How to notify POD in statefull set about other PODS in Kubernetes

Question

I was reading the tutorial on deploying a Cassandra ring and zookeeper with statefulsets. What I don't understand is if I decide to add another replica into the statefulset, how do I notify the other PODS that there is another one. What are best practices for it? I want to be able for one POD to redirect request to another POD in my custom application in case the request doesn't belong to it (ie. it doesn't have the data)

Answer 1

Well, seems like you want to run a clustered application inside kubernetes. It is not something that kubernetes is directly responsible for. The cluster coordination for given solution should be handled within it, and a response to a "how to" question can not be generic.

Most of the softwares out there will have some kind of coordination, discovery and registration mechanism. Be it preconfigured members, external dioscovery catalog/db or some networ broadcasting.

StatefulSet helps a lot in it by retaining network identity under service/pod, or helping to keep storage, so you can ie. always point your new replicas to register with first replica (or preferably one of the first two, cause what if your no.1 is the one that restarted), but as a wrote above, this is pretty much depending on capabilities available on the solution you want to deploy.