Kubernetes share files among pods without persistence

Question

Is there a way to share files among pods without persistence?

With persistence I just use ReadWriteMany accessMode and mount it to somewhere:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
  - ReadWriteMany
  storageClassName: some-sc
  resources:
    requests:
      storage: 1Gi

I need to do something like this without PVC or with PVC that uses a storage-class which just mimic persistence by using only the memory.

I could solve this with a different pod which redistributes the file by using K8s api.
But I feel it a bit overwhelming for a simple task like that.

Edit: using configmap is out of question because the file should be writable.

I don't think there's really a way to do this (how would the pods know what to mount without the PVC declaration? how would they share memory if they're on different nodes?). Can your application pass the content over HTTP, or use a message queue like RabbitMQ, instead of relying on a filesystem? — David Maze, Nov 13 '21 at 11:42
Does this answer your question? [How to share storage between Kubernetes pods?](https://stackoverflow.com/questions/31693529/how-to-share-storage-between-kubernetes-pods) — tmarwen, Nov 13 '21 at 12:01
Hi @beatrice, any progress? Did you thought about implementing a message queue? — Mikolaj S., Nov 18 '21 at 08:40

score 0 · Answer 1 · edited Nov 29 '21 at 09:27

Posted community wiki for better visibility with a general solution as there are no further details provided. Feel free to expand it.

As @DavidMaze mentioned in his comment:

I don't think there's really a way to do this (how would the pods know what to mount without the PVC declaration? How would they share memory if they're on different nodes?)

There is no such possibility in Kubernetes to share files among pods without persistence.

If you want to share storage between containers in the same pods you can take a look into emptyDir volume. It can use memory (tmpfs) system:

Depending on your environment, emptyDir volumes are stored on whatever medium that backs the node such as disk or SSD, or network storage. However, if you set the emptyDir.medium field to "Memory", Kubernetes mounts a tmpfs (RAM-backed filesystem) for you instead. While tmpfs is very fast, be aware that, unlike disks, tmpfs is cleared on node reboot and any files you write count against your container's memory limit.

As @DavidMaze mentioned in his comment, if your app is capable of passing the content over HTTP you can use a message queue:

Can your application pass the content over HTTP, or use a message queue like RabbitMQ, instead of relying on a filesystem?

Check RabbitMQ and Apache Kafaka.

Check also this topic with different answers/solutions about sharing storage between pods (but with persistence).

Hi @beatrice, if you find my answer helpful, please [consider up-voting / accepting it](https://stackoverflow.com/help/someone-answers). — Mikolaj S., Dec 02 '21 at 11:45

Kubernetes share files among pods without persistence

1 Answers1