Require sum with count for histograms.

This is so the average can be calculated.

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Author: brian-brazil

prometheus_client/metrics_core.py

@@ -216,11 +216,11 @@ def add_metric(self, labels, buckets, sum_value, timestamp=None):
                 timestamp,
                 exemplar,
             ))
-        # +Inf is last and provides the count value.
-        self.samples.append(
-                Sample(self.name + '_count', dict(zip(self._labelnames, labels)), buckets[-1][1], timestamp))
-        # Don't iunclude sum if there's negative buckets.
+        # Don't iunclude sum and thus count if there's negative buckets.
         if float(buckets[0][0]) >= 0 and sum_value is not None:
+            # +Inf is last and provides the count value.
+            self.samples.append(
+                    Sample(self.name + '_count', dict(zip(self._labelnames, labels)), buckets[-1][1], timestamp))
             self.samples.append(
                     Sample(self.name + '_sum', dict(zip(self._labelnames, labels)), sum_value, timestamp))
 

prometheus_client/openmetrics/parser.py

@@ -398,6 +398,12 @@ def do_checks():
             raise ValueError("+Inf bucket missing: " + name)
         if count is not None and value != count:
             raise ValueError("Count does not match +Inf value: " + name)
+        if has_sum and count is None:
+            raise ValueError("_count must be present if _sum is present: " + name)
+        if has_gsum and count is None:
+            raise ValueError("_gcount must be present if _gsum is present: " + name)
+        if not (has_sum or has_gsum) and count is not None:
+            raise ValueError("_sum/_gsum must be present if _count is present: " + name)
         if has_negative_buckets and has_sum:
             raise ValueError("Cannot have _sum with negative buckets: " + name)
         if not has_negative_buckets and has_negative_gsum:
@@ -413,6 +419,7 @@ def do_checks():
             bucket = None
             has_negative_buckets = False
             has_sum = False
+            has_gsum = False
             has_negative_gsum = False
             value = 0
         group = g
@@ -432,8 +439,10 @@ def do_checks():
             count = s.value
         elif suffix in ['_sum']:
             has_sum = True
-        elif suffix in ['_gsum'] and s.value < 0:
-            has_negative_gsum = True
+        elif suffix in ['_gsum']:
+            has_gsum = True
+            if s.value < 0:
+                has_negative_gsum = True
 
     if group is not None:
         do_checks()

tests/openmetrics/test_parser.py

@@ -142,7 +142,6 @@ def test_negative_bucket_histogram(self):
 a_bucket{le="-1.0"} 0
 a_bucket{le="1.0"} 1
 a_bucket{le="+Inf"} 3
-a_count 3
 # EOF
 """)
         self.assertEqual([HistogramMetricFamily("a", "help", buckets=[("-1.0", 0.0), ("1.0", 1.0), ("+Inf", 3.0)])],
@@ -744,7 +743,11 @@ def test_invalid_input(self):
             ('# TYPE a summary\na{quantile="0.5"} -1\n# EOF\n'),
             # Bad histograms.
             ('# TYPE a histogram\na_sum 1\n# EOF\n'),
+            ('# TYPE a histogram\na_bucket{le="+Inf"} 0\n#a_sum 0\n# EOF\n'),
+            ('# TYPE a histogram\na_bucket{le="+Inf"} 0\n#a_count 0\n# EOF\n'),
             ('# TYPE a gaugehistogram\na_gsum 1\n# EOF\n'),
+            ('# TYPE a gaugehistogram\na_bucket{le="+Inf"} 0\na_gsum 0\n# EOF\n'),
+            ('# TYPE a gaugehistogram\na_bucket{le="+Inf"} 0\na_gcount 0\n# EOF\n'),
             ('# TYPE a histogram\na_count 1\na_bucket{le="+Inf"} 0\n# EOF\n'),
             ('# TYPE a histogram\na_bucket{le="+Inf"} 0\na_count 1\n# EOF\n'),
             ('# TYPE a histogram\na_bucket{le="0"} 0\na_bucket{le="+Inf"} 0\n# EOF\n'),