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In this tutorial, we will learn how to set up Prometheus rules and configure Alertmanager to send alerts to a Slack channel. Prometheus is a popular monitoring and alerting solution in the Kubernetes ecosystem, while Alertmanager handles alert management and routing. By integrating with Slack, you can receive real-time notifications for any issues or anomalies in your Kubernetes cluster. Let’s get started 👨🏻‍💻!

Table of Contents:

  1. Prerequisites
  2. Setting Up Prometheus Rules
  3. Configuring Alertmanager
  4. Integrating with Slack
  5. Testing the Setup
  6. Conclusion

🚦Prerequisites:

  • Access to a Kubernetes cluster
  • Prometheus and Alertmanager installed in the cluster
  • Basic knowledge of Kubernetes and YAML syntax

1 — Setting Up Prometheus Rules :

Prometheus rules define conditions for generating alerts based on metrics collected by Prometheus. In this example, we will create a PrometheusRule resource named z4ck404-alerts in the monitoring namespace.

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    apiVersion: monitoring.coreos.com/v1
    kind: PrometheusRule
    metadata:
      name: z4ck404-alerts
      namespace: monitoring
    spec:
      groups:
      - name: blackbox.alerts
        rules:
        - alert: backbox probe check failed!
          expr: |
            probe_success != 1
          for: 2m
          labels:
            severity: warning
            namespace: monitoring
          annotations:
            summary:  BlackBox prob check failed. Service might be down
            description: 'Target {{`{{`}} printf "%v" $labels.target {{`}}`}} probe is down.'

Explanation of the provided example YAML:

  • The “apiVersion” and “kind” specify the PrometheusRule resource.
  • Under “metadata,” we set the name and namespace for the rule.
  • The “spec” section contains the rule groups, each with a name and a list of rules.
  • In this example, we define a rule named blackbox.alerts with an expression that checks if probe_success is not equal to 1.
  • We set the alert duration (for) to 2 minutes and define labels and annotations for the alert.

2 — Configuring Alertmanager:

Alertmanager handles the routing and sending of alerts to different receivers. In this step, we will create an AlertmanagerConfig resource to configure Alertmanager.

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    apiVersion: monitoring.coreos.com/v1alpha1
    kind: AlertmanagerConfig
    metadata:
      name: z4ck404-alertmanagerconfig
    spec:
      route:
        groupBy: ['alertname', 'job']
        groupWait: 10s
        groupInterval: 5m
        repeatInterval: 12h
        continue: true
        matchers:
          - name: severity
            matchType: "="
            value: "warning"
        receiver: slack
      receivers:
        - name: slack
          slackConfigs:
            - channel: "#alerts"
              apiURL:
                key: slack_webhook
                name: alertmanager-slack-notification
              sendResolved: true
              title: >-
                {{`{{`}} if eq .Status "firing" {{`}}`}}:fire: *FIRING* {{`{{`}} else {{`}}`}}:ok_hand: *RESOLVED* {{`{{`}} end {{`}}`}}
              text: >-
                {{`{{`}} range .Alerts {{`}}`}}
                    {{`{{`}} if .Annotations.summary {{`}}`}}*Alert:* {{`{{`}} .Annotations.summary {{`}}`}} - `{{`{{`}} .Labels.severity {{`}}`}}`{{`{{`}} end {{`}}`}}
                    {{`{{`}} if .Annotations.description {{`}}`}}*Description:* {{`{{`}} .Annotations.description {{`}}`}}{{`{{`}} end {{`}}`}}
                    *Details:*
                    {{`{{`}} range .Labels.SortedPairs {{`}}`}} • *{{`{{`}} .Name {{`}}`}}:* `{{`{{`}} .Value {{`}}`}}`
                    {{`{{`}} end {{`}}`}}
                {{`{{`}} end {{`}}`}}
              footer: "z4ck404-alertmanager"

Explanation of the provided example YAML:

  • The “apiVersion” and “kind” specify the AlertmanagerConfig resource.
  • Under “metadata,” we set the name for the config.
  • In the “spec” section, we define the routing rules for alerts.
  • The “groupBy” field determines how alerts are grouped in notifications.
  • We set “groupWait,” “groupInterval,” and “repeatInterval” for timing-related configurations.
  • The “matchers” section filters alerts based on label values.
  • The “receiver” field specifies the receiver to use for matched alerts.
  • Under “receivers,” we define a receiver named “slack” with Slack-specific configurations.

3 — Integrating with Slack:

To receive alerts in a Slack channel, we need to configure Alertmanager with the appropriate Slack webhook URL. We’ll create a Secret resource to store the webhook URL securely.

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    apiVersion: v1
    kind: Secret
    metadata:
      name: alertmanager-slack-notification
    type: Opaque
    data:
      slack_webhook: "https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX"

Explanation of the provided example YAML:

  • The “apiVersion” and “kind” specify the Secret resource.
  • Under “metadata,” we set the name and type for the secret.
  • In the “data” section, we encode the Slack webhook URL using Base64 encoding.

4 — Testing the Setup:

After applying the YAML manifests to the Kubernetes cluster, we can test the setup by triggering an alert condition. For example, if the “probe_success” metric is not equal to 1, an alert will be generated. Alertmanager will route the alert to the Slack channel configured in the receiver.

Conclusion:

In this tutorial, we covered the process of setting up Prometheus rules and configuring Alertmanager to send alerts to a Slack channel. By leveraging these tools, you can ensure timely notifications for any critical issues in your Kubernetes cluster.

GitHub - Z4ck404/prometheus-alertmanager-k8s: Examples for setting up monitoring and alerting using Prometheus and Alertmanager.

Monitoring Kubernetes with Prometheus and Alertmanager: Setting Up Alerts with Slack Integration was originally published in AWS Morocco on Medium, where people are continuing the conversation by highlighting and responding to this story.

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