how to determine which PHP code opens MySQL connections that aren't getting closed

Question

We have an application that is comprised of a couple of off the shelf PHP applications (ExpressionEngine and XCart) as well as our own custom code.

I did not do the actual analysis so I don't know precisely how it was determined, but am not surprised to hear that too many MySQL connections are being left unclosed (I am not surprised because I have been seeing significant memory leakage on our dev server, where over the course of a day or two, starting from 100MB upon initial boot, the entire gig of ram gets consumed, and very little of it is cached).

So, how do we go about determining precisely which PHP code is the culprit? I've got prior experience with XDebug, and have suggested that, when we've gotten our separate, staging environment reasonably stable, that we retrofit XDebug on dev and use that to do some analysis. Is this reasonable, and/or does anybody else have more specific and/or additional suggestions?

Answer 1

You can use the

 SHOW PROCESSLIST  

SQL command to see what processes are running. That will tell you the username, host, database, etc that are in use by each process. That should give you some idea what's going on, especially if you have a number of databases being accessed.

More here: https://dev.mysql.com/doc/refman/8.0/en/show-processlist.html