Join Windows worker nodes to your cluster

Estimated reading time: 7 minutes

Docker Enterprise Edition supports worker nodes that run on Windows Server 2016. Only worker nodes are supported on Windows, and all manager nodes in the cluster must run on Linux.

Follow these steps to enable a worker node on Windows.

  1. Install Docker EE Engine on Windows Server 2016.
  2. Configure the Windows node.
  3. Join the Windows node to the cluster.

Install Docker EE Engine on Windows Server 2016

Install Docker EE Engine on a Windows Server 2016 instance to enable joining a cluster that’s managed by Docker Enterprise Edition.

Configure the Windows node

Follow these steps to configure the docker daemon and the Windows environment.

  1. Add a label to the node.
  2. Pull the Windows-specific image of ucp-agent, which is named ucp-agent-win.
  3. Run the Windows worker setup script provided with ucp-agent-win.
  4. Join the cluster with the token provided by the Docker EE web UI or CLI.

Add a label to the node

Configure the Docker Engine running on the node to have a label. This makes it easier to deploy applications on nodes with this label.

Create the file C:\ProgramData\docker\config\daemon.json with the following content:

{
  "labels": ["os=windows"]
}

Restart Docker for the changes to take effect:

Restart-Service docker

Pull the Windows-specific images

On a manager node, run the following command to list the images that are required on Windows nodes.

docker container run --rm docker/ucp:3.0.2 images --list --enable-windows
docker/ucp-agent-win:3.0.2
docker/ucp-dsinfo-win:3.0.2

On Windows Server 2016, in a PowerShell terminal running as Administrator, log in to Docker Hub with the docker login command and pull the listed images.

docker image pull docker/ucp-agent-win:3.0.2
docker image pull docker/ucp-dsinfo-win:3.0.2

Run the Windows node setup script

You need to open ports 2376 and 12376, and create certificates for the Docker daemon to communicate securely. Use this command to run the Windows node setup script:

$script = [ScriptBlock]::Create((docker run --rm docker/ucp-agent-win:3.0.2 windows-script | Out-String))

Invoke-Command $script

Docker daemon restart

When you run windows-script, the Docker service is unavailable temporarily.

The Windows node is ready to join the cluster. Run the setup script on each instance of Windows Server that will be a worker node.

Compatibility with daemon.json

The script may be incompatible with installations that use a config file at C:\ProgramData\docker\config\daemon.json. If you use such a file, make sure that the daemon runs on port 2376 and that it uses certificates located in C:\ProgramData\docker\daemoncerts. If certificates don’t exist in this directory, run ucp-agent-win generate-certs, as shown in Step 2 of the procedure in Set up certs for the dockerd service.

In the daemon.json file, set the tlscacert, tlscert, and tlskey options to the corresponding files in C:\ProgramData\docker\daemoncerts:

{
...
		"debug":     true,
		"tls":       true,
		"tlscacert": "C:\ProgramData\docker\daemoncerts\ca.pem",
		"tlscert":   "C:\ProgramData\docker\daemoncerts\cert.pem",
		"tlskey":    "C:\ProgramData\docker\daemoncerts\key.pem",
		"tlsverify": true,
...
}

Join the Windows node to the cluster

Now you can join the cluster by using the docker swarm join command that’s provided by the Docker EE web UI and CLI.

  1. Log in to the Docker EE web UI with an administrator account.
  2. Navigate to the Nodes page.
  3. Click Add Node to add a new node.
  4. In the Node Type section, click Windows.
  5. In the Step 2 section, click the checkbox for “I’m ready to join my windows node.”
  6. Check the Use a custom listen address option to specify the address and port where new node listens for inbound cluster management traffic.
  7. Check the Use a custom listen address option to specify the IP address that’s advertised to all members of the cluster for API access.

Copy the displayed command. It looks similar to the following:

docker swarm join --token <token> <ucp-manager-ip>

You can also use the command line to get the join token. Using your UCP client bundle, run:

docker swarm join-token worker

Run the docker swarm join command on each instance of Windows Server that will be a worker node.

Configure a Windows worker node manually

The following sections describe how to run the commands in the setup script manually to configure the dockerd service and the Windows environment. The script opens ports in the firewall and sets up certificates for dockerd.

To see the script, you can run the windows-script command without piping to the Invoke-Expression cmdlet.

docker container run --rm docker/ucp-agent-win:3.0.2 windows-script

Open ports in the Windows firewall

Docker EE requires that ports 2376 and 12376 are open for inbound TCP traffic.

In a PowerShell terminal running as Administrator, run these commands to add rules to the Windows firewall.

netsh advfirewall firewall add rule name="docker_local" dir=in action=allow protocol=TCP localport=2376
netsh advfirewall firewall add rule name="docker_proxy" dir=in action=allow protocol=TCP localport=12376

Set up certs for the dockerd service

  1. Create the directory C:\ProgramData\docker\daemoncerts.
  2. In a PowerShell terminal running as Administrator, run the following command to generate certificates.

    docker container run --rm -v C:\ProgramData\docker\daemoncerts:C:\certs docker/ucp-agent-win:3.0.2 generate-certs
    
  3. To set up certificates, run the following commands to stop and unregister the dockerd service, register the service with the certificates, and restart the service.

    Stop-Service docker
    dockerd --unregister-service
    dockerd -H npipe:// -H 0.0.0.0:2376 --tlsverify --tlscacert=C:\ProgramData\docker\daemoncerts\ca.pem --tlscert=C:\ProgramData\docker\daemoncerts\cert.pem --tlskey=C:\ProgramData\docker\daemoncerts\key.pem --register-service
    Start-Service docker
    

The dockerd service and the Windows environment are now configured to join a Docker EE cluster.

TLS certificate setup

If the TLS certificates aren’t set up correctly, the Docker EE web UI shows the following warning.

Node WIN-NOOQV2PJGTE is a Windows node that cannot connect to its local Docker daemon.

Windows nodes limitations

Some features are not yet supported on Windows nodes:

  • Networking
    • The cluster mode routing mesh can’t be used on Windows nodes. You can expose a port for your service in the host where it is running, and use the HTTP routing mesh to make your service accessible using a domain name.
    • Encrypted networks are not supported. If you’ve upgraded from a previous version, you’ll also need to recreate the ucp-hrm network to make it unencrypted.
  • Secrets
    • When using secrets with Windows services, Windows stores temporary secret files on disk. You can use BitLocker on the volume containing the Docker root directory to encrypt the secret data at rest.
    • When creating a service which uses Windows containers, the options to specify UID, GID, and mode are not supported for secrets. Secrets are currently only accessible by administrators and users with system access within the container.
  • Mounts
    • On Windows, Docker can’t listen on a Unix socket. Use TCP or a named pipe instead.
Docker EE, UCP, cluster, scale, worker, Windows