Join Windows worker nodes to your cluster

Estimated reading time: 8 minutes

This topic applies to Docker Enterprise.

The Docker Enterprise platform business, including products, customers, and employees, has been acquired by Mirantis, inc., effective 13-November-2019. For more information on the acquisition and how it may affect you and your business, refer to the Docker Enterprise Customer FAQ.

Docker Enterprise 3.0 supports worker nodes that run on Windows Server 2016 and Windows Server 2019. Only worker nodes are supported on Windows, and all manager nodes in the cluster must run on Linux. Additionally Windows worker nodes can only be used by the Swarm Orchestrator.

To enable a worker node on Windows:

  1. Install Docker Engine - Enterprise on Windows Server 2016 or 2019.
  2. Configure the Windows node.
  3. Join the Windows node to the cluster.

Note

Refer to the Docker compatibility matrix for complete Docker compatibility information with Windows Server.

Install Docker Engine - Enterprise on Windows Server

Install Docker Engine - Enterprise on a Windows Server 2016 or 2019 instance before joining the node to a Docker Enterprise Cluster.

Configure the Windows node

To configure the docker daemon and the Windows environment:

  1. Pull the Windows-specific image of ucp-agent, which is named ucp-agent-win.
  2. Run the Windows worker setup script provided with ucp-agent-win.
  3. Join the cluster with the token provided by the Docker UCP web interface or CLI.

Add a label to the node

As of Docker Enterprise 2.1, which includes UCP 3.1, this step is no longer necessary. Windows nodes are automatically assigned the ostype label ostype=windows.

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:3.2.4 images --list --enable-windows
docker/ucp-agent-win:3.2.4
docker/ucp-dsinfo-win:3.2.4

On a Windows Server node, 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:3.2.4
docker image pull docker/ucp-dsinfo-win:3.2.4

If the cluster is deployed in an offline site, where the nodes do not have access to the Docker Hub, UCP images can be sideloaded onto the Windows Server nodes. Follow the instructions on the install offline page to sideload the images.

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:3.2.4 windows-script | Out-String))

Invoke-Command $script

Note

If you run windows-script when restarting Docker daemon, 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

To join the cluster using the docker swarm join command provided by the Docker UCP web interface and CLI:

  1. Log in to the Docker UCP web interface 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, select the check box for “I have followed the instructions and I’m ready to join my Windows node.”
  6. Select the Use a custom listen address option to specify the address and port where new node listens for inbound cluster management traffic.
  7. Select 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. dockerd is the persistent process that manages containers. 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:3.2.4 windows-script

Open ports in the Windows firewall

Docker Enterprise 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

To 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:3.2.4 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 Enterprise cluster.

Note

If the TLS certificates aren’t set up correctly, the Docker UCP web interface shows the following warning:

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

Windows nodes limitations

The following features are not yet supported on Windows Server 2016 or 2019:

  • Networking
    • 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.
  • Orchestration
    • Windows Containers can only be scheduled by the Docker Swarm orchestrator.

The following features are not yet supported on Windows Server 2016:

  • 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.

Known Issues

Refer to the Docker Enterprise UCP release notes for Known Issues information.

Docker Enterprise, UCP, cluster, scale, worker, Windows