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title description keywords ui_tabs cli_tabs next_steps
Join nodes to your cluster Learn how to scale a Docker Enterprise Edition cluster by adding manager and worker nodes. Docker EE, UCP, cluster, scale, worker, manager
version orhigher
ucp-3.0 true
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ucp-2.2 true
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docker-cli-linux
path title
/deploy/install-and-configure/join-windows-nodes-to-cluster Join Windows worker nodes to a cluster
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/deploy/install-and-configure/set-orchestrator-type Change the orchestrator for a node

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Docker EE is designed for scaling horizontally as your applications grow in size and usage. You can add or remove nodes from the cluster to scale it to your needs. You can join Windows Server 2016, IBM z System, and Linux nodes to the cluster.

Because Docker EE leverages the clustering functionality provided by Docker Engine, you use the docker swarm join command to add more nodes to your cluster. When you join a new node, Docker EE services start running on the node automatically.

Node roles

When you join a node to a cluster, you specify its role: manager or worker.

  • Manager: Manager nodes are responsible for cluster management functionality and dispatching tasks to worker nodes. Having multiple manager nodes allows your swarm to be highly available and tolerant of node failures.

    Manager nodes also run all Docker EE components in a replicated way, so by adding additional manager nodes, you're also making the cluster highly available. Learn more about the Docker EE architecture.

  • Worker: Worker nodes receive and execute your services and applications. Having multiple worker nodes allows you to scale the computing capacity of your cluster.

    When deploying Docker Trusted Registry in your cluster, you deploy it to a worker node.

Join a node to the cluster

You can join Windows Server 2016, IBM z System, and Linux nodes to the cluster, but only Linux nodes can be managers.

To join nodes to the cluster, go to the Docker EE web UI and navigate to the Nodes page.

  1. Click Add Node to add a new node.
  2. Select the type of node to add, Windows or Linux.
  3. Click Manager if you want to add the node as a manager.
  4. Check the Use a custom listen address option to specify the address and port where new node listens for inbound cluster management traffic.
  5. 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.

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Copy the displayed command, use SSH to log in to the host that you want to join to the cluster, and run the docker swarm join command on the host.

To add a Windows node, click Windows and follow the instructions in Join Windows worker nodes to a cluster.

After you run the join command in the node, the node is displayed on the Nodes page in the Docker EE web UI. From there, you can change the node's cluster configuration, including its assigned orchestrator type. Learn how to change the orchestrator for a node.

Pause or drain a node

Once a node is part of the cluster, you can configure the node's availability so that it is:

  • Active: the node can receive and execute tasks.
  • Paused: the node continues running existing tasks, but doesn't receive new tasks.
  • Drained: the node won't receive new tasks. Existing tasks are stopped and replica tasks are launched in active nodes.

Pause or drain a node from the Edit Node page:

  1. In the Docker EE web UI, browse to the Nodes page and select the node.
  2. In the details pane, click Configure and select Details to open the Edit Node page.
  3. In the Availability section, click Active, Pause, or Drain.
  4. Click Save to change the availability of the node.

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Promote or demote a node

As your cluster architecture changes, you may need to promote worker nodes to managers or demote manger nodes to workers. Change the current role of node on the Edit node page.

If you remove a manager node from the cluster, always demote the node before removing it.

Load balancing

If you're load-balancing user requests to Docker EE across multiple manager nodes, don't forget to remove these nodes from your load-balancing pool when you demote them to workers. {: .important}

To promote or demote a manager node:

  1. Navigate to the Nodes page, and click the node that you want to demote.
  2. In the details pane, click Configure and select Details to open the Edit Node page.
  3. In the Role section, click Manager or Worker.
  4. Click Save and wait until the operation completes.
  5. Navigate to the Nodes page, and confirm that the node role has changed.

Remove a node from the cluster

Before you remove a node from the cluster, ensure that it's not a manager node. If it is, demote it to a worker before you remove it from the cluster.

To remove a node:

  1. Navigate to the Nodes page and select the node.
  2. In the details pane, click Actions and select Remove.
  3. Click Confirm when you're prompted.

If the status of the worker node is Ready, you need to force the node to leave the cluster manually. To do this, connect to the target node through SSH and run docker swarm leave --force directly against the local Docker EE Engine.

Loss of quorum

Don't perform this step if the node is still a manager, as this may cause loss of quorum. {: .important}

When the status of the node is reported as Down, you can remove the node from the cluster.

If you want to join the removed node to the cluster again, you need to force the node to leave the cluster manually. To do this, connect to the target node through SSH and run docker swarm leave --force directly against the local Docker EE Engine.

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Learn how to scale your cluster.

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You can use the command line to join a node to a Docker EE cluster. To get the join token, run the following command on a manager node:

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docker swarm join-token worker

If you want to add a new manager node instead of a worker node, use docker swarm join-token manager instead. If you want to use a custom listen address, add the --listen-addr arg:

$ docker swarm join \
    --token SWMTKN-1-2o5ra9t7022neymg4u15f3jjfh0qh3yof817nunoioxa9i7lsp-dkmt01ebwp2m0wce1u31h6lmj \
    --listen-addr 234.234.234.234 \
    192.168.99.100:2377

Once your node is added, you can see it by running docker node ls on a manager:

docker node ls

To change the node's availability, use:

docker node update --availability drain node2

You can set the availability to active, pause, or drain.

Remove nodes from the cluster

If the target node is a manager, you need to demote the node to a worker before proceeding with the removal.

  1. Log in to a manager node, other than the one you'll be demoting, by using SSH.
  2. Run docker node ls and identify the nodeID or hostname of the target node.
  3. Run docker node demote <nodeID or hostname>.

When the status of the node is reported as Down, you can remove the node from the cluster.

docker node rm <nodeID or hostname>

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