Troubleshooting AlertmanagerFailedToSendAlerts alert in OpenShift Container Platform 4.

Issue

The following alert indicates that at least one AlertManager instance is unable to route the alert to the corresponding integration:

• AlertmanagerFailedToSendAlerts:

(rate(alertmanager_notifications_failed_total{job="alertmanager-main",namespace="openshift-monitoring"}[5m]) / rate(alertmanager_notifications_total{job="alertmanager-main",namespace="openshift-monitoring"}[5m])) > 0.01

Another instance could be able to send the notification, unless AlertmanagerClusterFailedToSendAlerts is also triggered for the same integration, so this alert could be impact-less, but still, it would require to analyze why one instance is not able to forward and route the alert.