gb vendor fetch github.com/opentracing/go-opentracing

vendor/manifest

@@ -151,6 +151,12 @@
 			"branch": "master",
 			"path": "/i18n"
 		},
+		{
+			"importpath": "github.com/opentracing/opentracing-go",
+			"repository": "https://github.com/opentracing/opentracing-go",
+			"revision": "8ebe5d4e236eed9fd88e593c288bfb804d630b8c",
+			"branch": "master"
+		},
 		{
 			"importpath": "github.com/pelletier/go-toml",
 			"repository": "https://github.com/pelletier/go-toml",

vendor/src/github.com/opentracing/opentracing-go/CHANGELOG.md

@@ -0,0 +1,14 @@
+Changes by Version
+==================
+
+1.1.0 (unreleased)
+-------------------
+
+- Deprecate InitGlobalTracer() in favor of SetGlobalTracer()
+
+
+1.0.0 (2016-09-26)
+-------------------
+
+- This release implements OpenTracing Specification 1.0 (http://opentracing.io/spec)
+

vendor/src/github.com/opentracing/opentracing-go/LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2016 The OpenTracing Authors
+
+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.

vendor/src/github.com/opentracing/opentracing-go/Makefile

@@ -0,0 +1,32 @@
+PACKAGES := . ./mocktracer/... ./ext/...
+
+.DEFAULT_GOAL := test-and-lint
+
+.PHONE: test-and-lint
+
+test-and-lint: test lint
+
+.PHONY: test
+test:
+	go test -v -cover ./...
+
+cover:
+	@rm -rf cover-all.out
+	$(foreach pkg, $(PACKAGES), $(MAKE) cover-pkg PKG=$(pkg) || true;)
+	@grep mode: cover.out > coverage.out
+	@cat cover-all.out >> coverage.out
+	go tool cover -html=coverage.out -o cover.html
+	@rm -rf cover.out cover-all.out coverage.out
+
+cover-pkg:
+	go test -coverprofile cover.out $(PKG)
+	@grep -v mode: cover.out >> cover-all.out
+
+.PHONY: lint
+lint:
+	go fmt ./...
+	golint ./...
+	@# Run again with magic to exit non-zero if golint outputs anything.
+	@! (golint ./... | read dummy)
+	go vet ./...
+

vendor/src/github.com/opentracing/opentracing-go/README.md

@@ -0,0 +1,163 @@
+[![Gitter chat](http://img.shields.io/badge/gitter-join%20chat%20%E2%86%92-brightgreen.svg)](https://gitter.im/opentracing/public) [![Build Status](https://travis-ci.org/opentracing/opentracing-go.svg?branch=master)](https://travis-ci.org/opentracing/opentracing-go) [![GoDoc](https://godoc.org/github.com/opentracing/opentracing-go?status.svg)](http://godoc.org/github.com/opentracing/opentracing-go)
+[![Sourcegraph Badge](https://sourcegraph.com/github.com/opentracing/opentracing-go/-/badge.svg)](https://sourcegraph.com/github.com/opentracing/opentracing-go?badge)
+
+# OpenTracing API for Go
+
+This package is a Go platform API for OpenTracing.
+
+## Required Reading
+
+In order to understand the Go platform API, one must first be familiar with the
+[OpenTracing project](http://opentracing.io) and
+[terminology](http://opentracing.io/documentation/pages/spec.html) more specifically.
+
+## API overview for those adding instrumentation
+
+Everyday consumers of this `opentracing` package really only need to worry
+about a couple of key abstractions: the `StartSpan` function, the `Span`
+interface, and binding a `Tracer` at `main()`-time. Here are code snippets
+demonstrating some important use cases.
+
+#### Singleton initialization
+
+The simplest starting point is `./default_tracer.go`. As early as possible, call
+
+```go
+    import "github.com/opentracing/opentracing-go"
+    import ".../some_tracing_impl"
+
+    func main() {
+        opentracing.InitGlobalTracer(
+            // tracing impl specific:
+            some_tracing_impl.New(...),
+        )
+        ...
+    }
+```
+
+##### Non-Singleton initialization
+
+If you prefer direct control to singletons, manage ownership of the
+`opentracing.Tracer` implementation explicitly.
+
+#### Creating a Span given an existing Go `context.Context`
+
+If you use `context.Context` in your application, OpenTracing's Go library will
+happily rely on it for `Span` propagation. To start a new (blocking child)
+`Span`, you can use `StartSpanFromContext`.
+
+```go
+    func xyz(ctx context.Context, ...) {
+        ...
+        span, ctx := opentracing.StartSpanFromContext(ctx, "operation_name")
+        defer span.Finish()
+        span.LogFields(
+            log.String("event", "soft error"),
+            log.String("type", "cache timeout"),
+            log.Int("waited.millis", 1500))
+        ...
+    }
+```
+
+#### Starting an empty trace by creating a "root span"
+
+It's always possible to create a "root" `Span` with no parent or other causal
+reference.
+
+```go
+    func xyz() {
+        ...
+        sp := opentracing.StartSpan("operation_name")
+        defer sp.Finish()
+        ...
+    }
+```
+
+#### Creating a (child) Span given an existing (parent) Span
+
+```go
+    func xyz(parentSpan opentracing.Span, ...) {
+        ...
+        sp := opentracing.StartSpan(
+            "operation_name",
+            opentracing.ChildOf(parentSpan.Context()))
+        defer sp.Finish()
+        ...
+    }
+```
+
+#### Serializing to the wire
+
+```go
+    func makeSomeRequest(ctx context.Context) ... {
+        if span := opentracing.SpanFromContext(ctx); span != nil {
+            httpClient := &http.Client{}
+            httpReq, _ := http.NewRequest("GET", "http://myservice/", nil)
+
+            // Transmit the span's TraceContext as HTTP headers on our
+            // outbound request.
+            opentracing.GlobalTracer().Inject(
+                span.Context(),
+                opentracing.HTTPHeaders,
+                opentracing.HTTPHeadersCarrier(httpReq.Header))
+
+            resp, err := httpClient.Do(httpReq)
+            ...
+        }
+        ...
+    }
+```
+
+#### Deserializing from the wire
+
+```go
+    http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
+        var serverSpan opentracing.Span
+        appSpecificOperationName := ...
+        wireContext, err := opentracing.GlobalTracer().Extract(
+            opentracing.HTTPHeaders,
+            opentracing.HTTPHeadersCarrier(req.Header))
+        if err != nil {
+            // Optionally record something about err here
+        }
+
+        // Create the span referring to the RPC client if available.
+        // If wireContext == nil, a root span will be created.
+        serverSpan = opentracing.StartSpan(
+            appSpecificOperationName,
+            ext.RPCServerOption(wireContext))
+
+        defer serverSpan.Finish()
+
+        ctx := opentracing.ContextWithSpan(context.Background(), serverSpan)
+        ...
+    }
+```
+
+#### Conditionally capture a field using `log.Noop`
+
+In some situations, you may want to dynamically decide whether or not
+to log a field.  For example, you may want to capture additional data,
+such as a customer ID, in non-production environments:
+
+```go
+    func Customer(order *Order) log.Field {
+        if os.Getenv("ENVIRONMENT") == "dev" {
+            return log.String("customer", order.Customer.ID)
+        }
+        return log.Noop()
+    }
+```
+
+#### Goroutine-safety
+
+The entire public API is goroutine-safe and does not require external
+synchronization.
+
+## API pointers for those implementing a tracing system
+
+Tracing system implementors may be able to reuse or copy-paste-modify the `basictracer` package, found [here](https://github.com/opentracing/basictracer-go). In particular, see `basictracer.New(...)`.
+
+## API compatibility
+
+For the time being, "mild" backwards-incompatible changes may be made without changing the major version number. As OpenTracing and `opentracing-go` mature, backwards compatibility will become more of a priority.

