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Coerce label values to strings in MetricFamily add_metric #1221

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14add3f
Coerce label values to strings in MetricFamily add_metric
cpruijsen Oct 13, 2026
041878f
Coerce Info and StateSet dict values to strings and widen hints
cpruijsen Oct 18, 2026
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65 changes: 36 additions & 29 deletions prometheus_client/metrics_core.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
from typing import Dict, List, Optional, Sequence, Tuple, Union
from typing import Any, Dict, List, Mapping, Optional, Sequence, Tuple, Union

from .samples import Exemplar, NativeHistogram, Sample, Timestamp
from .validation import _validate_metric_name
Expand Down Expand Up @@ -86,13 +86,14 @@ def __init__(self,
if value is not None:
self.add_metric([], value)

def add_metric(self, labels: Sequence[str], value: float, timestamp: Optional[Union[Timestamp, float]] = None) -> None:
def add_metric(self, labels: Sequence[object], value: float, timestamp: Optional[Union[Timestamp, float]] = None) -> None:
"""Add a metric to the metric family.
Args:
labels: A list of label values
value: The value of the metric.
"""
self.samples.append(Sample(self.name, dict(zip(self._labelnames, labels)), value, timestamp))
label_values = tuple(str(l) for l in labels)
self.samples.append(Sample(self.name, dict(zip(self._labelnames, label_values)), value, timestamp))


# For backward compatibility.
Expand Down Expand Up @@ -127,7 +128,7 @@ def __init__(self,
self.add_metric([], value, created, exemplar=exemplar)

def add_metric(self,
labels: Sequence[str],
labels: Sequence[object],
value: float,
created: Optional[float] = None,
timestamp: Optional[Union[Timestamp, float]] = None,
Expand All @@ -140,9 +141,10 @@ def add_metric(self,
value: The value of the metric
created: Optional unix timestamp the child was created at.
"""
self.samples.append(Sample(self.name + '_total', dict(zip(self._labelnames, labels)), value, timestamp, exemplar))
label_values = tuple(str(l) for l in labels)
self.samples.append(Sample(self.name + '_total', dict(zip(self._labelnames, label_values)), value, timestamp, exemplar))
if created is not None:
self.samples.append(Sample(self.name + '_created', dict(zip(self._labelnames, labels)), created, timestamp))
self.samples.append(Sample(self.name + '_created', dict(zip(self._labelnames, label_values)), created, timestamp))


class GaugeMetricFamily(Metric):
Expand All @@ -167,14 +169,15 @@ def __init__(self,
if value is not None:
self.add_metric([], value)

def add_metric(self, labels: Sequence[str], value: float, timestamp: Optional[Union[Timestamp, float]] = None) -> None:
def add_metric(self, labels: Sequence[object], value: float, timestamp: Optional[Union[Timestamp, float]] = None) -> None:
"""Add a metric to the metric family.

Args:
labels: A list of label values
value: A float
"""
self.samples.append(Sample(self.name, dict(zip(self._labelnames, labels)), value, timestamp))
label_values = tuple(str(l) for l in labels)
self.samples.append(Sample(self.name, dict(zip(self._labelnames, label_values)), value, timestamp))


class SummaryMetricFamily(Metric):
Expand Down Expand Up @@ -204,7 +207,7 @@ def __init__(self,
self.add_metric([], count_value, sum_value)

def add_metric(self,
labels: Sequence[str],
labels: Sequence[object],
count_value: int,
sum_value: float,
timestamp:
Expand All @@ -217,8 +220,9 @@ def add_metric(self,
count_value: The count value of the metric.
sum_value: The sum value of the metric.
"""
self.samples.append(Sample(self.name + '_count', dict(zip(self._labelnames, labels)), count_value, timestamp))
self.samples.append(Sample(self.name + '_sum', dict(zip(self._labelnames, labels)), sum_value, timestamp))
label_values = tuple(str(l) for l in labels)
self.samples.append(Sample(self.name + '_count', dict(zip(self._labelnames, label_values)), count_value, timestamp))
self.samples.append(Sample(self.name + '_sum', dict(zip(self._labelnames, label_values)), sum_value, timestamp))


class HistogramMetricFamily(Metric):
Expand Down Expand Up @@ -247,7 +251,7 @@ def __init__(self,
self.add_metric([], buckets, sum_value)

