在Kubernetes中的主机和Pod容器之间绑定挂载卷

Question

I have a legacy application that stores some config/stats in one of the directory on OS partition (eg /config/), and I am trying to run this as a stateful container in Kubernetes cluster.

I am able to run it as a container but due to the inherent ephemeral nature of containers, whatever data my container is writing to the OS partition directory /config/ is lost when the container goes down/destroyed.

I have the Kubernetes deployment file written in such a way that the container is brought back to life, albeit as a new instance either on same host or on another host, but this new container has no access to the data written by previous instance of the container.

If it was a docker container I could get this working using bind-mounts, so that whatever data the container writes to its OS partition directory is saved on the host directory, so that any new instance would have access to the data written by previous instance.

But I could not find any alternative for this in Kubernetes.

I could use hostpath provisioning, but hostpath-provisioning right now works only for single-node kubernetes cluster.

Is there a way I could get this working in a multi-node Kubernetes cluster? Any other option other than hostpath provisioning? I can get the containers talk to each other and sync-the data between nodes, but how do we bind-mount a host directory to container?

Thanks for your help in advance!

Answer 1

This is what you have Volumes and VolumeMounts for in your POD definition. Your lead about hostPath is the right direction, but you need a different volume type when you host data in a cluster (as you seen your self).

Take a look at https://kubernetes.io/docs/concepts/storage/volumes/ for a list of supported storage backends. Depending on your infrastructure you might find one that suits your needs, or you might need to actually create a backing service for one (ie. NFS server, Gluster, Ceph and so on).

If you want to add another abstraction layer to make a universal manifest that can work on different environments (ie. with storage based on cloud provider, or just manualy provisioned depending on particular needs). You will want to get familiar with PV and PVC ( https://kubernetes.io/docs/concepts/storage/persistent-volumes/ ), but as I said they are esntially an abstraction over the basic volumes, so you need to crack that first issue anyway.