vendor/src/github.com/opentracing/opentracing-go/ext/tags.go

@@ -0,0 +1,210 @@
+package ext
+
+import opentracing "github.com/opentracing/opentracing-go"
+
+// These constants define common tag names recommended for better portability across
+// tracing systems and languages/platforms.
+//
+// The tag names are defined as typed strings, so that in addition to the usual use
+//
+//     span.setTag(TagName, value)
+//
+// they also support value type validation via this additional syntax:
+//
+//    TagName.Set(span, value)
+//
+var (
+	//////////////////////////////////////////////////////////////////////
+	// SpanKind (client/server or producer/consumer)
+	//////////////////////////////////////////////////////////////////////
+
+	// SpanKind hints at relationship between spans, e.g. client/server
+	SpanKind = spanKindTagName("span.kind")
+
+	// SpanKindRPCClient marks a span representing the client-side of an RPC
+	// or other remote call
+	SpanKindRPCClientEnum = SpanKindEnum("client")
+	SpanKindRPCClient     = opentracing.Tag{Key: string(SpanKind), Value: SpanKindRPCClientEnum}
+
+	// SpanKindRPCServer marks a span representing the server-side of an RPC
+	// or other remote call
+	SpanKindRPCServerEnum = SpanKindEnum("server")
+	SpanKindRPCServer     = opentracing.Tag{Key: string(SpanKind), Value: SpanKindRPCServerEnum}
+
+	// SpanKindProducer marks a span representing the producer-side of a
+	// message bus
+	SpanKindProducerEnum = SpanKindEnum("producer")
+	SpanKindProducer     = opentracing.Tag{Key: string(SpanKind), Value: SpanKindProducerEnum}
+
+	// SpanKindConsumer marks a span representing the consumer-side of a
+	// message bus
+	SpanKindConsumerEnum = SpanKindEnum("consumer")
+	SpanKindConsumer     = opentracing.Tag{Key: string(SpanKind), Value: SpanKindConsumerEnum}
+
+	//////////////////////////////////////////////////////////////////////
+	// Component name
+	//////////////////////////////////////////////////////////////////////
+
+	// Component is a low-cardinality identifier of the module, library,
+	// or package that is generating a span.
+	Component = stringTagName("component")
+
+	//////////////////////////////////////////////////////////////////////
+	// Sampling hint
+	//////////////////////////////////////////////////////////////////////
+
+	// SamplingPriority determines the priority of sampling this Span.
+	SamplingPriority = uint16TagName("sampling.priority")
+
+	//////////////////////////////////////////////////////////////////////
+	// Peer tags. These tags can be emitted by either client-side of
+	// server-side to describe the other side/service in a peer-to-peer
+	// communications, like an RPC call.
+	//////////////////////////////////////////////////////////////////////
+
+	// PeerService records the service name of the peer.
+	PeerService = stringTagName("peer.service")
+
+	// PeerAddress records the address name of the peer. This may be a "ip:port",
+	// a bare "hostname", a FQDN or even a database DSN substring
+	// like "mysql://username@127.0.0.1:3306/dbname"
+	PeerAddress = stringTagName("peer.address")
+
+	// PeerHostname records the host name of the peer
+	PeerHostname = stringTagName("peer.hostname")
+
+	// PeerHostIPv4 records IP v4 host address of the peer
+	PeerHostIPv4 = ipv4Tag("peer.ipv4")
+
+	// PeerHostIPv6 records IP v6 host address of the peer
+	PeerHostIPv6 = stringTagName("peer.ipv6")
+
+	// PeerPort records port number of the peer
+	PeerPort = uint16TagName("peer.port")
+
+	//////////////////////////////////////////////////////////////////////
+	// HTTP Tags
+	//////////////////////////////////////////////////////////////////////
+
+	// HTTPUrl should be the URL of the request being handled in this segment
+	// of the trace, in standard URI format. The protocol is optional.
+	HTTPUrl = stringTagName("http.url")
+
+	// HTTPMethod is the HTTP method of the request, and is case-insensitive.
+	HTTPMethod = stringTagName("http.method")
+
+	// HTTPStatusCode is the numeric HTTP status code (200, 404, etc) of the
+	// HTTP response.
+	HTTPStatusCode = uint16TagName("http.status_code")
+
+	//////////////////////////////////////////////////////////////////////
+	// DB Tags
+	//////////////////////////////////////////////////////////////////////
+
+	// DBInstance is database instance name.
+	DBInstance = stringTagName("db.instance")
+
+	// DBStatement is a database statement for the given database type.
+	// It can be a query or a prepared statement (i.e., before substitution).
+	DBStatement = stringTagName("db.statement")
+
+	// DBType is a database type. For any SQL database, "sql".
+	// For others, the lower-case database category, e.g. "redis"
+	DBType = stringTagName("db.type")
+
+	// DBUser is a username for accessing database.
+	DBUser = stringTagName("db.user")
+
+	//////////////////////////////////////////////////////////////////////
+	// Message Bus Tag
+	//////////////////////////////////////////////////////////////////////
+
+	// MessageBusDestination is an address at which messages can be exchanged
+	MessageBusDestination = stringTagName("message_bus.destination")
+
+	//////////////////////////////////////////////////////////////////////
+	// Error Tag
+	//////////////////////////////////////////////////////////////////////
+
+	// Error indicates that operation represented by the span resulted in an error.
+	Error = boolTagName("error")
+)
+
+// ---
+
+// SpanKindEnum represents common span types
+type SpanKindEnum string
+
+type spanKindTagName string
+
+// Set adds a string tag to the `span`
+func (tag spanKindTagName) Set(span opentracing.Span, value SpanKindEnum) {
+	span.SetTag(string(tag), value)
+}
+
+type rpcServerOption struct {
+	clientContext opentracing.SpanContext
+}
+
+func (r rpcServerOption) Apply(o *opentracing.StartSpanOptions) {
+	if r.clientContext != nil {
+		opentracing.ChildOf(r.clientContext).Apply(o)
+	}
+	SpanKindRPCServer.Apply(o)
+}
+
+// RPCServerOption returns a StartSpanOption appropriate for an RPC server span
+// with `client` representing the metadata for the remote peer Span if available.
+// In case client == nil, due to the client not being instrumented, this RPC
+// server span will be a root span.
+func RPCServerOption(client opentracing.SpanContext) opentracing.StartSpanOption {
+	return rpcServerOption{client}
+}
+
+// ---
+
+type stringTagName string
+
+// Set adds a string tag to the `span`
+func (tag stringTagName) Set(span opentracing.Span, value string) {
+	span.SetTag(string(tag), value)
+}
+
+// ---
+
+type uint32TagName string
+
+// Set adds a uint32 tag to the `span`
+func (tag uint32TagName) Set(span opentracing.Span, value uint32) {
+	span.SetTag(string(tag), value)
+}
+
+// ---
+
+type uint16TagName string
+
+// Set adds a uint16 tag to the `span`
+func (tag uint16TagName) Set(span opentracing.Span, value uint16) {
+	span.SetTag(string(tag), value)
+}
+
+// ---
+
+type boolTagName string
+
+// Add adds a bool tag to the `span`
+func (tag boolTagName) Set(span opentracing.Span, value bool) {
+	span.SetTag(string(tag), value)
+}
+
+type ipv4Tag string
+
+// Set adds IP v4 host address of the peer as an uint32 value to the `span`, keep this for backward and zipkin compatibility
+func (tag ipv4Tag) Set(span opentracing.Span, value uint32) {
+	span.SetTag(string(tag), value)
+}
+
+// SetString records IP v4 host address of the peer as a .-separated tuple to the `span`. E.g., "127.0.0.1"
+func (tag ipv4Tag) SetString(span opentracing.Span, value string) {
+	span.SetTag(string(tag), value)
+}

vendor/src/github.com/opentracing/opentracing-go/ext/tags_test.go

@@ -0,0 +1,148 @@
+package ext_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/opentracing/opentracing-go/mocktracer"
+)
+
+func TestPeerTags(t *testing.T) {
+	if ext.PeerService != "peer.service" {
+		t.Fatalf("Invalid PeerService %v", ext.PeerService)
+	}
+	tracer := mocktracer.New()
+	span := tracer.StartSpan("my-trace")
+	ext.PeerService.Set(span, "my-service")
+	ext.PeerAddress.Set(span, "my-hostname:8080")
+	ext.PeerHostname.Set(span, "my-hostname")
+	ext.PeerHostIPv4.Set(span, uint32(127<<24|1))
+	ext.PeerHostIPv6.Set(span, "::")
+	ext.PeerPort.Set(span, uint16(8080))
+	ext.SamplingPriority.Set(span, uint16(1))
+	ext.SpanKind.Set(span, ext.SpanKindRPCServerEnum)
+	ext.SpanKindRPCClient.Set(span)
+	span.Finish()
+
+	rawSpan := tracer.FinishedSpans()[0]
+	assert.Equal(t, map[string]interface{}{
+		"peer.service":  "my-service",
+		"peer.address":  "my-hostname:8080",
+		"peer.hostname": "my-hostname",
+		"peer.ipv4":     uint32(127<<24 | 1),
+		"peer.ipv6":     "::",
+		"peer.port":     uint16(8080),
+		"span.kind":     ext.SpanKindRPCClientEnum,
+	}, rawSpan.Tags())
+	assert.True(t, span.Context().(mocktracer.MockSpanContext).Sampled)
+	ext.SamplingPriority.Set(span, uint16(0))
+	assert.False(t, span.Context().(mocktracer.MockSpanContext).Sampled)
+}
+
+func TestHTTPTags(t *testing.T) {
+	tracer := mocktracer.New()
+	span := tracer.StartSpan("my-trace", ext.SpanKindRPCServer)
+	ext.HTTPUrl.Set(span, "test.biz/uri?protocol=false")
+	ext.HTTPMethod.Set(span, "GET")
+	ext.HTTPStatusCode.Set(span, 301)
+	span.Finish()
+
+	rawSpan := tracer.FinishedSpans()[0]
+	assert.Equal(t, map[string]interface{}{
+		"http.url":         "test.biz/uri?protocol=false",
+		"http.method":      "GET",
+		"http.status_code": uint16(301),
+		"span.kind":        ext.SpanKindRPCServerEnum,
+	}, rawSpan.Tags())
+}
+
+func TestDBTags(t *testing.T) {
+	tracer := mocktracer.New()
+	span := tracer.StartSpan("my-trace", ext.SpanKindRPCClient)
+	ext.DBInstance.Set(span, "127.0.0.1:3306/customers")
+	ext.DBStatement.Set(span, "SELECT * FROM user_table")
+	ext.DBType.Set(span, "sql")
+	ext.DBUser.Set(span, "customer_user")
+	span.Finish()
+
+	rawSpan := tracer.FinishedSpans()[0]
+	assert.Equal(t, map[string]interface{}{
+		"db.instance":  "127.0.0.1:3306/customers",
+		"db.statement": "SELECT * FROM user_table",
+		"db.type":      "sql",
+		"db.user":      "customer_user",
+		"span.kind":    ext.SpanKindRPCClientEnum,
+	}, rawSpan.Tags())
+}
+
+func TestMiscTags(t *testing.T) {
+	tracer := mocktracer.New()
+	span := tracer.StartSpan("my-trace")
+	ext.Component.Set(span, "my-awesome-library")
+	ext.SamplingPriority.Set(span, 1)
+	ext.Error.Set(span, true)
+
+	span.Finish()
+
+	rawSpan := tracer.FinishedSpans()[0]
+	assert.Equal(t, map[string]interface{}{
+		"component": "my-awesome-library",
+		"error":     true,
+	}, rawSpan.Tags())
+}
+
+func TestRPCServerOption(t *testing.T) {
+	tracer := mocktracer.New()
+	parent := tracer.StartSpan("my-trace")
+	parent.SetBaggageItem("bag", "gage")
+
+	carrier := opentracing.HTTPHeadersCarrier{}
+	err := tracer.Inject(parent.Context(), opentracing.HTTPHeaders, carrier)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	parCtx, err := tracer.Extract(opentracing.HTTPHeaders, carrier)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tracer.StartSpan("my-child", ext.RPCServerOption(parCtx)).Finish()
+
+	rawSpan := tracer.FinishedSpans()[0]
+	assert.Equal(t, map[string]interface{}{
+		"span.kind": ext.SpanKindRPCServerEnum,
+	}, rawSpan.Tags())
+	assert.Equal(t, map[string]string{
+		"bag": "gage",
+	}, rawSpan.Context().(mocktracer.MockSpanContext).Baggage)
+}
+
+func TestMessageBusProducerTags(t *testing.T) {
+	tracer := mocktracer.New()
+	span := tracer.StartSpan("my-trace", ext.SpanKindProducer)
+	ext.MessageBusDestination.Set(span, "topic name")
+	span.Finish()
+
+	rawSpan := tracer.FinishedSpans()[0]
+	assert.Equal(t, map[string]interface{}{
+		"message_bus.destination": "topic name",
+		"span.kind":               ext.SpanKindProducerEnum,
+	}, rawSpan.Tags())
+}
+
+func TestMessageBusConsumerTags(t *testing.T) {
+	tracer := mocktracer.New()
+	span := tracer.StartSpan("my-trace", ext.SpanKindConsumer)
+	ext.MessageBusDestination.Set(span, "topic name")
+	span.Finish()
+
+	rawSpan := tracer.FinishedSpans()[0]
+	assert.Equal(t, map[string]interface{}{
+		"message_bus.destination": "topic name",
+		"span.kind":               ext.SpanKindConsumerEnum,
+	}, rawSpan.Tags())
+}

