Jenkins – How to Trigger a Replay Build from API with Custom Pipeline

Welcome to this comprehensive guide on triggering a replay build from API with a custom pipeline in Jenkins. Are you tired of manually rebuilding projects in Jenkins every time you make changes? Do you want to automate the build process and save time? Look no further! In this article, we’ll take you through a step-by-step process of triggering a replay build from API with a custom pipeline in Jenkins.

What is Jenkins?

Jenkins is an open-source automation server that helps developers and teams automate their build, test, and deployment processes. It’s a popular tool used by millions of developers worldwide. With Jenkins, you can automate repetitive tasks, monitor builds, and ensure quality control.

What is a Replay Build?

A replay build is a feature in Jenkins that allows you to re-run a previous build with the same parameters as the original build. This comes in handy when you want to re-run a build with the same configuration, but with some changes. For instance, you might want to re-run a build with the same commit, but with a different set of environment variables.

What is a Custom Pipeline?

A custom pipeline in Jenkins is a set of automated tasks that are executed in a specific order. You can create a custom pipeline to automate your build, test, and deployment processes. With a custom pipeline, you can define your own steps, use plugins, and integrate with other tools to create a tailored workflow for your project.

Why Trigger a Replay Build from API?

Triggering a replay build from API is useful when you want to automate the build process programmatically. For instance, you might want to trigger a replay build from your CI/CD pipeline, or from a script that monitors changes in your repository. By triggering a replay build from API, you can automate the entire process and save time.

Prerequisites

• Jenkins installed and configured on your server
• A custom pipeline created in Jenkins
• API token generated in Jenkins
• Your favorite programming language and HTTP client library

Generating an API Token in Jenkins

Before you can trigger a replay build from API, you need to generate an API token in Jenkins. Here’s how:

1. Log in to your Jenkins instance
2. Click on your username in the top right corner
3. Click on “Configure Jenkins”
4. Scroll down to the “Security” section
5. Click on “API Tokens”
6. Click on “Add new token”
7. Enter a name for your token
8. Click on “Generate”

Note down the generated API token. You’ll need it later.

Triggering a Replay Build from API

Now that you have your API token, let’s trigger a replay build from API using your favorite programming language and HTTP client library.

Using Python and Requests Library

import requests

# Replace with your Jenkins instance URL
jenkins_url = "https://your-jenkins-instance.com"

# Replace with your API token
api_token = "your-api-token"

# Replace with the job name and build number
job_name = "your-job-name"
build_number = 123

# Construct the API URL
api_url = f"{jenkins_url}/job/{job_name}/{build_number}/replay"

# Set API token in headers
headers = {
    "Authorization": f"Bearer {api_token}"
}

# Trigger the replay build
response = requests.post(api_url, headers=headers)

# Check if the build was triggered successfully
if response.status_code == 201:
    print("Replay build triggered successfully!")
else:
    print("Error triggering replay build:", response.text)

Using Java and OkHttp Library

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

// Replace with your Jenkins instance URL
String jenkinsUrl = "https://your-jenkins-instance.com";

// Replace with your API token
String apiToken = "your-api-token";

// Replace with the job name and build number
String jobName = "your-job-name";
int buildNumber = 123;

// Construct the API URL
String apiUrl = String.format("%s/job/%s/%d/replay", jenkinsUrl, jobName, buildNumber);

// Set API token in headers
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
        .url(apiUrl)
        .post(RequestBody.create((byte[]) null))
        .header("Authorization", "Bearer " + apiToken)
        .build();

// Trigger the replay build
Response response = client.newCall(request).execute();

// Check if the build was triggered successfully
if (response.code() == 201) {
    System.out.println("Replay build triggered successfully!");
} else {
    System.out.println("Error triggering replay build: " + response.body().string());
}

Triggering a Replay Build with Custom Pipeline

Now that you know how to trigger a replay build from API, let’s take it to the next level by triggering a replay build with a custom pipeline.

Creating a Custom Pipeline in Jenkins

First, you need to create a custom pipeline in Jenkins. Here’s an example pipeline script:

pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                echo 'Building the project...'
                sh 'mvn clean package'
            }
        }
        stage('Test') {
            steps {
                echo 'Running tests...'
                sh 'mvn test'
            }
        }
    }
}

Save this pipeline script as a file (e.g., `pipeline.groovy`) and upload it to Jenkins.

Triggering a Replay Build with Custom Pipeline

Now, let’s modify the API request to trigger a replay build with the custom pipeline:

import requests

# Replace with your Jenkins instance URL
jenkins_url = "https://your-jenkins-instance.com"

# Replace with your API token
api_token = "your-api-token"

# Replace with the job name and build number
job_name = "your-job-name"
build_number = 123

# Replace with the pipeline name
pipeline_name = "your-pipeline-name"

# Construct the API URL
api_url = f"{jenkins_url}/job/{job_name}/{build_number}/replayWithParameters"

# Set API token and pipeline name in headers
headers = {
    "Authorization": f"Bearer {api_token}",
    "Content-Type": "application/json"
}

# Set pipeline parameters
params = {
    "pipeline": pipeline_name
}

# Trigger the replay build with custom pipeline
response = requests.post(api_url, headers=headers, json=params)

# Check if the build was triggered successfully
if response.status_code == 201:
    print("Replay build triggered successfully with custom pipeline!")
else:
    print("Error triggering replay build with custom pipeline:", response.text)

Conclusion

In this article, we’ve shown you how to trigger a replay build from API with a custom pipeline in Jenkins. By following these steps, you can automate the build process and save time. Remember to replace the placeholders with your own values, and don’t hesitate to reach out if you encounter any issues.

Keyword	Frequency
Jenkins	10
Replay Build	5
Custom Pipeline	4
API	3
Trigger	2

Note: The frequency of the keywords is just for demonstration purposes.

FAQs

Q: What is the difference between a replay build and a regular build?

A: A replay build is a re-run of a previous build with the same parameters, whereas a regular build is a new build with potentially different parameters.

Q: Can I trigger a replay build from API without a custom pipeline?

A: Yes, you can trigger a replay build from API without a custom pipeline. The API request remains the same, but you won’t be able to customize the pipeline steps.

Q: How do I troubleshoot issues with triggering a replay build from API?

A: Check the Jenkins logs for errors, verify your API token and credentials, and ensure that the job and build number exist.

We hope this article has been informative and helpful. Happy automating!

Frequently Asked Question

Get ready to unleash the power of Jenkins with these frequently asked questions about triggering a replay build from API with custom pipeline!