[openssl-dev] ssl external session caching

[Sreekanth M]

Hi,
I was doing load testing using openssl external session caching feature and was facing some issues. Details are as below:
Test setup
I used nginx-1.0.10 and tested it for shared memory cache.  Client sends around 200 Requests/sec  and 50% of requests reuses ssl session.
OpenSSL version used is OpenSSL 1.0.1e-fips 11 Feb 2013.
The operational mode used for session caching is as below:
SSL_CTX_set_session_cache_ mode(ssl->ctx, SSL_SESS_CACHE_ SERVER | SSL_SESS_CACHE_NO_INTERNAL);
SSL_SESS_CACHE_NO_INTERNAL is to ensure that OpenSSL does not store sessions internally and do any internal lookups .

Results:I am seeing increase in response times and it looks like an issue with OpenSSL.  As you can see, the connect time increases over time from 30 ms (t = 100 s) to 120 ms (at t = 500 s).  Requests per sec remains the same over this time . 
I suspect the issue is with OpenSSL framework which does some operations over large lists. 
Please find attached the connect and request time graph for reference.
Any feed back would be appreciated.
Thanks,Sreekanth
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