Troubleshooting Common Issues in Prometheus
1. Prometheus Not Starting
If Prometheus fails to start, it can be due to various reasons such as configuration errors or missing directories.
Example: Check the logs for errors by running the following command:
Common log entries might indicate syntax errors in your configuration file. Ensure your prometheus.yml is correctly formatted.
2. Metrics Not Being Collected
Sometimes Prometheus may not collect metrics from the target endpoints. This could be due to network issues or misconfiguration.
Example: Validate that the target is reachable:
If the endpoint is not reachable, check your network settings, firewall rules, or the target service status.
3. High Memory Usage
Prometheus can consume a lot of memory, especially if scraping a large number of targets or retaining a lot of time series data.
Example: You can check the current memory usage by using:
To mitigate high memory usage, consider configuring retention settings in prometheus.yml:
This command will reduce the retention time of the data to 30 days.
4. Alerting Rules Not Firing
If your alerting rules are not firing, there might be an issue with their configuration or the evaluation conditions.
Example: Check the alerting rules by inspecting the configuration file:
Ensure that your alerting rules are correctly defined and that the conditions for firing them are being met.
5. Unable to Access the UI
If you cannot access the Prometheus web UI, it could be due to firewall settings or incorrect port configuration.
Example: Verify that Prometheus is running on the expected port:
Make sure that port 9090 is open in your firewall and accessible from your browser.