. This filter uses combinations of regular expressions, that parses the data from the input. The plugin comes with more then 100 patterns pre-made that helps the development. Another useful tool in the use of grok is a site where we could test our expressions before use. Both links are available on the links section at the end of this post.

Finally, we use the mongodb plugin, where we reference our logstash for a database and collection of a mongodb instance, where we will insert the data from the file into mongodb’s documents. We also used again the rubydebug codec, so we can also see the processing of the files on the console. The reader will note that we used a “if” statement before the configuration of the mongodb output. After we parse the data with grok, we can use the newly created fields to do some logic on our stream. In this case, we filter to only process data with the type “2”, so only the order’s data goes to the collection on mongodb, instead of all the data. We could have expanded more on this example, like saving the data into two different collections, but for the idea of passing a general view of the structure of logstash for the reader, the present logic will suffice.

PS: This example assumes the reader has mongodb installed and running on the default port of his environment, with a db “mydb” and a collection “testData” created. If the reader doesn’t have mongodb, the instructions can be found on the official documentation.

Finally, with everything installed and configured, we run the script, with the following command:

./logstash -f config2.conf

After logstash’s start, if we run our program to generate a file, we will see logstash working the data, like the screen bellow:

And finally, if we query the collection on mongodb, we see the data is persisted:

Conclusion

And so we conclude the first part of our series. With a simple usage, logstash prove to be a useful tool in the integration of information from different formats and sources, specially log-related. In the next part of our series, we will dive in the next tool of our stack: ElasticSearch. Until next time

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Hands-on: Using Google API to make searches on your applications

3017047-poster-1280-google
Standard

Welcome, dear reader, to another post of my blog. On this post, we will learn to use Google’s custom search API. With this API, you can make searches using Google’s infrastructure, enriching searching business features, like a web crawler, for example.

Pre-steps

Before we start coding, we need to create the keys to make our authentication with the API. One key is the API key itself and the other one is the search engine key. A search engine key is a key to a search engine you create to pre-filter the types of domains you want to make for your searches, so you dont end up searching sites in chinese, for example, if your application only want sites from England.

To start, access the site https://console.developers.google.com. After inputting our credentials, we get to the main site, where we can create a project, activate/deactivate APIs and generate a API key for the project. This tutorial from Google explain how to create API keys.

After that, we need to create the search engine key, on the site https://www.google.com/cse/all. We can follow this tutorial from Google to create the key.

Hands-on

On this hands-on, we will use Eclipse Luna and Maven 3.2.1. First, create a Maven project, without a archetype:

After creating our project, we add the dependencies. Instead of offering a Java library for the consumption, Google’s API consists of a URL, which is called by a simple GET execution, and returns a JSON structure. For the return, we will use a JSON API we used on our previous post. First, we add the following dependencies in our pom.xml:

<dependencies>
<dependency>
<groupId>javax.json</groupId>
<artifactId>javax.json-api</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.0.4</version>
</dependency>
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.7.2</version>
</dependency>
</dependencies>

Finally, with the dependencies included, we write our code. In this example, we will make a call to the API for a search with the string “java+android”. The API has a limit usage of 100 results per search – in the free mode -, and uses a pagination format of 10 results per page, so we will make 10 calls to the API. The following code make our example:

package com.technology.alexandreesl;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.net.HttpURLConnection;
import java.net.URL;

import javax.json.Json;
import javax.json.stream.JsonParser;
import javax.json.stream.JsonParser.Event;

public class GoogleAPIJava {

final static String apiKey = “<insert your API Key here>”;
final static String customSearchEngineKey = “<insert your search engine key here>”;

// base url for the search query
final static String searchURL = “https://www.googleapis.com/customsearch/v1?&#8221;;

public static void main(String[] args) {

int inicio = 1;

int contador = 0;

while (contador < 10) {

System.out
.println(“***************** SEARCH **************************”);
System.out.println(“”);

String result = “”;

result = read(“java+android”, inicio, 10);

JsonParser parser = Json.createParser(new StringReader(result));

while (parser.hasNext()) {
Event event = parser.next();

if (event == Event.KEY_NAME) {

if (parser.getString().equals(“htmlTitle”)) {
Event value = parser.next();

if (value == Event.VALUE_STRING)
System.out.println(“Title (HTML): ”
+ parser.getString());
}

if (parser.getString().equals(“link”)) {

Event value = parser.next();

if (value == Event.VALUE_STRING)
System.out.println(“Link: ” + parser.getString());
}

