Support for multiple samples within same metric (#1181)

Signed-off-by: João Vilaça <jvilaca@redhat.com>

Signed-off-by: João Vilaça <jvilaca@redhat.com>

prometheus/registry.go

@@ -21,6 +21,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"sort"
+	"strconv"
 	"strings"
 	"sync"
 	"unicode/utf8"
@@ -933,6 +934,10 @@ func checkMetricConsistency(
 		h.WriteString(lp.GetValue())
 		h.Write(separatorByteSlice)
 	}
+	if dtoMetric.TimestampMs != nil {
+		h.WriteString(strconv.FormatInt(*(dtoMetric.TimestampMs), 10))
+		h.Write(separatorByteSlice)
+	}
 	hSum := h.Sum64()
 	if _, exists := metricHashes[hSum]; exists {
 		return fmt.Errorf(

prometheus/registry_test.go

@@ -1288,3 +1288,48 @@ func ExampleRegistry_grouping() {
 		}(i)
 	}
 }
+
+type customCollector struct {
+	collectFunc func(ch chan<- prometheus.Metric)
+}
+
+func (co *customCollector) Describe(_ chan<- *prometheus.Desc) {}
+
+func (co *customCollector) Collect(ch chan<- prometheus.Metric) {
+	co.collectFunc(ch)
+}
+
+// TestCheckMetricConsistency
+func TestCheckMetricConsistency(t *testing.T) {
+	reg := prometheus.NewRegistry()
+	timestamp := time.Now()
+
+	desc := prometheus.NewDesc("metric_a", "", nil, nil)
+	metric := prometheus.MustNewConstMetric(desc, prometheus.CounterValue, 1)
+
+	validCollector := &customCollector{
+		collectFunc: func(ch chan<- prometheus.Metric) {
+			ch <- prometheus.NewMetricWithTimestamp(timestamp.Add(-1*time.Minute), metric)
+			ch <- prometheus.NewMetricWithTimestamp(timestamp, metric)
+		},
+	}
+	reg.MustRegister(validCollector)
+	_, err := reg.Gather()
+	if err != nil {
+		t.Error("metric validation should succeed:", err)
+	}
+	reg.Unregister(validCollector)
+
+	invalidCollector := &customCollector{
+		collectFunc: func(ch chan<- prometheus.Metric) {
+			ch <- prometheus.NewMetricWithTimestamp(timestamp, metric)
+			ch <- prometheus.NewMetricWithTimestamp(timestamp, metric)
+		},
+	}
+	reg.MustRegister(invalidCollector)
+	_, err = reg.Gather()
+	if err == nil {
+		t.Error("metric validation should return an error")
+	}
+	reg.Unregister(invalidCollector)
+}