Prometheus is an open-source systems monitoring and alerting toolkit originally built at SoundCloud. It is designed to record real-time metrics in a time-series database, built using an HTTP pull model, with flexible queries and real-time alerting. Prometheus is a powerful tool for monitoring applications and infrastructure, providing insights into system performance and health.
One common issue users encounter with Prometheus is that it stops scraping metrics from configured targets. This symptom is typically observed when there are no new data points being recorded in the Prometheus database for certain metrics, or when alerts are triggered due to missing data.
The root cause of Prometheus not scraping is often due to incorrect scrape configurations or network connectivity issues. Scrape configuration errors can occur if the target endpoints are misconfigured in the prometheus.yml file. Network issues might arise if there are firewall rules blocking access or if the target service is down.
Errors in the prometheus.yml file can prevent Prometheus from accessing the targets. This includes incorrect job names, target URLs, or missing configurations.
Network issues can prevent Prometheus from reaching the target endpoints. This could be due to firewall settings, DNS resolution issues, or the target service being unavailable.
To resolve the issue of Prometheus not scraping, follow these steps:
Check the prometheus.yml file for any misconfigurations. Ensure that the job names and target URLs are correct. For more information on configuring Prometheus, refer to the Prometheus Configuration Documentation.
scrape_configs:
- job_name: 'my_service'
static_configs:
- targets: ['localhost:9090']
Ensure that Prometheus can reach the target endpoints. Use tools like curl or ping to test connectivity. If there are network issues, check firewall settings and DNS configurations.
curl http://localhost:9090/metrics
Review the Prometheus logs for any errors related to scraping. Logs can provide insights into what might be going wrong. You can access logs using:
docker logs prometheus_container_name
If changes were made to the configuration, restart Prometheus to apply them. This can be done using:
systemctl restart prometheus
By following these steps, you should be able to diagnose and resolve issues related to Prometheus not scraping. Ensuring correct configurations and network connectivity is crucial for Prometheus to function effectively. For further reading, visit the Prometheus Overview.
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