Serverless Jenkins Pipelines with Fn Project

This post was originally written by Carlos Sanchez on his blog. Thanks Carlos!

The Jenkinsfile-Runner-Fn project is an Fn Project (a container-native, cloud-agnostic serverless platform) function to run Jenkins pipelines. It will process a GitHub webhook, git clone the repository and execute the Jenkinsfile in that git repository. It allows scalability and pay per use with zero cost if not used.

This function allows Jenkinsfile execution without needing a persistent Jenkins master running in the same way as Jenkins X Serverless, but using the Fn Project platform (and supported providers like Oracle Functions) instead of Kubernetes.

Fn Project vs AWS Lambda

The function is very similar to the one in jenkinsfile-runner-lambda with just a small change in the signature. The main difference between Lambda and Fn is in the packaging, as Lambda layers are limited in size and are expanded in /optwhile Fn allows a custom Dockerfile where you can install whatever you want in a much easier way, just need to include the function code and entrypoint from fnproject/fn-java-fdk.

Oracle Functions

Oracle Functions is a cloud service providing Project Fn function execution (currently in limited availability). jenkinsfile-runner-fn function runs in Oracle Functions, with the caveat that it needs a syslog server running somewhere to get the logs (see below).

Limitations

Current implementation limitations:

• checkout scm does not work, change it to sh 'git clone https://github.com/carlossg/jenkinsfile-runner-fn-example.git'
• Jenkinsfile must use /tmp for any tool that needs writing files, see the example

Example

See the jenkinsfile-runner-fn-example project for an example that is tested and works.

Extending

You can add your plugins to plugins.txt. You could also add the Configuration as Code plugin for configuration.

Other tools can be added to the Dockerfile.

Installation

Install Fn

Building

Build the function

mvn clean package

Publishing

Create and deploy the function locally

fn create app jenkinsfile-runner
fn --verbose deploy --app jenkinsfile-runner --local

Execution

Invoke the function

cat src/test/resources/github.json | fn invoke jenkinsfile-runner jenkinsfile-runner

Logging

Get the logs for the last execution

fn get logs jenkinsfile-runner jenkinsfile-runner \
$(fn ls calls jenkinsfile-runner jenkinsfile-runner | grep 'ID:' | head -n 1 | sed -e 's/ID: //')

Syslog

Alternatively, start a syslog server to see the logs

docker run -d --rm -it -p 5140:514 --name syslog-ng balabit/syslog-ng:latest
docker exec -ti syslog-ng tail -f /var/log/messages-kv.log

Update the function to send logs to the syslog server

fn update app jenkinsfile-runner --syslog-url tcp://logs-01.loggly.com:514

GitHub events

Add a GitHub json webhook to your git repo pointing to the function url.

More information in the Jenkinsfile-Runner-Fn GitHub page.