OpenVZ: Choosing right MySQL-Server depending on host
- by Scheintod
What I have:
Two servers running Wheezy/OpenVZ with
One MySQL container on each host master/master replicated (mysql1/mysql2)
Replicated DNS on each host (dns1/dns2)
different web-containers on each host but regulary backuped to the other.
What I want:
Each container should use the "local" MySQL-Server (the one which runs on the same hardware-node). I'd like to be able to move the web-containers between the to hosts. Each container should choose the MySQL-Server (semi) automatically. This scheme should continue working if one host is down.
What I tried:
Currently I'm keeping track on which container should run on which host by DNS entries which are queries by scripts e.g. for questions like: "Which container should be backuped on/to which host."
For choosing the right MySQL server I have one extra entry like "mysql.container_abc" which resolves to either mysql1/mysql2. So in the applications in the container I can use "mysql.container_abc" for e.g. mysql_connect and if I want to move the container around I just need to change the dns.
Now I notices one problem with this approach: Every mysql_connect generates one DNS query because the dns is not cached and this slows the request down unnecessarily.
What I would like better:
Some way of passing the information on which host we are running to the container and using it directly instead of using DNS. E.g. some way of setting a custom /etc/hosts entry in the container. Or any other great idea. Doesn't have to include DNS but shouldn't require to much special "magic" inside the container.
