Re: [X-POST] PHP script to make sure MySQL is up?

On Thu, March 1, 2007 1:37 pm, Brian Dunning wrote: > I host at Rackspace, and one thing that their monitoring service does > NOT catch is a problem when too many connections hit MySQL, and for > some reason it remains hung up until the service is manually > restarted. In the meantime, this is happening to us once or twice a > month. It gets hammered with a huge number of brief connections from > other Apache servers. > > Slow queries and mysql_close() are NOT the problem. It's just too > many connections, even though they're super fast. Are you using mysql_pconnect? Because that is essentially going to lock one MySQL connection to each Apache child, and if you have a bigger httpd.conf MAX_CHILDREN than you have /etc/my.cnf number of connections, then, by definition, you are going to have problems all the time, because you have more "users" than "connections" available. Note also that each username/password gets its own persistent connection, so if you have two DB roles in your application, then you have just doubled the number of connections needed. In something like a shared hosting environment, pconnect is probably a death knell, since every little user will be tying up a connection for their app. There are, of course, ways around this, such as dedicated apache pools per client, or super-short connection time-out on the persitence or... But most shared hosts aren't going to go to this length. > Is there such a thing as a PHP script that I can put on a cron job to > run every minute and make a test query, and upon failure, restart the > service and maybe send an email to Rackspace support? I don't know > how you'd check that the query was refused due to too many > connections, and I also don't know how PHP would restart the MySQL > service. I think mysql_connect should be providing you with a nice error message if this does happen. Are you checking mysql_error right after your mysql_connect call? And you almost-for-sure don't want any random old php script capable of bouncing the MySQL server... [shudder] -- Some people have a "gift" link here. Know what I want? I want you to buy a CD from some starving artist. http://cdbaby.com/browse/from/lynch Yeah, I get a buck. So?