Add a clear() method to metric objects to remove all labelsets (#642)

Add a clear() method to metric objects to remove all labelsets

Author: aarbouin

prometheus_client/metrics.py

@@ -186,6 +186,11 @@ def remove(self, *labelvalues):
         with self._lock:
             del self._metrics[labelvalues]
 
+    def clear(self):
+        """Remove all labelsets from the metric"""
+        with self._lock:
+            self._metrics = {}
+
     def _samples(self):
         if self._is_parent():
             return self._multi_samples()

tests/test_core.py

@@ -456,6 +456,15 @@ def test_remove(self):
         self.assertEqual(None, self.registry.get_sample_value('c_total', {'l': 'x'}))
         self.assertEqual(2, self.registry.get_sample_value('c_total', {'l': 'y'}))
 
+    def test_clear(self):
+        self.counter.labels('x').inc()
+        self.counter.labels('y').inc(2)
+        self.assertEqual(1, self.registry.get_sample_value('c_total', {'l': 'x'}))
+        self.assertEqual(2, self.registry.get_sample_value('c_total', {'l': 'y'}))
+        self.counter.clear()
+        self.assertEqual(None, self.registry.get_sample_value('c_total', {'l': 'x'}))
+        self.assertEqual(None, self.registry.get_sample_value('c_total', {'l': 'y'}))
+
     def test_incorrect_label_count_raises(self):
         self.assertRaises(ValueError, self.counter.labels)
         self.assertRaises(ValueError, self.counter.labels, 'a', 'b')