kubernetes - Ignite ReadinessProbe

Question

Deploying an ignite cluster within Kubernetes, I cam across an issue that prevents cluster members from joining the group. If I use a readinessProbe and a livenessProbe, even with a delay as low as 10 seconds, they nodes never join each other. If I remove those probes, they find each other just fine.

So, my question is: can you use these probes to monitor node health, and if so, what are appropriate settings. On top of that, what would be good, fast health checks for Ignite, anyway?

Answer 1

Update:

After posting on the ignite mailing list, it looks like StatefulSets are the way to go. (Thanks Dmitry!)

I think I'm going to leave in the below logic to self-heal any segmentation issues although hopefully it won't be triggered often.

Original answer:

We are having the same issue and I think we have a workable solution. The Kubernetes discovery spi lists services as they become ready.

This means that if there are no ready pods at startup time, ignite instances all think that they are the first and create their own grid.

The cluster should be able to self heal if we have a deterministic way to fail pods if they aren't part of an 'authoritative' grid.

In order to do this, we keep a reference to the TcpDiscoveryKubernetesIpFinder and use it to periodically check the list of ignite pods.

If the instance is part of a cluster that doesn't contain the alphabetical first ip in the list, we know we have a segmented topology. Killing the pods that get into that state should cause them to come up again, look at service list and join the correct topology.