Set up Slack alerts for a Kubernetes cluster

This guide explains how to configure Slack alerts for a Kubernetes cluster using Prometheus Alertmanager.

Introduction

Alerting is essential for monitoring modern systems, ensuring issues are detected and communicated in real-time. In Kubernetes, tools like Prometheus and Alertmanager handle metrics monitoring and alert routing to channels like Slack or email. Effective alerting minimizes downtime, improves response times, and maintains system performance.

Prerequisites

• A Kubernetes cluster with Prometheus and Alertmanager installed. It comes by default when installing cattle-monitoring-system.

• A Slack workspace with a channel for receiving alerts.

• Permissions to create and manage Slack webhooks.

Procedure

1. Create a Slack Incoming Webhook.

   1. Go to the Slack API Webhooks page.

   2. Create a new Slack App (if you don’t have one already).

   3. Add an Incoming Webhook to the app.

   4. Select the Slack channel where you want alerts to appear.

   5. Copy the generated Webhook URL (e.g., https://hooks.slack.com/services/...).

2. Deploy alerting configuration to kuberenets cluster.

   1. Clone the repository to you local and update the required changes mentioned below.

   2. Update slack_api_url and channel in alertmanager.yaml

   3. Modify the routes and receivers in the alertmanager.yaml configuration to customize which alerts are sent to Slack., as shown below.

      routes:
      - match:
          alertname: Watchdog
        receiver: 'null'

   4. The monitoring package provided by Rancher includes various default alerting rules, which are often sufficient for most use cases. Sample custom alerts are available under the custom-alerts directory. Modify these as needed.

   5. Add cluster name in, patch-cluster-name.yaml

   6. Run install.sh to apply the configuration for alertmanager.

   7. And restart the alert-manager service on k8s-cluster.

   8. Verify whether the alerts are firing from the Prometheus UI and check if Slack notifications are being received.

      

      Prometheus dashboard

      

      slack channel