Chapter 3. Configuring external alertmanager instances

The OpenShift Container Platform monitoring stack includes a local Alertmanager instance that routes alerts from Prometheus. You can add external Alertmanager instances by configuring the cluster-monitoring-config config map in either the openshift-monitoring project or the user-workload-monitoring-config project.

If you add the same external Alertmanager configuration for multiple clusters and disable the local instance for each cluster, you can then manage alert routing for multiple clusters by using a single external Alertmanager instance.

Prerequisites

  • You have installed the OpenShift CLI (oc).

  • If you are configuring core OpenShift Container Platform monitoring components in the openshift-monitoring project:

    • You have access to the cluster as a user with the cluster-admin cluster role.
    • You have created the cluster-monitoring-config config map.

  • If you are configuring components that monitor user-defined projects:

    • You have access to the cluster as a user with the cluster-admin cluster role, or as a user with the user-workload-monitoring-config-edit role in the openshift-user-workload-monitoring project.
    • You have created the user-workload-monitoring-config config map.

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
        Note

        Configurations applied to the user-workload-monitoring-config ConfigMap object are not activated unless a cluster administrator has enabled monitoring for user-defined projects.

  2. Save the file to apply the changes to the ConfigMap object. The new component placement configuration is applied automatically.

3.1. Attaching additional labels to your time series and alerts

You can attach custom labels to all time series and alerts leaving Prometheus by using the external labels feature of Prometheus.

Prerequisites

  • If you are configuring core OpenShift Container Platform monitoring components:

    • You have access to the cluster as a user with the cluster-admin cluster role.
    • You have created the cluster-monitoring-config ConfigMap object.

  • If you are configuring components that monitor user-defined projects:

    • You have access to the cluster as a user with the cluster-admin cluster role, or as a user with the user-workload-monitoring-config-edit role in the openshift-user-workload-monitoring project.
    • You have created the user-workload-monitoring-config ConfigMap object.
  • You have installed the OpenShift CLI (oc).

Procedure

  1. Edit the ConfigMap object:

    • To attach custom labels to all time series and alerts leaving the Prometheus instance that monitors core OpenShift Container Platform projects:

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

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

      2. Define a map of labels you want to add for every metric under data/config.yaml: 

        apiVersion: v1
kind: ConfigMap
metadata:
  name: cluster-monitoring-config
  namespace: openshift-monitoring
data:
  config.yaml: |
    prometheusK8s:
      externalLabels:
        <key>: <value> 1
        1
        Substitute <key>: <value> with a map of key-value pairs where <key> is a unique name for the new label and <value> is its value.
        Warning
        • Do not use prometheus or prometheus_replica as key names, because they are reserved and will be overwritten.
        • Do not use cluster or managed_cluster as key names. Using them can cause issues where you are unable to see data in the developer dashboards.

        For example, to add metadata about the region and environment to all time series and alerts, use the following example: 

        apiVersion: v1
kind: ConfigMap
metadata:
  name: cluster-monitoring-config
  namespace: openshift-monitoring
data:
  config.yaml: |
    prometheusK8s:
      externalLabels:
        region: eu
        environment: prod

    • To attach custom labels to all time series and alerts leaving the Prometheus instance that monitors user-defined projects:

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

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

      2. Define a map of labels you want to add for every metric under data/config.yaml: 

        apiVersion: v1
kind: ConfigMap
metadata:
  name: user-workload-monitoring-config
  namespace: openshift-user-workload-monitoring
data:
  config.yaml: |
    prometheus:
      externalLabels:
        <key>: <value> 1
        1
        Substitute <key>: <value> with a map of key-value pairs where <key> is a unique name for the new label and <value> is its value.
        Warning
        • Do not use prometheus or prometheus_replica as key names, because they are reserved and will be overwritten.
        • Do not use cluster or managed_cluster as key names. Using them can cause issues where you are unable to see data in the developer dashboards.
        Note

        In the openshift-user-workload-monitoring project, Prometheus handles metrics and Thanos Ruler handles alerting and recording rules. Setting externalLabels for prometheus in the user-workload-monitoring-config ConfigMap object will only configure external labels for metrics and not for any rules.

        For example, to add metadata about the region and environment to all time series and alerts related to user-defined projects, use the following example: 

        apiVersion: v1
kind: ConfigMap
metadata:
  name: user-workload-monitoring-config
  namespace: openshift-user-workload-monitoring
data:
  config.yaml: |
    prometheus:
      externalLabels:
        region: eu
        environment: prod

  2. Save the file to apply the changes. The new configuration is applied automatically.

    Note

    Configurations applied to the user-workload-monitoring-config ConfigMap object are not activated unless a cluster administrator has enabled monitoring for user-defined projects.

    Warning

    When changes are saved to a monitoring config map, the pods and other resources in the related project might be redeployed. The running monitoring processes in that project might also be restarted.

Additional resources