One of the things I wish I had found in Google faster when trying to figure out why PHP script refuses to connect to remote MySQL server issuing an error SQLSTATE[HY000] [2003] Can't connect to MySQL server on 'xxx.xxxx.xxx.xxx' (13) I am able to connect from local shell, so first thought was if something wrong with recent Zend Framework upgrade, but after a while I figured out that answer is very simple – SELinux was blocking remote connections from PHP scripts executed by Apache web server. The error code (13) at the end of error message means “permission denied”, so that’s...

We are using FogBugz application for the bugs and support requests tracking. And it’s configured to receive support@companyname.com emails (means tons of spam). Once the database size hit approximately 20,000 requests, we started really wonder: why so slow? It looks like there was another table BugEvent which size is around 200,000 records at that time. It could be some other application, could be your own code. Doesn’t matter – just it happens, one database size grows, performance of the application is degrading. First step to troubleshoot – enable slow queries log in the MySQL...