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Add remove_matching() method for metric label deletion by hazel-shen · Pull Request #1121 · prometheus/client_python · GitHub

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Add remove_matching() method for metric label deletion - #1121

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csmarchbanks merged 3 commits into
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hazel-shen:feature/remove-matching
Oct 28, 2025
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Add remove_matching() method for metric label deletion#1121
csmarchbanks merged 3 commits into
prometheus:masterfrom
hazel-shen:feature/remove-matching

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hazel-shen commented Aug 13, 2025 •
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Description
Fixes #1118
This PR introduces a new remove_by_labels() method to allow removing metric samples by matching a set of label values.

Changes

  • Added remove_by_labels() to MetricWrapperBase for selective deletion of metrics by label.
  • Included validation for label names and types.
  • Added safeguards for multi-process mode (warning issued if used).
  • Kept the return value consistent with remove(): returns None, and acts as a no-op if no series match.

Motivation
Currently, the Python client does not support removing metrics with specific label values without clearing the whole metric. This feature enables more granular control, which can be useful for scenarios such as:

  • Cleaning up metrics for tenants after deprovisioning
  • Removing outdated or irrelevant labeled data without impacting other metrics

Example Usage

from prometheus_client import Counter

c = Counter('my_counter', 'Example counter', ['tenant', 'status'])
c.labels(tenant='acme', status='ok').inc()
c.labels(tenant='acme', status='fail').inc()

# remove all series with tenant='acme', regardless of status
c.remove_by_labels({'tenant': 'acme'})

@csmarchbanks Would you take a look when you have a chance?

Add remove_matching() method for metric label deletion
edb0e7c 
Signed-off-by: Hazel <hazel@hazel.localdomain>
csmarchbanks reviewed Aug 15, 2025
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Thanks! A couple comments/questions to start with

Comment thread prometheus_client/metrics.py Outdated
if labelvalues in self._metrics:
del self._metrics[labelvalues]

def remove_matching(self, partial: dict[str, str]) -> int:

csmarchbanks Aug 15, 2025

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

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.

hazel-shen Aug 18, 2025 •
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

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.

Comment thread prometheus_client/metrics.py Outdated

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

deleted = 0

csmarchbanks Aug 15, 2025

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

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.

hazel-shen Aug 18, 2025

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

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.

Hazel added 2 commits August 18, 2025 17:03
Rename function name, and the parameter's name
ac8b74e 
Signed-off-by: Hazel <hazel@hazel.localdomain>
Make remove_by_labels() consistent with remove(): return None
fc3fc1e 
Signed-off-by: Hazel <hazel@hazel.localdomain>
hazel-shen force-pushed the feature/remove-matching branch from 213940c to fc3fc1e Compare August 18, 2025 10:19

TheGameProfi commented Oct 7, 2025

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Thanks for the updated code, @csmarchbanks could we get another review on this PR?

csmarchbanks approved these changes Oct 28, 2025
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Thanks!

csmarchbanks merged commit 378510b into prometheus:master Oct 28, 2025
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csmarchbanks csmarchbanks approved these changes
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TheGameProfi TheGameProfi approved these changes
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Implement deletion of Gauge metrics based on partially specified labels

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