Add timer helper function

prometheus/timer.go

@@ -0,0 +1,29 @@
+// Copyright 2016 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prometheus
+
+import "time"
+
+type Observable interface {
+	Observe(float64)
+}
+
+type TimerFunc func(Observable)
+
+func NewTimer() TimerFunc {
+	begin := time.Now()
+	return func(obs Observable) {
+		obs.Observe(time.Since(begin).Seconds())
+	}
+}

prometheus/timer_test.go

@@ -0,0 +1,41 @@
+// Copyright 2016 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prometheus
+
+import (
+	"testing"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
+func TestTimerObserve(t *testing.T) {
+	his := NewHistogram(
+		HistogramOpts{
+			Name: "test_histogram",
+		},
+	)
+
+	stop := NewTimer()
+	stop(his)
+	m := &dto.Metric{}
+	his.Write(m)
+
+	for _, b := range m.Histogram.Bucket {
+		if int(b.GetCumulativeCount()) > 0 {
+			return
+		}
+	}
+
+	t.Fatalf("no counts recorded")
+}