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Add remove_matching() method for metric label deletion #1121

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Add remove_matching() method for metric label deletion #1121

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edb0e7c
Add remove_matching() method for metric label deletion
Aug 13, 2025
ac8b74e
Rename function name, and the parameter's name
Aug 18, 2025
fc3fc1e
Make remove_by_labels() consistent with remove(): return None
Aug 18, 2025
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35 changes: 35 additions & 0 deletions prometheus_client/metrics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,41 @@ def remove(self, *labelvalues: Any) -> None:
if labelvalues in self._metrics:
del self._metrics[labelvalues]

def remove_matching(self, partial: dict[str, str]) -> int:
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What would you think of remove_partial_match for the name of this function? When I first see matching I think that all labelnames/values need to match to be removed not a partial. The name of the variable helps, but could also then be labels instead of partial which helps with confusion around thinking it could be a partial function.

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@hazel-shen hazel-shen Aug 18, 2025 •
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Thanks for the suggestion! I’ve renamed the method to remove_by_labels and the argument to labels.
I also added a short docstring to clarify that this removes series where the provided (key, value) pairs are a partial match of the labelset.
This should reduce confusion with full-match semantics.

if 'prometheus_multiproc_dir' in os.environ or 'PROMETHEUS_MULTIPROC_DIR' in os.environ:
warnings.warn(
"Removal of labels has not been implemented in multi-process mode yet.",
UserWarning
)

if not self._labelnames:
raise ValueError('No label names were set when constructing %s' % self)

if not isinstance(partial, dict):
raise TypeError("partial must be a dict of {label_name: label_value}")

if not partial:
return 0

invalid = [k for k in partial.keys() if k not in self._labelnames]
if invalid:
raise ValueError(
'Unknown label names: %s; expected %s' % (invalid, self._labelnames)
)

pos_filter = {self._labelnames.index(k): str(v) for k, v in partial.items()}

deleted = 0
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What's the reasoning for returning the number of deleted items? We don't do that in remove today, but if there is a good use case I am not opposed.

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Good point on consistency. The initial version returned the number of deleted series, but I’ve updated it to return None, matching the behavior of remove(): idempotent and a no-op if nothing matches.
If there’s a strong use case for counts in the future, I’m happy to follow up with a separate helper that reports the number of removed series, without changing the main API.

with self._lock:
for lv in list(self._metrics.keys()):
if all(lv[pos] == want for pos, want in pos_filter.items()):
if lv in self._metrics:
del self._metrics[lv]
deleted += 1

return deleted


def clear(self) -> None:
"""Remove all labelsets from the metric"""
if 'prometheus_multiproc_dir' in os.environ or 'PROMETHEUS_MULTIPROC_DIR' in os.environ:
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30 changes: 30 additions & 0 deletions tests/test_core.py
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Expand Up @@ -630,6 +630,36 @@ def test_labels_coerced_to_string(self):
self.counter.remove(None)
self.assertEqual(None, self.registry.get_sample_value('c_total', {'l': 'None'}))

def test_remove_matching(self):
from prometheus_client import Counter

c = Counter('c2', 'help', ['tenant', 'endpoint'], registry=self.registry)
c.labels('acme', '/').inc()
c.labels('acme', '/checkout').inc()
c.labels('globex', '/').inc()


deleted = c.remove_matching({'tenant': 'acme'})
self.assertEqual(2, deleted)

self.assertIsNone(self.registry.get_sample_value('c2_total', {'tenant': 'acme', 'endpoint': '/'}))
self.assertIsNone(self.registry.get_sample_value('c2_total', {'tenant': 'acme', 'endpoint': '/checkout'}))
self.assertEqual(1, self.registry.get_sample_value('c2_total', {'tenant': 'globex', 'endpoint': '/'}))

def test_remove_matching_invalid_label_name(self):
from prometheus_client import Counter
c = Counter('c3', 'help', ['tenant', 'endpoint'], registry=self.registry)
c.labels('acme', '/').inc()
with self.assertRaises(ValueError):
c.remove_matching({'badkey': 'x'})

def test_remove_matching_empty_is_noop(self):
from prometheus_client import Counter
c = Counter('c4', 'help', ['tenant', 'endpoint'], registry=self.registry)
c.labels('acme', '/').inc()
self.assertEqual(0, c.remove_matching({}))
self.assertEqual(1, self.registry.get_sample_value('c4_total', {'tenant': 'acme', 'endpoint': '/'}))

def test_non_string_labels_raises(self):
class Test:
__str__ = None
Expand Down