Apologies in advance if this is tracked elsewhere but I didn't find anything on Phabricator :)
It happened more than once that while debugging some mediawiki memcache errors reported in logstash I came across reference to nutcrackerThis task was originally meant only to remove nutcracker from the MediaWiki's config, like the following:
https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2019.01.21/mediawiki?id=AWhum3hkzpjgITg6U7ZH&_g=h@44136fabut why not be bold and expand its scope!
A quick grep in mediawiki config reveals other things (the Redis bits are hidden):Nutcracker is currently used in the following:
wmf-config/mc-labs.php:$wgMainCacheType = 'nutcracker+mcrouter';
wmf-config/mc-labs.php:$wgObjectCaches['nutcracker-memcached'] = [
wmf-config/mc-labs.php:$wgObjectCaches['mcrouter+nutcracker'] = [
wmf-config/mc-labs.php: // old nutcracker consistent hash scheme (uses shard tag);
wmf-config/mc-labs.php: 'args' => [ 'nutcracker-memcached' ],
wmf-config/mc-labs.php:$wgObjectCaches['nutcracker+mcrouter'] = [
wmf-config/mc-labs.php: 'args' => [ 'nutcracker-memcached' ]
wmf-config/mc-labs.php: 'args' => [ 'mcrouter+nutcracker' ]
wmf-config/mc.php: ? [ '/var/run/nutcracker/nutcracker.sock:0' ][ ] MediaWiki's config - its only usage is for wikitech
wmf-config/mc.php: $wgMainCacheType = 'memcached-pecl'; // nutcracker only;[ ] Thumbor
The configuration on app/api appservers for memcached has been removed with https://gerrit.wikimedia.org/r/#/c/operations/puppet/+/510697, no mcrouter present
```and it will get applied upon the next round of reboots (so nutcracker will restart without impacting the session handling in Redis). We have tested the change in canaries and nothing weird has been noticed/reported/found.
Would it be possible to do a final clean up? If not, can we check if logstash errors like the above are problematic or not?
The idea for this task is to migrate tools using nutcracker to mcrouter (if possible) to avoid maintaining in the long run two code bases (the nutcracker's one is basically abandoned).