We are trying to write a web backend using google app engine. We have several different pages but they have a lot of stuff in common. So far I've gotten our cost per average user per month down to about 9 cents, but I feel like that's still too expensive. Our php code runs into 2 bottlenecks right now, sessions with memcache and mysql database connections.
So a request to one of our pages might look like this:
- Get session data: 20ms ( uses memcache )
- Open mysql connection: 20ms ( using mysqli )
- Call stored procedure in mysql ( 2-3 ms )
- Total: 50ms
For the session info, an interesting note is that the Trace page on the App Engine Dashboard shows memcache RPC taking only 1ms, yet when I log out with time stamps how long it takes, it looks like it's around 20ms before the code can continue executing.
It seems to me that maybe we should change our sessions to use the database, because then we'd only have to open the connection once and hopefully the query for adding session data would be just as fast as our other query at 2-3 ms. So maybe that would reduce 15ms if I'm lucky, but would be a decent amount of work.
Then I've also read that you can do persistent database connections or connection pooling for mysql, which maybe could reduce the other 20ms for connecting to the database. However, thus far I haven't been able to figure out how to do that. The standard of using "p:" in the hostname for mysqli_connect doesn't seem to be supported on App Engine, since if you don't pass in null for the first parameter it errors out. When I try to do it with PDO I get an error 500 every 5 requests that I haven't been able to figure out and regular mysql_pconnect is deprecated on the php website, so I figured I shouldn't use that.
Any thoughts on what can be done? It seems like this is a relatively simple problem that other people must have solved before, but despite my searching I can't find a good resource on how to set up the connection pooling or using persistent connections for google app engine.