ensure that counts of prometheus histograms are integers (elastic#1354)

* ensure that counts of prometheus histograms are integers

* update changelog

CHANGELOG.asciidoc

@@ -30,6 +30,18 @@ endif::[]
 //===== Bug fixes
 
 
+=== Unreleased
+
+// Unreleased changes go here
+// When the next release happens, nest these changes under the "Python Agent version 6.x" heading
+//[float]
+//===== Features
+//
+//
+[float]
+===== Bug fixes
+ * ensure that Prometheus histograms are encoded correctly for APM Server {pull}1354[#1354]
+
 [[release-notes-6.x]]
 === Python Agent version 6.x
 

elasticapm/metrics/sets/prometheus.py

@@ -95,7 +95,7 @@ def _prom_histogram_handler(self, name, samples, unit):
             sample = samples[sample_pos]
             if "le" in sample.labels:
                 values.append(float(sample.labels["le"]))
-                counts.append(sample.value - prev_val)
+                counts.append(int(sample.value - prev_val))
                 prev_val = sample.value
                 sample_pos += 1
 

tests/metrics/prometheus_tests.py

@@ -133,11 +133,14 @@ def test_histogram(elasticapm_client, prometheus):
     data = list(metricset.collect())
     assert data[0]["samples"]["prometheus.metrics.histo"]["values"] == [0.5, 5.5, 55.0, 100.0]
     assert data[0]["samples"]["prometheus.metrics.histo"]["counts"] == [2, 1, 3, 1]
+    assert all(isinstance(v, int) for v in data[0]["samples"]["prometheus.metrics.histo"]["counts"])
 
     assert data[1]["samples"]["prometheus.metrics.histowithlabel"]["values"] == [0.5, 5.5, 55.0, 100.0]
     assert data[1]["samples"]["prometheus.metrics.histowithlabel"]["counts"] == [1, 1, 1, 0]
+    assert all(isinstance(v, int) for v in data[1]["samples"]["prometheus.metrics.histowithlabel"]["counts"])
     assert data[1]["tags"] == {"alabel": "foo", "anotherlabel": "baz"}
 
     assert data[2]["samples"]["prometheus.metrics.histowithlabel"]["values"] == [0.5, 5.5, 55.0, 100.0]
     assert data[2]["samples"]["prometheus.metrics.histowithlabel"]["counts"] == [0, 0, 0, 1]
+    assert all(isinstance(v, int) for v in data[2]["samples"]["prometheus.metrics.histowithlabel"]["counts"])
     assert data[2]["tags"] == {"alabel": "foo", "anotherlabel": "bazzinga"}