Implement Timeout for MemcacheLock

[sqlalchemy-bot]

Migrated issue, originally created by Anonymous

Similar to the REDIS backend, the Memcache backend supports distributed locking. It looks like there is no lock_timeout configurable for the distributed lock in Memcached:

https://bitbucket.org/zzzeek/dogpile.cache/src/4c19440ad41a8f36ddf6ae41618a7f3b7fb8dd32/dogpile/cache/backends/memcached.py?at=master#cl-34

Compared to redis: https://bitbucket.org/zzzeek/dogpile.cache/src/4c19440ad41a8f36ddf6ae41618a7f3b7fb8dd32/dogpile/cache/backends/redis.py?at=master#cl-106

This means that in some cases you could achieve a state with bad locking that could cause a (near) endless loop.

[sqlalchemy-bot]

Morgan Fainberg () wrote:

Whoops, wasn't logged in when I reported this. Tagging my name to it. If i get a chance in the next couple days I'll submit a pull request.

[sqlalchemy-bot]

Michael Bayer (zzzeek) wrote:

it's easy for us to support timeout for the redis lock because we are using the lock implementation that comes with the Python redis client. If such a lock exists for memcached, that might be preferable (e.g. if there's something on pypi which is widely used and super-well-written, I'd consider it). otherwise, if submitting a pull req please try to make sure the timeout parameter is tested and does what it advertises.

[sqlalchemy-bot]

Morgan Fainberg () wrote:

I have some tentative code that I'm using in a wrapper for dogpile. I'll see if I can distill it. Of course, testing in this case is super important. I will 2x check to see if we have some "lock" mechanism that makes sense to use on pypi before trying to use the more-domain specific code I've developed.

[sqlalchemy-bot]

Matthew Phipps () wrote:

Morgan, did you figure this out?

[sqlalchemy-bot]

Morgan Fainberg () wrote:

Finally got around to contributing the code, This is addressed in pull-request: https://bitbucket.org/zzzeek/dogpile.cache/pull-request/31/add-in-timeout-for-memcache-distributed/diff

[sqlalchemy-bot]

Michael Bayer (zzzeek) wrote:

updated to pr: https://bitbucket.org/zzzeek/dogpile.cache/pull-requests/37/unit-tests-are-passing-with-the-time-in/diff

[sqlalchemy-bot]

Michael Bayer (zzzeek) wrote:

• changelog for ref Implement Timeout for MemcacheLock #54

→ 2af09b2

[sqlalchemy-bot]

Michael Bayer (zzzeek) wrote:

pr is merged

[sqlalchemy-bot]

Changes by Michael Bayer (zzzeek):

• changed status to closed