Drop the use of double locking in values and metrics modules

It's hard to justify the overhead of double locking there.

Signed-off-by: Przemysław Suliga <mail@suligap.net>

Author: suligap

prometheus_client/metrics.py

@@ -1,4 +1,5 @@
 import os
+from threading import Lock
 import time
 import types
 from typing import (
@@ -12,7 +13,7 @@
 from .metrics_core import Metric
 from .registry import Collector, CollectorRegistry, REGISTRY
 from .samples import Exemplar, Sample
-from .utils import floatToGoString, INF, WarnLock
+from .utils import floatToGoString, INF
 from .validation import (
     _validate_exemplar, _validate_labelnames, _validate_metric_name,
 )
@@ -119,7 +120,7 @@ def __init__(self: T,
 
         if self._is_parent():
             # Prepare the fields needed for child metrics.
-            self._lock = WarnLock()
+            self._lock = Lock()
             self._metrics: Dict[Sequence[str], T] = {}
 
         if self._is_observable():
@@ -672,7 +673,7 @@ class Info(MetricWrapperBase):
 
     def _metric_init(self):
         self._labelname_set = set(self._labelnames)
-        self._lock = WarnLock()
+        self._lock = Lock()
         self._value = {}
 
     def info(self, val: Dict[str, str]) -> None:
@@ -734,7 +735,7 @@ def __init__(self,
 
     def _metric_init(self) -> None:
         self._value = 0
-        self._lock = WarnLock()
+        self._lock = Lock()
 
     def state(self, state: str) -> None:
         """Set enum metric state."""

prometheus_client/values.py

@@ -1,8 +1,8 @@
 import os
+from threading import Lock
 import warnings
 
 from .mmap_dict import mmap_key, MmapedDict
-from .utils import WarnLock
 
 
 class MutexValue:
@@ -13,7 +13,7 @@ class MutexValue:
     def __init__(self, typ, metric_name, name, labelnames, labelvalues, help_text, **kwargs):
         self._value = 0.0
         self._exemplar = None
-        self._lock = WarnLock()
+        self._lock = Lock()
 
     def inc(self, amount):
         with self._lock:
@@ -49,7 +49,7 @@ def MultiProcessValue(process_identifier=os.getpid):
     pid = {'value': process_identifier()}
     # Use a single global lock when in multi-processing mode.
     # This avoids the need to also have mutexes in __MmapDict.
-    lock = WarnLock()
+    lock = Lock()
 
     class MmapedValue:
         """A float protected by a mutex backed by a per-process mmaped file."""

tests/test_core.py

@@ -135,19 +135,6 @@ def test_exemplar_too_long(self):
             'y123456': '7+15 characters',
         })
 
-    def test_single_thread_deadlock_detection(self):
-        counter = self.counter
-
-        class Tracked(float):
-            def __radd__(self, other):
-                counter.inc(10)
-                return self + other
-
-        expected_msg = 'Attempt to enter a non reentrant context from a single thread.'
-        self.assertRaisesRegex(
-            PrometheusClientRuntimeError, expected_msg, counter.inc, Tracked(100)
-        )
-
 
 class TestDisableCreated(unittest.TestCase):
     def setUp(self):