def add_metric(self,
labels: Sequence[str],
labels: Sequence[object],
buckets: Sequence[Union[Tuple[str, float], Tuple[str, float, Exemplar]]],
sum_value: Optional[float],
timestamp: Optional[Union[Timestamp, float]] = None) -> None:
Expand All @@ -261,14 +265,15 @@ def add_metric(self,
The buckets must be sorted, and +Inf present.
sum_value: The sum value of the metric.
"""
label_values = tuple(str(l) for l in labels)
for b in buckets:
bucket, value = b[:2]
exemplar = None
if len(b) == 3:
exemplar = b[2] # type: ignore
self.samples.append(Sample(
self.name + '_bucket',
dict(list(zip(self._labelnames, labels)) + [('le', bucket)]),
dict(list(zip(self._labelnames, label_values)) + [('le', bucket)]),
value,
timestamp,
exemplar,
Expand All @@ -277,9 +282,9 @@ def add_metric(self,
if float(buckets[0][0]) >= 0 and sum_value is not None:
# +Inf is last and provides the count value.
self.samples.append(
Sample(self.name + '_count', dict(zip(self._labelnames, labels)), buckets[-1][1], timestamp))
Sample(self.name + '_count', dict(zip(self._labelnames, label_values)), buckets[-1][1], timestamp))
self.samples.append(
Sample(self.name + '_sum', dict(zip(self._labelnames, labels)), sum_value, timestamp))
Sample(self.name + '_sum', dict(zip(self._labelnames, label_values)), sum_value, timestamp))


class GaugeHistogramMetricFamily(Metric):
Expand All @@ -306,7 +311,7 @@ def __init__(self,
self.add_metric([], buckets, gsum_value)

def add_metric(self,
labels: Sequence[str],
labels: Sequence[object],
buckets: Sequence[Tuple[str, float]],
gsum_value: Optional[float],
timestamp: Optional[Union[float, Timestamp]] = None,
Expand All @@ -319,16 +324,17 @@ def add_metric(self,
The buckets must be sorted, and +Inf present.
gsum_value: The sum value of the metric.
"""
label_values = tuple(str(l) for l in labels)
for bucket, value in buckets:
self.samples.append(Sample(
self.name + '_bucket',
dict(list(zip(self._labelnames, labels)) + [('le', bucket)]),
dict(list(zip(self._labelnames, label_values)) + [('le', bucket)]),
value, timestamp))
# +Inf is last and provides the count value.
self.samples.extend([
Sample(self.name + '_gcount', dict(zip(self._labelnames, labels)), buckets[-1][1], timestamp),
Sample(self.name + '_gcount', dict(zip(self._labelnames, label_values)), buckets[-1][1], timestamp),
# TODO: Handle None gsum_value correctly. Currently a None will fail exposition but is allowed here.
Sample(self.name + '_gsum', dict(zip(self._labelnames, labels)), gsum_value, timestamp), # type: ignore
Sample(self.name + '_gsum', dict(zip(self._labelnames, label_values)), gsum_value, timestamp), # type: ignore
])


Expand All @@ -341,7 +347,7 @@ class InfoMetricFamily(Metric):
def __init__(self,
name: str,
documentation: str,
value: Optional[Dict[str, str]] = None,
value: Optional[Mapping[str, object]] = None,
labels: Optional[Sequence[str]] = None,
):
Metric.__init__(self, name, documentation, 'info')
Expand All @@ -354,8 +360,8 @@ def __init__(self,
self.add_metric([], value)

def add_metric(self,
labels: Sequence[str],
value: Dict[str, str],
labels: Sequence[object],
value: Mapping[str, object],
timestamp: Optional[Union[Timestamp, float]] = None,
) -> None:
"""Add a metric to the metric family.
Expand All @@ -364,9 +370,10 @@ def add_metric(self,
labels: A list of label values
value: A dict of labels
"""
label_values = tuple(str(l) for l in labels)
self.samples.append(Sample(
self.name + '_info',
dict(dict(zip(self._labelnames, labels)), **value),
dict(dict(zip(self._labelnames, label_values)), **{k: str(v) for k, v in value.items()}),
1,
timestamp,
))
Expand All @@ -381,7 +388,7 @@ class StateSetMetricFamily(Metric):
def __init__(self,
name: str,
documentation: str,
value: Optional[Dict[str, bool]] = None,
value: Optional[Mapping[Any, bool]] = None,
labels: Optional[Sequence[str]] = None,
):
Metric.__init__(self, name, documentation, 'stateset')
Expand All @@ -394,8 +401,8 @@ def __init__(self,
self.add_metric([], value)

