Merge pull request #871 from prometheus/beorn7/doc

Document implications of negative observations
prometheus · Jun 1, 2021 · f22935d · f22935d
2 parents 11aba26 + f34145a
commit f22935d
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Showing 2 changed files with 12 additions and 2 deletions.
diff --git a/prometheus/histogram.go b/prometheus/histogram.go
@@ -47,7 +47,12 @@ type Histogram interface {
 	Metric
 	Collector
 
-	// Observe adds a single observation to the histogram.
+	// Observe adds a single observation to the histogram. Observations are
+	// usually positive or zero. Negative observations are accepted but
+	// prevent current versions of Prometheus from properly detecting
+	// counter resets in the sum of observations. See
+	// https://prometheus.io/docs/practices/histograms/#count-and-sum-of-observations
+	// for details.
 	Observe(float64)
 }
 

diff --git a/prometheus/summary.go b/prometheus/summary.go
@@ -55,7 +55,12 @@ type Summary interface {
 	Metric
 	Collector
 
-	// Observe adds a single observation to the summary.
+	// Observe adds a single observation to the summary. Observations are
+	// usually positive or zero. Negative observations are accepted but
+	// prevent current versions of Prometheus from properly detecting
+	// counter resets in the sum of observations. See
+	// https://prometheus.io/docs/practices/histograms/#count-and-sum-of-observations
+	// for details.
 	Observe(float64)
 }