Set up high availability

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Docker Universal Control Plane is designed for high availability (HA). You can join multiple manager nodes to the cluster, so that if one manager node fails, another can automatically take its place without impact to the cluster.

Having multiple manager nodes in your cluster, allows you to:

  • Handle manager node failures,
  • Load-balance user requests across all manager nodes.

Size your deployment

To make the cluster tolerant to more failures, add additional replica nodes to your cluster.

Manager nodes Failures tolerated
1 0
3 1
5 2
7 3

For production-grade deployments, follow these rules of thumb:

  • When a manager node fails, the number of failures tolerated by your cluster decreases. Don’t leave that node offline for too long.
  • You should distribute your manager nodes across different availability zones. This way your cluster can continue working even if an entire availability zone goes down.
  • Adding many manager nodes to the cluster might lead to performance degradation, as changes to configurations need to be replicated across all manager nodes. The maximum advisable is having 7 manager nodes.

After provisioning the new nodes, you can add them to the cluster.

Load-balancing on UCP

Docker UCP does not include a load balancer. You can configure your own load balancer to balance user requests across all manager nodes. Learn more about the UCP reference architecture.

Since Docker UCP uses mutual TLS, make sure you configure your load balancer to:

  • Load-balance TCP traffic on port 443,
  • Not terminate HTTPS connections,
  • Use the /_ping endpoint on each manager node, to check if the node is healthy and if it should remain on the load balancing pool or not.

Where to go next

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