threading.groovy

//http://chrisbroadfoot.id.au/2008/08/06/groovy-threads/
//http://docs.groovy-lang.org/latest/html/gapi/groovy/transform/Synchronized.html
//https://github.com/jenkinsci/jenkins-scripts/blob/master/scriptler/findOfflineSlaves.groovy

import java.util.concurrent.locks.ReentrantLock 
 
ReentrantLock.metaClass.withLock = {
  lock()
  try {
    it()
  }
  finally {
      unlock()
  }
}
 
def lock = new ReentrantLock()

List<Thread> threads = []

List results = []

threads << Thread.start {
  sleep(1000)
  //protect this shared data from a race condition
  lock.withLock {
   results << "hello"
  }
  println "Hello sam"
}

threads << Thread.start {
  //protect this shared data from a race condition while modifying it
  lock.withLock {
   results << "hello2"
  }
  println "Hello sam"
}

//gate to wait for all threads
threads.each {
  it.join()
}

//notice hello2 is in the results list first even though it was defined after hello in this file
results