#35166: Return python-memcached support
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Reporter: Matej Spiller Muys | Owner: nobody
Type: New feature | Status: closed
Component: Core (Cache system) | Version: 5.0
Severity: Normal | Resolution: wontfix
Keywords: memcached | Triage Stage:
performance get_many | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Matej Spiller Muys):
We already have our own backend since Django 4.1 because of performance
issues.
> I forgot point out that this is not making a persuasive argument when
the linked issue that you have written contains no performance comparison.
It is really simple to reproduce/mesaure. We have 4 memcached servers on
AWS each having around 1 ms roundtrip.
Now if get_many needs to fetch from all 4, it takes 4 ms for pymemcache
(doing 4x loop of send & receive) and 1 ms for python-memcached (4x send
then 4x receive ...). I didn't write the measurements at that time because
it was clear to the author of pymemcache what the problem is and that is
would be solved if refactored the same way as python-memcached logic.
Basically you shouldn't wait for response after each send before sending
to another server (but hash.py in pymemcache just loops around base.py
code making it harder to optimise).
The author of pymemcache is using mcrouter that works the same as python-
memcached (first 4x send and then 4x receive). We don't want to use
mcrouter, it would help but still adds a bit of extra hop latency or as
alternative deploy it as side car with extra deploy complexity.
--
Ticket URL: <https://code.djangoproject.com/ticket/35166#comment:7>
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