Project: mesos
Issue MESOS-2891: Performance regression in hierarchical allocator.
For large clusters, the 0.23.0 allocator cannot keep up with the volume of slaves. After the following slave was re-registered, it took the allocator a long time to work through the backlog of slaves to add: {noformat:title=45 minute delay} I0618 18:55:40.738399 10172 master.cpp:3419] Re-registered slave 20150422-211121-2148346890-5050-3253-S4695 I0618 19:40:14.960636 10164 hierarchical.hpp:496] Added slave 20150422-211121-2148346890-5050-3253-S4695 {noformat} Empirically, [addSlave|https://github.com/apache/mesos/blob/dda49e688c7ece603ac7a04a977fc7085c713dd1/src/master/allocator/mesos/hierarchical.hpp#L462] and [updateSlave|https://github.com/apache/mesos/blob/dda49e688c7ece603ac7a04a977fc7085c713dd1/src/master/allocator/mesos/hierarchical.hpp#L533] have become expensive. Some timings from a production cluster reveal that the allocator spending in the low tens of milliseconds for each call to {{addSlave}} and {{updateSlave}}, when there are tens of thousands of slaves this amounts to the large delay seen above. We also saw a slow steady increase in memory consumption, hinting further at a queue backup in the allocator. A synthetic benchmark like we did for the registrar would be prudent here, along with visibility into the allocator's queue size.
Story points: 3