This is a good question. It looks like a fairness mechanism should be in
place to ensure that a thread under high message pressure will stop in a
timely manner.
On the other hand, I think it's reasonable to assume that the
application that does feature such a high throughput message source
would also send _that_ thread a termination message. That means that the
high-frequency message emitter will ultimately stop, then the pressured
receiver will stop too, and everybody's happy.
I suggest we continue with this strategy and only tweak it if the
necessity appears.
Andrei
On 6/17/10 7:53 PDT, Sean Kelly wrote:
Section 13.8 of TDPL has this to say on how thread termination should behave:
"The most important manifestation of the owner/owned relationship is that when the
owner thread terminates, the calls to receive in the owned thread will throw the Own- 5
erTerminated exception. The exception is only thrown if receive has no more match- ing
messages and must wait for a new message; as long as receive has something to fetch from
the mailbox, it will not throw. In other words, when the owner thread termi- nates, the
owned threads’ calls to receive (or receiveOnly for that matter) will throw
OwnerTerminated if and only if they would otherwise block waiting for a new message."
This is how it's currently implemented, but I've been wondering about this
behavior vs. simply throwing when processing of the message queue encounters
the OwnerTerminated message. If an owned thread receives a steady stream of
messages from other sources, it will never terminate under the current model.
Is this really the desired behavior? I think a case could be made either way,
but I haven't come up with a conclusive argument in support of either approach.
I mostly bring this up because the current behavior treats the OwnerTerminated
message differently from all other messages, and I'm wondering if the special
treatment is warranted. The file copy example would work exactly the same
either way. The only difference would be with more complex cases where an
owned thread was talking to other threads as well.
Thoughts?
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