Hey Joe,
I'm still using my Spring-Hibernate-CloudSQL framework, but I'm seeing some crazily unpredictable Cloud SQL response times. I have a trivial DB "poke" servlet that just opens a session, runs "SELECT 1", and reports an elapsed time. I have a cron job that hits the poke every five minutes and the execution time is all over the place. Here's a series of response times with me hitting the poke servlet and refreshing the page over and over again (in millis):
67
117
59
37
317
2764
2404
2080
35
28
1459
29
31
23
3959
68
132
The variability of these results just confounds me. If the code was doing something horribly inefficient, the results should be more uniformly terrible. But it's obviously capable of running the poke well enough. It's the 1000-3000ms responses that are freaking me out. I had zero other load during these tests.
On DB-heavy pages, *each* DB hit can scale up to similar 3000+ms times, causing the whole page to take an awful 12-15 seconds to load. And then the next request a second later might take 250ms.
At first I thought it was just a warmup issue (thus the creation of the poke task) -- and it does seem to do better when it's fielding constant requests -- but then a long load will happen again at unpredictable times (and not related to an /_ah/warmup).
I have some issues on my end -- Spring isn't closing my Hibernate connections and I can't figure out why. But as request load increases, I tend to see better, more stable performance. Obviously we'd expect the opposite if those stale connections were bogging down the system. I'm not using a connection pool layer with Hibernate.
I don't know if it's specifically a Cloud SQL issue, but that seems the most likely culprit at the moment.
What other info can I provide to help diagnose what's going on?
