How can I make sure that I don't accidentally terminate a server that has active sessions?
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Background Information
In the Cloud, you should always use discretion before terminating servers. Remember, if you terminate a server, you will end any active sessions. For example, let's say you're performing a minor software upgrade in the Cloud where you're replacing old application servers with new ones. Although, you've already removed the old application servers from the load balancing pool so that they will no longer receive any new requests by running the LB app to HA proxy disconnect operational RightScript, it's important that you still preserve any active sessions during this upgrade. You need to find a way of determining when the old application servers are no longer being used so that you can safely terminate the servers.
Answer
There are several different ways that you can check to make sure that a server is no longer being used.
- Check a Server's Apache monitoring graphs for active sessions under its Monitoring tab.
- Check the TTL on your application servers. Once its TTL has expired, it's safe to terminate the server.
- Configure Apache so that it automatically shuts down when no connections exist. See example code below.
$ httpd -k graceful-stop
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