Post section (success, failure, always) in Jenkins - Mini Project: Build & Apply

Using the Post Section in Jenkins Pipelines

📖 Scenario: You are setting up a Jenkins pipeline to build a simple project. You want to run specific actions after the build finishes, depending on whether it succeeded, failed, or always after the build.

🎯 Goal: Build a Jenkins pipeline script that uses the post section with success, failure, and always blocks to print messages based on the build result.

📋 What You'll Learn

Create a Jenkins pipeline with a pipeline block

Add a stage named Build that runs a simple shell command

Add a post section with success, failure, and always blocks

Print Build succeeded! on success

Print Build failed! on failure

Print This always runs. regardless of build result

💡 Why This Matters

🌍 Real World

In real projects, Jenkins pipelines automate building, testing, and deploying software. The post section helps run cleanup, notifications, or reports after builds.

💼 Career

Understanding Jenkins post sections is essential for DevOps roles to ensure proper build lifecycle management and notifications.

1

Create the basic Jenkins pipeline structure

Write a Jenkins pipeline script starting with pipeline { and add an agent any line inside it.

Jenkins

pipeline {
    agent any
    // Your code here
}

Hint

Start your Jenkinsfile with pipeline { and specify agent any to run on any available agent.

2

Add a Build stage with a shell command

Inside the pipeline block, add a stages section with one stage named Build. Inside this stage, add a steps block that runs the shell command echo Building... using sh.

Jenkins

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                // Your code here
            }
        }
    }
}

Hint

Use stages to group your build steps. Inside the Build stage, use sh 'echo Building...' to run the shell command.

3

Add the post section with success, failure, and always blocks

Add a post section inside the pipeline block but outside stages. Inside post, add success, failure, and always blocks. In each block, add a steps section that runs echo commands printing exactly these messages: Build succeeded! for success, Build failed! for failure, and This always runs. for always.

Jenkins

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                sh 'echo Building...'
            }
        }
    }
    // Your code here
}

Hint

The post section goes after stages. Use success, failure, and always blocks with steps inside to print messages.

4

Print the final pipeline script

Print the entire Jenkins pipeline script you wrote so far.

Jenkins

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                sh 'echo Building...'
            }
        }
    }
    post {
        success {
            steps {
                echo 'Build succeeded!'
            }
        }
        failure {
            steps {
                echo 'Build failed!'
            }
        }
        always {
            steps {
                echo 'This always runs.'
            }
        }
    }
}

# Your code here

Hint

Use print to show the message pipeline script complete confirming your script is ready.

Practice

1. What is the purpose of the post section in a Jenkins pipeline?

easy

A. To run steps after the main pipeline or stage finishes

B. To define environment variables for the pipeline

C. To specify the build agent for the pipeline

D. To declare input parameters for the pipeline

Solution

1. Step 1: Understand the role of the post section

   The post section is designed to run steps after the main pipeline or stage finishes, regardless of success or failure.

2. Step 2: Compare with other pipeline sections

   Other sections like environment, agent, and parameters serve different purposes, not for post-run steps.

3. Final Answer:

   To run steps after the main pipeline or stage finishes -> Option A

4. Quick Check:

   Post section = run after pipeline [OK]

Hint: Post section always runs after pipeline ends [OK]

Common Mistakes:

• Confusing post with environment or agent sections
• Thinking post runs before pipeline starts
• Assuming post only runs on failure

2. Which of the following is the correct syntax to run a step only when the pipeline succeeds in the post section?

easy

A. post { always { echo 'Done' } }

B. post { success { echo 'Build succeeded' } }

C. post { failure { echo 'Build failed' } }

D. post { cleanup { echo 'Cleaning up' } }

Solution

1. Step 1: Identify the correct post condition for success

   The success block runs only when the pipeline finishes successfully.

2. Step 2: Check syntax correctness

   post { success { ... } } is the correct syntax. Other options use wrong conditions or invalid keywords.