}

}

inicio = inicio + 10;

contador++;

System.out
.println(“**************************************************”);

}

}

private static String read(String qSearch, int start, int numOfResults) {
try {

String toSearch = searchURL + “key=” + apiKey + “&cx=”
+ customSearchEngineKey + “&q=”;

toSearch += qSearch;

toSearch += “&alt=json”;

toSearch += “&start=” + start;

toSearch += “&num=” + numOfResults;

URL url = new URL(toSearch);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
BufferedReader br = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
StringBuffer buffer = new StringBuffer();
while ((line = br.readLine()) != null) {
buffer.append(line);
}
return buffer.toString();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

}

As we can see above, we make use of the java.net standard classes to make the calls. Using counters to control the calls for the API. The result when we run the program is a list of sites for the search string printed on the console:

***************** SEARCH **************************

Title (HTML): Java Manager; Emulate <b>Java</b> – <b>Android</b> Apps on Google Play
Link: https://play.google.com/store/apps/details?id=com.java.manager
Title (HTML): How do I get <b>Java</b> for Mobile device?
Link: https://www.java.com/en/download/faq/java_mobile.xml
Title (HTML): AIDE – <b>Android</b> IDE – <b>Java</b>, C++ – <b>Android</b> Apps on Google Play
Link: https://play.google.com/store/apps/details?id=com.aide.ui
Title (HTML): Como obtenho o <b>Java</b> para Dispositivos Móveis?
Link: https://www.java.com/pt_BR/download/faq/java_mobile.xml
Title (HTML): Download <b>java</b> for <b>android</b> tablet – <b>Android</b> – <b>Android</b> Smartphones
Link: http://www.tomsguide.com/forum/id-1608121/download-java-android-tablet.html
Title (HTML): <b>java</b>.lang | <b>Android</b> Developers
Link: http://developer.android.com/reference/java/lang/package-summary.html
Title (HTML): Comparison of <b>Java</b> and <b>Android</b> API – Wikipedia, the free <b>…</b>
Link: http://en.wikipedia.org/wiki/Comparison_of_Java_and_Android_API
Title (HTML): Learn <b>Java</b> for <b>Android</b> Development: Introduction to <b>Java</b> – Tuts+ <b>…</b>
Link: http://code.tutsplus.com/tutorials/learn-java-for-android-development-introduction-to-java–mobile-2604
Title (HTML): <b>java</b>.text | <b>Android</b> Developers
Link: http://developer.android.com/reference/java/text/package-summary.html
Title (HTML): Apostila <b>Java</b> – Desenvolvimento Mobile com <b>Android</b> | K19
Link: http://www.k19.com.br/downloads/apostilas/java/k19-k41-desenvolvimento-mobile-com-android
**************************************************
***************** SEARCH **************************

Title (HTML): How can I access a <b>Java</b>-based website on an <b>Android</b> phone?
Link: http://www.makeuseof.com/answers/access-javabased-website-android-phone/
Title (HTML): Introduction to <b>Java</b> Variables | Build a Simple <b>Android</b> App (retired <b>…</b>
Link: http://teamtreehouse.com/library/build-a-simple-android-app/getting-started-with-android/introduction-to-java-variables-2
Title (HTML): <b>Java</b> Basics for <b>Android</b> Development – Part 1 – Treehouse Blog
Link: http://blog.teamtreehouse.com/java-basics-for-android-development-part-1
Title (HTML): GC: <b>android</b> – GrepCode <b>Java</b> Project Source
Link: http://grepcode.com/project/repository.grepcode.com/java/ext/com.google.android/android
Title (HTML): <b>Java</b> Essentials for <b>Android</b>
Link: https://www.udemy.com/java-essentials-for-android/
Title (HTML): How to Get <b>Java</b> on <b>Android</b>: 10 Steps (with Pictures) – wikiHow
Link: http://www.wikihow.com/Get-Java-on-Android
Title (HTML): Learn <b>Android</b> 4.0 Programming in <b>Java</b>
Link: https://www.udemy.com/android-tutorial/
Title (HTML): Trending <b>Java</b> repositories on GitHub today · GitHub
Link: https://github.com/trending?l=java
Title (HTML): Developing for <b>Android</b> in Eclipse: R.<b>java</b> not generating – Stack <b>…</b>
Link: http://stackoverflow.com/questions/2757107/developing-for-android-in-eclipse-r-java-not-generating
Title (HTML): Cling – <b>Java</b>/<b>Android</b> UPnP library and tools
Link: http://4thline.org/projects/cling/
**************************************************
***************** SEARCH **************************

