Understanding up vs. probe_success: Troubleshooting Prometheus and Blackbox Exporter Issues

Explore common issues with Prometheus UI and Blackbox Exporter, particularly the distinction between the `up` and `probe_success` metrics, and learn how to effectively troubleshoot them. --- This video is based on the question https://stackoverflow.com/q/65790296/ asked by the user 'Rui Mao' ( https://stackoverflow.com/u/5783496/ ) and on the answer https://stackoverflow.com/a/65791248/ provided by the user 'Andreas Jägle' ( https://stackoverflow.com/u/4854965/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Prometheus UI always returns 1 even blackbox_exporter returns 0 manually Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Understanding Prometheus UI and Blackbox Exporter Metrics Setting up Prometheus alongside the Blackbox Exporter can initially seem straightforward, but some common issues may arise, particularly regarding the metrics displayed in the Prometheus UI. A frequently encountered problem is when the Prometheus UI consistently shows a value of 1 for the up metric while the Blackbox Exporter indicates a value of 0 for the same target when checked manually. This discrepancy can be confusing for many users trying to monitor their systems effectively. The Problem Explained In the situation described, you have the following example: You configured Prometheus and the Blackbox Exporter to monitor a specific URL (http://wiki.itsmwork.com). When you manually check the URL using a command like curl, the result indicates success, and the Blackbox Exporter returns a 0, which indicates that the monitored target is not responding as expected. However, when you look at the Prometheus UI, the query up{instance="http://wiki.itsmwork.com", job="blackbox"} returns 1. This can be perplexing, as you would expect up to reflect the actual state of the target being monitored. Understanding the Metrics Key Definitions The confusion often stems from misunderstanding what each metric signifies: up Metric: This metric indicates whether the Blackbox Exporter itself is up and reachable. If up returns 1, it means that Prometheus can communicate with the Blackbox Exporter successfully. probe_success Metric: This metric reflects whether the Blackbox Exporter could successfully probe the specified target. If probe_success returns 0, it indicates that the target is not responding as expected when sampled. Breakdown of Your Scenario From your setup: Prometheus Can Reach the Blackbox Exporter: The up metric indicating 1 means that the Blackbox Exporter is running, and Prometheus can reach it without issue. Problem with the Monitored Target: The probe_success metric showing 0 communicates that the actual service at http://wiki.itsmwork.com is not responding as intended when checked by the Blackbox Exporter. This aligns with your manual curl checks, which confirm that although Blackbox Exporter itself is functioning, the service you are trying to monitor is failing or not replying properly. How to Troubleshoot Here are some steps and considerations to clear up any confusion and troubleshoot the situation effectively: Confirm the Blackbox Exporter's Availability: Run checks against the Blackbox Exporter endpoint (e.g., curl http://localhost:9115/probe) to verify its operational status. Examine Target Availability: Ensure that the target http://wiki.itsmwork.com is online and capable of responding. Use various methods (like curl and web browser access) to rule out any network issues. Use Combined Metrics for Clarity: When monitoring via Prometheus, always consider both the up and probe_success metrics. This provides a clearer picture of both the monitoring setup and the status of the target. Identify Misconfigurations: Double-check configuration files for any potential errors. For example: Review networking or DNS settings to ensure the Blackbox Exporter can reach the target. Confirm the target is defined correctly in the Blackbox Exporter's configuration. Consult Logs: Check the logs of both Prometheus and the Blackbox Exporter for error messages or warnings that could point to the source of the problem. By following these steps, you can effectively monitor your systems with Prometheus and the Blackbox Exporter while understanding the distinctions among the various metrics presented in the dashboard. Conclusion In conclusion, under