Jenkinsfile Explained with Example

Agent

Let’s start with agent where certain phase will be executed. It can be the entire pipeline or certain stage. At top level agent, we set it to none so we need to set each stage what agent we want to use.

Let’s discus about the kind of agent below:

agent {
  docker {
    image 'alxibra/forstok-apigateway:0.0.1'
    label 'slave'
  }
}

It means we run our stage in docker environment with base image alxibra/forstok-apigateway:0.0.1 . label means which server with certain label you want to execute. we have 2 servers to run Jenkins, we label our server with master and slave .

For more information about agent you can read the documentation about agent.

Environment

Nothing much we can explain here, because it is explained itself. But if you wonder where credential come from. We can go to Manage Jenkins > Security > Manage Credentials

AWS_KEY = credentials('AWS_KEY')

When

when directive is used to which condition the stage should run. the when condition below has meaning that the stage always running except in branch master

when {
  not {
    branch 'master'
  }
}

For more information see this documentation.

Steps

steps what is to be done to complete the stage

steps('test') {
  sh 'bundle exec rspec'
}

The script above we need to run command bundle exec rspec . We can have more than one command each steps . for current condition we just need one command.

Parallel

We can run multiple stages parallelly. First we need to make parent stage , inside the stage put parallel directive. Inside parallel put how many stage s you want to.

stage('QA'){
  paralle {
    stage('linter'){
      .......
    }
    stage('test') {
      ........
    }
  }
}

for more information see this documentation

Post

post section is additional step after certain stage is done or fail. We define 2 conditions the success and failure . They both send notification to our slack the status. More about conditions in post see the documentation.

Now I try to explain the what is Jenkinsfile is doing in the file above

when branch is not master

When branch is not master we just run linter and test parallelly without executing the build image and deploy to production .

when branch is master

Now we want to release our application, we need to deploy it to production. First we need to build the application, after building is completed now we can deploy it to production. if status deploy is success or failure, jenkins will send the status to slack.