DDevelopment & Design

Gerrit notifications via Rocket.Chat

Case

Gerrit often sends a lot of emails, especially if you take part in many projects. For a while we felt that sometimes it’s hard to notice the most important ones, like reviewers’ and Sputnik‘s comments on our changes. We use Rocket.Chat for text communication inside the company and most of us are connected throughout the day, so we thought it might be useful to get chat message notification every time a comment is added on one’s changes.

Gerrit hooks

Gerrit has a built-in mechanism for running hooks – scripts that are called whenever a specific event occurs. The script must be named the same as the hook. We created a bash script named comment-added, which is run every time someone adds a comment. Gerrit provides it with a lot of useful parameters, like project name, comment author, score, change owner, etc. Full documentation can be found here. After parsing those parameters, we can send a message to change owner on Rocket.Chat.

Gerrit hooks script have to be placed in a certain location. To avoid manually updating the files there, we set up a repository for hook scripts. They are periodically pulled to the correct location which simplifies the process of making changes to the scripts.

Integration with Rocket.Chat

Rocket.Chat has a pretty versatile REST API that allows us to send messages by calling curl from the comment-added script. Full documentation for the API can be found here. Currently, the API is in beta version, but so far we haven’t had any issues with it.

We previously set up a user that sends Jenkins automatic messages to our team chat and we reuse this user here. Firstly, we have to log in by calling api/v1/login endpoint:

curl https://<Rocket.Chat server address>/api/v1/login -d "username=<username>&password=<password>"

In response, we get a JSON with the logged user’s id and authorization token:

{
  "status": "success",
  "data": {
    "authToken": "<authorization token>",
    "userId": "<user id>"
  }
}

Next, we send a direct message to user by their username (in our case, we can get the username from change owner’s email), calling api/v1/chat.postMessage endpoint. This sends a direct message to the user, even if there was no previous conversation between the users – no need to set up a room or open chat. Example:

curl -H "X-Auth-Token: <authorization token>" \
  -H "X-User-Id: <user id>" \
  -H "Content-Type: application/json" \
  -d "{\"channel\": \"@<recipient username>\", \"text\": \"<message>\"}" \
  https://<Rocket.Chat server address>/api/v1/chat.postMessage

Summary

We created a simple script to solve the issue of getting notified when we get comments on our changes. So far, the team seems pleased with how this works and finds it quite useful. We hope that it would be useful for you as well – full code can be found here.

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DDevelopment & Design

Multi module Gradle project with IDE support

This article is a short how-to about multi-module project setup with usage of the Gradle automation build tool.

Here's how Rich Seller, a StackOverflow user, describes Gradle:
Gradle promises to hit the sweet spot between Ant and Maven. It uses Ivy's approach for dependency resolution. It allows for convention over configuration but also includes Ant tasks as first class citizens. It also wisely allows you to use existing Maven/Ivy repositories.
So why would one use yet another JVM build tool such as Gradle? The answer is simple: to avoid frustration involved by Ant or Maven.

Short story

I was fooling around with some fresh proof of concept and needed a build tool. I'm pretty familiar with Maven so created project from an artifact, and opened the build file, pom.xml for further tuning.
I had been using Grails with its own build system (similar to Gradle, btw) already for some time up then, so after quite a time without Maven, I looked on the pom.xml and found it to be really repulsive.

Once again I felt clearly: XML is not for humans.

After quick googling I found Gradle. It was still in beta (0.8 version) back then, but it's configured with Groovy DSL and that's what a human likes :)

Where are we

In the time Ant can be met but among IT guerrillas, Maven is still on top and couple of others like for example Ivy conquer for the best position, Gradle smoothly went into its mature age. It's now available in 1.3 version, released at 20th of November 2012. I'm glad to recommend it to anyone looking for relief from XML configured tools, or for anyone just looking for simple, elastic and powerful build tool.

Lets build

I have already written about basic project structure so I skip this one, reminding only the basic project structure:
<project root>

│

├── build.gradle

└── src

    ├── main

    │   ├── java

    │   └── groovy

    │

    └── test

        ├── java

        └── groovy
Have I just referred myself for the 1st time? Achievement unlocked! ;)

Gradle as most build tools is run from a command line with parameters. The main parameter for Gradle is a 'task name', for example we can run a command: gradle build.
There is no 'create project' task, so the directory structure has to be created by hand. This isn't a hassle though.
Java and groovy sub-folders aren't always mandatory. They depend on what compile plugin is used.

Parent project

Consider an example project 'the-app' of three modules, let say:
  1. database communication layer
  2. domain model and services layer
  3. web presentation layer
Our project directory tree will look like:
the-app

│

├── dao-layer

│   └── src

│

├── domain-model

│   └── src

│

├── web-frontend

│   └── src

│

├── build.gradle

└── settings.gradle
the-app itself has no src sub-folder as its purpose is only to contain sub-projects and build configuration. If needed it could've been provided with own src though.

To glue modules we need to fill settings.gradle file under the-app directory with a single line of content specifying module names:
include 'dao-layer', 'domain-model', 'web-frontend'
Now the gradle projects command can be executed to obtain such a result:
:projects


------------------------------------------------------------

Root project

------------------------------------------------------------


Root project 'the-app'

+--- Project ':dao-layer'

+--- Project ':domain-model'

\--- Project ':web-frontend'
...so we know that Gradle noticed the modules. However gradle build command won't run successful yet because build.gradle file is still empty.

