[PEAK] Re: [TransWarp] releasing component subtrees
Phillip J. Eby
pje at telecommunity.com
Tue Oct 21 15:45:14 EDT 2003
At 09:18 PM 10/21/03 +0300, alexander smishlajev wrote:
>Phillip J. Eby wrote, at 21.10.2003 18:45:
>>>our application from time to time is runnung tasks that should die after
>>>doing their job. but my colleague found that the dead tasks remain in
>>>memory because of circular references between parent and child
>>>components that are not detected by python gc.
>>Python doesn't do GC on objects that have __del__ methods. If you get
>>rid of the __del__ method in your example, the GC should run.
>thank you. it appears that nobody of our python programmers knew that.
>>There's an easier way, at least for your example. Declare your 'task1'
>>and 'task2' bindings as 'noCache=True'.
>i am sorry, i cannot figure out how to use 'noCache'. everything i try
>in this example ends up with the same result: 'task1' and 'task2' stop
>reporting their creation and run.
That sounds odd. noCache should result in task1 and task2 being created,
but then immediately discarded. Oh, I know what the problem is, and it's
almost explicitly documented in the current docstrings. :( When you use
noCache=True, suggestParent is effectively False, so the binding.Make
doesn't give the tasks parents, so they never do anything (because they
don't get an assembly event. Here's what you'd have to do:
task1 = binding.Make(lambda self: TestTask(self), noCache=True)
Then, referencing 'self.task1' should create the task, but not keep a
reference to it. (Of course, each subsequent reference to self.task1 will
also create a *new* task.)
>>>below is a simple example. it creates a task with two subtasks. each
>>>of these tasks terminates as soon as it is run. no reference is kept to
>>>the container task,
>>Not true; every component has a reference to its parent; that's how they
>>find their parents.
>of course. i meant that no reference is kept outside the subtree in
>question. sorry for being imprecise.
No problem. I just wanted to make sure that others were not confused;
that's why I challenge such imprecisions when they come up, to make sure
that nobody takes them as precise descriptions of how the system works.
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