Why Post section (success, failure, always) in Jenkins? - Purpose & Use Cases

The Big Idea

Discover how a simple Post section can save you from messy, error-prone build scripts!

The Scenario

Imagine you run a Jenkins job that builds your project. After the build, you want to send an email only if the build succeeds, or maybe clean up resources if it fails. Doing this manually means adding separate steps everywhere and checking build results yourself.

The Problem

Manually checking build results and adding conditional steps is slow and error-prone. You might forget to add cleanup on failure or send notifications on success. This leads to messy pipelines and missed alerts.

The Solution

The Post section in Jenkins pipelines lets you define actions that run automatically after the main steps, based on build results like success, failure, or always. This keeps your pipeline clean and reliable.

Before vs After

✗ Before

if (currentBuild.result == 'SUCCESS') { sendEmail() } else if (currentBuild.result == 'FAILURE') { cleanup() }

✓ After

post {
  success {
    sendEmail()
  }
  failure {
    cleanup()
  }
  always {
    archiveArtifacts()
  }
}

What It Enables

You can automate follow-up tasks clearly and reliably, ensuring your pipeline reacts correctly to every build outcome.

Real Life Example

After a deployment job finishes, you want to notify your team only if it succeeded, clean temporary files if it failed, and always archive logs regardless of the result.

Key Takeaways

Manual checks for build results are slow and error-prone.

Post sections let you run steps on success, failure, or always.

This makes pipelines cleaner, reliable, and easier to maintain.

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