Proposed title of this feature request:

Filter Alerts Sent to External AlertManager Instance

What is the nature and description of the request?

When the external AlertManager instance is configured, and we want to receive only specific alerts, it is impossible to configure it in the cluster-monitoring-config configmap. The only workaround is configuring a webhook in the alertmanager to forward the alert to the external alertmanager via receiver and routes.

Configuring external Alertmanager instances
https://docs.openshift.com/container-platform/4.15/monitoring/configuring-the-monitoring-stack.html#monitoring-configuring-external-alertmanagers_configuring-the-monitoring-stack

Why does the customer need this?

The customer wants to forward all critical and error alerts to their external alertmanager instance, which collects alerts from all openshift clusters. And keep warnings only visible in the cluster itself. Looking to have filtered alerting for ticket generation to avoid opening unnecessary tickets. So, reducing noise in alerting systems and better customization of alerts based on severity levels.

List any affected packages or components:

• cluster-monitoring-config
• user-workload-monitoring-config