Скачать или смотреть How to Create Effective Alerts for Application Errors in Prometheus

Discover a step-by-step solution to create Prometheus alerts that trigger only on the first occurrence of application errors, ensuring you catch that critical moment without false alarms.
---
This video is based on the question https://stackoverflow.com/q/65287330/ asked by the user 'passwd' ( https://stackoverflow.com/u/6167229/ ) and on the answer https://stackoverflow.com/a/65289889/ provided by the user 'passwd' ( https://stackoverflow.com/u/6167229/ ) 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 alerts first counter value

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.
---
How to Create Effective Alerts for Application Errors in Prometheus

Monitoring applications is crucial for understanding their performance and stability. One significant aspect of monitoring is catching errors as they happen. In this guide, we will address a common problem encountered while setting up alerts for application errors using Prometheus, and we will provide a comprehensive solution to ensure you correctly detect the first occurrence of an error.

The Problem: Catching the First Instance of an Error

Imagine you have a metric that counts errors in your application. You intend to create an alert that notifies you whenever an error occurs. However, when you attempt to catch an increase in the metric using the increase function, it always returns 0. This can lead to confusion and a lack of effective monitoring.

Example Scenario

You might have the following query to detect increases in application errors over the past hour:

[[See Video to Reveal this Text or Code Snippet]]

However, the query returns 0, indicating no error occurrences. Even if you attempt to use an offset to examine historical data:

[[See Video to Reveal this Text or Code Snippet]]

It still doesn't yield the first error encounter. This leads to the pressing question: How can you catch the very first instance of an error metric effectively?

Solution: Using the unless Operator

The solution to this problem involves utilizing the unless operator in Prometheus. By applying this operator cleverly, you can filter the results in a way that accurately reflects the first occurrence of an error. Let's break down the solution step by step.

Step 1: Understanding the unless Operator

The unless operator in Prometheus is used to return the left side of the expression unless there are matches found on the right side of the expression. This operator is handy for filtering out unwanted results based on specific conditions.

Step 2: Constructing the Query

To implement this solution, you will use the following query:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Query

app_error: This represents the metric that counts the errors in your application.

unless: This operator helps to exclude any counts from the right side of the expression from appearing on the left side.

app_error offset 1h: This checks for any existing error counts one hour prior. It effectively filters out any subsequent counts, allowing you to catch the first error without it being masked by subsequent occurrences.

Step 3: Testing the Alert

Once you implement the query, it's vital to test the alert to ensure that it correctly triggers notifications on the first occurrence of application errors. Monitor your Prometheus server and verify that alerts fire as expected when the first error is logged.

Conclusion

By using the unless operator in Prometheus, you can accurately detect and alert on the first instance of an error occurrence in your application. This method not only improves your monitoring strategies but also helps in reducing false positives, ensuring you are notified only when it truly matters.

Now you have the tools to set up effective alerts for application errors with Prometheus. Implement this strategy and refine your monitoring practice to act swiftly in response to potential issues in your application.