rule: expression with max_over_time no return data

[ximito]

Prometheus and Golang version used:
Thanos 0.36.1

Object Storage Provider: None

What happened:

I'm using the rule component. I have defined an expression where the "max_over_time" function is used. In the evaluation time of the rule, nothing is returned, and no information is returned in the log either. But this expression returns data correctly from Thanos Query.

What you expected to happen:
Return the same value like a Thanos query

[dosubot]

Hey @ximito, I'm here to help you with any bugs, questions, or contributions you have. Let's get that issue sorted for you!

The issue you're experiencing with the max_over_time function in the Thanos rule component not returning data, while it works in Thanos Query, could be due to several factors:

1. Evaluation Failures: Ensure that the rule expression is correctly defined and that there are no evaluation failures. Check for any alerts like ThanosRuleHighRuleEvaluationFailures that might indicate issues with the query API endpoint used ^[1].

2. Configuration Issues: Verify that the Thanos rule component is correctly configured with the necessary query URLs and rule files. Ensure that the --grpc-query-endpoint is correctly set to point to the Thanos Query component ^[2].

3. Logging Configuration: Since no information is returned in the log, consider adjusting the logging level to DEBUG to capture more detailed logs. This can help identify any underlying issues during rule evaluation ^[3].

4. Query Reliability: The Thanos rule component relies on the Thanos Query component for data. Ensure that the query endpoints are reliable and accessible. Any network issues or DNS failures could prevent data from being fetched ^[1].

5. Time Series Data Handling: There might be differences in how the rule component handles time series data compared to the query component. Ensure that the data is available and correctly queried by the rule component.

By checking these aspects, you should be able to diagnose and resolve the issue with the max_over_time function in your Thanos rule expression.

To continue talking to Dosu, mention @dosu.

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[AgustinICAI]

I can ensure that happens, that Thanos ruler 0.36.1 is not able to evaluate functions with range-vectors, although thanos query is able to do it.