Alertmanager Cluster Crashlooping

AlertmanagerClusterCrashlooping #

Meaning #

Half or more of the Alertmanager instances within the same cluster are crashlooping.

Impact #

Alerts could be notified multiple time unless pods are crashing to fast and no alerts can be sent.

Diagnosis #

kubectl get pod -l app=alertmanager

NAMESPACE   NAME                    READY   STATUS              RESTARTS    AGE
default     alertmanager-main-0     1/2     CrashLoopBackOff    37107 2d
default     alertmanager-main-1     2/2     Running             0 43d
default     alertmanager-main-2     2/2     Running             0 43d 

Find the root cause by looking to events for a given pod/deployement

kubectl get events --field-selector

Mitigation #

Make sure pods have enough resources (CPU, MEM) to work correctly.