Can Vertx executeBlocking be used on a list? - vert.x

Question

Trying to process a list of long running jobs in a vertx way
One would hope one could do something like:
use the executeBlocking to process the long running job in an async manner
use the composite future to wait for the futures to complete
I'm aware this approach does not work .. the list of Futures is not complete before the code drops into the CompositeFuture.
Is there a executeBlocking approach or does one have to use either the eventbus, vertx utils that support lists?
java.util.ArrayList futureList = new ArrayList()
for (i = 0; i < 100; i ++){
vertx.executeBlocking({ future ->
int id = i
println "Running " + id
java.lang.Thread.sleep(1000)
println "Thread done " + id
future.complete()
}, true , { res ->
if (res.succeeded()) {
print "."
} else {
print "x"
}
})
}
CompositeFuture.join(futureList).setHandler({ ar ->
if (ar.succeeded()) {
System.err.println "all threads should be done.."
}
})
Results in .. "all threads should be done" printing early
Running 84
Running 87
Running 87
Running 95
all threads should be done..
done.
Thread done 3
Thread done 36
Thread done 3
Thread done 0

Answer 1

In your example, futureList is empty so CompositeFuture.join(futureList) is completed immediately.
Change your example like this:
java.util.ArrayList futureList = new ArrayList()
for (i = 0; i < 100; i ++){
Future jobFuture = Future.future()
futureList.add(jobFuture)
vertx.executeBlocking({ future ->
int id = i
println "Running " + id
java.lang.Thread.sleep(1000)
println "Thread done " + id
future.complete()
}, true , { res ->
if (res.succeeded()) {
print "."
} else {
print "x"
}
jobFuture.complete()
})
}
Notice the jobFuture creation:
Future jobFuture = Future.future()
futureList.add(jobFuture)
As well as completion:
jobFuture.complete()
Now the CompositeFuture.join(futureList) handler will be executed only after all jobs complete.