def add_metric(self,
labels: Sequence[str],
value: Dict[str, bool],
labels: Sequence[object],
value: Mapping[Any, bool],
timestamp: Optional[Union[Timestamp, float]] = None,
) -> None:
"""Add a metric to the metric family.
Expand All @@ -404,12 +411,12 @@ def add_metric(self,
labels: A list of label values
value: A dict of string state names to booleans
"""
labels = tuple(labels)
for state, enabled in sorted(value.items()):
label_values = tuple(str(l) for l in labels)
for state, enabled in sorted((str(s), e) for s, e in value.items()):
v = (1 if enabled else 0)
self.samples.append(Sample(
self.name,
dict(zip(self._labelnames + (self.name,), labels + (state,))),
dict(zip(self._labelnames + (self.name,), label_values + (state,))),
v,
timestamp,
))
50 changes: 50 additions & 0 deletions tests/test_core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
StateSetMetricFamily, Summary, SummaryMetricFamily, UntypedMetricFamily,
)
from prometheus_client.decorator import getargspec
from prometheus_client.exposition import generate_latest
from prometheus_client.metrics import _get_use_created
from prometheus_client.validation import (
disable_legacy_validation, enable_legacy_validation,
Expand Down Expand Up @@ -889,6 +890,55 @@ def test_stateset_labels(self):
self.assertEqual(0, self.registry.get_sample_value('s', {'foo': 'bar', 's': 'a'}))
self.assertEqual(0, self.registry.get_sample_value('s', {'foo': 'bar', 's': 'b'}))

def test_labels_coerced_to_string(self):
umf = UntypedMetricFamily('u', 'help', labels=['a'])
umf.add_metric([1], 2)
self.custom_collector(umf)
self.assertEqual(2, self.registry.get_sample_value('u', {'a': '1'}))

cmf = CounterMetricFamily('c', 'help', labels=['a'])
cmf.add_metric([1], 2, created=3)
self.custom_collector(cmf)
self.assertEqual(2, self.registry.get_sample_value('c_total', {'a': '1'}))
self.assertEqual(3, self.registry.get_sample_value('c_created', {'a': '1'}))

gmf = GaugeMetricFamily('g', 'help', labels=['a'])
gmf.add_metric([1], 2)
self.custom_collector(gmf)
self.assertEqual(2, self.registry.get_sample_value('g', {'a': '1'}))

smf = SummaryMetricFamily('s', 'help', labels=['a'])
smf.add_metric([1], count_value=1, sum_value=2)
self.custom_collector(smf)
self.assertEqual(1, self.registry.get_sample_value('s_count', {'a': '1'}))
self.assertEqual(2, self.registry.get_sample_value('s_sum', {'a': '1'}))

hmf = HistogramMetricFamily('h', 'help', labels=['a'])
hmf.add_metric([1], buckets=[('0', 1), ('+Inf', 2)], sum_value=3)
self.custom_collector(hmf)
self.assertEqual(1, self.registry.get_sample_value('h_bucket', {'a': '1', 'le': '0'}))
self.assertEqual(2, self.registry.get_sample_value('h_count', {'a': '1'}))
self.assertEqual(3, self.registry.get_sample_value('h_sum', {'a': '1'}))

ghmf = GaugeHistogramMetricFamily('gh', 'help', labels=['a'])
ghmf.add_metric([1], buckets=[('0', 1), ('+Inf', 2)], gsum_value=3)
self.custom_collector(ghmf)
self.assertEqual(1, self.registry.get_sample_value('gh_bucket', {'a': '1', 'le': '0'}))
self.assertEqual(2, self.registry.get_sample_value('gh_gcount', {'a': '1'}))
self.assertEqual(3, self.registry.get_sample_value('gh_gsum', {'a': '1'}))

imf = InfoMetricFamily('i', 'help', labels=['a'])
imf.add_metric([1], {'c': 2})
self.custom_collector(imf)
self.assertEqual(1, self.registry.get_sample_value('i_info', {'a': '1', 'c': '2'}))

ssf = StateSetMetricFamily('ss', 'help', labels=['a'])
ssf.add_metric([1], {3: True})
self.custom_collector(ssf)
self.assertEqual(1, self.registry.get_sample_value('ss', {'a': '1', 'ss': '3'}))

self.assertIn(b'g{a="1"} 2.0', generate_latest(self.registry))

def test_bad_constructors(self):
self.assertRaises(ValueError, UntypedMetricFamily, 'u', 'help', value=1, labels=[])
self.assertRaises(ValueError, UntypedMetricFamily, 'u', 'help', value=1, labels=['a'])
Expand Down