jenkins_last_good_commit.rb

require 'net/http'
require 'json'

# We could just use localhost, but it's nice to print usable urls in debug
@jenkins = `hostname`.strip

# Get the list of jobs on the Jenkins instance
res = Net::HTTP.get_response(URI('http://'+@jenkins+'/api/json'))
jobs = JSON.parse(res.body)['jobs']

# Iterate through the jobs finding the first and last jobs
jobs.each do |job|
  res = Net::HTTP.get_response(URI(job['url']+'api/json'))
  data = JSON.parse(res.body)
  if data['upstreamProjects'] == []
    @first_project = job['url']
  elsif data['downstreamProjects'] == []
    @last_project = job['url']
    @last_green_job = data['lastSuccessfulBuild']['url']
  end
end

#puts 'Last green job was ' + @last_green_job

# @param [String] url url of a green job
# @return [Object] git sha1 hash of the the last successful pipeline build (or false if there isn't one)
def get_sha_or_false(url)
  res = Net::HTTP.get_response(URI(url+'api/json'))


  # Sometimes we might reference builds which Jenkins has archived off
  # Return false if this is the case
  if res.code != '200'
    false
  else
    # If this has git revision numbers then use them
    data = JSON.parse(res.body)
    if data['actions'][1] != nil and data['actions'][1].has_key? 'lastBuiltRevision'
      data['actions'][1]['lastBuiltRevision']['SHA1']
      # We haven't got a git hash, ask the previous job in the pipeline if there is one
    elsif data['actions'][0]['causes'][0]['upstreamUrl'] != nil
      get_sha_or_false('http://'+@jenkins+'/'+data['actions'][0]['causes'][0]['upstreamUrl']+data['actions'][0]['causes'][0]['upstreamBuild'].to_s + '/')
    else
      # There aren't any git commit hashes in this pipeline
      false
    end
  end
end

# Pass in the latest job of the latest green pipeline run, searching for git hashes
hash = get_sha_or_false(@last_green_job)
puts hash.to_s