Try-catch-finally in pipelines in Jenkins - Step-by-Step Execution

Process Flow - Try-catch-finally in pipelines

Start Pipeline

↓

Try Block: Run Steps

↓

Error Occurs?

No→Skip Catch

Yes↓

Catch Block: Handle Error

↓

Finally Block: Always Runs

↓

End Pipeline

The pipeline runs the try block steps first. If an error happens, it jumps to catch. Finally always runs at the end.

Execution Sample

Jenkins

pipeline {
  agent any
  stages {
    stage('Example') {
      steps {
        script {
          try {
            sh 'exit 1'
          } catch (err) {
            echo "Caught error: ${err}"
          } finally {
            echo 'Always runs'
          }
        }
      }
    }
  }
}

This pipeline tries to run a failing shell command, catches the error, then runs the finally block.

Process Table

Step	Action	Result	Next Step
1	Start pipeline and enter try block	No error yet	Run shell command
2	Run shell command 'exit 1'	Command fails with error code 1	Jump to catch block
3	Catch block runs	Error caught and message printed	Run finally block
4	Finally block runs	Message 'Always runs' printed	Pipeline ends

💡 Pipeline ends after finally block runs

Status Tracker

Variable	Start	After Step 2	After Step 3	Final
err	null	error object from shell failure	error object retained	error object retained

Key Moments - 2 Insights

Why does the pipeline run the finally block even after an error?

The finally block always runs regardless of errors, as shown in execution_table step 4, ensuring cleanup or final steps happen.

What happens if no error occurs in the try block?

If no error occurs, the catch block is skipped and the pipeline goes directly to finally, as shown by the 'No error yet' in step 1 and skipping step 3.

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 2?

A The shell command fails with error code 1

B The shell command runs successfully

C The catch block runs

D The finally block runs

💡 Hint

Check the 'Result' column for step 2 in the execution_table

At which step does the pipeline print the error message?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the 'Catch block runs' action in the execution_table

If the shell command succeeded, which step would be skipped?

A Step 2

B Step 3

C Step 4

D Step 1

💡 Hint

Refer to key_moments about what happens if no error occurs

Concept Snapshot

Try-catch-finally in Jenkins pipelines:
- try: run steps that may fail
- catch: handle errors if try fails
- finally: always runs after try/catch
- ensures cleanup or messages run no matter what
- catch skipped if no error
- finally always runs

Full Transcript

In Jenkins pipelines, the try-catch-finally structure helps manage errors. The pipeline starts by running the try block steps. If an error occurs, it jumps to the catch block to handle it. Regardless of error or not, the finally block always runs at the end. This ensures important cleanup or messages always happen. For example, running a shell command that fails triggers the catch block to print the error, then the finally block runs. If the command succeeds, the catch block is skipped but finally still runs. This flow helps keep pipelines reliable and clear.