Memcache get() failure

I am facing some issues with memcached under heavy load.

I am using ab to stress test my site. I use one instance of memcached to store php sessions and another one to store objects.

While benchmarking the site, I often get exceptions from the site which have to do w开发者_运维知识库ith failing get() from memcache.

The key definitely exists in memcached.

I have configured max connections to 4096 and I run ab as

ab -c 200 -t 60

I am using php-memcache-2.2.6 client library.

Also I am monitoring memcached during the test and the

curr_connections variable never goes higher than 250

Additionally, listen_disabled_num is 0

What could be causing such failures?

Thanks

It turns out that iptables was the culprit of all my problems.

It was blocking requests when the number was increasing

Stopping the damned thing solved all my problems.

Hope it will help someone in the future