Build and deploy Spring Boot app to GCP Compute Engine using Jenkin

Target

Using Jenkin:

• Build a Spring Boot app to Jar file. Source code is on Github.
• Upload Jar file to a GCP Compute engine and run.
• In Jenkin job, can select the branch to deploy.

Prerequisites

• Jenkin with plugins installed:
  • Office 365 Connector
  • Git
• A compute engine in GCP
  • start-up script to install Java 8 and lsof

    apt-get update
    apt-get install openjdk-8-jdk lsof -y
    

• A Spring Boot app with Gradle, pushed Github. I use my CORS demo app.

Let's go

Setup Compute engine

We need to config compute engine (VM) so that it can accept request at port 8080:

• create a firewall rule that accept tcp 8080 with target tag spring
• add target tag spring to the VM.

Create the Jenkin job

• Add a parameter option to Office 365 Connector to choose the branch to deploy

• Add git repo URL to Source Code Management, specify Branch as ${GIT_BRANCH} to select the value in Office 365 Connector parameter.

• Build Jar file

  • In order to build a Jar file, add the following task to build.gradle

  bootJar {
      archiveFileName = "${archiveBaseName.get()}.${archiveExtension.get()}"
  }
  

  • As we open port 8080 in the VM, we need to specify the port we execute the Spring boot app, to do so, add the following to build.gradle file

  bootRun {
  systemProperties = System.properties
  }
  

  Now we can run the app manually by command

  java -Dserver.port=8080 -jar demo-cors.jar
  

  Let's Jenkin build the jar file by adding a Invoke Gradle Script step to Build:

• Upload Jar file to VM
  The idea is to use scp to upload the Jar file to VM (a remote server). First we need to generate a pair of public, private key:

# login to jenkins user, if forgot the password use `sudo passwd jenkins` to change password
su - jenkins
ssh-keygen

Now a pair of key is generated at .ssh

ASRHQ614:~ jenkins$ ls .ssh/
id_rsa		id_rsa.pub	known_hosts

Add the public key content (id_rsa.pub) to VM by going to VM instance > Edit > SSH Keys

Test the connection:

su - jenkins
ssh <your-VM-ip>

Add a Execute Shell step to Build with following command:

scp -Cq -o StrictHostKeyChecking=no "build/libs/demo-cors.jar" "<your-VM-ip>:/home/jenkins/demo-cors.jar"

• Execute the jar file

Add one more command to above Execute Shell step:

ssh jenkins@<your-VM-ip> -f 'kill -9 $(lsof -t -i:8080 -sTCP:LISTEN); java -Dserver.port=8080 -jar demo-cors.jar'

-f option : to run exit the ssh before running the commands
kill -9 $(lsof -t -i:8080 -sTCP:LISTEN): to kill the current app
java -Dserver.port=8080 -jar demo-cors.jar: execute the new jar file

Access <your-VP-ip>:8080 to see the result