On 2/11/2017 3:46 AM, Peter Levart wrote:
On 11/01/17 13:34, David Holmes wrote:
On 1/11/2017 10:20 PM, Peter Levart wrote:
On 11/01/17 10:04, David Holmes wrote:
On 1/11/2017 6:16 PM, Peter Levart wrote:
On 11/01/17 02:49, David Holmes wrote:
Hi Roger,
On 31/10/2017 11:58 PM, Roger Riggs wrote:
Hi Peter,
Only native resources that do not map to the heap allocation/gc
cycle need any kind
of cleanup. I would work toward a model that encapsulates the
reference to a native resource
with a corresponding allocation/release mechanism as you've
described here and in the
thread on zip.
For cleanup purposes, the independence of each resource may
improve robustness
by avoiding dependencies and opportunities for entanglements and
bugs due to exceptions
and other failures.
In the case of TPE, the native resources are Threads, which keep
running even if they are
unreferenced and are kept referenced via ThreadGroups.
I don't know the Executor code well enough to do more than
speculate, but would suggest
that a cleaner (or similar) should be registered for each thread .
Threads are not native resources to be managed by Cleaners! A live
Thread can never be cleaned. A dead thread has nothing to clean!
Right, but an idle thread, waiting for a task that will never come
since the only entry point for submitting tasks is not reachable
(the pool), may be cleaned...
cleaned? It can be interrupted if you know about it and find locate
it. But it will not be eligible for cleaning ala Cleaner as it will
always be strongly reachable.
Ah I see what you meant before. Yes, tracking Thread object with a
Cleaner does not have any sense. But tracking thread pool object with
a Cleaner and cleaning (stopping) threads as a result makes sense...
No, because live Threads will keep the thread pool strongly reachable.
If you manage to structure things such that the Threads don't keep the
pool strongly reachable then you risk having the pool cleaned while
still actively in use.
Pool is actively in use when it is still reachable. Only in that case
can new tasks be submitted. When it is not reachable any more, no new
tasks can be submitted and it can be shutdown():
/**
* Initiates an orderly shutdown in which previously submitted
* tasks are executed, but no new tasks will be accepted...
Didn't we already determine that a Cleaner can't call shutdown() because
that requires a strong reference it doesn't have?
I think Doug already summed this up. The existing finalize() is
pointless because when it could be called there is nothing left to be
"cleaned up". There's no need for any use of Cleaner (even if it could
do anything useful).
David
Regards, Peter
