Recording Rules in Prometheus

Introduction Key Concepts Creating Recording Rules Best Practices FAQ

1. Introduction

Recording rules in Prometheus allow users to precompute frequently needed or computationally expensive expressions and store them as new time series. This improves query performance and reduces the load on Prometheus during querying.

2. Key Concepts

2.1 What are Recording Rules?

Recording rules are a way to define how to aggregate and store metrics in Prometheus. They allow users to create new time series based on existing ones.

2.2 Benefits of Using Recording Rules

Improved query performance.
Reduced computational load during querying.
Facilitates complex metric analysis.

3. Creating Recording Rules

Recording rules are defined in the Prometheus configuration file. The rules are specified under the rule_files section.

Note: Changes to recording rules require a reload of the Prometheus configuration.

3.1 Example of a Recording Rule

Here’s an example of how to define a recording rule in a YAML file:


groups:
- name: example
  rules:
  - record: job:http_requests:sum
    expr: sum(rate(http_requests_total[5m])) by (job)
    labels:
      environment: production

This rule aggregates the total number of HTTP requests over the last 5 minutes by job.

4. Best Practices

Use clear and descriptive names for your recording rules.
Limit the number of recording rules to avoid excessive load.
Regularly review and optimize existing recording rules.

5. FAQ

What is the difference between recording rules and alerting rules?

Recording rules are used to create new time series, while alerting rules are used to generate alerts based on certain conditions of existing time series.

How can I view the recorded metrics?

You can view the recorded metrics in the Prometheus web UI or query them using PromQL.

Can I modify existing recording rules?

Yes, you can modify existing recording rules, but you will need to reload the Prometheus configuration for changes to take effect.

6. Flowchart of Recording Rules Process


graph TD;
    A[Define Recording Rule] --> B[Save to Configuration File]
    B --> C[Reload Prometheus]
    C --> D[Query New Time Series]