Memcache lock implementation for drupal 6

Changing title and status since there is a patch to be reviewed.

I've done some initial testing of this and it appears to work. I'm rather surprised that this port is in fact a single line change, but I guess thats a good thing.

-N

How I can implement this? This is new file, we need only to copy it in the memcache module folder?

@teri@uhaaa.com, you'd include the memcache-lock.inc file in your sites/all/modules/memcache directory, then add
$conf['lock_inc'] = './sites/all/modules/memcache/memcache-lock.inc'; in settings.php.

Note that if this gets committed I'm changing the file to memcache_lock.inc - it drives me nuts that the memcache-session.inc file has a dash instead of underscore.

Where does this file/variable get used in code?
Having added the line in #4 to settings.php and stored the file of #1 (renamed to memcache-lock.inc, of course), nothing changed with this patch regarding low hit-rates. But i couldn't find any place in the code, where this file/variable is ever used ... so am i missing a small but important information here?

It is a memcache implementation that replaces http://api.drupal.org/api/drupal/includes--lock.inc - it should help with contention on high traffic sites, the low hit rate issue is a separate problem being dealt with in #911232: A high percentage of getMulti operations are failing to hit cache.

I have committed this include file to the D6 project, thanks!

We now need patches to update the documentation. Marking as needs work.

This totally did not work for me. I tested in my staging env and everything worked fine. I deployed to production and the site just fell over. Pages mostly would time out, but a few would load. I tried a few times to be sure that this was the problem.

This is unfortunate as semaphore queries are showing in my slow query log. Perhaps something is initiating locks on a regular basis that shouldn't be.

@dalin - please try the latest dev of memcache - it has some fixes for the lock implementation. Also #969998: Shorter lock_wait() polling time will allow processes to continue quicker once the lock becomes available.