Nomad batch job not detaching volume

Nomad
1

Hi,
I’m using the Digital Ocean CSI plugin.
Volumes are mounted fine and released with a service job that completes (ie I stop the job).
However, if I use a batch job, that completes successfully, the volume stays attached to the nomad host where the job ran.

I created a very simple batch job using a linux container that lists the volume root to see this behaviour.

job "volume-batch-test" {
  datacenters = ["lon1"]
  priority = 20
  type = "batch"

  group "volume-batch-test" {
    
    volume "backup-volume" {
      access_mode     = "single-node-writer"
      attachment_mode = "file-system"
      per_alloc = false
      read_only = false
      source    = "volume-lon1-gcuk-staging-backup"
      type      = "csi"
      mount_options {
        fs_type     = "ext4"
      }
    }

    task "directory_ls" {
      driver = "docker"

      config {
        image = "rockylinux/rockylinux"
        command = "/bin/bash"
        args = [
          "-c",
          <<EOA
ls -l /var/lib/backups
EOA
        ]
      }

      volume_mount {
        volume      = "backup-volume"
        destination = "/var/lib/backups"
      }
    }
  }
}

The volume appears not to be attached to an allocation:

ID                   = volume-lon1-gcuk-staging-backup
Name                 = volume-lon1-gcuk-staging-backup
External ID          = xxxxx
Plugin ID            = do-block
Provider             = dobs.csi.digitalocean.com
Version              = v4.0.0
Schedulable          = true
Controllers Healthy  = 3
Controllers Expected = 3
Nodes Healthy        = 3
Nodes Expected       = 3
Access Mode          = <none>
Attachment Mode      = <none>
Mount Options        = <none>
Namespace            = default

Allocations
No allocations placed

Storage volume not mounted on the nomad client either.

But Digital Ocean has it attached to the host.

This doesn’t happen with service job, though, only batch.