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UCP says I have unhealthy controllers/managers. What should I do?

For Docker Universal Control Plane to be highly available and fault-tolerant, you need to join multiple controller nodes (also known as manager nodes):

Controllers/managers Failures tolerated
1 0
3 1
5 2
7 3

UCP displays a warning message when one or more controller nodes are not healthy, as this can reduce the fault-tolerance of UCP. Troubleshoot and find what's keeping these nodes unhealthy.

To learn more about troubleshooting UCP, visit http://docs.docker.com/ucp/monitor/troubleshoot-ucp/.