vendor/src/github.com/opentracing/opentracing-go/globaltracer.go

@@ -0,0 +1,32 @@
+package opentracing
+
+var (
+	globalTracer Tracer = NoopTracer{}
+)
+
+// SetGlobalTracer sets the [singleton] opentracing.Tracer returned by
+// GlobalTracer(). Those who use GlobalTracer (rather than directly manage an
+// opentracing.Tracer instance) should call SetGlobalTracer as early as
+// possible in main(), prior to calling the `StartSpan` global func below.
+// Prior to calling `SetGlobalTracer`, any Spans started via the `StartSpan`
+// (etc) globals are noops.
+func SetGlobalTracer(tracer Tracer) {
+	globalTracer = tracer
+}
+
+// GlobalTracer returns the global singleton `Tracer` implementation.
+// Before `SetGlobalTracer()` is called, the `GlobalTracer()` is a noop
+// implementation that drops all data handed to it.
+func GlobalTracer() Tracer {
+	return globalTracer
+}
+
+// StartSpan defers to `Tracer.StartSpan`. See `GlobalTracer()`.
+func StartSpan(operationName string, opts ...StartSpanOption) Span {
+	return globalTracer.StartSpan(operationName, opts...)
+}
+
+// InitGlobalTracer is deprecated. Please use SetGlobalTracer.
+func InitGlobalTracer(tracer Tracer) {
+	SetGlobalTracer(tracer)
+}

vendor/src/github.com/opentracing/opentracing-go/gocontext.go

@@ -0,0 +1,57 @@
+package opentracing
+
+import "golang.org/x/net/context"
+
+type contextKey struct{}
+
+var activeSpanKey = contextKey{}
+
+// ContextWithSpan returns a new `context.Context` that holds a reference to
+// `span`'s SpanContext.
+func ContextWithSpan(ctx context.Context, span Span) context.Context {
+	return context.WithValue(ctx, activeSpanKey, span)
+}
+
+// SpanFromContext returns the `Span` previously associated with `ctx`, or
+// `nil` if no such `Span` could be found.
+//
+// NOTE: context.Context != SpanContext: the former is Go's intra-process
+// context propagation mechanism, and the latter houses OpenTracing's per-Span
+// identity and baggage information.
+func SpanFromContext(ctx context.Context) Span {
+	val := ctx.Value(activeSpanKey)
+	if sp, ok := val.(Span); ok {
+		return sp
+	}
+	return nil
+}
+
+// StartSpanFromContext starts and returns a Span with `operationName`, using
+// any Span found within `ctx` as a ChildOfRef. If no such parent could be
+// found, StartSpanFromContext creates a root (parentless) Span.
+//
+// The second return value is a context.Context object built around the
+// returned Span.
+//
+// Example usage:
+//
+//    SomeFunction(ctx context.Context, ...) {
+//        sp, ctx := opentracing.StartSpanFromContext(ctx, "SomeFunction")
+//        defer sp.Finish()
+//        ...
+//    }
+func StartSpanFromContext(ctx context.Context, operationName string, opts ...StartSpanOption) (Span, context.Context) {
+	return startSpanFromContextWithTracer(ctx, GlobalTracer(), operationName, opts...)
+}
+
+// startSpanFromContextWithTracer is factored out for testing purposes.
+func startSpanFromContextWithTracer(ctx context.Context, tracer Tracer, operationName string, opts ...StartSpanOption) (Span, context.Context) {
+	var span Span
+	if parentSpan := SpanFromContext(ctx); parentSpan != nil {
+		opts = append(opts, ChildOf(parentSpan.Context()))
+		span = tracer.StartSpan(operationName, opts...)
+	} else {
+		span = tracer.StartSpan(operationName, opts...)
+	}
+	return span, ContextWithSpan(ctx, span)
+}

vendor/src/github.com/opentracing/opentracing-go/gocontext_test.go

@@ -0,0 +1,81 @@
+package opentracing
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/net/context"
+)
+
+func TestContextWithSpan(t *testing.T) {
+	span := &noopSpan{}
+	ctx := ContextWithSpan(context.Background(), span)
+	span2 := SpanFromContext(ctx)
+	if span != span2 {
+		t.Errorf("Not the same span returned from context, expected=%+v, actual=%+v", span, span2)
+	}
+
+	ctx = context.Background()
+	span2 = SpanFromContext(ctx)
+	if span2 != nil {
+		t.Errorf("Expected nil span, found %+v", span2)
+	}
+
+	ctx = ContextWithSpan(ctx, span)
+	span2 = SpanFromContext(ctx)
+	if span != span2 {
+		t.Errorf("Not the same span returned from context, expected=%+v, actual=%+v", span, span2)
+	}
+}
+
+func TestStartSpanFromContext(t *testing.T) {
+	testTracer := testTracer{}
+
+	// Test the case where there *is* a Span in the Context.
+	{
+		parentSpan := &testSpan{}
+		parentCtx := ContextWithSpan(context.Background(), parentSpan)
+		childSpan, childCtx := startSpanFromContextWithTracer(parentCtx, testTracer, "child")
+		if !childSpan.Context().(testSpanContext).HasParent {
+			t.Errorf("Failed to find parent: %v", childSpan)
+		}
+		if !childSpan.(testSpan).Equal(SpanFromContext(childCtx)) {
+			t.Errorf("Unable to find child span in context: %v", childCtx)
+		}
+	}
+
+	// Test the case where there *is not* a Span in the Context.
+	{
+		emptyCtx := context.Background()
+		childSpan, childCtx := startSpanFromContextWithTracer(emptyCtx, testTracer, "child")
+		if childSpan.Context().(testSpanContext).HasParent {
+			t.Errorf("Should not have found parent: %v", childSpan)
+		}
+		if !childSpan.(testSpan).Equal(SpanFromContext(childCtx)) {
+			t.Errorf("Unable to find child span in context: %v", childCtx)
+		}
+	}
+}
+
+func TestStartSpanFromContextOptions(t *testing.T) {
+	testTracer := testTracer{}
+
+	// Test options are passed to tracer
+
+	startTime := time.Now().Add(-10 * time.Second) // ten seconds ago
+	span, ctx := startSpanFromContextWithTracer(
+		context.Background(), testTracer, "parent", StartTime(startTime), Tag{"component", "test"})
+
+	assert.Equal(t, "test", span.(testSpan).Tags["component"])
+	assert.Equal(t, startTime, span.(testSpan).StartTime)
+
+	// Test it also works for a child span
+
+	childStartTime := startTime.Add(3 * time.Second)
+	childSpan, _ := startSpanFromContextWithTracer(
+		ctx, testTracer, "child", StartTime(childStartTime))
+
+	assert.Equal(t, childSpan.(testSpan).Tags["component"], nil)
+	assert.Equal(t, childSpan.(testSpan).StartTime, childStartTime)
+}

