Rescheduling timers doesn't work with asyncioreactor

[twisted-trac]

	@IlyaSkriblovsky reported
Trac ID	trac#9780
Type	defect
Created	2020-03-19 20:04:00Z

AsyncioSelectorReactor.callLater() returns DelayedCalls whose reset() method doesn't work as expected.

1. reset() to later time simply doesn't work: timer gets fired at original time

2. reset() to earlier works, but original internal asyncio's timer isn't cancelled and this causes an exception in AsyncioSelectorReactor's internal code

3. This is not neccessarily a bug, but worth to be fixed too: current implementation of AsyncioSelectorReactor.callLater() leaves many cyclically linked objects after timer is fired. For the app that uses timers heavily this leads to significally higher memory usage (and cpu too due to much more often GC invocations)

Here the gist with runnable demos of all three issues:
https://gist.github.com/IlyaSkriblovsky/58876c9f97c617875e7b739fd0447807

Also attaching graph of ram usage % on my servers that I've eventually tried to run on asyncioreactor instead of epollreactor, but was forced to rollback due to unusual memory usage.

Attachments:

• 2020-03-19_22-51.png (21486 bytes) - added by IlyaSkriblovsky on 2020-03-19 20:05:07Z - RAM Usage % graph that encouraged me to investigate the issue

Searchable metadata

trac-id__9780 9780
type__defect defect
reporter__IlyaSkriblovsky IlyaSkriblovsky
priority__normal normal
milestone__None None
branch__ 
branch_author__ 
status__closed closed
resolution__fixed fixed
component__core core
keywords__asyncio__callLater__review asyncio, callLater, review
time__1584648240812878 1584648240812878
changetime__1587596005321646 1587596005321646
version__None None
owner__Wim_Lewis__wiml_____ Wim Lewis <wiml@...>

[twisted-trac]

	@IlyaSkriblovsky commented

Link to PR: #1232

[twisted-trac]

	@wiml set owner to @wiml @wiml set status to closed

In changeset bc7fef3

#!CommitTicketReference repository="" revision="bc7fef3ed53d1b839089bb4d1fca8ff25ab76266"
Fix AsyncioSelectorReactor.callLater().reset() and fix memory leaks

Author: IlyaSkriblovsky
Reviewer: wiml, roderigc
Fixes: ticket:9780