Alertmanager exporter should allow additional labels

[JettJones]

Component(s)

No response

Is your feature request related to a problem? Please describe.

Alertmanager routing can select different routes based on labels on incoming alerts. But the altermanager exporter creates only two labels: severity and event_name.

My desired use case is to route alerts based on the service name, and severity, with overrides for some library events. I expect the mapping of teams handling alerts is fairly unique by company, so more flexibility is helpful here.

Describe the solution you'd like

Accept in configuration a list of event annotations to promote to labels.

When an annotation is present, add its value to the LabelSet of the created alert, here:
https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/exporter/alertmanagerexporter/alertmanager_exporter.go#L116

Describe alternatives you've considered

To get similar behavior of passing routing information into alertmanager:

• concatenate multiple labels into event_name and use regex matchers in alertmanager to separate them again.
• fork this exporter, and add label support.

Additional context

No response

[github-actions]

Pinging code owners for exporter/alertmanager: @sokoide @mcube8. See Adding Labels via Comments if you do not have permissions to add labels yourself. For example, comment '/label priority:p2 -needs-triaged' to set the priority and remove the needs-triaged label.

[mcube8]

/label priority:p3 -needs-triage