vendor/src/github.com/opentracing/opentracing-go/log/field.go

@@ -0,0 +1,269 @@
+package log
+
+import (
+	"fmt"
+	"math"
+)
+
+type fieldType int
+
+const (
+	stringType fieldType = iota
+	boolType
+	intType
+	int32Type
+	uint32Type
+	int64Type
+	uint64Type
+	float32Type
+	float64Type
+	errorType
+	objectType
+	lazyLoggerType
+	noopType
+)
+
+// Field instances are constructed via LogBool, LogString, and so on.
+// Tracing implementations may then handle them via the Field.Marshal
+// method.
+//
+// "heavily influenced by" (i.e., partially stolen from)
+// https://github.com/uber-go/zap
+type Field struct {
+	key          string
+	fieldType    fieldType
+	numericVal   int64
+	stringVal    string
+	interfaceVal interface{}
+}
+
+// String adds a string-valued key:value pair to a Span.LogFields() record
+func String(key, val string) Field {
+	return Field{
+		key:       key,
+		fieldType: stringType,
+		stringVal: val,
+	}
+}
+
+// Bool adds a bool-valued key:value pair to a Span.LogFields() record
+func Bool(key string, val bool) Field {
+	var numericVal int64
+	if val {
+		numericVal = 1
+	}
+	return Field{
+		key:        key,
+		fieldType:  boolType,
+		numericVal: numericVal,
+	}
+}
+
+// Int adds an int-valued key:value pair to a Span.LogFields() record
+func Int(key string, val int) Field {
+	return Field{
+		key:        key,
+		fieldType:  intType,
+		numericVal: int64(val),
+	}
+}
+
+// Int32 adds an int32-valued key:value pair to a Span.LogFields() record
+func Int32(key string, val int32) Field {
+	return Field{
+		key:        key,
+		fieldType:  int32Type,
+		numericVal: int64(val),
+	}
+}
+
+// Int64 adds an int64-valued key:value pair to a Span.LogFields() record
+func Int64(key string, val int64) Field {
+	return Field{
+		key:        key,
+		fieldType:  int64Type,
+		numericVal: val,
+	}
+}
+
+// Uint32 adds a uint32-valued key:value pair to a Span.LogFields() record
+func Uint32(key string, val uint32) Field {
+	return Field{
+		key:        key,
+		fieldType:  uint32Type,
+		numericVal: int64(val),
+	}
+}
+
+// Uint64 adds a uint64-valued key:value pair to a Span.LogFields() record
+func Uint64(key string, val uint64) Field {
+	return Field{
+		key:        key,
+		fieldType:  uint64Type,
+		numericVal: int64(val),
+	}
+}
+
+// Float32 adds a float32-valued key:value pair to a Span.LogFields() record
+func Float32(key string, val float32) Field {
+	return Field{
+		key:        key,
+		fieldType:  float32Type,
+		numericVal: int64(math.Float32bits(val)),
+	}
+}
+
+// Float64 adds a float64-valued key:value pair to a Span.LogFields() record
+func Float64(key string, val float64) Field {
+	return Field{
+		key:        key,
+		fieldType:  float64Type,
+		numericVal: int64(math.Float64bits(val)),
+	}
+}
+
+// Error adds an error with the key "error" to a Span.LogFields() record
+func Error(err error) Field {
+	return Field{
+		key:          "error",
+		fieldType:    errorType,
+		interfaceVal: err,
+	}
+}
+
+// Object adds an object-valued key:value pair to a Span.LogFields() record
+func Object(key string, obj interface{}) Field {
+	return Field{
+		key:          key,
+		fieldType:    objectType,
+		interfaceVal: obj,
+	}
+}
+
+// LazyLogger allows for user-defined, late-bound logging of arbitrary data
+type LazyLogger func(fv Encoder)
+
+// Lazy adds a LazyLogger to a Span.LogFields() record; the tracing
+// implementation will call the LazyLogger function at an indefinite time in
+// the future (after Lazy() returns).
+func Lazy(ll LazyLogger) Field {
+	return Field{
+		fieldType:    lazyLoggerType,
+		interfaceVal: ll,
+	}
+}
+
+// Noop creates a no-op log field that should be ignored by the tracer.
+// It can be used to capture optional fields, for example those that should
+// only be logged in non-production environment:
+//
+//     func customerField(order *Order) log.Field {
+//          if os.Getenv("ENVIRONMENT") == "dev" {
+//              return log.String("customer", order.Customer.ID)
+//          }
+//          return log.Noop()
+//     }
+//
+//     span.LogFields(log.String("event", "purchase"), customerField(order))
+//
+func Noop() Field {
+	return Field{
+		fieldType: noopType,
+	}
+}
+
+// Encoder allows access to the contents of a Field (via a call to
+// Field.Marshal).
+//
+// Tracer implementations typically provide an implementation of Encoder;
+// OpenTracing callers typically do not need to concern themselves with it.
+type Encoder interface {
+	EmitString(key, value string)
+	EmitBool(key string, value bool)
+	EmitInt(key string, value int)
+	EmitInt32(key string, value int32)
+	EmitInt64(key string, value int64)
+	EmitUint32(key string, value uint32)
+	EmitUint64(key string, value uint64)
+	EmitFloat32(key string, value float32)
+	EmitFloat64(key string, value float64)
+	EmitObject(key string, value interface{})
+	EmitLazyLogger(value LazyLogger)
+}
+
+// Marshal passes a Field instance through to the appropriate
+// field-type-specific method of an Encoder.
+func (lf Field) Marshal(visitor Encoder) {
+	switch lf.fieldType {
+	case stringType:
+		visitor.EmitString(lf.key, lf.stringVal)
+	case boolType:
+		visitor.EmitBool(lf.key, lf.numericVal != 0)
+	case intType:
+		visitor.EmitInt(lf.key, int(lf.numericVal))
+	case int32Type:
+		visitor.EmitInt32(lf.key, int32(lf.numericVal))
+	case int64Type:
+		visitor.EmitInt64(lf.key, int64(lf.numericVal))
+	case uint32Type:
+		visitor.EmitUint32(lf.key, uint32(lf.numericVal))
+	case uint64Type:
+		visitor.EmitUint64(lf.key, uint64(lf.numericVal))
+	case float32Type:
+		visitor.EmitFloat32(lf.key, math.Float32frombits(uint32(lf.numericVal)))
+	case float64Type:
+		visitor.EmitFloat64(lf.key, math.Float64frombits(uint64(lf.numericVal)))
+	case errorType:
+		if err, ok := lf.interfaceVal.(error); ok {
+			visitor.EmitString(lf.key, err.Error())
+		} else {
+			visitor.EmitString(lf.key, "<nil>")
+		}
+	case objectType:
+		visitor.EmitObject(lf.key, lf.interfaceVal)
+	case lazyLoggerType:
+		visitor.EmitLazyLogger(lf.interfaceVal.(LazyLogger))
+	case noopType:
+		// intentionally left blank
+	}
+}
+
+// Key returns the field's key.
+func (lf Field) Key() string {
+	return lf.key
+}
+
+// Value returns the field's value as interface{}.
+func (lf Field) Value() interface{} {
+	switch lf.fieldType {
+	case stringType:
+		return lf.stringVal
+	case boolType:
+		return lf.numericVal != 0
+	case intType:
+		return int(lf.numericVal)
+	case int32Type:
+		return int32(lf.numericVal)
+	case int64Type:
+		return int64(lf.numericVal)
+	case uint32Type:
+		return uint32(lf.numericVal)
+	case uint64Type:
+		return uint64(lf.numericVal)
+	case float32Type:
+		return math.Float32frombits(uint32(lf.numericVal))
+	case float64Type:
+		return math.Float64frombits(uint64(lf.numericVal))
+	case errorType, objectType, lazyLoggerType:
+		return lf.interfaceVal
+	case noopType:
+		return nil
+	default:
+		return nil
+	}
+}
+
+// String returns a string representation of the key and value.
+func (lf Field) String() string {
+	return fmt.Sprint(lf.key, ":", lf.Value())
+}

vendor/src/github.com/opentracing/opentracing-go/log/field_test.go

@@ -0,0 +1,51 @@
+package log
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestFieldString(t *testing.T) {
+	testCases := []struct {
+		field    Field
+		expected string
+	}{
+		{
+			field:    String("key", "value"),
+			expected: "key:value",
+		},
+		{
+			field:    Bool("key", true),
+			expected: "key:true",
+		},
+		{
+			field:    Int("key", 5),
+			expected: "key:5",
+		},
+		{
+			field:    Error(fmt.Errorf("err msg")),
+			expected: "error:err msg",
+		},
+		{
+			field:    Error(nil),
+			expected: "error:<nil>",
+		},
+		{
+			field:    Noop(),
+			expected: ":<nil>",
+		},
+	}
+	for i, tc := range testCases {
+		if str := tc.field.String(); str != tc.expected {
+			t.Errorf("%d: expected '%s', got '%s'", i, tc.expected, str)
+		}
+	}
+}
+
+func TestNoopDoesNotMarshal(t *testing.T) {
+	mockEncoder := struct {
+		Encoder
+	}{}
+	f := Noop()
+	f.Marshal(mockEncoder) // panics if any Encoder method is invoked
+}

vendor/src/github.com/opentracing/opentracing-go/log/util.go

@@ -0,0 +1,54 @@
+package log
+
+import "fmt"
+
+// InterleavedKVToFields converts keyValues a la Span.LogKV() to a Field slice
+// a la Span.LogFields().
+func InterleavedKVToFields(keyValues ...interface{}) ([]Field, error) {
+	if len(keyValues)%2 != 0 {
+		return nil, fmt.Errorf("non-even keyValues len: %d", len(keyValues))
+	}
+	fields := make([]Field, len(keyValues)/2)
+	for i := 0; i*2 < len(keyValues); i++ {
+		key, ok := keyValues[i*2].(string)
+		if !ok {
+			return nil, fmt.Errorf(
+				"non-string key (pair #%d): %T",
+				i, keyValues[i*2])
+		}
+		switch typedVal := keyValues[i*2+1].(type) {
+		case bool:
+			fields[i] = Bool(key, typedVal)
+		case string:
+			fields[i] = String(key, typedVal)
+		case int:
+			fields[i] = Int(key, typedVal)
+		case int8:
+			fields[i] = Int32(key, int32(typedVal))
+		case int16:
+			fields[i] = Int32(key, int32(typedVal))
+		case int32:
+			fields[i] = Int32(key, typedVal)
+		case int64:
+			fields[i] = Int64(key, typedVal)
+		case uint:
+			fields[i] = Uint64(key, uint64(typedVal))
+		case uint64:
+			fields[i] = Uint64(key, typedVal)
+		case uint8:
+			fields[i] = Uint32(key, uint32(typedVal))
+		case uint16:
+			fields[i] = Uint32(key, uint32(typedVal))
+		case uint32:
+			fields[i] = Uint32(key, typedVal)
+		case float32:
+			fields[i] = Float32(key, typedVal)
+		case float64:
+			fields[i] = Float64(key, typedVal)
+		default:
+			// When in doubt, coerce to a string
+			fields[i] = String(key, fmt.Sprint(typedVal))
+		}
+	}
+	return fields, nil
+}

