Chapter 9. Deploying machine health checks

MachineHealthChecks automatically repairs unhealthy Machines in a particular MachinePool.

To monitor machine health, you create a resource to define the configuration for a controller. You set a condition to check for, such as staying in the NotReady status for 15 minutes or displaying a permanent condition in the node-problem-detector, and a label for the set of machines to monitor.

The controller that observes a MachineHealthCheck resource checks for the status that you defined. If a machine fails the health check, it is automatically deleted and a new one is created to take its place. When a machine is deleted, you see a machine deleted event. To limit disruptive impact of the machine deletion, the controller drains and deletes only one node at a time.

To stop the check, you remove the resource.

The MachineHealthCheck resource resembles the following YAML file:

apiVersion: healthchecking.openshift.io/v1alpha1
kind: MachineHealthCheck
metadata:
 name: example 
 namespace: openshift-machine-api
Spec:
  Selector:
    matchLabels:

      machine.openshift.io/cluster-api-machine-role: <label> 
      machine.openshift.io/cluster-api-machine-type: <label> 
      machine.openshift.io/cluster-api-machineset: <cluster_name>-<label>-<AWS-zone> 

apiVersion: healthchecking.openshift.io/v1alpha1
kind: MachineHealthCheck
metadata:
 name: example 

 namespace: openshift-machine-api
Spec:
  Selector:
    matchLabels:

      machine.openshift.io/cluster-api-machine-role: <label> 

      machine.openshift.io/cluster-api-machine-type: <label> 

      machine.openshift.io/cluster-api-machineset: <cluster_name>-<label>-<AWS-zone> 

You can create a MachineHealthCheck resource for all MachinePools in your cluster except the master pool.