On 31/10/2017 5:36 PM, Peter Levart wrote:
On 10/31/17 05:12, David Holmes wrote:
On 31/10/2017 1:02 AM, David Lloyd wrote:
On Mon, Oct 30, 2017 at 9:43 AM, Roger Riggs <[email protected]>
wrote:
ThreadPoolExecutor has a responsibility to cleanup any native
resources it
has allocated (threads) and it should be free to use whatever
mechanism is appropriate.
I wonder though whether TPE.finalize() is ever actually hit in
practice: TPE is (by definition) a thread pool, and every live thread
in that pool has (by way of TPE.Worker) a strong reference to the TPE
itself via an outer class reference which is passed around in enough
places to make me think that it would never actually be collectable in
a real-world situation, unless all core threads were allowed to time
out.
The docs for TPE cover this in detail: [1]
Finalization
A pool that is no longer referenced in a program AND has no
remaining threads will be shutdown automatically. If you would like to
ensure that unreferenced pools are reclaimed even if users forget to
call shutdown(), then you must arrange that unused threads eventually
die, by setting appropriate keep-alive times, using a lower bound of
zero core threads and/or setting allowCoreThreadTimeOut(boolean).
I'm trying to understand the purpose of finalize() in TPE, but can't.
I'm surely missing something. If the pool is no longer referenced AND
there are no active threads, what is there left to shutdown() actually?
All that remains is garbage that will eventually be GCed.
Ummmmm .... I'm going to have to do some archaeology here ...
David
Regards, Peter
David
-----
[1]
https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/ThreadPoolExecutor.html