vendor/src/github.com/opentracing/opentracing-go/mocktracer/mocklogrecord.go

@@ -0,0 +1,105 @@
+package mocktracer
+
+import (
+	"fmt"
+	"reflect"
+	"time"
+
+	"github.com/opentracing/opentracing-go/log"
+)
+
+// MockLogRecord represents data logged to a Span via Span.LogFields or
+// Span.LogKV.
+type MockLogRecord struct {
+	Timestamp time.Time
+	Fields    []MockKeyValue
+}
+
+// MockKeyValue represents a single key:value pair.
+type MockKeyValue struct {
+	Key string
+
+	// All MockLogRecord values are coerced to strings via fmt.Sprint(), though
+	// we retain their type separately.
+	ValueKind   reflect.Kind
+	ValueString string
+}
+
+// EmitString belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitString(key, value string) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitBool belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitBool(key string, value bool) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitInt belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitInt(key string, value int) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitInt32 belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitInt32(key string, value int32) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitInt64 belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitInt64(key string, value int64) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitUint32 belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitUint32(key string, value uint32) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitUint64 belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitUint64(key string, value uint64) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitFloat32 belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitFloat32(key string, value float32) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitFloat64 belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitFloat64(key string, value float64) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitObject belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitObject(key string, value interface{}) {
+	m.Key = key
+	m.ValueKind = reflect.TypeOf(value).Kind()
+	m.ValueString = fmt.Sprint(value)
+}
+
+// EmitLazyLogger belongs to the log.Encoder interface
+func (m *MockKeyValue) EmitLazyLogger(value log.LazyLogger) {
+	var meta MockKeyValue
+	value(&meta)
+	m.Key = meta.Key
+	m.ValueKind = meta.ValueKind
+	m.ValueString = meta.ValueString
+}

vendor/src/github.com/opentracing/opentracing-go/mocktracer/mockspan.go

@@ -0,0 +1,282 @@
+package mocktracer
+
+import (
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/opentracing/opentracing-go/log"
+)
+
+// MockSpanContext is an opentracing.SpanContext implementation.
+//
+// It is entirely unsuitable for production use, but appropriate for tests
+// that want to verify tracing behavior in other frameworks/applications.
+//
+// By default all spans have Sampled=true flag, unless {"sampling.priority": 0}
+// tag is set.
+type MockSpanContext struct {
+	TraceID int
+	SpanID  int
+	Sampled bool
+	Baggage map[string]string
+}
+
+var mockIDSource = uint32(42)
+
+func nextMockID() int {
+	return int(atomic.AddUint32(&mockIDSource, 1))
+}
+
+// ForeachBaggageItem belongs to the SpanContext interface
+func (c MockSpanContext) ForeachBaggageItem(handler func(k, v string) bool) {
+	for k, v := range c.Baggage {
+		if !handler(k, v) {
+			break
+		}
+	}
+}
+
+// WithBaggageItem creates a new context with an extra baggage item.
+func (c MockSpanContext) WithBaggageItem(key, value string) MockSpanContext {
+	var newBaggage map[string]string
+	if c.Baggage == nil {
+		newBaggage = map[string]string{key: value}
+	} else {
+		newBaggage = make(map[string]string, len(c.Baggage)+1)
+		for k, v := range c.Baggage {
+			newBaggage[k] = v
+		}
+		newBaggage[key] = value
+	}
+	// Use positional parameters so the compiler will help catch new fields.
+	return MockSpanContext{c.TraceID, c.SpanID, c.Sampled, newBaggage}
+}
+
+// MockSpan is an opentracing.Span implementation that exports its internal
+// state for testing purposes.
+type MockSpan struct {
+	sync.RWMutex
+
+	ParentID int
+
+	OperationName string
+	StartTime     time.Time
+	FinishTime    time.Time
+
+	// All of the below are protected by the embedded RWMutex.
+	SpanContext MockSpanContext
+	tags        map[string]interface{}
+	logs        []MockLogRecord
+	tracer      *MockTracer
+}
+
+func newMockSpan(t *MockTracer, name string, opts opentracing.StartSpanOptions) *MockSpan {
+	tags := opts.Tags
+	if tags == nil {
+		tags = map[string]interface{}{}
+	}
+	traceID := nextMockID()
+	parentID := int(0)
+	var baggage map[string]string
+	sampled := true
+	if len(opts.References) > 0 {
+		traceID = opts.References[0].ReferencedContext.(MockSpanContext).TraceID
+		parentID = opts.References[0].ReferencedContext.(MockSpanContext).SpanID
+		sampled = opts.References[0].ReferencedContext.(MockSpanContext).Sampled
+		baggage = opts.References[0].ReferencedContext.(MockSpanContext).Baggage
+	}
+	spanContext := MockSpanContext{traceID, nextMockID(), sampled, baggage}
+	startTime := opts.StartTime
+	if startTime.IsZero() {
+		startTime = time.Now()
+	}
+	return &MockSpan{
+		ParentID:      parentID,
+		OperationName: name,
+		StartTime:     startTime,
+		tags:          tags,
+		logs:          []MockLogRecord{},
+		SpanContext:   spanContext,
+
+		tracer: t,
+	}
+}
+
+// Tags returns a copy of tags accumulated by the span so far
+func (s *MockSpan) Tags() map[string]interface{} {
+	s.RLock()
+	defer s.RUnlock()
+	tags := make(map[string]interface{})
+	for k, v := range s.tags {
+		tags[k] = v
+	}
+	return tags
+}
+
+// Tag returns a single tag
+func (s *MockSpan) Tag(k string) interface{} {
+	s.RLock()
+	defer s.RUnlock()
+	return s.tags[k]
+}
+
+// Logs returns a copy of logs accumulated in the span so far
+func (s *MockSpan) Logs() []MockLogRecord {
+	s.RLock()
+	defer s.RUnlock()
+	logs := make([]MockLogRecord, len(s.logs))
+	copy(logs, s.logs)
+	return logs
+}
+
+// Context belongs to the Span interface
+func (s *MockSpan) Context() opentracing.SpanContext {
+	return s.SpanContext
+}
+
+// SetTag belongs to the Span interface
+func (s *MockSpan) SetTag(key string, value interface{}) opentracing.Span {
+	s.Lock()
+	defer s.Unlock()
+	if key == string(ext.SamplingPriority) {
+		if v, ok := value.(uint16); ok {
+			s.SpanContext.Sampled = v > 0
+			return s
+		}
+		if v, ok := value.(int); ok {
+			s.SpanContext.Sampled = v > 0
+			return s
+		}
+	}
+	s.tags[key] = value
+	return s
+}
+
+// SetBaggageItem belongs to the Span interface
+func (s *MockSpan) SetBaggageItem(key, val string) opentracing.Span {
+	s.Lock()
+	defer s.Unlock()
+	s.SpanContext = s.SpanContext.WithBaggageItem(key, val)
+	return s
+}
+
+// BaggageItem belongs to the Span interface
+func (s *MockSpan) BaggageItem(key string) string {
+	s.RLock()
+	defer s.RUnlock()
+	return s.SpanContext.Baggage[key]
+}
+
+// Finish belongs to the Span interface
+func (s *MockSpan) Finish() {
+	s.Lock()
+	s.FinishTime = time.Now()
+	s.Unlock()
+	s.tracer.recordSpan(s)
+}
+
+// FinishWithOptions belongs to the Span interface
+func (s *MockSpan) FinishWithOptions(opts opentracing.FinishOptions) {
+	s.Lock()
+	s.FinishTime = opts.FinishTime
+	s.Unlock()
+
+	// Handle any late-bound LogRecords.
+	for _, lr := range opts.LogRecords {
+		s.logFieldsWithTimestamp(lr.Timestamp, lr.Fields...)
+	}
+	// Handle (deprecated) BulkLogData.
+	for _, ld := range opts.BulkLogData {
+		if ld.Payload != nil {
+			s.logFieldsWithTimestamp(
+				ld.Timestamp,
+				log.String("event", ld.Event),
+				log.Object("payload", ld.Payload))
+		} else {
+			s.logFieldsWithTimestamp(
+				ld.Timestamp,
+				log.String("event", ld.Event))
+		}
+	}
+
+	s.tracer.recordSpan(s)
+}
+
+// String allows printing span for debugging
+func (s *MockSpan) String() string {
+	return fmt.Sprintf(
+		"traceId=%d, spanId=%d, parentId=%d, sampled=%t, name=%s",
+		s.SpanContext.TraceID, s.SpanContext.SpanID, s.ParentID,
+		s.SpanContext.Sampled, s.OperationName)
+}
+
+// LogFields belongs to the Span interface
+func (s *MockSpan) LogFields(fields ...log.Field) {
+	s.logFieldsWithTimestamp(time.Now(), fields...)
+}
+
+// The caller MUST NOT hold s.Lock
+func (s *MockSpan) logFieldsWithTimestamp(ts time.Time, fields ...log.Field) {
+	lr := MockLogRecord{
+		Timestamp: ts,
+		Fields:    make([]MockKeyValue, len(fields)),
+	}
+	for i, f := range fields {
+		outField := &(lr.Fields[i])
+		f.Marshal(outField)
+	}
+
+	s.Lock()
+	defer s.Unlock()
+	s.logs = append(s.logs, lr)
+}
+
+// LogKV belongs to the Span interface.
+//
+// This implementations coerces all "values" to strings, though that is not
+// something all implementations need to do. Indeed, a motivated person can and
+// probably should have this do a typed switch on the values.
+func (s *MockSpan) LogKV(keyValues ...interface{}) {
+	if len(keyValues)%2 != 0 {
+		s.LogFields(log.Error(fmt.Errorf("Non-even keyValues len: %v", len(keyValues))))
+		return
+	}
+	fields, err := log.InterleavedKVToFields(keyValues...)
+	if err != nil {
+		s.LogFields(log.Error(err), log.String("function", "LogKV"))
+		return
+	}
+	s.LogFields(fields...)
+}
+
+// LogEvent belongs to the Span interface
+func (s *MockSpan) LogEvent(event string) {
+	s.LogFields(log.String("event", event))
+}
+
+// LogEventWithPayload belongs to the Span interface
+func (s *MockSpan) LogEventWithPayload(event string, payload interface{}) {
+	s.LogFields(log.String("event", event), log.Object("payload", payload))
+}
+
+// Log belongs to the Span interface
+func (s *MockSpan) Log(data opentracing.LogData) {
+	panic("MockSpan.Log() no longer supported")
+}
+
+// SetOperationName belongs to the Span interface
+func (s *MockSpan) SetOperationName(operationName string) opentracing.Span {
+	s.Lock()
+	defer s.Unlock()
+	s.OperationName = operationName
+	return s
+}
+
+// Tracer belongs to the Span interface
+func (s *MockSpan) Tracer() opentracing.Tracer {
+	return s.tracer
+}

