Add exemplar support to CounterMetricFamily (#1063)

Fixes #1062

Signed-off-by: David Tulloh <[email protected]>

Author: lod

prometheus_client/metrics_core.py

@@ -116,6 +116,7 @@ def __init__(self,
                  labels: Optional[Sequence[str]] = None,
                  created: Optional[float] = None,
                  unit: str = '',
+                 exemplar: Optional[Exemplar] = None,
                  ):
         # Glue code for pre-OpenMetrics metrics.
         if name.endswith('_total'):
@@ -127,13 +128,14 @@ def __init__(self,
             labels = []
         self._labelnames = tuple(labels)
         if value is not None:
-            self.add_metric([], value, created)
+            self.add_metric([], value, created, exemplar=exemplar)
 
     def add_metric(self,
                    labels: Sequence[str],
                    value: float,
                    created: Optional[float] = None,
                    timestamp: Optional[Union[Timestamp, float]] = None,
+                   exemplar: Optional[Exemplar] = None,
                    ) -> None:
         """Add a metric to the metric family.
 
@@ -142,7 +144,7 @@ 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))
+        self.samples.append(Sample(self.name + '_total', dict(zip(self._labelnames, labels)), value, timestamp, exemplar))
         if created is not None:
             self.samples.append(Sample(self.name + '_created', dict(zip(self._labelnames, labels)), created, timestamp))
 

tests/test_core.py

@@ -724,6 +724,21 @@ def test_counter_labels(self):
         self.custom_collector(cmf)
         self.assertEqual(2, self.registry.get_sample_value('c_total', {'a': 'b', 'c_total': 'd'}))
 
+    def test_counter_exemplars_oneline(self):
+        cmf = CounterMetricFamily('c_total', 'help', value=23, exemplar={"bob": "osbourne"})
+        self.custom_collector(cmf)
+        sample = [c.samples for c in self.registry.collect()][0][0]
+        self.assertDictEqual({"bob": "osbourne"}, sample.exemplar)
+
+    def test_counter_exemplars_add(self):
+        cmf = CounterMetricFamily('c_total', 'help')
+        cmf.add_metric([], 12, exemplar={"bob": "osbourne"}, created=23)
+        self.custom_collector(cmf)
+        total_sample, created_sample = [c.samples for c in self.registry.collect()][0]
+        self.assertEqual("c_created", created_sample.name)
+        self.assertDictEqual({"bob": "osbourne"}, total_sample.exemplar)
+        self.assertIsNone(created_sample.exemplar)
+
     def test_gauge(self):
         self.custom_collector(GaugeMetricFamily('g', 'help', value=1))
         self.assertEqual(1, self.registry.get_sample_value('g', {}))