Sub project

As in Maven we can create separate build config file per each module. Let say we starting from DAO layer.
Thus we create a new file the-app/dao-layer/build.gradle with a line of basic build info (notice the new build.gradle was created under sub-project directory):
apply plugin: 'java'
This single line of config for any of modules is enough to execute gradle build command under the-app directory with following result:
:dao-layer:compileJava

:dao-layer:processResources UP-TO-DATE

:dao-layer:classes

:dao-layer:jar

:dao-layer:assemble

:dao-layer:compileTestJava UP-TO-DATE

:dao-layer:processTestResources UP-TO-DATE

:dao-layer:testClasses UP-TO-DATE

:dao-layer:test

:dao-layer:check

:dao-layer:build


BUILD SUCCESSFUL


Total time: 3.256 secs
To use Groovy plugin slightly more configuration is needed:
apply plugin: 'groovy'


repositories {

    mavenLocal()

    mavenCentral()

}


dependencies {

    groovy 'org.codehaus.groovy:groovy-all:2.0.5'

}
At lines 3 to 6 Maven repositories are set. At line 9 dependency with groovy library version is specified. Of course plugin as 'java', 'groovy' and many more can be mixed each other.

If we have settings.gradle file and a build.gradle file for each module, there is no need for parent the-app/build.gradle file at all. Sure that's true but we can go another, better way.

One file to rule them all

Instead of creating many build.gradle config files, one per each module, we can use only the parent's one and make it a bit more juicy. So let us move the the-app/dao-layer/build.gradle a level up to the-app/build-gradle and fill it with new statements to achieve full project configuration:
def langLevel = 1.7


allprojects {


    apply plugin: 'idea'


    group = 'com.tamashumi'

    version = '0.1'

}


subprojects {


    apply plugin: 'groovy'


    sourceCompatibility = langLevel

    targetCompatibility = langLevel


    repositories {

        mavenLocal()

        mavenCentral()

    }


    dependencies {

        groovy 'org.codehaus.groovy:groovy-all:2.0.5'

        testCompile 'org.spockframework:spock-core:0.7-groovy-2.0'

    }

}


project(':dao-layer') {


    dependencies {

        compile 'org.hibernate:hibernate-core:4.1.7.Final'

    }

}


project(':domain-model') {


    dependencies {

        compile project(':dao-layer')

    }

}


project(':web-frontend') {


    apply plugin: 'war'


    dependencies {

        compile project(':domain-model')

        compile 'org.springframework:spring-webmvc:3.1.2.RELEASE'

    }

}


idea {

    project {

        jdkName = langLevel

        languageLevel = langLevel

    }

}
At the beginning simple variable langLevel is declared. It's worth knowing that we can use almost any Groovy code inside build.gradle file, statements like for example if conditions, for/while loops, closures, switch-case, etc... Quite an advantage over inflexible XML, isn't it?

Next the allProjects block. Any configuration placed in it will influence - what a surprise - all projects, so the parent itself and sub-projects (modules). Inside of the block we have the IDE (Intellij Idea) plugin applied which I wrote more about in previous article (look under "IDE Integration" heading). Enough to say that with this plugin applied here, command gradle idea will generate Idea's project files with modules structure and dependencies. This works really well and plugins for other IDEs are available too.
Remaining two lines at this block define group and version for the project, similar as this is done by Maven.

After that subProjects block appears. It's related to all modules but not the parent project. So here the Groovy language plugin is applied, as all modules are assumed to be written in Groovy.
Below source and target language level are set.
After that come references to standard Maven repositories.
At the end of the block dependencies to groovy version and test library - Spock framework.

Following blocks, project(':module-name'), are responsible for each module configuration. They may be omitted unless allProjects or subProjects configure what's necessary for a specific module. In the example per module configuration goes as follow:
  • Dao-layer module has dependency to an ORM library - Hibernate
  • Domain-model module relies on dao-layer as a dependency. Keyword project is used here again for a reference to other module.
  • Web-frontend applies 'war' plugin which build this module into java web archive. Besides it referes to domain-model module and also use Spring MVC framework dependency.

At the end in idea block is basic info for IDE plugin. Those are parameters corresponding to the Idea's project general settings visible on the following screen shot.


jdkName should match the IDE's SDK name otherwise it has to be set manually under IDE on each Idea's project files (re)generation with gradle idea command.

Is that it?

In the matter of simplicity - yes. That's enough to automate modular application build with custom configuration per module. Not a rocket science, huh? Think about Maven's XML. It would take more effort to setup the same and still achieve less expressible configuration quite far from user-friendly.

Check the online user guide for a lot of configuration possibilities or better download Gradle and see the sample projects.
As a tasty bait take a look for this short choice of available plugins:
  • java
  • groovy
  • scala
  • cpp
  • eclipse
  • netbeans
  • ida
  • maven
  • osgi
  • war
  • ear
  • sonar
  • project-report
  • signing
and more, 3rd party plugins...