Ability to synchronize threads on a particular request step in a load test

def testRunnerContext = context.getProperty("LoadTestRunner").context
def threadPool = testRunnerContext.getProperty("threadPool")

log.info "Thread " + Thread.currentThread().id + " starting, threadPool size = " + threadPool.size

if (threadPool.size() >= 4) {
 threadPool.each { thread ->
  thread.interrupt()
 }
} else {
 threadPool.add(Thread.currentThread())
 try {
  sleep(10000);
 }
 catch (InterruptedException ie) {
  log.info "Thread " + Thread.currentThread().id + " interrupted."
 }
}

log.info "Thread " + Thread.currentThread().id + " finished."

def testRunnerContext = context.getProperty("LoadTestRunner").context
def threadPool = testRunnerContext.getProperty("threadPool")
def currentThread = Thread.currentThread()

log.info "Thread " + currentThread.id + " starting, threadPool size = " + threadPool.size

if (threadPool.size() >= 4) {
 threadPool.each { thread ->
  thread.interrupt()
 }
} else {
 synchronized( this )  {
  threadPool.add(currentThread)
 }
 log.info threadPool.size
 try {
  currentThread.sleep(10000);
 }
 catch (InterruptedException ie) {
  currentThread.interrupt()
  log.info "Thread " + currentThread.id + " interrupted."
 }
}

log.info "Thread " + Thread.currentThread().id + " finished."

if ( context.getProperty("LoadTestRunner") == null) {

 // if no LoadTestRunner object we are single threaded
 return 0
}

def testRunnerContext = context.getProperty("LoadTestRunner").context // get the context of the load test runner
ArrayList waitingThreads = testRunnerContext.getProperty("waitingThreads") 
assert waitingThreads != null : "Missing arraylist for threads."
Integer waitTimeout = testRunnerContext.getProperty("waitTimeout") // max time for threads to sleep unless interrupted
assert waitTimeout >= 0 : "Wait timeout must be non-negative"
Integer threadSetSize = testRunnerContext.getProperty("threadSetSize")  // number of threads to a set
assert threadSetSize >= 0 : "Thread set size must be non-negative"
def currentThread = Thread.currentThread() 
def threadLimitReached = false  
def waitStartTime = 0
def sleepTime = 0

synchronized( waitingThreads ) {
 log.info "Thread " + currentThread.id + " starting, waiting threads = " + waitingThreads.size
 if (waitingThreads.size >= threadSetSize - 1) {
  // thread set filled, release all sleeping threads
  threadLimitReached = true
  for (def t = waitingThreads.size - 1; t >= 0; t--) {
   waitingThreads.get(t).interrupt()
   waitingThreads.remove(t)
  }
 } else {
  // add this thread to waiting list
  waitingThreads.add(currentThread)
  if (waitingThreads.size == 1) {
   // first thread in set, set the start time
   testRunnerContext.setProperty("waitStartTime", System.currentTimeMillis())
  }
  waitStartTime = testRunnerContext.getProperty("waitStartTime")  // get the wait start time for this thread set
  // calculate how long this thread should sleep if not interrupted
  def currTime = System.currentTimeMillis() 
  sleepTime = waitTimeout - (currTime - waitStartTime)
  sleepTime = sleepTime > 0 ? sleepTime : 0  // if code is right shouldn't need this...
 }
} 

if (!threadLimitReached) {  // don't sleep if this is the last thread in the set
 try {
  currentThread.sleep(sleepTime);
 }
 catch (InterruptedException ie) {
  currentThread.interrupt()
 }
}