Opentracing support

vendor/github.com/uber/jaeger-lib/metrics/factory.go

@@ -0,0 +1,35 @@
+// Copyright (c) 2017 Uber Technologies, Inc.
+//
+// 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 metrics
+
+// Factory creates new metrics
+type Factory interface {
+	Counter(name string, tags map[string]string) Counter
+	Timer(name string, tags map[string]string) Timer
+	Gauge(name string, tags map[string]string) Gauge
+
+	// Namespace returns a nested metrics factory.
+	Namespace(name string, tags map[string]string) Factory
+}
+
+// NullFactory is a metrics factory that returns NullCounter, NullTimer, and NullGauge.
+var NullFactory Factory = nullFactory{}
+
+type nullFactory struct{}
+
+func (nullFactory) Counter(name string, tags map[string]string) Counter   { return NullCounter }
+func (nullFactory) Timer(name string, tags map[string]string) Timer       { return NullTimer }
+func (nullFactory) Gauge(name string, tags map[string]string) Gauge       { return NullGauge }
+func (nullFactory) Namespace(name string, tags map[string]string) Factory { return NullFactory }