Is it possible for Jenkins to automatically detect and build newly created tags in a git repo?

Question

It would be nice for our Jenkins CI server to automatically detect, deploy and build tags as they are created in our Github repository.

Is this possible?

Answer 1

You can install a post-receive hook, which checks if a tag was commited, and creates a build in jenkins.

The hook can look something like this [*]:

#!/usr/bin/env python

import sys
from subprocess import Popen, PIPE, check_call

def call_git(command, args):
    return Popen(['git', command] + args, stdout=PIPE).communicate()[0]
JENKINS = 'http://localhost:8002/jenkins'
TOKEN = 'asdf8saffwedssdf'
jobname = 'project-tag'

def handle_ref(old, new, ref):
     print 'handle_ref(%s, %s, %s)' % (old, new, ref)
     if not ref.startswith('refs/tags/'):
          return
     url = '%s/job/%s/buildWithParameters?token=%s&branch=%s' % (
        JENKINS, jobname, TOKEN, new)
     print "queueing jenkins job " + jobname + " for " + new
     check_call(["wget", "-O/dev/null", "--quiet", url])
if __name__ == '__main__':
    for line in sys.stdin:
        handle_ref(*line.split())

[*] note: this is just a quick conversion from a slightly different script, so it's quite probable that there are some small bugs here. This is mostly to show the idea.

On the jenkins side, you need to configure a parametrized job. The only parameter is 'branch'.

1. Check 'this build is parametrized' and add the parameter
2. In 'source code management -> branches to build' put '$branch'

This gives a fairly secure and robust way to build. To test, run a build through the web interface, it'll ask for the value of the parameter.