Introduction

Thanos is a highly scalable open-source Prometheus setup that aggregates data from multiple Prometheus instances. It offers a global view of all your metrics and allows you to store those metrics backends, such as object storage. One of the Thanos components often used in this architecture is the Thanos Query/Query-Frontend, which provides a single query endpoint for all your metrics.

Unfortunately, there can be issues where the Thanos Query/Query-Frontend does not show any metrics. This article delves into the possible causes, technical explanations, and solutions for this issue.

Common Causes of Metric Absence

Setup Misconfiguration

1. Store API Endpoints:
   • Thanos Query relies on `StoreAPI` endpoints to retrieve metrics.
   • Ensure that the `--store` flag is correctly pointing to the Store Gateway, Sidecar, or any other Store API provider.
   • Use the following command to test connectivity:
   • Double-check that DNS resolution is functioning correctly for the Store API endpoints specified.

• Firewalls or network policies could be blocking traffic between Thanos Query and the Store APIs.
• Validate network policies and firewall rules:
• Version mismatch between Thanos components can lead to failed communication.
• Ensure compatibility by checking the Thanos release notes.
• Incorrect cache settings can cause Thanos Query-Frontend to not display metrics.
• Validate configuration settings:
• Ensure that any TLS settings or authentication credentials are correct.
• If using mTLS:
• Examine logs using logging output from all Thanos components:
• Look for common issues such as `connection refused`, `store not available`, or `TLS handshake error`.
• Test endpoints of Prometheus instances to confirm they are up and exposing metrics:
• Confirm the state of the Store Gateway:
• Use the Thanos Query UI to add new Stores or check which ones are currently connected.
• Version Management:
  • Keep all Thanos components updated to ensure compatibility.
• Robust Network Configuration:
  • Use dedicated virtual networks to ensure proper isolation.
• Comprehensive Monitoring:
  • Incorporate continuous monitoring, including both metric and log management solutions.
• Automated Tests:
  • Implement automated tests to verify connectivity and config sanity during deployments.