I'm using Scout to monitor a Rails app of mine. What I'm noticing is
that all of the pages in the site take a fraction of a second to
complete. This is totally acceptable. However, occasionally I'll have
a request that takes 189 seconds to complete. It's very consistent. A
request takes a fraction of a second 99% of the time and takes either
189 seconds or 3.5 seconds that last 1% of the time. Naturally, that
1% of the time is when clients, friends, family, etc. are viewing the
site. The actual page that takes 189 or 3.5 seconds to process varies
- sometimes it is the homepage, sometimes it is something like the
About Us page.
My server setup is as follows. The server is a quad-core machine with
2GB of RAM running RHEL 5. I'm using Nginx as the proxy and
mongrel_cluster running 15 mongrel instances. Other than that, I've
got MySql, Sphix, and backgroundRB runnning. The server is under very
low utilization, only getting a few hundred visitors a day and never
consuming more than 1% of the processor and 50% of the memory.
Does anyone have any ideas on how best to troubleshoot this?