vendor/src/github.com/opentracing/opentracing-go/mocktracer/mocktracer.go

@@ -0,0 +1,105 @@
+package mocktracer
+
+import (
+	"sync"
+
+	"github.com/opentracing/opentracing-go"
+)
+
+// New returns a MockTracer opentracing.Tracer implementation that's intended
+// to facilitate tests of OpenTracing instrumentation.
+func New() *MockTracer {
+	t := &MockTracer{
+		finishedSpans: []*MockSpan{},
+		injectors:     make(map[interface{}]Injector),
+		extractors:    make(map[interface{}]Extractor),
+	}
+
+	// register default injectors/extractors
+	textPropagator := new(TextMapPropagator)
+	t.RegisterInjector(opentracing.TextMap, textPropagator)
+	t.RegisterExtractor(opentracing.TextMap, textPropagator)
+
+	httpPropagator := &TextMapPropagator{HTTPHeaders: true}
+	t.RegisterInjector(opentracing.HTTPHeaders, httpPropagator)
+	t.RegisterExtractor(opentracing.HTTPHeaders, httpPropagator)
+
+	return t
+}
+
+// MockTracer is only intended for testing OpenTracing instrumentation.
+//
+// It is entirely unsuitable for production use, but appropriate for tests
+// that want to verify tracing behavior in other frameworks/applications.
+type MockTracer struct {
+	sync.RWMutex
+	finishedSpans []*MockSpan
+	injectors     map[interface{}]Injector
+	extractors    map[interface{}]Extractor
+}
+
+// FinishedSpans returns all spans that have been Finish()'ed since the
+// MockTracer was constructed or since the last call to its Reset() method.
+func (t *MockTracer) FinishedSpans() []*MockSpan {
+	t.RLock()
+	defer t.RUnlock()
+	spans := make([]*MockSpan, len(t.finishedSpans))
+	copy(spans, t.finishedSpans)
+	return spans
+}
+
+// Reset clears the internally accumulated finished spans. Note that any
+// extant MockSpans will still append to finishedSpans when they Finish(),
+// even after a call to Reset().
+func (t *MockTracer) Reset() {
+	t.Lock()
+	defer t.Unlock()
+	t.finishedSpans = []*MockSpan{}
+}
+
+// StartSpan belongs to the Tracer interface.
+func (t *MockTracer) StartSpan(operationName string, opts ...opentracing.StartSpanOption) opentracing.Span {
+	sso := opentracing.StartSpanOptions{}
+	for _, o := range opts {
+		o.Apply(&sso)
+	}
+	return newMockSpan(t, operationName, sso)
+}
+
+// RegisterInjector registers injector for given format
+func (t *MockTracer) RegisterInjector(format interface{}, injector Injector) {
+	t.injectors[format] = injector
+}
+
+// RegisterExtractor registers extractor for given format
+func (t *MockTracer) RegisterExtractor(format interface{}, extractor Extractor) {
+	t.extractors[format] = extractor
+}
+
+// Inject belongs to the Tracer interface.
+func (t *MockTracer) Inject(sm opentracing.SpanContext, format interface{}, carrier interface{}) error {
+	spanContext, ok := sm.(MockSpanContext)
+	if !ok {
+		return opentracing.ErrInvalidCarrier
+	}
+	injector, ok := t.injectors[format]
+	if !ok {
+		return opentracing.ErrUnsupportedFormat
+	}
+	return injector.Inject(spanContext, carrier)
+}
+
+// Extract belongs to the Tracer interface.
+func (t *MockTracer) Extract(format interface{}, carrier interface{}) (opentracing.SpanContext, error) {
+	extractor, ok := t.extractors[format]
+	if !ok {
+		return nil, opentracing.ErrUnsupportedFormat
+	}
+	return extractor.Extract(carrier)
+}
+
+func (t *MockTracer) recordSpan(span *MockSpan) {
+	t.Lock()
+	defer t.Unlock()
+	t.finishedSpans = append(t.finishedSpans, span)
+}

vendor/src/github.com/opentracing/opentracing-go/mocktracer/mocktracer_test.go

@@ -0,0 +1,268 @@
+package mocktracer
+
+import (
+	"net/http"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/opentracing/opentracing-go/log"
+)
+
+func TestMockTracer_StartSpan(t *testing.T) {
+	tracer := New()
+	span1 := tracer.StartSpan(
+		"a",
+		opentracing.Tags(map[string]interface{}{"x": "y"}))
+
+	span2 := span1.Tracer().StartSpan(
+		"", opentracing.ChildOf(span1.Context()))
+	span2.Finish()
+	span1.Finish()
+	spans := tracer.FinishedSpans()
+	assert.Equal(t, 2, len(spans))
+
+	parent := spans[1]
+	child := spans[0]
+	assert.Equal(t, map[string]interface{}{"x": "y"}, parent.Tags())
+	assert.Equal(t, child.ParentID, parent.Context().(MockSpanContext).SpanID)
+}
+
+func TestMockSpan_SetOperationName(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("")
+	span.SetOperationName("x")
+	assert.Equal(t, "x", span.(*MockSpan).OperationName)
+}
+
+func TestMockSpanContext_Baggage(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("x")
+	span.SetBaggageItem("x", "y")
+	assert.Equal(t, "y", span.BaggageItem("x"))
+	assert.Equal(t, map[string]string{"x": "y"}, span.Context().(MockSpanContext).Baggage)
+
+	baggage := make(map[string]string)
+	span.Context().ForeachBaggageItem(func(k, v string) bool {
+		baggage[k] = v
+		return true
+	})
+	assert.Equal(t, map[string]string{"x": "y"}, baggage)
+
+	span.SetBaggageItem("a", "b")
+	baggage = make(map[string]string)
+	span.Context().ForeachBaggageItem(func(k, v string) bool {
+		baggage[k] = v
+		return false // exit early
+	})
+	assert.Equal(t, 2, len(span.Context().(MockSpanContext).Baggage))
+	assert.Equal(t, 1, len(baggage))
+}
+
+func TestMockSpan_Tag(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("x")
+	span.SetTag("x", "y")
+	assert.Equal(t, "y", span.(*MockSpan).Tag("x"))
+}
+
+func TestMockSpan_Tags(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("x")
+	span.SetTag("x", "y")
+	assert.Equal(t, map[string]interface{}{"x": "y"}, span.(*MockSpan).Tags())
+}
+
+func TestMockTracer_FinishedSpans_and_Reset(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("x")
+	span.SetTag("x", "y")
+	span.Finish()
+	spans := tracer.FinishedSpans()
+	assert.Equal(t, 1, len(spans))
+	assert.Equal(t, map[string]interface{}{"x": "y"}, spans[0].Tags())
+
+	tracer.Reset()
+	spans = tracer.FinishedSpans()
+	assert.Equal(t, 0, len(spans))
+}
+
+func zeroOutTimestamps(recs []MockLogRecord) {
+	for i := range recs {
+		recs[i].Timestamp = time.Time{}
+	}
+}
+
+func TestMockSpan_LogKV(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("s")
+	span.LogKV("key0", "string0")
+	span.LogKV("key1", "string1", "key2", uint32(42))
+	span.Finish()
+	spans := tracer.FinishedSpans()
+	assert.Equal(t, 1, len(spans))
+	actual := spans[0].Logs()
+	zeroOutTimestamps(actual)
+	assert.Equal(t, []MockLogRecord{
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "key0", ValueKind: reflect.String, ValueString: "string0"},
+			},
+		},
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "key1", ValueKind: reflect.String, ValueString: "string1"},
+				MockKeyValue{Key: "key2", ValueKind: reflect.Uint32, ValueString: "42"},
+			},
+		},
+	}, actual)
+}
+
+func TestMockSpan_LogFields(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("s")
+	span.LogFields(log.String("key0", "string0"))
+	span.LogFields(log.String("key1", "string1"), log.Uint32("key2", uint32(42)))
+	span.LogFields(log.Lazy(func(fv log.Encoder) {
+		fv.EmitInt("key_lazy", 12)
+	}))
+	span.FinishWithOptions(opentracing.FinishOptions{
+		LogRecords: []opentracing.LogRecord{
+			{Timestamp: time.Now(), Fields: []log.Field{log.String("key9", "finish")}},
+		}})
+	spans := tracer.FinishedSpans()
+	assert.Equal(t, 1, len(spans))
+	actual := spans[0].Logs()
+	zeroOutTimestamps(actual)
+	assert.Equal(t, []MockLogRecord{
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "key0", ValueKind: reflect.String, ValueString: "string0"},
+			},
+		},
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "key1", ValueKind: reflect.String, ValueString: "string1"},
+				MockKeyValue{Key: "key2", ValueKind: reflect.Uint32, ValueString: "42"},
+			},
+		},
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				// Note that the LazyLogger gets to control the key as well as the value.
+				MockKeyValue{Key: "key_lazy", ValueKind: reflect.Int, ValueString: "12"},
+			},
+		},
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "key9", ValueKind: reflect.String, ValueString: "finish"},
+			},
+		},
+	}, actual)
+}
+
+func TestMockSpan_DeprecatedLogs(t *testing.T) {
+	tracer := New()
+	span := tracer.StartSpan("x")
+	span.LogEvent("x")
+	span.LogEventWithPayload("y", "z")
+	span.LogEvent("a")
+	span.FinishWithOptions(opentracing.FinishOptions{
+		BulkLogData: []opentracing.LogData{{Event: "f"}}})
+	spans := tracer.FinishedSpans()
+	assert.Equal(t, 1, len(spans))
+	actual := spans[0].Logs()
+	zeroOutTimestamps(actual)
+	assert.Equal(t, []MockLogRecord{
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "event", ValueKind: reflect.String, ValueString: "x"},
+			},
+		},
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "event", ValueKind: reflect.String, ValueString: "y"},
+				MockKeyValue{Key: "payload", ValueKind: reflect.String, ValueString: "z"},
+			},
+		},
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "event", ValueKind: reflect.String, ValueString: "a"},
+			},
+		},
+		MockLogRecord{
+			Fields: []MockKeyValue{
+				MockKeyValue{Key: "event", ValueKind: reflect.String, ValueString: "f"},
+			},
+		},
+	}, actual)
+}
+
+func TestMockTracer_Propagation(t *testing.T) {
+	textCarrier := func() interface{} {
+		return opentracing.TextMapCarrier(make(map[string]string))
+	}
+	textLen := func(c interface{}) int {
+		return len(c.(opentracing.TextMapCarrier))
+	}
+
+	httpCarrier := func() interface{} {
+		httpHeaders := http.Header(make(map[string][]string))
+		return opentracing.HTTPHeadersCarrier(httpHeaders)
+	}
+	httpLen := func(c interface{}) int {
+		return len(c.(opentracing.HTTPHeadersCarrier))
+	}
+
+	tests := []struct {
+		sampled bool
+		format  opentracing.BuiltinFormat
+		carrier func() interface{}
+		len     func(interface{}) int
+	}{
+		{sampled: true, format: opentracing.TextMap, carrier: textCarrier, len: textLen},
+		{sampled: false, format: opentracing.TextMap, carrier: textCarrier, len: textLen},
+		{sampled: true, format: opentracing.HTTPHeaders, carrier: httpCarrier, len: httpLen},
+		{sampled: false, format: opentracing.HTTPHeaders, carrier: httpCarrier, len: httpLen},
+	}
+	for _, test := range tests {
+		tracer := New()
+		span := tracer.StartSpan("x")
+		span.SetBaggageItem("x", "y:z") // colon should be URL encoded as %3A
+		if !test.sampled {
+			ext.SamplingPriority.Set(span, 0)
+		}
+		mSpan := span.(*MockSpan)
+
+		assert.Equal(t, opentracing.ErrUnsupportedFormat,
+			tracer.Inject(span.Context(), opentracing.Binary, nil))
+		assert.Equal(t, opentracing.ErrInvalidCarrier,
+			tracer.Inject(span.Context(), opentracing.TextMap, span))
+
+		carrier := test.carrier()
+
+		err := tracer.Inject(span.Context(), test.format, carrier)
+		require.NoError(t, err)
+		assert.Equal(t, 4, test.len(carrier), "expect baggage + 2 ids + sampled")
+		if test.format == opentracing.HTTPHeaders {
+			c := carrier.(opentracing.HTTPHeadersCarrier)
+			assert.Equal(t, "y%3Az", c["Mockpfx-Baggage-X"][0])
+		}
+
+		_, err = tracer.Extract(opentracing.Binary, nil)
+		assert.Equal(t, opentracing.ErrUnsupportedFormat, err)
+		_, err = tracer.Extract(opentracing.TextMap, tracer)
+		assert.Equal(t, opentracing.ErrInvalidCarrier, err)
+
+		extractedContext, err := tracer.Extract(test.format, carrier)
+		require.NoError(t, err)
+		assert.Equal(t, mSpan.SpanContext.TraceID, extractedContext.(MockSpanContext).TraceID)
+		assert.Equal(t, mSpan.SpanContext.SpanID, extractedContext.(MockSpanContext).SpanID)
+		assert.Equal(t, test.sampled, extractedContext.(MockSpanContext).Sampled)
+		assert.Equal(t, "y:z", extractedContext.(MockSpanContext).Baggage["x"])
+	}
+}

