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Docker Swarm Hetzner Cloud CSI plugin

Currently in Beta. Please consult the Docker Swarm documentation for cluster volumes (=CSI) support at https://github.com/moby/moby/blob/master/docs/cluster_volumes.md

The community is tracking the state of support for CSI in Docker Swarm over at https://github.com/olljanat/csi-plugins-for-docker-swarm

How to install the plugin

Run the following steps on all nodes (especially master nodes). The simplest way to achieve this

  1. Create a read+write API token in the Hetzner Cloud Console.

  2. Install the plugin

Note that docker plugins without a tag in the alias currently get :latest appended. To prevent this from happening, we will use the fake tag :swarm instead.

docker plugin install --disable --alias hetznercloud/hcloud-csi-driver:swarm --grant-all-permissions hetznercloud/hcloud-csi-driver:<version>-swarm
  1. Set HCLOUD_TOKEN
docker plugin set hetznercloud/hcloud-csi-driver:swarm HCLOUD_TOKEN=<your token>
  1. Enable plugin
docker plugin enable hetznercloud/hcloud-csi-driver:swarm

How to create a volume

Example: Create a volume with size 50G in Nuremberg:

docker volume create --driver hetznercloud/hcloud-csi-driver:swarm --required-bytes 50G --type mount --sharing onewriter --scope single hcloud-debug1 --topology-required csi.hetzner.cloud/location=nbg1

We can now use this in a service:

docker service create --name hcloud-debug-serv1   --mount type=cluster,src=hcloud-debug1,dst=/srv/www   nginx:alpine

Note that only scope single is supported as Hetzner Cloud volumes can only be attached to one node at a time

We can however share the volume on multiple containers on the same host:

docker volume create --driver hetznercloud/hcloud-csi-driver:swarm --required-bytes 50G --type mount --sharing all --scope single hcloud-debug1 --topology-required csi.hetzner.cloud/location=nbg1

After creation we can now use this volume with --sharing all in more than one replica:

docker service create --name hcloud-debug-serv2  --mount type=cluster,src=hcloud-debug2,dst=/srv/www   nginx:alpine
docker service scale hcloud-debug-serv2=2

How to resize a docker swarm Hetzner CSI volume

Currently, the Docker Swarm CSI support does not come with support for volume resizing. See this ticket for the current state on the Docker side. The following explains a step by step guide on how to do this manually instead.

Please test the following on a Swarm with the same version as your target cluster as this strongly depends on the logic of docker volume rm -f not deleting the cloud volume.

Steps

  1. Drain Volume
docker volume update <volume-name> --availability drain

This way, we ensure that all services stop using the volume.

  1. Force remove volume on cluster
docker volume rm -f <volume-name>
  1. Resize Volume in Hetzner UI
  2. Attach Volume to temporary server manually
  3. Run resize2fs manually
  4. Detach Volume from temporary server manually
  5. Recreate Volume with new size to make it known to Swarm again
docker volume create --driver hetznercloud/hcloud-csi-driver:swarm --required-bytes <new-size>  --type mount   --sharing onewriter   --scope single <volume-name>
  1. Verify that volume exists again:
docker volume ls --cluster