Preq Docs

preq (prounounced "preek") is a free and open community-driven reliability problem detector. Use preq to:

• detect the latest bugs, misconfigurations, anti-patterns, and known issues from a community of practitioners
• provide engineers, on-call support, and SRE agents with impact and community recommended mitigations
• hunt for new problems in logs

preq is powered by Common Reliability Enumerations (CREs) that are contributed by the community and Prequel's Reliability Research Team. Reliability intelligence helps teams see a broad range of problems earlier, so they can prioritize, pinpoint, and reduce the risk of outages.

Install

Download the latest release on Github.

Download  

Follow the easy installation instructions and learn about CREs and the simple problem detection syntax.

Play

Try the playground with schema validation. It uses WebAssembly and runs 100% in your browser. No data leaves it!

How it Works

preq can run community CREs on any data source with a timestamp and line delimiter.

Example CRE Rule

preq is powered by a rules engine that performs matching and correlation of sequences of events to detect reliability problems. CREs provides accurate and timely context for a human or SRE agent to take action on problems.

Below is simple rule that looks for a sequence of events in a single log source over a window of time along with a negative condition (an event that should not occur during the window).

cre-2024-0007.yaml

rules:
  - cre:
      id: CRE-2024-0007
      severity: 0
      title: RabbitMQ Mnesia overloaded recovering persistent queues
      category: message-queue-problems
      author: Prequel
      description: |
        - The RabbitMQ cluster is processing a large number of persistent mirrored queues at boot. 
      cause: |
        - The Erlang process, Mnesia, is overloaded while recovering persistent queues on boot. 
      impact: |
        - RabbitMQ is unable to process any new messages and can cause outages in consumers and producers.
      tags: 
        - cre-2024-0007
        - known-problem
        - rabbitmq
      mitigation: |
        - Adjusting mirroring policies to limit the number of mirrored queues
        - Remove high-availability policies from queues
        - Add additional CPU resources and restart the RabbitMQ cluster
        - Use [lazy queues](https://www.rabbitmq.com/docs/lazy-queues) to avoid incurring the costs of writing data to disk 
      references:
        - https://groups.google.com/g/rabbitmq-users/c/ekV9tTBRZms/m/1EXw-ruuBQAJ
      applications:
        - name: "rabbitmq"
          version: "3.9.x"
    metadata:
      kind: prequel
      id: 5UD1RZxGC5LJQnVpAkV11A
      generation: 1
    rule:
      sequence:
        window: 30s
        event:
          source: rabbitmq
        order:
          - regex: "Discarding message(.+)in an old incarnation(.+)of this node"
          - "Mnesia is overloaded"
        negate:
          - "SIGTERM received - shutting down"