PersistentVolumeClaim

container services, tasks and tests can all mount volumes using this module type. To mount a volume, you need to define a volume module, and reference it using the volumes key on your services, tasks and/or tests.

Example:

kind: Module
name: my-volume
type: persistentvolumeclaim
spec:
  accessModes: [ReadWriteOnce]
  resources:
    requests:
      storage: 1Gi
---
kind: Module
name: my-module
type: container
services:
  - name: my-service
    replicas: 1  # <- Important! Unless your volume supports ReadWriteMany, you can't run multiple replicas with it
    volumes:
      - name: my-volume
        module: my-volume
        containerPath: /volume
    ...

This will mount the my-volume PVC at /volume in the my-service service when it is run. The my-volume module creates a PersistentVolumeClaim resource in your project namespace, and the spec field is passed directly to the same field on the PVC resource.

Notice the accessModes field in the volume module above. The default storage classes in Kubernetes generally don't support being mounted by multiple Pods at the same time. If your volume module doesn't support the ReadWriteMany access mode, you must take care not to use the same volume in multiple services, tasks or tests, or multiple replicas. See Shared volumes below for how to share a single volume with multiple Pods.

You can do the same for tests and tasks using the tests.volumes and tasks.volumes fields. persistentvolumeclaim volumes can of course also be referenced in kubernetes and helm modules, since they are deployed as standard PersistentVolumeClaim resources.

Take a look at the persistentvolumeclaim and container module reference docs for more details.

Shared volumes

For a volume to be shared between multiple replicas, or multiple services, tasks and/or tests, it needs to be configured with a storage class (using the storageClassName field) that supports the ReadWriteMany (RWX) access mode. The available storage classes that support RWX vary by cloud providers and cluster setups, and in many cases you need to define a StorageClass or deploy a storage class provisioner to your cluster.

You can find a list of storage options and their supported access modes here. Here are a few commonly used RWX provisioners and storage classes:

• NFS Server Provisioner

• Azure File

• AWS EFS Provisioner

• Ceph (via Rook)

Once any of those is set up you can create a persistentvolumeclaim module that uses the configured storage class. Here, for example, is how you might use a shared volume with a configured azurefile storage class:

kind: Module
name: shared-volume
type: persistentvolumeclaim
spec:
  accessModes: [ReadWriteMany]
  resources:
    requests:
      storage: 1Gi
  storageClassName: azurefile
---
kind: Module
name: my-module
type: container
services:
  - name: my-service
    volumes:
      - &volume   # <- using a YAML anchor to re-use the volume spec in tasks and tests
        name: shared-volume
        module: shared-volume
        containerPath: /volume
    ...
tasks:
  - name: my-task
    volumes:
      - *volume
    ...
tests:
  - name: my-test
    volumes:
      - *volume
    ...

Here the same volume is used across a service, task and a test in the same module. You could similarly use the same volume across multiple container modules.