add opentracing spans for metrics

vendor/github.com/opentracing/opentracing-go/testtracer_test.go

@@ -0,0 +1,138 @@
+package opentracing
+
+import (
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/opentracing/opentracing-go/log"
+)
+
+const testHTTPHeaderPrefix = "testprefix-"
+
+// testTracer is a most-noop Tracer implementation that makes it possible for
+// unittests to verify whether certain methods were / were not called.
+type testTracer struct{}
+
+var fakeIDSource = 1
+
+func nextFakeID() int {
+	fakeIDSource++
+	return fakeIDSource
+}
+
+type testSpanContext struct {
+	HasParent bool
+	FakeID    int
+}
+
+func (n testSpanContext) ForeachBaggageItem(handler func(k, v string) bool) {}
+
+type testSpan struct {
+	spanContext   testSpanContext
+	OperationName string
+	StartTime     time.Time
+	Tags          map[string]interface{}
+}
+
+func (n testSpan) Equal(os Span) bool {
+	other, ok := os.(testSpan)
+	if !ok {
+		return false
+	}
+	if n.spanContext != other.spanContext {
+		return false
+	}
+	if n.OperationName != other.OperationName {
+		return false
+	}
+	if !n.StartTime.Equal(other.StartTime) {
+		return false
+	}
+	if len(n.Tags) != len(other.Tags) {
+		return false
+	}
+
+	for k, v := range n.Tags {
+		if ov, ok := other.Tags[k]; !ok || ov != v {
+			return false
+		}
+	}
+
+	return true
+}
+
+// testSpan:
+func (n testSpan) Context() SpanContext                                  { return n.spanContext }
+func (n testSpan) SetTag(key string, value interface{}) Span             { return n }
+func (n testSpan) Finish()                                               {}
+func (n testSpan) FinishWithOptions(opts FinishOptions)                  {}
+func (n testSpan) LogFields(fields ...log.Field)                         {}
+func (n testSpan) LogKV(kvs ...interface{})                              {}
+func (n testSpan) SetOperationName(operationName string) Span            { return n }
+func (n testSpan) Tracer() Tracer                                        { return testTracer{} }
+func (n testSpan) SetBaggageItem(key, val string) Span                   { return n }
+func (n testSpan) BaggageItem(key string) string                         { return "" }
+func (n testSpan) LogEvent(event string)                                 {}
+func (n testSpan) LogEventWithPayload(event string, payload interface{}) {}
+func (n testSpan) Log(data LogData)                                      {}
+
+// StartSpan belongs to the Tracer interface.
+func (n testTracer) StartSpan(operationName string, opts ...StartSpanOption) Span {
+	sso := StartSpanOptions{}
+	for _, o := range opts {
+		o.Apply(&sso)
+	}
+	return n.startSpanWithOptions(operationName, sso)
+}
+
+func (n testTracer) startSpanWithOptions(name string, opts StartSpanOptions) Span {
+	fakeID := nextFakeID()
+	if len(opts.References) > 0 {
+		fakeID = opts.References[0].ReferencedContext.(testSpanContext).FakeID
+	}
+
+	return testSpan{
+		OperationName: name,
+		StartTime:     opts.StartTime,
+		Tags:          opts.Tags,
+		spanContext: testSpanContext{
+			HasParent: len(opts.References) > 0,
+			FakeID:    fakeID,
+		},
+	}
+}
+
+// Inject belongs to the Tracer interface.
+func (n testTracer) Inject(sp SpanContext, format interface{}, carrier interface{}) error {
+	spanContext := sp.(testSpanContext)
+	switch format {
+	case HTTPHeaders, TextMap:
+		carrier.(TextMapWriter).Set(testHTTPHeaderPrefix+"fakeid", strconv.Itoa(spanContext.FakeID))
+		return nil
+	}
+	return ErrUnsupportedFormat
+}
+
+// Extract belongs to the Tracer interface.
+func (n testTracer) Extract(format interface{}, carrier interface{}) (SpanContext, error) {
+	switch format {
+	case HTTPHeaders, TextMap:
+		// Just for testing purposes... generally not a worthwhile thing to
+		// propagate.
+		sm := testSpanContext{}
+		err := carrier.(TextMapReader).ForeachKey(func(key, val string) error {
+			switch strings.ToLower(key) {
+			case testHTTPHeaderPrefix + "fakeid":
+				i, err := strconv.Atoi(val)
+				if err != nil {
+					return err
+				}
+				sm.FakeID = i
+			}
+			return nil
+		})
+		return sm, err
+	}
+	return nil, ErrSpanContextNotFound
+}