Nginx shows error page from time to time

I am running a VPS on digitalocean. I have daily traffic of 500 unique users. I was having CPU and RAM utilization problems on Apache. Now I am using Nginx because it's lightweight. My CPU and RAM is under control but still Nginx shows an error message from time to time, which I believe is due to load/wrong configuration.

I am getting this error in my log files:

ngx_slab_alloc() failed: no memory in SSL session

I have the following configuration for my nginx server:

keepalive_timeout 20;
ssl_session_timeout 7200m;
ssl_session_cache shared:SSL:150m;
ssl_stapling on;
ssl_stapling_verify on;
add_header Strict-Transport-Security max-age=15768000;

What is the right configuration for me, considering I am running a VPS with 1Gb RAM?

Would using a database sessions table (as in Laravel) solve my problem, independent from the Nginx configuration?

1 Answer

Reduce ssl_session_timeout and ssl_session_cache values. Please check the link for nginx https server configuration and server optimization.