Chapter 4. Configuring external Alertmanager instances

Procedure

1. Edit the ConfigMap object.

   • To configure additional Alertmanagers for routing alerts from core OpenShift Container Platform projects:

     1. Edit the cluster-monitoring-config config map in the openshift-monitoring project:

        $ oc -n openshift-monitoring edit configmap cluster-monitoring-config

     2. Add an additionalAlertmanagerConfigs: section under data/config.yaml/prometheusK8s.

     3. Add the configuration details for additional Alertmanagers in this section:

        apiVersion: v1
        kind: ConfigMap
        metadata:
          name: cluster-monitoring-config
          namespace: openshift-monitoring
        data:
          config.yaml: |
            prometheusK8s:
              additionalAlertmanagerConfigs:
              - <alertmanager_specification>

        For <alertmanager_specification>, substitute authentication and other configuration details for additional Alertmanager instances. Currently supported authentication methods are bearer token (bearerToken) and client TLS (tlsConfig). The following sample config map configures an additional Alertmanager using a bearer token with client TLS authentication:

        apiVersion: v1
        kind: ConfigMap
        metadata:
          name: cluster-monitoring-config
          namespace: openshift-monitoring
        data:
          config.yaml: |
            prometheusK8s:
              additionalAlertmanagerConfigs:
              - scheme: https
                pathPrefix: /
                timeout: "30s"
                apiVersion: v1
                bearerToken:
                  name: alertmanager-bearer-token
                  key: token
                tlsConfig:
                  key:
                    name: alertmanager-tls
                    key: tls.key
                  cert:
                    name: alertmanager-tls
                    key: tls.crt
                  ca:
                    name: alertmanager-tls
                    key: tls.ca
                staticConfigs:
                - external-alertmanager1-remote.com
                - external-alertmanager1-remote2.com

   • To configure additional Alertmanager instances for routing alerts from user-defined projects:

     1. Edit the user-workload-monitoring-config config map in the openshift-user-workload-monitoring project:

        $ oc -n openshift-user-workload-monitoring edit configmap user-workload-monitoring-config

     2. Add a <component>/additionalAlertmanagerConfigs: section under data/config.yaml/.

     3. Add the configuration details for additional Alertmanagers in this section:

        apiVersion: v1
        kind: ConfigMap
        metadata:
          name: user-workload-monitoring-config
          namespace: openshift-user-workload-monitoring
        data:
          config.yaml: |
            <component>:
              additionalAlertmanagerConfigs:
              - <alertmanager_specification>

        For <component>, substitute one of two supported external Alertmanager components: prometheus or thanosRuler.

        For <alertmanager_specification>, substitute authentication and other configuration details for additional Alertmanager instances. Currently supported authentication methods are bearer token (bearerToken) and client TLS (tlsConfig). The following sample config map configures an additional Alertmanager using Thanos Ruler with a bearer token and client TLS authentication:

        apiVersion: v1
        kind: ConfigMap
        metadata:
          name: user-workload-monitoring-config
          namespace: openshift-user-workload-monitoring
        data:
          config.yaml: |
            thanosRuler:
              additionalAlertmanagerConfigs:
              - scheme: https
                pathPrefix: /
                timeout: "30s"
                apiVersion: v1
                bearerToken:
                  name: alertmanager-bearer-token
                  key: token
                tlsConfig:
                  key:
                    name: alertmanager-tls
                    key: tls.key
                  cert:
                    name: alertmanager-tls
                    key: tls.crt
                  ca:
                    name: alertmanager-tls
                    key: tls.ca
                staticConfigs:
                - external-alertmanager1-remote.com
                - external-alertmanager1-remote2.com

2. Save the file to apply the changes. The pods affected by the new configuration are automatically redeployed.