NHC and List of supported problems

[Safadi Mohi]

What is the list of supported problems which could be detected by node Health check? as I read on FAQ

"Can I create my own definition of what counts as a healthy node?

Yes. Node Healthcheck determines node health based on NodeConditions. There are a set of basic conditions built into Kubernetes, but additional conditions can be defined and then referenced by Node Healthcheck. Node Problem Detector is a common tool for creating and updating NodeConditions based on log scraping.

It means that in case of FileSystem Readonly, or any another problem on the node, the NHC will not report that node is not ready?

so it supports just 
node condition

["Ready", "DiskPressure", "MemoryPressure", "PIDPressure" and "NetworkUnavailable"]

so such problem as [ReadonlyFilesystem] it won't be detected by NHC?

So to have better results, we have to run NHC and NDP on the node? with self node remediation?

how it looks like if we need to have best practices to detect all known issues on the node?

Node Problem detector has such list as below

https://github.com/kubernetes/node-problem-detector

[Marc Sluiter]

Hi.

Sorry, it's not clear to me what the actual question is.

NHC is looking at node conditions indeed. The condition types which trigger NHC can be configured in the NodeHealthCheck CR.

NHC does not care if those are "built in" condition types, or if they are set on the node by a 3rd party tool like Node Problem Detector.

Just be aware that NPD is not supported by Red Hat, in case that matters.

Hope this helps,

Marc

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[Safadi Mohi]

Ok, got it.

This what I wanted to get clear.

NHC is just checking node conditions which are ( DEFINED) for node. these node conditions could be defined by 3d part (as node-detect-problem). it just monitor these conditions and make some action in case if one is failed.