MySQL database connection errors... could modifying php.ini cause these...

MarkB423

The following errors are occurring on two different web sites... it seems like modifying php.ini may have caused them, but I am not certain... these errors are only intermittent, so I am not sure what the problem is:

Warning: MySQL: Link to server lost, unable to reconnect in /home/www/...snipped.../file.inc on line 9
Database error: pconnect(localhost, root, $Password) failed.
MySQL Error: ()
Session halted.

AND

Warning: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111) in /home/www/...snipped.../file.inc on line 59

Warning: MySQL Connection Failed: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111) in /home/www/purdwd.leverworks.com/www/inc/database.inc on line 59
Could not connect to MYSQL database on machine localhost.
Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)

Any ideas?

Sxooter

What lines did you change in php.ini?

Are you running out of backend connections?

Are you using persistant connects?

MarkB423

The only line that I modified was the include_path variable...

but is there any outside chance that anything else could have caused the problem in php.ini?

Yes, most scripts are using persistent connections, and I am not sure what you mean by running out of back end connections... does that mean too many scripts are accessing the MySQL db at the same time?

maximum pconnects and maximum links are both unlimited...

Also, the problem is only intermittent... I personally haven't seen the error yet, but this is what was reported...

Sxooter

The way Apache/PHP does persistant connections means that you HAVE to configure your database and web server in a very specific way or your site will die under load. Basically, your database has to be able to supply a connection to each possible apache child, since persistant connections live on a single apache backend and don't get shared across them.

I.e. if apache is configured for 150 children max, then your database has to be able to handle at least 150 concurrent connects.

But, since each backend uses a certain amount of memory sitting at idle, it may well be that having persistant connects will result in a slower site, since there's less memory left for apache and buffers and such.

The basic rule of PHP and persistant connects is to only use them when you HAVE to, and to test for load to make sure your config is right.

Unless you have tested your site under load and found that you need persistant connects to handle load, I'd recommend you stay away from them.