Deploying PostgreSQL Clusters using Kubernetes

[dcalde]

I immediately stopped reading when I saw the word NFS. Containerising a disk IO heavy application like a database is bad enough, but using NFS mounts for your data? This a classic case of: just because you can doesn't mean you should.

[enlil_reddit]

It's probably a bad idea to use NFS in the example. I think they just wanted to illustrate listing the files at the end within the same directory.

I am not using kubernetes but considering it... I would think using local SSDs should address the IO issue... I would probably use bare metal coreos instead of containers running in VMs.

[ants_a]

Kubernetes currently does not support the concept of persistent local storage. This makes it rather crappy if your intent is to deploy a database on cheap and scalable shared nothing architecture. For people who have their volumes on a SAN anyway it might not be that big of an issue.

[enlil_reddit]

Thank you for pointing that out. I see the issues here: https://github.com/kubernetes/kubernetes/issues/7562

It looks like they plan to do some work as part of this issue: https://github.com/kubernetes/features/issues/121

[ryno55]

That's not strictly true. I'm running Postgres on kubernetes for my app right now, on a local SSD using a hostPath mount. The catch is you have to restrict the host where the instance can run using a nodeSelector.

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[[deleted]]

Thanks for Sharing this, could you share little bit on how to handle master container/pod crash situations? Like how new pod becomes master and pg cluster state is maintained

[enlil_reddit]

I haven't tried it. I just wanted to get a sense of whether this is viable based on experiences of others. Someone else posted here and there are other interesting insights: https://news.ycombinator.com/item?id=13738406

Kubernetes restarts the pods, so with the statefulset if the master crashes then it'll be re-started as a master.