Terminate existing pool when all work is done - groovy

Question

Alright, brand new to gpars so please forgive me if this has an obvious answer.
Here is my scenario. We currently have a piece of our code wrapped in a Thread.start {} block. It does this so it can send messages to an message queue in the background and not block the user request. An issue we have recently ran into with this is for large blocks of work, it is possible for the users to perform another action which would cause this block to execute again. As it is threaded, it is possible for the second batch of messages to get sent before the first causing corrupted data.
I would like to change this process to work as a queue flow with gpars. I've seen examples of creating pools such as
def pool = GParsPool.createPool()
or
def pool = new ForkJoinPool()
and then using the pool as
GParsPool.withExistingPool(pool) {
...
}
This seems like it would account for the case that if the user performs an action again, I could reuse the created pool and the actions would not be performed out of order, provided I have a pool size of one.
My question is, is this the best way to do this with gpars? And furthermore, how do I know when the pool is finished all of its work? Does it terminate when all the work is finished? If so, is there a method that can be used to check if the pool has finished/terminated to know I need a new one?
Any help would be appreciated.

Answer 1

No, explicitly created pools do not terminate by themselves. You have to call shutdown() on them explicitly.
Using withPool() {} command, however, will guarantee that the pool is destroyed once the code block is finished.

Answer 2

Here is the current solution we have to our issue. It should be noted that we followed this route due to our requirements
Work is grouped by some context
Work within a given context is ordered
Work within a given context is synchronous
Additional work for a context should execute after the preceding work
Work should not block the user request
Contexts are asynchronous between each other
Once work for a context is finished, the context should clean up after itself
Given the above, we've implemented the following:
class AsyncService {
def queueContexts
def AsyncService() {
queueContexts = new QueueContexts()
}
def queue(contextString, closure) {
queueContexts.retrieveContextWithWork(contextString, true).send(closure)
}
class QueueContexts {
def contextMap = [:]
def synchronized retrieveContextWithWork(contextString, incrementWork) {
def context = contextMap[contextString]
if (context) {
if (!context.hasWork(incrementWork)) {
contextMap.remove(contextString)
context.terminate()
}
} else {
def queueContexts = this
contextMap[contextString] = new QueueContext({->
queueContexts.retrieveContextWithWork(contextString, false)
})
}
contextMap[contextString]
}
class QueueContext {
def workCount
def actor
def QueueContext(finishClosure) {
workCount = 1
actor = Actors.actor {
loop {
react { closure ->
try {
closure()
} catch (Throwable th) {
log.error("Uncaught exception in async queue context", th)
}
finishClosure()
}
}
}
}
def send(closure) {
actor.send(closure)
}
def terminate(){
actor.terminate()
}
def hasWork(incrementWork) {
workCount += (incrementWork ? 1 : -1)
workCount > 0
}
}
}
}