Opentracing support

vendor/github.com/uber/jaeger-client-go/propagation.go

@@ -0,0 +1,303 @@
+// Copyright (c) 2016 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package jaeger
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"log"
+	"net/url"
+	"strings"
+	"sync"
+
+	opentracing "github.com/opentracing/opentracing-go"
+)
+
+// Injector is responsible for injecting SpanContext instances in a manner suitable
+// for propagation via a format-specific "carrier" object. Typically the
+// injection will take place across an RPC boundary, but message queues and
+// other IPC mechanisms are also reasonable places to use an Injector.
+type Injector interface {
+	// Inject takes `SpanContext` and injects it into `carrier`. The actual type
+	// of `carrier` depends on the `format` passed to `Tracer.Inject()`.
+	//
+	// Implementations may return opentracing.ErrInvalidCarrier or any other
+	// implementation-specific error if injection fails.
+	Inject(ctx SpanContext, carrier interface{}) error
+}
+
+// Extractor is responsible for extracting SpanContext instances from a
+// format-specific "carrier" object. Typically the extraction will take place
+// on the server side of an RPC boundary, but message queues and other IPC
+// mechanisms are also reasonable places to use an Extractor.
+type Extractor interface {
+	// Extract decodes a SpanContext instance from the given `carrier`,
+	// or (nil, opentracing.ErrSpanContextNotFound) if no context could
+	// be found in the `carrier`.
+	Extract(carrier interface{}) (SpanContext, error)
+}
+
+type textMapPropagator struct {
+	tracer      *Tracer
+	encodeValue func(string) string
+	decodeValue func(string) string
+}
+
+func newTextMapPropagator(tracer *Tracer) *textMapPropagator {
+	return &textMapPropagator{
+		tracer: tracer,
+		encodeValue: func(val string) string {
+			return val
+		},
+		decodeValue: func(val string) string {
+			return val
+		},
+	}
+}
+
+func newHTTPHeaderPropagator(tracer *Tracer) *textMapPropagator {
+	return &textMapPropagator{
+		tracer: tracer,
+		encodeValue: func(val string) string {
+			return url.QueryEscape(val)
+		},
+		decodeValue: func(val string) string {
+			// ignore decoding errors, cannot do anything about them
+			if v, err := url.QueryUnescape(val); err == nil {
+				return v
+			}
+			return val
+		},
+	}
+}
+
+type binaryPropagator struct {
+	tracer  *Tracer
+	buffers sync.Pool
+}
+
+func newBinaryPropagator(tracer *Tracer) *binaryPropagator {
+	return &binaryPropagator{
+		tracer:  tracer,
+		buffers: sync.Pool{New: func() interface{} { return &bytes.Buffer{} }},
+	}
+}
+
+func (p *textMapPropagator) Inject(
+	sc SpanContext,
+	abstractCarrier interface{},
+) error {
+	textMapWriter, ok := abstractCarrier.(opentracing.TextMapWriter)
+	if !ok {
+		return opentracing.ErrInvalidCarrier
+	}
+
+	// Do not encode the string with trace context to avoid accidental double-encoding
+	// if people are using opentracing < 0.10.0. Our colon-separated representation
+	// of the trace context is already safe for HTTP headers.
+	textMapWriter.Set(TracerStateHeaderName, sc.String())
+	for k, v := range sc.baggage {
+		safeKey := addBaggageKeyPrefix(k)
+		safeVal := p.encodeValue(v)
+		textMapWriter.Set(safeKey, safeVal)
+	}
+	return nil
+}
+
+func (p *textMapPropagator) Extract(abstractCarrier interface{}) (SpanContext, error) {
+	textMapReader, ok := abstractCarrier.(opentracing.TextMapReader)
+	if !ok {
+		return emptyContext, opentracing.ErrInvalidCarrier
+	}
+	var ctx SpanContext
+	var baggage map[string]string
+	err := textMapReader.ForeachKey(func(rawKey, value string) error {
+		key := strings.ToLower(rawKey) // TODO not necessary for plain TextMap
+		if key == TracerStateHeaderName {
+			var err error
+			safeVal := p.decodeValue(value)
+			if ctx, err = ContextFromString(safeVal); err != nil {
+				return err
+			}
+		} else if key == JaegerDebugHeader {
+			ctx.debugID = p.decodeValue(value)
+		} else if key == JaegerBaggageHeader {
+			if baggage == nil {
+				baggage = make(map[string]string)
+			}
+			for k, v := range parseCommaSeparatedMap(value) {
+				baggage[k] = v
+			}
+		} else if strings.HasPrefix(key, TraceBaggageHeaderPrefix) {
+			if baggage == nil {
+				baggage = make(map[string]string)
+			}
+			safeKey := removeBaggageKeyPrefix(key)
+			safeVal := p.decodeValue(value)
+			baggage[safeKey] = safeVal
+		}
+		return nil
+	})
+	if err != nil {
+		p.tracer.metrics.DecodingErrors.Inc(1)
+		return emptyContext, err
+	}
