Re: [cdi-dev] What, if any, guarantees are made about invoking asynchronous event observer methods?
Hi Laird,
if I understand you correctly, there is no guarantee for that in Weld. If you fire an
async event it will spin another thread (or more), where it will start notifying async
observers.
Only after it is done, it will come back to the main thread with result. There is no
synchronization around this - that would kind of go against the nature of truly
asynchronous calls, wouldn't it?
As for spec interpretation, I don't think the implication you suggest is intended
there.
It's a shame we haven't clarified this earlier though.
What exactly is your use case?
Matej
----- Original Message -----
From: "Laird Nelson" <ljnelson(a)gmail.com>
To: "cdi-dev" <cdi-dev(a)lists.jboss.org>
Sent: Thursday, May 11, 2017 9:30:17 PM
Subject: [cdi-dev] What, if any, guarantees are made about invoking asynchronous event
observer methods?
I'm using CDI 2.0 and Weld 3.0.0.CR2 in "SE mode".
If I fire an asynchronous event without any special notification options, my
understanding is that the container will arrange for that event to be
delivered to asynchronous observers.
Is (appropriate) asynchronous observer method invocation guaranteed to happen
at some point? Section 10.2.2 seems to hint that it is:
"Event fired [sic] with the fireAsync() method is [sic] fired asynchronously.
All the resolved asynchronous observers (as defined in Observer resolution)
are called in one or more different threads."
To me, this says that if I use fireAsync() to fire an event, then if I have a
(resolved) asynchronous observer method for it it will be notified before
the container closes no matter what.
(I believe I am observing a race condition somewhere in here that might show
that Weld's default asynchronous event delivery machinery does not actually
get around to delivering the event I've queued up before the container
closes. Sometimes the event is received, sometimes it is not. Obviously if
there is no such guarantee this could be permitted behavior.)
Best,
Laird
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