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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