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Metrics without labels missing breaks some codepath #949
Description
When initialized without labels, it seems that the resulting metrics objects will lack some instance variables.
Minimal example:
from prometheus_client import Gauge, generate_latest
cc = Gauge("dummy_count", "POC")
if __name__ == '__main__':
cc.set(42)
print(generate_latest().decode()) # OK
cc.clear() # raises
"""
Traceback (most recent call last):
File "prom_example.py", line 10, in <module>
cc.clear() # raises
^^^^^^^^^^
File …/site-packages/prometheus_client/metrics.py", line 213, in clear
with self._lock:
^^^^^^^^^^
AttributeError: 'Gauge' object has no attribute '_lock'
"""The same code with declared labels will properly clear the metrics data
I came up upon this when adding a new metric and forgetting to add the labels.
(I'm using .clear() to reset the metrics during tests)
Activity
romuald commentedon Aug 2, 2023
I've tried to add a
_lock: contextlib.contextmanager = contextlib.nullcontext()inMetricWrapperBaseThis fixes the problem, but the
.clear()does not do anything anyway (it simply creates a_metrics = {}on the object, the values are kept)Not sure how to properly fix this, or if this is even desirable
roidelapluie commentedon Aug 8, 2023
clear()is indeed not intended for metrics without labels.You could use e.g.
.set(-1)if your testsfix: raise ValueError when clear() called on metric without labels (p…