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[whatwg] Workers: What can be done in a worker after call to close()?

From: Dmitry Titov <dimich@chromium.org>
Date: Tue, 30 Mar 2010 16:44:18 -0700
Message-ID: <z2m28040fc61003301644kf81dc233mf6301e645e20e16e@mail.gmail.com>
Hi!

Trying to fix some bugs for Workers, I've got some questions about close()
method on WorkerGlobalScope<http://www.whatwg.org/specs/web-workers/current-work/#workerglobalscope>
.

In particular, the spec seems to imply that after calling close() inside the
worker, the JS does not get terminated right away, but rather continue to
execute, while an internal 'closing' flag is set and a message
queue associated with the worker discards all the tasks, existing and
future. Also, all ports are immediately disentangled.

This seems to leave some questions without explicit answer, with differences
in current implementations:

1. Does this code in a worker continues looping until the parent page
unloads:
 ...
 close();
 while(true) {}

WebKit V8 terminates, WebKit JCS terminates after a timeout, FF does not
terminate.

2. Do the errors propagate back to Worker object after close()?
...
close();
nonExistingFunction();  <<-- throws, if not processed locally, posts error
info to the Worker object.

In WebKit and FF errors propagate, although it does not seem consistent
while worker closed all the ports and is in a dormant state.

3. Should synchronous operations work after close()? Asynchronous ones
perhaps should not, because of the event loop queue which is stopped...
...
close();
xhr.open("GET", "foo.com", *false*);
xhr.send();

WebKit: does not work (mostly), FF - does work.

Perhaps it would be simpler to either say nothing is executed/posted/fired
after close() (immediate termination), or to enable worker run unimpeded
(with ports open, etc) until it naturally yields from JS.

Any opinions?

Thanks,
Dmitry
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