+	if !ctx.traceID.IsValid() && ctx.debugID == "" && len(baggage) == 0 {
+		return emptyContext, opentracing.ErrSpanContextNotFound
+	}
+	ctx.baggage = baggage
+	return ctx, nil
+}
+
+func (p *binaryPropagator) Inject(
+	sc SpanContext,
+	abstractCarrier interface{},
+) error {
+	carrier, ok := abstractCarrier.(io.Writer)
+	if !ok {
+		return opentracing.ErrInvalidCarrier
+	}
+
+	// Handle the tracer context
+	if err := binary.Write(carrier, binary.BigEndian, sc.traceID); err != nil {
+		return err
+	}
+	if err := binary.Write(carrier, binary.BigEndian, sc.spanID); err != nil {
+		return err
+	}
+	if err := binary.Write(carrier, binary.BigEndian, sc.parentID); err != nil {
+		return err
+	}
+	if err := binary.Write(carrier, binary.BigEndian, sc.flags); err != nil {
+		return err
+	}
+
+	// Handle the baggage items
+	if err := binary.Write(carrier, binary.BigEndian, int32(len(sc.baggage))); err != nil {
+		return err
+	}
+	for k, v := range sc.baggage {
+		if err := binary.Write(carrier, binary.BigEndian, int32(len(k))); err != nil {
+			return err
+		}
+		io.WriteString(carrier, k)
+		if err := binary.Write(carrier, binary.BigEndian, int32(len(v))); err != nil {
+			return err
+		}
+		io.WriteString(carrier, v)
+	}
+
+	return nil
+}
+
+func (p *binaryPropagator) Extract(abstractCarrier interface{}) (SpanContext, error) {
+	carrier, ok := abstractCarrier.(io.Reader)
+	if !ok {
+		return emptyContext, opentracing.ErrInvalidCarrier
+	}
+	var ctx SpanContext
+
+	if err := binary.Read(carrier, binary.BigEndian, &ctx.traceID); err != nil {
+		return emptyContext, opentracing.ErrSpanContextCorrupted
+	}
+	if err := binary.Read(carrier, binary.BigEndian, &ctx.spanID); err != nil {
+		return emptyContext, opentracing.ErrSpanContextCorrupted
+	}
+	if err := binary.Read(carrier, binary.BigEndian, &ctx.parentID); err != nil {
+		return emptyContext, opentracing.ErrSpanContextCorrupted
+	}
+	if err := binary.Read(carrier, binary.BigEndian, &ctx.flags); err != nil {
+		return emptyContext, opentracing.ErrSpanContextCorrupted
+	}
+
+	// Handle the baggage items
+	var numBaggage int32
+	if err := binary.Read(carrier, binary.BigEndian, &numBaggage); err != nil {
+		return emptyContext, opentracing.ErrSpanContextCorrupted
+	}
+	if iNumBaggage := int(numBaggage); iNumBaggage > 0 {
+		ctx.baggage = make(map[string]string, iNumBaggage)
+		buf := p.buffers.Get().(*bytes.Buffer)
+		defer p.buffers.Put(buf)
+
+		var keyLen, valLen int32
+		for i := 0; i < iNumBaggage; i++ {
+			if err := binary.Read(carrier, binary.BigEndian, &keyLen); err != nil {
+				return emptyContext, opentracing.ErrSpanContextCorrupted
+			}
+			buf.Reset()
+			buf.Grow(int(keyLen))
+			if n, err := io.CopyN(buf, carrier, int64(keyLen)); err != nil || int32(n) != keyLen {
+				return emptyContext, opentracing.ErrSpanContextCorrupted
+			}
+			key := buf.String()
+
+			if err := binary.Read(carrier, binary.BigEndian, &valLen); err != nil {
+				return emptyContext, opentracing.ErrSpanContextCorrupted
+			}
+			buf.Reset()
+			buf.Grow(int(valLen))
+			if n, err := io.CopyN(buf, carrier, int64(valLen)); err != nil || int32(n) != valLen {
+				return emptyContext, opentracing.ErrSpanContextCorrupted
+			}
+			ctx.baggage[key] = buf.String()
+		}
+	}
+
+	return ctx, nil
+}
+
+// Converts a comma separated key value pair list into a map
+// e.g. key1=value1, key2=value2, key3 = value3
+// is converted to map[string]string { "key1" : "value1",
+//                                     "key2" : "value2",
+//                                     "key3" : "value3" }
+func parseCommaSeparatedMap(value string) map[string]string {
+	baggage := make(map[string]string)
+	value, err := url.QueryUnescape(value)
+	if err != nil {
+		log.Printf("Unable to unescape %s, %v", value, err)
+		return baggage
+	}
+	for _, kvpair := range strings.Split(value, ",") {
+		kv := strings.Split(strings.TrimSpace(kvpair), "=")
+		if len(kv) == 2 {
+			baggage[kv[0]] = kv[1]
+		} else {
+			log.Printf("Malformed value passed in for %s", JaegerBaggageHeader)
+		}
+	}
+	return baggage
+}
+
+// Converts a baggage item key into an http header format,
+// by prepending TraceBaggageHeaderPrefix and encoding the key string
+func addBaggageKeyPrefix(key string) string {
+	// TODO encodeBaggageKeyAsHeader add caching and escaping
+	return fmt.Sprintf("%v%v", TraceBaggageHeaderPrefix, key)
+}
+
+func removeBaggageKeyPrefix(key string) string {
+	// TODO decodeBaggageHeaderKey add caching and escaping
+	return key[len(TraceBaggageHeaderPrefix):]
+}