How to Get the Last Successful Git Commit SHA in Jenkins

In this article, we will explore how to get a Git commit SHA from the last successful Jenkins build for further use in the upstream builds on different agents.

Prerequisites:

• Jenkins (Freestyle project) with at least one or more Jenkins agents.
• GIT.
• Groovy.

In Jenkins, we need to install the Groovy plugin. For that step you need to go Manage Jenkins → Manage Plugins → Available Plugin

After plugin installation, In Jenkins job configuration, in the field “Build Steps“ choose “Execute system groovy script”.

Script section:

In this section, we can choose between the Groovy command and the Groovy script file(you can put Groovy file wherever you want on the slave node or git repository).

Add the following groovy script:

import hudson.EnvVars
import hudson.model.*

// Get current name of running job. Example: "Test-Job"

def jobName = build.project.name;

// Get instance of the current job for specified name

def job = hudson.model.Hudson.instance.getItem(jobName);

// Get list of the builds (objects) for current job. Example: [Test-Job #1, Test-Job #N] 

def builds = job.getBuilds();

// Find the first build with environment variables equals 'YES'. Descending numbering. It means [99, 98, , 1]. The first is 99

def successfulBuild = builds.find { build -> (build.envVars['IS_BUILD_SUCCESSFUL'] == 'YES') };

if (successfulBuild == null) {
  return;
}

// Get git commit for successful build

def gitCommitForSuccessfulBuild =  successfulBuild.envVars['GIT_COMMIT'];
def isLastSuccessFullBuild = successfulBuildToSF.envVars['IS_BUILD_SUCCESSFUL'];

println('Successful build number');
println(successfulBuild.envVars['BUILD_NUMBER']);
println(isLastSuccessFullBuild);

// Prepare a variable for export to environment in order to be accessible from next jobs

if (gitCommitForSuccessfulBuild) {
  def varForExport = [
    GIT_COMMIT_FOR_LAST_SUCCESSFUL_BUILD:  gitCommitForSuccessfulBuild,
    IS_LAST_SUCCESSFUL: isLastSuccessFullBuild
  ];
  build.environments.add(0, Environment.create(new EnvVars(varForExport)));
};

Now we need to add our new variable “IS_BUILD_SUCCESSFUL“ to the build process and Inject environment variables.

For this, we need to add “Execute Shell” and “Inject environment variables“ in the last steps of our build.

Inside “Execute Shell” we are writing our variable and put it inside the env.properties file:

echo IS_BUILD_SUCCESSFUL="YES" > env.properties

Inside “Inject environment variables“ we are writing the name of the file with the variable:

Summary

In this scenario, we explored the step-by-step instructions for how can we get the GIT commit SHA from a successful downstream build to an upstream build. Also, in a similar example, we can get any variable used in the downstream build.