vendor/src/github.com/opentracing/opentracing-go/mocktracer/propagation.go

@@ -0,0 +1,120 @@
+package mocktracer
+
+import (
+	"fmt"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/opentracing/opentracing-go"
+)
+
+const mockTextMapIdsPrefix = "mockpfx-ids-"
+const mockTextMapBaggagePrefix = "mockpfx-baggage-"
+
+var emptyContext = MockSpanContext{}
+
+// 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 MockSpanContext, 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{}) (MockSpanContext, error)
+}
+
+// TextMapPropagator implements Injector/Extractor for TextMap and HTTPHeaders formats.
+type TextMapPropagator struct {
+	HTTPHeaders bool
+}
+
+// Inject implements the Injector interface
+func (t *TextMapPropagator) Inject(spanContext MockSpanContext, carrier interface{}) error {
+	writer, ok := carrier.(opentracing.TextMapWriter)
+	if !ok {
+		return opentracing.ErrInvalidCarrier
+	}
+	// Ids:
+	writer.Set(mockTextMapIdsPrefix+"traceid", strconv.Itoa(spanContext.TraceID))
+	writer.Set(mockTextMapIdsPrefix+"spanid", strconv.Itoa(spanContext.SpanID))
+	writer.Set(mockTextMapIdsPrefix+"sampled", fmt.Sprint(spanContext.Sampled))
+	// Baggage:
+	for baggageKey, baggageVal := range spanContext.Baggage {
+		safeVal := baggageVal
+		if t.HTTPHeaders {
+			safeVal = url.QueryEscape(baggageVal)
+		}
+		writer.Set(mockTextMapBaggagePrefix+baggageKey, safeVal)
+	}
+	return nil
+}
+
+// Extract implements the Extractor interface
+func (t *TextMapPropagator) Extract(carrier interface{}) (MockSpanContext, error) {
+	reader, ok := carrier.(opentracing.TextMapReader)
+	if !ok {
+		return emptyContext, opentracing.ErrInvalidCarrier
+	}
+	rval := MockSpanContext{0, 0, true, nil}
+	err := reader.ForeachKey(func(key, val string) error {
+		lowerKey := strings.ToLower(key)
+		switch {
+		case lowerKey == mockTextMapIdsPrefix+"traceid":
+			// Ids:
+			i, err := strconv.Atoi(val)
+			if err != nil {
+				return err
+			}
+			rval.TraceID = i
+		case lowerKey == mockTextMapIdsPrefix+"spanid":
+			// Ids:
+			i, err := strconv.Atoi(val)
+			if err != nil {
+				return err
+			}
+			rval.SpanID = i
+		case lowerKey == mockTextMapIdsPrefix+"sampled":
+			b, err := strconv.ParseBool(val)
+			if err != nil {
+				return err
+			}
+			rval.Sampled = b
+		case strings.HasPrefix(lowerKey, mockTextMapBaggagePrefix):
+			// Baggage:
+			if rval.Baggage == nil {
+				rval.Baggage = make(map[string]string)
+			}
+			safeVal := val
+			if t.HTTPHeaders {
+				// unescape errors are ignored, nothing can be done
+				if rawVal, err := url.QueryUnescape(val); err == nil {
+					safeVal = rawVal
+				}
+			}
+			rval.Baggage[lowerKey[len(mockTextMapBaggagePrefix):]] = safeVal
+		}
+		return nil
+	})
+	if rval.TraceID == 0 || rval.SpanID == 0 {
+		return emptyContext, opentracing.ErrSpanContextNotFound
+	}
+	if err != nil {
+		return emptyContext, err
+	}
+	return rval, nil
+}

vendor/src/github.com/opentracing/opentracing-go/noop.go

@@ -0,0 +1,64 @@
+package opentracing
+
+import "github.com/opentracing/opentracing-go/log"
+
+// A NoopTracer is a trivial, minimum overhead implementation of Tracer
+// for which all operations are no-ops.
+//
+// The primary use of this implementation is in libraries, such as RPC
+// frameworks, that make tracing an optional feature controlled by the
+// end user. A no-op implementation allows said libraries to use it
+// as the default Tracer and to write instrumentation that does
+// not need to keep checking if the tracer instance is nil.
+//
+// For the same reason, the NoopTracer is the default "global" tracer
+// (see GlobalTracer and SetGlobalTracer functions).
+//
+// WARNING: NoopTracer does not support baggage propagation.
+type NoopTracer struct{}
+
+type noopSpan struct{}
+type noopSpanContext struct{}
+
+var (
+	defaultNoopSpanContext = noopSpanContext{}
+	defaultNoopSpan        = noopSpan{}
+	defaultNoopTracer      = NoopTracer{}
+)
+
+const (
+	emptyString = ""
+)
+
+// noopSpanContext:
+func (n noopSpanContext) ForeachBaggageItem(handler func(k, v string) bool) {}
+
+// noopSpan:
+func (n noopSpan) Context() SpanContext                                  { return defaultNoopSpanContext }
+func (n noopSpan) SetBaggageItem(key, val string) Span                   { return defaultNoopSpan }
+func (n noopSpan) BaggageItem(key string) string                         { return emptyString }
+func (n noopSpan) SetTag(key string, value interface{}) Span             { return n }
+func (n noopSpan) LogFields(fields ...log.Field)                         {}
+func (n noopSpan) LogKV(keyVals ...interface{})                          {}
+func (n noopSpan) Finish()                                               {}
+func (n noopSpan) FinishWithOptions(opts FinishOptions)                  {}
+func (n noopSpan) SetOperationName(operationName string) Span            { return n }
+func (n noopSpan) Tracer() Tracer                                        { return defaultNoopTracer }
+func (n noopSpan) LogEvent(event string)                                 {}
+func (n noopSpan) LogEventWithPayload(event string, payload interface{}) {}
+func (n noopSpan) Log(data LogData)                                      {}
+
+// StartSpan belongs to the Tracer interface.
+func (n NoopTracer) StartSpan(operationName string, opts ...StartSpanOption) Span {
+	return defaultNoopSpan
+}
+
+// Inject belongs to the Tracer interface.
+func (n NoopTracer) Inject(sp SpanContext, format interface{}, carrier interface{}) error {
+	return nil
+}
+
+// Extract belongs to the Tracer interface.
+func (n NoopTracer) Extract(format interface{}, carrier interface{}) (SpanContext, error) {
+	return nil, ErrSpanContextNotFound
+}

