As you begin to design availability monitoring for your cloud, there are at least three schools of thought on the kinds of checks that should be executed. These should be mixed and matched as you deem appropriate to establish the coverage you need to monitor the services in your OpenStack cluster. You may also come across other methods of designing health checks that can be mixed with what is discussed in this chapter.
The first type of check is the service status check. This type of check runs a simple Linux service status check on each of the services. If the service status script returns successfully that the service is running, the health check is successful. The problem with relying on these is that many OpenStack services have the ability to automatically heal from a loss of communication with each other. You can run a service check on an OpenStack service that is up and running but is actively attempting to reconnect to the database or to the message bus. OpenStack...