Try-catch-finally in pipelines in Jenkins - Commands & Configuration

Introduction

Sometimes, parts of a Jenkins pipeline can fail. Try-catch-finally helps you handle these failures gracefully and always run cleanup steps.

When you want to catch errors in a build step and handle them without stopping the whole pipeline.

When you need to run cleanup tasks like deleting temporary files, no matter if the build succeeded or failed.

When you want to send notifications only if a part of the pipeline fails.

When you want to retry a step after catching an error.

When you want to ensure resources are released after pipeline execution.

Config File - Jenkinsfile

Jenkinsfile

pipeline {
  agent any
  stages {
    stage('Example') {
      steps {
        script {
          try {
            echo 'Running risky step'
            sh 'exit 1' // This simulates a failure
          } catch (Exception e) {
            echo "Caught error: ${e.message}"
          } finally {
            echo 'This always runs'
          }
        }
      }
    }
  }
}

This Jenkinsfile shows a pipeline with one stage that runs a risky step inside a try block.

If the step fails, the catch block runs and prints the error message.

The finally block always runs, whether the step succeeded or failed, useful for cleanup.

Commands

Check that Jenkins Job Builder is installed and working before running pipelines.

Terminal

jenkins-jobs --version

Expected Output

3.10.0

Start the Jenkins pipeline named 'example-pipeline' and wait for it to finish.

Terminal

jenkins-cli build example-pipeline -s

Expected Output

[Pipeline] Start of Pipeline

[Pipeline] echo

Running risky step

[Pipeline] sh

+ exit 1

[Pipeline] echo

Caught error: script returned exit code 1

[Pipeline] echo

This always runs

[Pipeline] End of Pipeline

Finished: SUCCESS

→

-s - Waits for the build to complete before returning output

View the console output of the last run of the 'example-pipeline' to verify try-catch-finally behavior.

Terminal

jenkins-cli console example-pipeline

Expected Output

[Pipeline] Start of Pipeline

[Pipeline] echo

Running risky step

[Pipeline] sh

+ exit 1

[Pipeline] echo

Caught error: script returned exit code 1

[Pipeline] echo

This always runs

[Pipeline] End of Pipeline

Finished: SUCCESS

Key Concept

If you remember nothing else from this pattern, remember: try-catch-finally lets you handle errors and always run cleanup steps in Jenkins pipelines.

Common Mistakes

Not using the 'script' block when writing try-catch-finally in declarative pipelines.

The try-catch-finally syntax is Groovy code and must be inside a 'script' block in declarative pipelines, otherwise it causes syntax errors.

Wrap try-catch-finally code inside a 'script' block within the steps section.

Leaving the finally block empty or missing it when cleanup is needed.

Without a finally block, cleanup steps may not run if an error occurs, causing resource leaks or stale state.

Always include a finally block for tasks that must run regardless of success or failure.

Catching generic Exception but not logging or handling it.

Swallowing errors without logging hides problems and makes debugging hard.

Log the caught exception message or take corrective action inside the catch block.

Summary

Use try-catch-finally inside a 'script' block to handle errors in Jenkins declarative pipelines.

The try block runs risky steps, catch handles errors, and finally always runs cleanup code.

This pattern helps keep pipelines stable and resources clean even when failures happen.

Practice

1. What is the main purpose of using try-catch-finally blocks in Jenkins pipelines?

easy

A. To create parallel stages automatically

B. To speed up the pipeline execution

C. To handle errors and ensure cleanup actions run

D. To deploy applications to production

Solution

1. Step 1: Understand the role of try-catch-finally

   The try block runs code that might fail, catch handles errors, and finally runs cleanup code regardless of success or failure.

2. Step 2: Identify the main purpose in Jenkins pipelines

   This structure helps manage errors gracefully and ensures cleanup steps always run, making pipelines reliable.