Title (HTML): Getting Started | <b>Android</b> Developers
Link: https://developer.android.com/training/
Title (HTML): <b>Java</b> API – <b>Android</b> | Vuforia Developer Portal
Link: https://developer.vuforia.com/resources/api/main
Title (HTML): <b>Java</b> Programming for <b>Android</b> Developers For Dummies: Burd <b>…</b>
Link: http://www.amazon.com/Java-Programming-Android-Developers-Dummies/dp/1118504380
Title (HTML): <b>Android</b> Quickstart – Firebase
Link: https://www.firebase.com/docs/android/quickstart.html
Title (HTML): Learn <b>Java</b> for <b>Android</b> Development: Jeff Friesen: 9781430264545 <b>…</b>
Link: http://www.amazon.com/Learn-Java-Android-Development-Friesen/dp/1430264543
Title (HTML): Unity – Manual: Building Plugins for <b>Android</b>
Link: http://docs.unity3d.com/Manual/PluginsForAndroid.html
Title (HTML): Eclipse, <b>Android</b> and <b>Java</b> training and support
Link: http://www.vogella.com/
Title (HTML): AIDE – <b>Android Java</b> IDE download – Baixaki
Link: http://www.baixaki.com.br/android/download/aide-android-java-ide.htm
Title (HTML): <b>Java</b> Multi-Platform and <b>Android</b> SDK | Philips Hue API
Link: http://www.developers.meethue.com/documentation/java-multi-platform-and-android-sdk
Title (HTML): <b>Android</b> Client Tutorial – <b>Java</b> — Google Cloud Platform
Link: https://cloud.google.com/appengine/docs/java/endpoints/getstarted/clients/android/
**************************************************
***************** SEARCH **************************

Title (HTML): Gradle Plugin User Guide – <b>Android</b> Tools Project Site
Link: http://tools.android.com/tech-docs/new-build-system/user-guide
Title (HTML): Where is a download for <b>java</b> for <b>android</b> tablet? – Download <b>…</b>
Link: http://www.tomshardware.com/forum/52818-34-where-download-java-android-tablet
Title (HTML): Download <b>android java</b>
Link: http://www.softonic.com.br/s/android-java
Title (HTML): Binding a <b>Java</b> Library | Xamarin
Link: http://developer.xamarin.com/guides/android/advanced_topics/java_integration_overview/binding_a_java_library_(.jar)/
Title (HTML): <b>java</b>-ide-droid – JavaIDEdroid allows you to create native <b>Android</b> <b>…</b>
Link: http://code.google.com/p/java-ide-droid/
Title (HTML): Code Style Guidelines for Contributors | <b>Android</b> Developers
Link: https://source.android.com/source/code-style.html
Title (HTML): Eclipse Downloads
Link: https://eclipse.org/downloads/
Title (HTML): Open source <b>Java</b> for <b>Android</b>? Don’t bet on it | InfoWorld
Link: http://www.infoworld.com/article/2615512/java/open-source-java-for-android–don-t-bet-on-it.html
Title (HTML): Make your First <b>Android</b> App! – YouTube
Link: http://www.youtube.com/watch?v=A_qaarY4_lY
Title (HTML): Runtime for <b>Android</b> apps – BlackBerry Developer
Link: http://developer.blackberry.com/android/
**************************************************
***************** SEARCH **************************

Title (HTML): <b>Java</b> Mobile <b>Android</b> Basic Course Online
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Title (HTML): samples/ApiDemos/src/com/example/<b>android</b>/apis/app <b>…</b>
Link: https://android.googlesource.com/platform/development/+/master/samples/ApiDemos/src/com/example/android/apis/app/FragmentRetainInstance.java
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Conclusion

And so we concluded our hands-on. With a simple usage, Google’s custom search API offers a simple but powerful tool in the belt of every developer who need to use a search engine of the internet in his solutions. Thank you for reading, until next time.

Source-code (Github)