Creating Alerts | Alerts | Prometheus Tutorial

Introduction

Alerts are a vital part of monitoring systems, enabling users to be notified when certain conditions are met. In Prometheus, alerts can be configured to trigger based on the metrics collected. This tutorial will guide you through the process of creating alerts in Prometheus, from setting up the alerting rules to testing the alerts.

Setting Up the Alerting Rules

To create alerts in Prometheus, you need to define alerting rules in a configuration file. These rules specify the conditions under which an alert should be triggered. Typically, these rules are placed in a file called alerts.yml.

Here is an example of a simple alerting rule that triggers when the CPU usage exceeds 80% for more than 5 minutes:


                    groups:
                      - name: example-alert
                        rules:
                          - alert: HighCPUUsage
                            expr: sum(rate(cpu_usage_seconds_total[5m])) by (instance) > 0.8
                            for: 5m
                            labels:
                              severity: warning
                            annotations:
                              summary: "High CPU usage detected"
                              description: "CPU usage is above 80% for more than 5 minutes."

In this example:

alert: The name of the alert.
expr: The expression to evaluate; if it evaluates to true, the alert is triggered.
for: Specifies how long the condition must be true for the alert to fire.
labels: Key-value pairs that provide additional information about the alert.
annotations: Provide descriptive information about the alert, which can be useful for alert notifications.

Configuring Alertmanager

Once you have defined your alerting rules, you need to configure Alertmanager to handle the alerts. Alertmanager is responsible for managing alerts, including de-duplication, grouping, and routing notifications.

Below is a basic configuration for Alertmanager that sends notifications via email when an alert is triggered:


                    global:
                      resolve_timeout: 5m
                      smtp_smarthost: 'smtp.example.com:587'
                      smtp_from: 'alertmanager@example.com'
                      smtp_auth_username: 'alertmanager'
                      smtp_auth_password: 'password'
                    route:
                      group_by: ['alertname']
                      group_wait: 30s
                      group_interval: 5m
                      repeat_interval: 3h
                      receiver: 'email'
                    receivers:
                      - name: 'email'
                        email_configs:
                          - to: 'recipient@example.com'
                            send_resolved: true

In this configuration:

global: Global settings for Alertmanager.
route: Defines how alerts are routed to receivers.
receivers: The list of notification receivers.

Testing Alerts

After setting up your alerting rules and Alertmanager, it's essential to test if the alerts are firing correctly. You can force an alert to trigger by simulating high CPU usage or by temporarily modifying the alerting rule to test different conditions.

To check if the alerts are working as expected, you can use the Prometheus UI:

Navigate to the "Alerts" tab in the Prometheus web interface.
Check the status of your defined alerts. You should see your alert listed and its status.

Conclusion

Creating alerts in Prometheus is a straightforward process that involves defining alerting rules and configuring Alertmanager. By monitoring your systems and receiving timely notifications, you can respond quickly to any issues that arise, ensuring optimal performance and reliability.

Creating Alerts in Prometheus

Introduction

Setting Up the Alerting Rules

Configuring Alertmanager

Testing Alerts

Conclusion