3. Final Answer:

   To handle errors and ensure cleanup actions run -> Option C

4. Quick Check:

   Error handling and cleanup = A [OK]

Hint: Remember: try for risky code, catch errors, finally cleans up [OK]

Common Mistakes:

• Thinking try-catch-finally speeds up pipelines
• Confusing try-catch-finally with deployment steps
• Assuming finally runs only on success

2. Which of the following is the correct syntax to catch an exception in a Jenkins scripted pipeline?

easy

A. try { ... } catch Exception e { ... } finally { ... }

B. try { ... } catch(Exception e) { ... } finally { ... }

C. try { ... } catch { Exception e } finally { ... }

D. try: { ... } except(Exception e) { ... } finally { ... }

Solution

1. Step 1: Recall Jenkins scripted pipeline syntax

   Jenkins scripted pipelines use Groovy syntax, where try { ... } catch(Exception e) { ... } finally { ... } is correct.

2. Step 2: Identify syntax errors in other options

   Options A, B, and C have incorrect keywords or misplaced braces not valid in Groovy.

3. Final Answer:

   try { ... } catch(Exception e) { ... } finally { ... } -> Option B

4. Quick Check:

   Groovy try-catch syntax = D [OK]

Hint: Groovy uses catch(Exception e) with braces, not colons or misplaced braces [OK]

Common Mistakes:

• Using Python-style except instead of catch
• Misplacing braces around catch block
• Omitting parentheses around exception

3. What will be the output of this Jenkins scripted pipeline snippet?

try {
  echo 'Start'
  error('Fail here')
  echo 'End'
} catch (Exception e) {
  echo 'Caught error'
} finally {
  echo 'Cleanup'
}

medium

A. Start\nCaught error\nCleanup

B. Caught error\nCleanup

C. Start\nEnd\nCleanup

D. Start\nCleanup

Solution

1. Step 1: Trace the try block execution

   The pipeline prints 'Start', then calls error('Fail here') which throws an exception, so 'End' is skipped.

2. Step 2: Understand catch and finally blocks

   The catch block runs and prints 'Caught error'. The finally block always runs and prints 'Cleanup'.

3. Final Answer:

   Start Caught error Cleanup -> Option A

4. Quick Check:

   Exception skips 'End', catch and finally run = C [OK]

Hint: Remember: error stops try, catch runs, finally always runs [OK]

Common Mistakes:

• Assuming code after error() runs
• Thinking finally runs before catch
• Ignoring that catch handles the error

4. Identify the error in this Jenkins pipeline snippet:

try {
  echo 'Running'
} catch {
  echo 'Error caught'
} finally {
  echo 'Done'
}

medium

A. try block must have a return statement

B. finally block cannot be used without catch

C. echo statements must be inside script block

D. Missing exception variable in catch block

Solution

1. Step 1: Check catch block syntax

   In Groovy/Jenkins, catch must declare an exception variable like catch (Exception e). Here it is missing.

2. Step 2: Verify other parts

   finally block is valid with catch, echo works outside script block in scripted pipeline, and try block does not require return.

3. Final Answer:

   Missing exception variable in catch block -> Option D

4. Quick Check:

   catch needs (Exception e) = A [OK]

Hint: Always declare exception variable in catch (e.g., catch(Exception e)) [OK]

Common Mistakes:

• Omitting exception variable in catch
• Thinking finally requires catch to be absent
• Assuming echo needs script block

5. You want to run a cleanup step in your Jenkins pipeline regardless of success or failure, but only if the try block ran without syntax errors. Which is the best way to structure your pipeline?

hard

A. Put cleanup code inside the finally block

B. Put cleanup code inside the catch block

C. Put cleanup code after the try-catch-finally block

D. Put cleanup code inside the try block after risky steps

Solution

1. Step 1: Understand when finally runs

   The finally block runs after try and catch, regardless of success or failure, but only if the pipeline syntax is valid and the try block started.

2. Step 2: Compare options for cleanup placement

   Cleanup in catch runs only on errors, after block runs only if no errors, and inside try risks skipping on errors. finally is best for guaranteed cleanup.

3. Final Answer:

   Put cleanup code inside the finally block -> Option A

4. Quick Check:

   Cleanup always runs in finally = B [OK]

Hint: Use finally for guaranteed cleanup after try-catch [OK]

Common Mistakes:

• Putting cleanup only in catch (misses success case)
• Placing cleanup after try-catch (may skip on errors)
• Putting cleanup inside try (skipped if error thrown early)