swarm: integrate OpenTracing; propagate ctx to internal APIs (#17169)

* swarm: propagate ctx, enable opentracing

* swarm/tracing: log error when tracing is misconfigured

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

@@ -0,0 +1,85 @@
+// 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
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// Init initializes the passed in metrics and initializes its fields using the passed in factory.
+func Init(metrics interface{}, factory Factory, globalTags map[string]string) {
+	if err := initMetrics(metrics, factory, globalTags); err != nil {
+		panic(err.Error())
+	}
+}
+
+// initMetrics uses reflection to initialize a struct containing metrics fields
+// by assigning new Counter/Gauge/Timer values with the metric name retrieved
+// from the `metric` tag and stats tags retrieved from the `tags` tag.
+//
+// Note: all fields of the struct must be exported, have a `metric` tag, and be
+// of type Counter or Gauge or Timer.
+func initMetrics(m interface{}, factory Factory, globalTags map[string]string) error {
+	// Allow user to opt out of reporting metrics by passing in nil.
+	if factory == nil {
+		factory = NullFactory
+	}
+
+	counterPtrType := reflect.TypeOf((*Counter)(nil)).Elem()
+	gaugePtrType := reflect.TypeOf((*Gauge)(nil)).Elem()
+	timerPtrType := reflect.TypeOf((*Timer)(nil)).Elem()
+
+	v := reflect.ValueOf(m).Elem()
+	t := v.Type()
+	for i := 0; i < t.NumField(); i++ {
+		tags := make(map[string]string)
+		for k, v := range globalTags {
+			tags[k] = v
+		}
+		field := t.Field(i)
+		metric := field.Tag.Get("metric")
+		if metric == "" {
+			return fmt.Errorf("Field %s is missing a tag 'metric'", field.Name)
+		}
+		if tagString := field.Tag.Get("tags"); tagString != "" {
+			tagPairs := strings.Split(tagString, ",")
+			for _, tagPair := range tagPairs {
+				tag := strings.Split(tagPair, "=")
+				if len(tag) != 2 {
+					return fmt.Errorf(
+						"Field [%s]: Tag [%s] is not of the form key=value in 'tags' string [%s]",
+						field.Name, tagPair, tagString)
+				}
+				tags[tag[0]] = tag[1]
+			}
+		}
+		var obj interface{}
+		if field.Type.AssignableTo(counterPtrType) {
+			obj = factory.Counter(metric, tags)
+		} else if field.Type.AssignableTo(gaugePtrType) {
+			obj = factory.Gauge(metric, tags)
+		} else if field.Type.AssignableTo(timerPtrType) {
+			obj = factory.Timer(metric, tags)
+		} else {
+			return fmt.Errorf(
+				"Field %s is not a pointer to timer, gauge, or counter",
+				field.Name)
+		}
+		v.Field(i).Set(reflect.ValueOf(obj))
+	}
+	return nil
+}