Trying to create two MySQL pods in kubernetes with same volume for high availability

Question

I am trying to deploy two MySQL pods with the same PVC, but I am getting CrashLoopBackoff state when I create the second pod with the error in logs: "innoDB check that you do not already have another mysqld process using the same innodb log files". How to resolve this error?

Answer 1

There are different options to solve high availability. If you are running kubernetes with an infrastructure that can provision the volume to different nodes (fe in the cloud) and your pod/node crashes, kubernetes will restart the database on a different node with the same volume. Aside from a short downtime you will have the database back up running in a relatively short time. The volume will be mounted to a single running mysql pod to prevent data corruption from concurrent access. (This is what mysql notices in your scenario as well, since it is no designed for shared storage as HA solution)

If you need more you can use the built in replication of mysql to create a mysql 'cluster' which can be used even if one node/pod should fail. Each instance of the mysql cluster will have an individual volume in that case. Look at the kubernetes stateful set example for this scenario: https://kubernetes.io/docs/tasks/run-application/run-replicated-stateful-application/