nginx ssl session caching

[Sreekanth M]

Hi,
I am doing ssl session caching using the NGINX shared memory cache and getting high response times in load testing.
Test setup:
clients ------->  NGINX --------> server
Client sends around 200 Requests/sec  and 50% of requests reuses ssl session.
NGINX version is 1.0.10 and OpenSSL version used is OpenSSL 1.0.1e-fips 11 Feb 2013.

Test Results:

Test shows that the connect time increases to 200 secs at time t = 700s (refer session_caching.png attachment). This looks like an issue with OpenSSL framework as there is some delay in processing SSL requests over period of time. 
Please note that the connect  time is just 70 ms when external session caching is OFF (refer no_session_caching.png attachment).
Has anyone faced similar issues with OpenSSL + NGINX  testing ? 
Any feed back would be appreciated.
Thanks,Sreekanth
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