run something async in Grails 2.3 - grails

Question

In My Grails service, there is a part of a method I wish to run asynchronously.
Following, the doc for 2.3.x http://grails.org/doc/2.3.0.M1/guide/async.html
I do
public class MyService {
public void myMethod() {
Promise p = task {
// Long running task
}
p.onError { Throwable err ->
println "An error occured ${err.message}"
}
p.onComplete { result ->
println "Promise returned $result"
}
// block until result is called
def result = p.get()
}
}
However, I want to execute mine without any blocking. The p.get() method blocks. How do I execute the promise without any sort of blocking. I don't care if myMethod() returns, it is a kinda of fire and forget method.

Answer 1

So, according to the documentation if you don't call .get() or .waitAll() but rather just make use of onComplete you can run your task without blocking the current thread.
Here is a very silly example that I worked up in the console to as a proof of concept.
import static grails.async.Promises.*
def p = task {
// Long running task
println 'Off to do something now ...'
Thread.sleep(5000)
println '... that took 5 seconds'
return 'the result'
}
p.onError { Throwable err ->
println "An error occured ${err.message}"
}
p.onComplete { result ->
println "Promise returned $result"
}
println 'Just to show some output, and prove the task is running in the background.'
Running the above example gives you the following output:
Off to do something now ...
Just to show some output, and prove the task is running in the background.
... that took 5 seconds
Promise returned the result