Fix operator precedence allowing exemplars on any metric type#1188
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sean-kim05 wants to merge 1 commit into
Open
Fix operator precedence allowing exemplars on any metric type#1188sean-kim05 wants to merge 1 commit into
sean-kim05 wants to merge 1 commit into
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_is_valid_exemplar_metric() guarded histograms with
if metric.type in ('histogram') and sample.name.endswith('_bucket') or sample.name == metric.name:
Because 'and' binds tighter than 'or', this parsed as
(metric.type in ('histogram') and sample.name.endswith('_bucket')) or (sample.name == metric.name)
so the trailing 'sample.name == metric.name' clause fired for every
metric type. As a result the OpenMetrics writer emitted exemplars on
gauges, info, stateset, summary and untyped metrics whenever a sample
name equalled the metric name -- output that the library's own
OpenMetrics parser rejects (only histogram/gaugehistogram buckets,
counter _total, and native histograms may carry exemplars).
Group the histogram condition correctly so the same-name clause (which
exists to allow native-histogram exemplars) only applies to histograms.
While here, replace the 'metric.type in (...)' single-string membership
checks with '==' -- they were doing substring matching, not the
intended equality.
Add test_gauge_exemplar, which asserts a gauge sample carrying an
exemplar raises ValueError, matching the existing untyped/non-bucket
exemplar tests.
Signed-off-by: Sean Kim <skim8705@gmail.com>
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_is_valid_exemplar_metric()inopenmetrics/exposition.pyguards histograms with:Since
andbinds tighter thanor, this is evaluated as:so the trailing
sample.name == metric.nameclause runs for every metric type, not just histograms. As a result the OpenMetrics writer attaches exemplars to gauge/info/stateset/summary/untyped metrics whenever a sample name equals the metric name — output that this library's own OpenMetrics parser then rejects (only histogram/gaugehistogram buckets and counters can have exemplars).Minimal repro:
The fix groups the histogram condition so the same-name clause — which exists to allow native-histogram exemplars, whose sample name equals the metric name — only applies to histograms. I also changed the two
metric.type in ('...')checks to==; with a single string argument they were doing substring matching rather than the intended equality.Added
test_gauge_exemplarnext to the existing untyped/non-bucket exemplar tests. It fails before the change (ValueError not raised) and passes after. Full test suite is green and flake8/isort/mypy pass.@csmarchbanks