admin: add invert_filter query param to /stats

[aakugan]

Commit Message

admin: add invert_filter query param to /stats

Additional Description

Adds an invert_filter query parameter to the admin /stats endpoint (text, json, and prometheus formats). When present alongside filter, the RE2 regex is inverted: stats whose names match the filter are excluded, and non-matching stats are returned.
Example: /stats?filter=server&invert_filter returns all stats except those matching server.
invert_filter without filter returns HTTP 400.

Needed because the re2 engine is not great at handling inversions like these.

Testing:

• stats_params_test: parse validation (invert_filter requires filter), shouldShowMetric positive/negative cases
• stats_handler_test: invert filter for text, json, and prometheus output
• stats_request_test: prometheus stat-map filtering with inverted filter
• admin_test: admin integration coverage

Risk Level

Low

[repokitteh-read-only]

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Please mark your PR as ready when you want it to be reviewed!

🐱

Caused by: #46073 was opened by aakugan.

see: more, trace.

[basundhara-c]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces an invert_filter query parameter to the /stats and /stats/prometheus admin endpoints, allowing users to exclude stats matching the specified regular expression. The changes include parameter parsing, logic to invert the regex matching results, updated documentation, and comprehensive unit tests. The review feedback suggests two improvements: using the more idiomatic query_.has() method to check for the presence of the query parameter, and defensively handling null filters within shouldShowMetricName to simplify callers and prevent potential null pointer dereferences.

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[basundhara-c]

@agrawroh could you TAL?