Referencing Cluster volumes

[cherbst]

Description

If I am correct it is currently not possible to use cluster volumes in a docker-compose.yml file like with docker commands: https://github.com/moby/moby/blob/master/docs/cluster_volumes.md On the service level the volume directive only supports pipe,npipe,tmpfs and volume . Probably a cluster type should be added or the top level volumedirective needs a type parameter.

[ndeloof]

According to this doc, such a volume can be created by docker volume create with adequate driver options, and listed by docker volume ls. So you should be able to do the same with a top-level volume (not by service) entry to use the required driver and driver-opts, or refer to an external volume by name if you want to use an existing one.

[jhrotko]

@cherbst we will close this issue as it seems to have been answered. If you think that is not the case, please re-open this issue. Thank you for your contributions!

[ppignet]

As far as I understand the code, there is no translation between compose-/stack-defined cluster volume definitions and actual cluster volumes as of yet.

Service-level volume entries can hold a reference to a cluster volume by using the type cluster, but inlining cluster volume options is left out: https://github.com/docker/cli/blob/7b4cde69673ee7c1d6929749d1a639d748749804/internal/volumespec/types.go#L38-L40

Top-level volume definitions do have a key that is related to cluster volume options (x-cluster-spec, https://github.com/docker/cli/blob/7b4cde69673ee7c1d6929749d1a639d748749804/cli/compose/types/types.go#L478-L486), but specifying that in compose is explicitly ignored by the extensions syntax rule: https://docs.docker.com/reference/compose-file/extension/

So it looks like, cluster volumes can neither be managed nor used through compose files, AS OF YET

Based on what's present it would probably look like this once implemented:

volumes:
  my-volume:
    driver: my-csi-driver
    x-cluster-spec:
      group: <group>
      access_mode:
        scope: <scope>
        sharing: <sharing>
        mount_volume:
          fs_type: <fstype>
      capacity_range:
        required_bytes: <req_bytes>
        limit_bytes: <limit_bytes>
      secrets:
        - key: <some_key>
          secret: <some_docker_secret_id>
      #availability: "active"    # not sure if needed in spec or only at runtime
    driver_opts:
      driver_specific_opt_A: <some_value>
      driver_specific_opt_B: <some_value>

 services:
  my-service:
    ...
    volumes:
      - type: cluster
        source: my-volume
        target: "/target/path/in/container"