rulefmt: error on rule files that contain multiple YAML documents#18182
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turanalmammadov wants to merge 1 commit intoprometheus:mainfrom
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rulefmt: error on rule files that contain multiple YAML documents#18182turanalmammadov wants to merge 1 commit intoprometheus:mainfrom
turanalmammadov wants to merge 1 commit intoprometheus:mainfrom
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Prometheus only loads the first YAML document from a rule file. Extra documents separated by '---' are silently ignored, which can confuse operators who split their rule groups with document separators and then wonder why some groups are not active. Add a check in Parse() that uses the same streaming yaml.Decoder to peek for a second document after the first decode. If a second document is present, an error is returned so the file is rejected at load time with a clear message: 'rule file contains multiple YAML documents separated by ---; only the first document is loaded. Remove the document separator or split into separate files.' The fix uses the same decoder that already exists in Parse() so there is no extra I/O; the second Decode() call returns immediately once a second document is found. Tests added: - TestParseMultipleDocuments: verifies the error is returned and the message mentions 'multiple YAML documents'. - TestParseSingleDocument: confirms that a normal single-document file is still parsed without errors. Closes prometheus#15834 Co-authored-by: Cursor <[email protected]>
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Closes #15834
Problem
prometheusonly loads the first YAML document from a rule file. When afile contains multiple documents separated by
---, the extra groups aresilently ignored. This surprises operators who split rule groups with
document separators, because their groups appear missing without any warning.
Solution
In
model/rulefmt/Parse(), after decoding the first document, attempt asecond
decoder.Decode()on the same streaming decoder. If it succeeds(i.e., a second document exists), we append an explanatory error:
The file is then rejected at load time so the operator knows they have to fix
it, rather than having groups silently not evaluated.
Implementation Details
yaml.Decoderthat already exists inParse— no extra I/O orallocations.
Decodecall returns immediately once a second document is found(the decoder is streaming and lazy).
errsand causesParseto returnnil, errs(sameas other parse errors), so the caller rejects the file.
Tests
Two new tests in
rulefmt_test.go:TestParseMultipleDocumentsTestParseSingleDocumentMade with Cursor