The Jenkins Git Plugin Starts Multiple Builds For The Same Branch

On my current project, we have recently moved to a CI infrastructure that poll and build from multiple branches — using a wildcard. We noticed with the version of the Git plugin we were using, there was a known bug that would kick off multiple builds when polling from multiple branches. This wouldn’t be a big deal except our resources are very constrained, and it would sometimes kick off 5 builds for the same branch all within a second of each other. In order to correct this issue, I created a simple perl script and a Jenkins job, to call the perl script. The logic of the perl script is simple. It compares hashes and uses the REST API to call a Jenkins job.

#!/usr/bin/perl
`git fetch --all`;
@branches = `git branch -a | grep "remotes/origin/Prefix-*"`;

#open file to read
open (INPUT, '<DIR/hash.txt');

#read file
%currentHashes=();
while (<INPUT>){
     my($line) = $_;
     chomp($line);
     @values = split(',', $line);
     $currentHashes{"$values[0]"} = "$values[1]";
}

#open file to write
open (OUTPUT, '>DIR/hash.txt');
foreach $branch (@branches){
     chomp($branch);
     $commit = `git log -n 1 --pretty=format:'%H' $branch`;
     $newHashes{"$branch"} = "$commit";
     print OUTPUT "$branch,$commit\n";
}

foreach $key (keys %newHashes){
     if($newHashes{$key} eq $currentHashes{$key}){
          print "the hashes are the same for branch:$key \n";
     }else{
          print "the hashes are different for branch:$key \n";
          #remove spaces
          $key =~ s/^[ ]*//g;
          #remove remotes/origin
          $key =~ s/remotes\/origin\/*//g;
          #call jenkins job through rest api
          `curl -X POST \"{JENKINS_IP}/job/{SPECIFIC JOB}/buildWithParameters?&GIT_BRANCH_NAME=$key\"`;
     }
}

#close files
close (INPUT);
close (OUTPUT);

The corresponding Jenkins job would then need to be a parameterized build that includes the parameter GIT_BRANCH_NAME, for more information on the corresponding Jenkins job, please see the next blog.