Post section (success, failure, always) in Jenkins - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output when the post { success } block runs?

Consider this Jenkins pipeline snippet:

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        echo 'Building...'
      }
    }
  }
  post {
    success {
      echo 'Build succeeded!'
    }
  }
}

What will Jenkins print if the build stage completes without errors?

Jenkins

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        echo 'Building...'
      }
    }
  }
  post {
    success {
      echo 'Build succeeded!'
    }
  }
}

A Building...\nBuild succeeded!

B Build succeeded!\nBuilding...

C Building...

D No output, post block does not run

💡 Hint

Remember, the post { success } block runs only if the build succeeds.

The echo 'Building...' runs during the build stage. After successful completion, the post { success } block runs and prints 'Build succeeded!'. So output is both lines in order.

💻 Command Output

intermediate

What happens when the post { failure } block is triggered?

Given this Jenkins pipeline:

pipeline {
  agent any
  stages {
    stage('Test') {
      steps {
        sh 'exit 1'
      }
    }
  }
  post {
    failure {
      echo 'Tests failed!'
    }
  }
}

What will Jenkins output if the shell command fails?

Jenkins

pipeline {
  agent any
  stages {
    stage('Test') {
      steps {
        sh 'exit 1'
      }
    }
  }
  post {
    failure {
      echo 'Tests failed!'
    }
  }
}

A Tests failed!

B No output, failure block does not run

C Pipeline succeeds without output

D Build succeeded!

💡 Hint

The post { failure } block runs only if any stage fails.

The shell command exits with code 1, causing the stage to fail. The post { failure } block then runs and prints 'Tests failed!'.

🔀 Workflow

advanced

Order the execution of post blocks in this Jenkins pipeline

Given this Jenkins pipeline snippet:

pipeline {
  agent any
  stages {
    stage('Deploy') {
      steps {
        echo 'Deploying...'
      }
    }
  }
  post {
    always {
      echo 'Cleaning up...'
    }
    success {
      echo 'Deployment succeeded!'
    }
    failure {
      echo 'Deployment failed!'
    }
  }
}

What is the correct order of post block execution if the deployment succeeds?

A 1,2,3

B 2,1,3

C 1,3,2

D 2,3,1

💡 Hint

The always block runs after success or failure blocks.

When deployment succeeds, success runs first, then always. The failure block does not run.

❓ Troubleshoot

advanced

Why does the post { always } block not run in this pipeline?

Look at this Jenkins pipeline:

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        error 'Forced failure'
      }
    }
  }
  post {
    always {
      echo 'This should always run'
    }
  }
}

Despite the error, the message in always does not appear. What is the most likely reason?

Jenkins

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        error 'Forced failure'
      }
    }
  }
  post {
    always {
      echo 'This should always run'
    }
  }
}

A The <code>post</code> block is misplaced outside the pipeline block

B The <code>error</code> step stops the entire Jenkins server

C The <code>always</code> block only runs on success

D The pipeline is scripted, but <code>post</code> is only for declarative pipelines

💡 Hint

Check if the pipeline syntax matches the post block usage.

The post section is valid only in declarative pipelines. If the pipeline is scripted, post blocks do not run.

✅ Best Practice

expert

Which post block usage ensures cleanup regardless of build result?

You want to delete temporary files after every build, no matter if it succeeds or fails. Which Jenkins post block snippet achieves this best?

post {
  A) success {
       sh 'rm -rf temp/'
     }
  B) failure {
       sh 'rm -rf temp/'
     }
  C) always {
       sh 'rm -rf temp/'
     }
  D) changed {
       sh 'rm -rf temp/'
     }
}

A Runs only if build succeeds, so may skip cleanup on failure

B Runs only if build fails, so may skip cleanup on success

C Runs after every build, ensuring cleanup always

D Runs only if build status changes, may skip some builds

💡 Hint

Think about which post condition always runs regardless of build outcome.

The always block runs after every build, success or failure, making it ideal for cleanup tasks.

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