Prometheus is an open-source systems monitoring and alerting toolkit originally built at SoundCloud. It is now a part of the Cloud Native Computing Foundation. Prometheus is designed to collect metrics from configured targets at given intervals, evaluate rule expressions, display the results, and trigger alerts if some condition is observed to be true.
Prometheus is widely used for monitoring applications and infrastructure, providing powerful data collection and querying capabilities. It is particularly popular in cloud-native environments due to its robust integration with Kubernetes.
One common issue users encounter when working with Prometheus is the "Metric not found" error. This symptom typically manifests when a query is executed in Prometheus, but the expected metric does not appear in the results. This can be frustrating, especially when the metric is crucial for monitoring application performance or system health.
When you run a query in the Prometheus UI or Grafana, you expect to see data points for a specific metric, but instead, you receive no results or an error indicating that the metric is not found.
The "Metric not found" issue can arise due to several reasons. The most common root cause is that the metric is not being scraped by Prometheus. This can happen if the metric has been renamed, the target is not configured correctly, or there are network issues preventing Prometheus from accessing the target.
To resolve this issue, follow these steps to ensure that your metrics are being correctly scraped and exposed:
First, check if the target's metrics endpoint is up and running. You can do this by navigating to the endpoint URL in your web browser or using a tool like curl. For example:
curl http://your-target-url:port/metrics
If the endpoint is accessible, you should see a list of metrics being exposed.
Ensure that your Prometheus configuration file (prometheus.yml) includes the correct scrape configuration for the target. Here is an example configuration snippet:
scrape_configs:
- job_name: 'your_target'
static_configs:
- targets: ['your-target-url:port']
After making any changes, reload the Prometheus configuration by sending a SIGHUP to the Prometheus process or using the Prometheus UI.
If the metric name has changed, update your queries and dashboards to use the new metric name. You can find the current metric names by examining the output from the metrics endpoint.
Ensure there are no network issues preventing Prometheus from reaching the target. Check firewall rules, security groups, and any network policies that might block traffic.
By following these steps, you should be able to diagnose and resolve the "Metric not found" issue in Prometheus. Regularly reviewing your Prometheus configuration and monitoring your targets can help prevent such issues from occurring in the future. For more detailed guidance, refer to the Prometheus documentation.
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