In diagnosing a situation where a Pike deployment was intermittently slower (in general), I discovered that it was (sometimes) exceeding memcached's maximum connection limit, which is set to 4096.

Looking closer, ~2750 of the connections are from 8 neutron-server process. neutron-server is configured with 8 API workers, and those 8 processes have a combined total of ~2750 connections to memcached:

# lsof -i TCP:11211 | awk '/^neutron-s/ {print $2}' | sort | uniq -c
    245 2611
    306 2612
    228 2613
    406 2614
    407 2615
    385 2616
    369 2617
    398 2618
#


There doesn't seem to be much turnover - comparing samples of the connections (incl. source port) 15 mins apart, two were dropped, and one new one added.

In neutron.conf, keystone_authtoken.memcached_servers is configured, but nothing else pertaining to caching, so keystone_authtoken.memcache_pool_maxsize should default to 10.

Am I misunderstanding something, or shouldn't I see a maximum of 10 connections from each of the neutron-server API workers, with this configuration?

Any known issues, or pointers to what I'm missing?

TIA,

    ~iain

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