Console Output Show the logs which can be inspected for debugging , or to inspect the Resources before Manual Approval.

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Jenkins Console Output:

The Console Output in Jenkins provides a detailed log of a job's execution, which is extremely useful for troubleshooting and monitoring builds. Here’s how you can use it effectively to inspect logs and diagnose issues.

A,  Accessing Console Output for a Jenkins Job

Step 1: Open Jenkins Dashboard

• Navigate to the Jenkins Dashboard.

Step 2: Select the Job

• Click on the job whose logs you want to inspect. This could be a Freestyle project or a Pipeline.

Step 3: Access the Build Logs

• In the job's page, click on the specific build number (e.g., #1, #2, etc.).
• Once inside the build page, you'll see a section called Console Output on the left-hand side.
  • If it’s not visible, you can click the Console Output link on the left sidebar to access it.

Step 4: Inspect the Logs

• The console output will show you logs from the execution of the job. For a Freestyle job, this includes every step, including shell commands, script outputs, and more.
• For Pipeline jobs, the console output includes logs for each stage and step, making it easier to see where issues may have occurred.

B,  Inspecting Logs for Specific Errors or Warnings

Step 1: Search in Console Output

• Use the browser's search function (Ctrl + F or Command + F) to quickly find specific text in the console output.
  • Look for error messages, exceptions, or warnings that may indicate what went wrong.

Step 2: Highlighting Important Information

• Error messages often include stack traces or failed commands. In the case of a failed shell command, Jenkins will output the exit code and possibly the output of the command that caused the failure.
• For Pipeline jobs, the logs are grouped by stages, which makes it easier to identify which specific part of the pipeline failed.

C,  Using Console Output to Debug Pipelines

If you're working with a Pipeline job (Declarative or Scripted), the Console Output will help you track:

• Stages: The execution of each defined stage in the pipeline.
• Steps: Logs for individual steps within each stage.
• Parallel Execution: If using parallel stages, logs will show which branch failed.

Example (Declarative Pipeline):

# groovy-script-template

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                echo 'Building the application...'
                sh 'make build'
            }
        }
        stage('Test') {
            steps {
                echo 'Running tests...'
                sh 'make test'
            }
        }
        stage('Deploy') {
            steps {
                echo 'Deploying application...'
                sh 'make deploy'
            }
        }
    }
}

• In the Console Output, you’ll see each stage and step’s output, and if a command like sh 'make test' fails, it will print the failure and exit code.

D,  Streaming Console Output for Active Builds

If you want to see the logs live while the build is running:

Step 1: Start the Build

• Go to the Jenkins job and click Build Now.

Step 2: Access Live Logs

• Click on the build number as the job is running.
• You’ll see the Console Output stream live as the build progresses.

This is particularly helpful for monitoring long-running jobs or for debugging builds that are still in progress.

E,  Saving and Exporting Logs for Later Inspection

If you need to save or export the console output for later analysis:

Step 1: Save Console Output as Text

• Inside the Console Output page, you can click on the "Save As" or "Download" button (depending on your Jenkins version) to save the logs as a .txt file.

Step 2: Export Logs

• You can also redirect the output to an external file during your build process by adding a step like:

  # groovy
  
  sh 'make build > build.log 2>&1'
  archiveArtifacts artifacts: 'build.log', allowEmptyArchive: true
  

This will save the log to the Jenkins workspace and make it available as an artifact.

F,  Handling Large Console Outputs

• Log truncation: Jenkins will truncate the console output for jobs with large logs by default. To avoid truncation, you can adjust the Jenkins settings:
  1. Go to Manage Jenkins → Configure System.
  2. Scroll down to Console Output and increase the max log size.
• Alternatively, you can archive logs in smaller chunks to avoid overwhelming the system.

G,  Useful Tips for Analyzing Console Output:

• Look for "FAIL" or "ERROR" in the logs.
• Look for any exit code != 0 (non-zero exit code) from shell commands.
• Review stage and step names in the output for a clearer picture of what happened.
• Use Jenkins plugins like Build Failure Analyzer to enhance error reporting and help with more structured diagnostics.

Summary: Using Console Output in Jenkins

• You can access the console output directly from a Jenkins job’s page.
• Search through the logs for errors, warnings, or specific messages.
• Live-stream the console output while the job is running.
• For Pipelines, view logs by stage and step to isolate failures.
• Save or export logs for long-term analysis.