Etcd Insufficient Members

etcdInsufficientMembers #

Meaning #

This alert fires when there are fewer instances available than are needed by etcd to be healthy. This means that etcd cluster has not enough members in the cluster to create quorum.

Impact #

When etcd does not have a majority of instances available the Kubernetes and OpenShift APIs will reject read and write requests and operations that preserve the health of workloads cannot be performed.

In general loosing quorum will switch etcd to read only, which effectively renders k8s api read only. It is possible to read the current state, but not possible to update it.

Diagnosis #

This can occur when multiple control plane nodes are powered off or are unable to connect to each other via the network. Check that all control plane nodes are powered on and that network connections between each machine are functional.

Check any other critical, warning or info alerts firing that can assist with the diagnosis.

Login to the cluster. Check health of master nodes if any of them is in NotReady state or not.

$ kubectl get nodes -l

General etcd health #

To run etcdctl commands, we need to exec into the etcdctl container of any etcd pod.

$ kubectl exec -c etcdctl -n openshift-etcd $(kubectl get po -l app=etcd -oname -n openshift-etcd | awk -F"/" 'NR==1{ print $2 }')

Validate that the etcdctl command is available:

$ etcdctl version

Run the following command to get the health of etcd:

$ etcdctl endpoint health -w table

Mitigation #

Disaster and recovery #

If an upgrade is in progress, the alert may automatically resolve in some time when the master node comes up again. If MCO is not working on the master node, check the cloud provider to verify if the master node instances are running or not.

In the case when you are running on AWS, the AWS instance retirement might need a manual reboot of the master node.

As a last resort if none of the above fix the issue and the alert is still firing, for etcd specific issues follow the steps described in the disaster-recovery.