How to make subfolders of a host_volume accessible to docker

Nomad
1

hi there. is there a way to make sub directories of a hosted volume accessible to jobs without needing to define new host_volumes in a client stanza each time, and restarting the nomad agent on a node?

Let’s imagine I have a nomad client, with this stanza in /etc/nomad/nomad.hcl:

client {
  host_volume "persistent_data" {
    path = "/mnt/some-directory-for-nomad"
    read_only = false
  }
}

And later on I have defined a job where I want to access this persistent_data volume, like so:

# make the volume available above accessible
volume "persistent_data_available_to_task" {
  type      = "host"
  read_only = false
  source    = "persistent_data"
}

# make the directory /mnt/some-directory-for-nomad accessible to the job, 
# mounted as /var/lib/rabbitmq for a job to write to and persist data
volume_mount {
  volume      = "persistent_data_available_to_task"
  destination = "/var/lib/rabbitmq"
  read_only   = false
}

This is fine, but when I find scenarios where a a new job needs some persistence on the host, but I don’t want to allow the other job to access the data, I need to define a new host_volume:

client {
  host_volume "persistent_data" {
    path = "/mnt/some-directory-for-nomad"
    read_only = false
  }

  host_volume "another_persistent_data" {
    path = "/mnt/a-different-directory-for-nomad"
    read_only = false
  }
}

And then, to be able to access this new host_volume in a different job I need to do this:

# make the volume available above accessible
volume "persistent_data_available_to_another_job" {
  type      = "host"
  read_only = false
  source    = "another_persistent_data"
}

# make the this second directory accessible to this job now
volume_mount {
  volume      = "persistent_data_available_to_another_job"
  destination = "/var/lib/some-other-programme"
  read_only   = false
}

I can do this, but it’s a pain, because I need to update the nomad client information then restart it each time to make the volume available.

Can I just make a subdirectory of a host volume accessible instead?

What I want to do is this - I want to define a persistent directory that the nomad client can make available to jobs, and that jobs can access between allocations. So in /etc/nomad.hcl I might have this:

client {
  host_volume "persistent_data" {
    path = "/mnt/some-directory-for-nomad"
    read_only = false
  }
}

And then in each of the jobs, I’d have something like this:

# make the volume available above accessible just to job_one
volume "persistent_data_available_to_just_one_job" {
  type      = "host"
  read_only = false
  source    = "persistent_data"

  # this isn't in the volume API, but I wish it was
  path        = "some-sub-directory-for-first-job"
}

then in another job, I’d be able to do something like this:

# make the volume available above, accessible just to the second job
volume "persistent_data_available_to_just_second_job" {
  type      = "host"
  read_only = false
  source    = "persistent_data"

  # again, wishful thinking
  path      = "some-sub-directory-for-second-job"
}

volume_mount {
  volume      = "persistent_data_available_to_just_second_job"
  destination = "/var/lib/rabbitmq"
  read_only   = false
}

Is something like this supported?

I see some extra config options for the client config pertaining to docker, like setting docker.volumes.enabled, but this isn’t something I’m familiar with yet - so apologies if this is already supported:

2

Seems like I’m looking for the same thing in my post (here)[Intermittent I/O Errors While Using NFS CSI plugin - #12 by nopersonalspace]. Anyone know a solution to this?