3. Final Answer:

   post { success { echo 'Build succeeded' } } -> Option B

4. Quick Check:

   Success block runs on success [OK]

Hint: Use 'success' block for success-only steps [OK]

Common Mistakes:

• Using 'always' instead of 'success' for success-only steps
• Using invalid keywords like 'cleanup'
• Confusing 'failure' with 'success'

3. Given this Jenkins pipeline snippet, what will be printed if the build fails?

pipeline {
  agent any
  stages {
    stage('Test') {
      steps {
        sh 'exit 1'
      }
    }
  }
  post {
    success {
      echo 'Build succeeded'
    }
    failure {
      echo 'Build failed'
    }
    always {
      echo 'Build finished'
    }
  }
}

medium

A. Build failed
Build finished

B. Build succeeded

C. Build succeeded
Build finished

D. Build finished

Solution

1. Step 1: Analyze the build result

   The shell command sh 'exit 1' causes the build to fail.

2. Step 2: Determine which post blocks run on failure

   The failure block runs on failure, printing 'Build failed'. The always block runs regardless, printing 'Build finished'. The success block does not run.

3. Final Answer:

   Build failed Build finished -> Option A

4. Quick Check:

   Failure + always blocks run on failure [OK]

Hint: Failure and always blocks run on failure [OK]

Common Mistakes:

• Assuming success block runs on failure
• Ignoring the always block
• Thinking only failure block runs

4. Identify the error in this Jenkins pipeline post section:

post {
  success {
    echo 'Success!'
  }
  failure {
    echo 'Failure!'
  }
  always {
    echo 'Always runs'
  }
  cleanup {
    echo 'Cleaning up'
  }
}

medium

A. The 'always' block should be named 'alwaysRun'

B. The 'failure' block must come before 'success'

C. The 'cleanup' block is invalid in the post section

D. The 'echo' commands must be inside 'steps' block

Solution

1. Step 1: Review valid post condition blocks

   Valid blocks are success, failure, always, unstable, and changed. There is no cleanup block.

2. Step 2: Check syntax of echo commands

   The echo commands can be used directly in post blocks. The order of blocks does not matter.

3. Final Answer:

   The 'cleanup' block is invalid in the post section -> Option C

4. Quick Check:

   Only success, failure, always allowed [OK]

Hint: Post section allows only specific blocks like success, failure, always [OK]

Common Mistakes:

• Adding unsupported blocks like 'cleanup'
• Thinking block order matters
• Wrapping echo in steps inside post (not needed)

5. You want to send a notification only if the build fails, but also always archive the build logs regardless of the result. Which post section correctly implements this?

hard

A. post { failure { mail to: '[e-mail]' archiveArtifacts 'logs/**' } }

B. post { always { mail to: '[e-mail]' } failure { archiveArtifacts 'logs/**' } }

C. post { success { mail to: '[e-mail]' } always { archiveArtifacts 'logs/**' } }

D. post { failure { mail to: '[e-mail]' } always { archiveArtifacts 'logs/**' } }

Solution

1. Step 1: Identify notification condition

   Notification should run only on failure, so it belongs in the failure block.

2. Step 2: Identify archiving condition

   Archiving logs should happen always, so it belongs in the always block.

3. Step 3: Check syntax correctness

   post { failure { mail to: '[e-mail]' } always { archiveArtifacts 'logs/**' } } correctly separates the two actions into failure and always blocks. post { failure { mail to: '[e-mail]' archiveArtifacts 'logs/**' } } puts both actions in the failure block, so archiving occurs only on failure.

4. Final Answer:

   post { failure { mail to: '[e-mail]' } always { archiveArtifacts 'logs/**' } } -> Option D

5. Quick Check:

   Failure for notify, always for archive [OK]

Hint: Use failure for notify, always for archive [OK]

Common Mistakes:

• Putting always steps inside failure block
• Sending notifications on success instead of failure
• Missing proper syntax for multiple steps