vendor/src/github.com/opentracing/opentracing-go/options_test.go

@@ -0,0 +1,31 @@
+package opentracing
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestChildOfAndFollowsFrom(t *testing.T) {
+	tests := []struct {
+		newOpt  func(SpanContext) SpanReference
+		refType SpanReferenceType
+		name    string
+	}{
+		{ChildOf, ChildOfRef, "ChildOf"},
+		{FollowsFrom, FollowsFromRef, "FollowsFrom"},
+	}
+
+	for _, test := range tests {
+		opts := new(StartSpanOptions)
+
+		test.newOpt(nil).Apply(opts)
+		require.Nil(t, opts.References, "%s(nil) must not append a reference", test.name)
+
+		ctx := new(noopSpanContext)
+		test.newOpt(ctx).Apply(opts)
+		require.Equal(t, []SpanReference{
+			SpanReference{ReferencedContext: ctx, Type: test.refType},
+		}, opts.References, "%s(ctx) must append a reference", test.name)
+	}
+}

vendor/src/github.com/opentracing/opentracing-go/propagation.go

@@ -0,0 +1,176 @@
+package opentracing
+
+import (
+	"errors"
+	"net/http"
+)
+
+///////////////////////////////////////////////////////////////////////////////
+// CORE PROPAGATION INTERFACES:
+///////////////////////////////////////////////////////////////////////////////
+
+var (
+	// ErrUnsupportedFormat occurs when the `format` passed to Tracer.Inject() or
+	// Tracer.Extract() is not recognized by the Tracer implementation.
+	ErrUnsupportedFormat = errors.New("opentracing: Unknown or unsupported Inject/Extract format")
+
+	// ErrSpanContextNotFound occurs when the `carrier` passed to
+	// Tracer.Extract() is valid and uncorrupted but has insufficient
+	// information to extract a SpanContext.
+	ErrSpanContextNotFound = errors.New("opentracing: SpanContext not found in Extract carrier")
+
+	// ErrInvalidSpanContext errors occur when Tracer.Inject() is asked to
+	// operate on a SpanContext which it is not prepared to handle (for
+	// example, since it was created by a different tracer implementation).
+	ErrInvalidSpanContext = errors.New("opentracing: SpanContext type incompatible with tracer")
+
+	// ErrInvalidCarrier errors occur when Tracer.Inject() or Tracer.Extract()
+	// implementations expect a different type of `carrier` than they are
+	// given.
+	ErrInvalidCarrier = errors.New("opentracing: Invalid Inject/Extract carrier")
+
+	// ErrSpanContextCorrupted occurs when the `carrier` passed to
+	// Tracer.Extract() is of the expected type but is corrupted.
+	ErrSpanContextCorrupted = errors.New("opentracing: SpanContext data corrupted in Extract carrier")
+)
+
+///////////////////////////////////////////////////////////////////////////////
+// BUILTIN PROPAGATION FORMATS:
+///////////////////////////////////////////////////////////////////////////////
+
+// BuiltinFormat is used to demarcate the values within package `opentracing`
+// that are intended for use with the Tracer.Inject() and Tracer.Extract()
+// methods.
+type BuiltinFormat byte
+
+const (
+	// Binary represents SpanContexts as opaque binary data.
+	//
+	// For Tracer.Inject(): the carrier must be an `io.Writer`.
+	//
+	// For Tracer.Extract(): the carrier must be an `io.Reader`.
+	Binary BuiltinFormat = iota
+
+	// TextMap represents SpanContexts as key:value string pairs.
+	//
+	// Unlike HTTPHeaders, the TextMap format does not restrict the key or
+	// value character sets in any way.
+	//
+	// For Tracer.Inject(): the carrier must be a `TextMapWriter`.
+	//
+	// For Tracer.Extract(): the carrier must be a `TextMapReader`.
+	TextMap
+
+	// HTTPHeaders represents SpanContexts as HTTP header string pairs.
+	//
+	// Unlike TextMap, the HTTPHeaders format requires that the keys and values
+	// be valid as HTTP headers as-is (i.e., character casing may be unstable
+	// and special characters are disallowed in keys, values should be
+	// URL-escaped, etc).
+	//
+	// For Tracer.Inject(): the carrier must be a `TextMapWriter`.
+	//
+	// For Tracer.Extract(): the carrier must be a `TextMapReader`.
+	//
+	// See HTTPHeadersCarrier for an implementation of both TextMapWriter
+	// and TextMapReader that defers to an http.Header instance for storage.
+	// For example, Inject():
+	//
+	//    carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
+	//    err := span.Tracer().Inject(
+	//        span.Context(), opentracing.HTTPHeaders, carrier)
+	//
+	// Or Extract():
+	//
+	//    carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
+	//    clientContext, err := tracer.Extract(
+	//        opentracing.HTTPHeaders, carrier)
+	//
+	HTTPHeaders
+)
+
+// TextMapWriter is the Inject() carrier for the TextMap builtin format. With
+// it, the caller can encode a SpanContext for propagation as entries in a map
+// of unicode strings.
+type TextMapWriter interface {
+	// Set a key:value pair to the carrier. Multiple calls to Set() for the
+	// same key leads to undefined behavior.
+	//
+	// NOTE: The backing store for the TextMapWriter may contain data unrelated
+	// to SpanContext. As such, Inject() and Extract() implementations that
+	// call the TextMapWriter and TextMapReader interfaces must agree on a
+	// prefix or other convention to distinguish their own key:value pairs.
+	Set(key, val string)
+}
+
+// TextMapReader is the Extract() carrier for the TextMap builtin format. With it,
+// the caller can decode a propagated SpanContext as entries in a map of
+// unicode strings.
+type TextMapReader interface {
+	// ForeachKey returns TextMap contents via repeated calls to the `handler`
+	// function. If any call to `handler` returns a non-nil error, ForeachKey
+	// terminates and returns that error.
+	//
+	// NOTE: The backing store for the TextMapReader may contain data unrelated
+	// to SpanContext. As such, Inject() and Extract() implementations that
+	// call the TextMapWriter and TextMapReader interfaces must agree on a
+	// prefix or other convention to distinguish their own key:value pairs.
+	//
+	// The "foreach" callback pattern reduces unnecessary copying in some cases
+	// and also allows implementations to hold locks while the map is read.
+	ForeachKey(handler func(key, val string) error) error
+}
+
+// TextMapCarrier allows the use of regular map[string]string
+// as both TextMapWriter and TextMapReader.
+type TextMapCarrier map[string]string
+
+// ForeachKey conforms to the TextMapReader interface.
+func (c TextMapCarrier) ForeachKey(handler func(key, val string) error) error {
+	for k, v := range c {
+		if err := handler(k, v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Set implements Set() of opentracing.TextMapWriter
+func (c TextMapCarrier) Set(key, val string) {
+	c[key] = val
+}
+
+// HTTPHeadersCarrier satisfies both TextMapWriter and TextMapReader.
+//
+// Example usage for server side:
+//
+//     carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
+//     clientContext, err := tracer.Extract(opentracing.HTTPHeaders, carrier)
+//
+// Example usage for client side:
+//
+//     carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
+//     err := tracer.Inject(
+//         span.Context(),
+//         opentracing.HTTPHeaders,
+//         carrier)
+//
+type HTTPHeadersCarrier http.Header
+
+// Set conforms to the TextMapWriter interface.
+func (c HTTPHeadersCarrier) Set(key, val string) {
+	h := http.Header(c)
+	h.Add(key, val)
+}
+
+// ForeachKey conforms to the TextMapReader interface.
+func (c HTTPHeadersCarrier) ForeachKey(handler func(key, val string) error) error {
+	for k, vals := range c {
+		for _, v := range vals {
+			if err := handler(k, v); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}

vendor/src/github.com/opentracing/opentracing-go/propagation_test.go

@@ -0,0 +1,93 @@
+package opentracing
+
+import (
+	"net/http"
+	"strconv"
+	"testing"
+)
+
+const testHeaderPrefix = "testprefix-"
+
+func TestTextMapCarrierInject(t *testing.T) {
+	m := make(map[string]string)
+	m["NotOT"] = "blah"
+	m["opname"] = "AlsoNotOT"
+	tracer := testTracer{}
+	span := tracer.StartSpan("someSpan")
+	fakeID := span.Context().(testSpanContext).FakeID
+
+	carrier := TextMapCarrier(m)
+	if err := span.Tracer().Inject(span.Context(), TextMap, carrier); err != nil {
+		t.Fatal(err)
+	}
+
+	if len(m) != 3 {
+		t.Errorf("Unexpected header length: %v", len(m))
+	}
+	// The prefix comes from just above; the suffix comes from
+	// testTracer.Inject().
+	if m["testprefix-fakeid"] != strconv.Itoa(fakeID) {
+		t.Errorf("Could not find fakeid at expected key")
+	}
+}
+
+func TestTextMapCarrierExtract(t *testing.T) {
+	m := make(map[string]string)
+	m["NotOT"] = "blah"
+	m["opname"] = "AlsoNotOT"
+	m["testprefix-fakeid"] = "42"
+	tracer := testTracer{}
+
+	carrier := TextMapCarrier(m)
+	extractedContext, err := tracer.Extract(TextMap, carrier)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if extractedContext.(testSpanContext).FakeID != 42 {
+		t.Errorf("Failed to read testprefix-fakeid correctly")
+	}
+}
+
+func TestHTTPHeaderInject(t *testing.T) {
+	h := http.Header{}
+	h.Add("NotOT", "blah")
+	h.Add("opname", "AlsoNotOT")
+	tracer := testTracer{}
+	span := tracer.StartSpan("someSpan")
+	fakeID := span.Context().(testSpanContext).FakeID
+
+	// Use HTTPHeadersCarrier to wrap around `h`.
+	carrier := HTTPHeadersCarrier(h)
+	if err := span.Tracer().Inject(span.Context(), HTTPHeaders, carrier); err != nil {
+		t.Fatal(err)
+	}
+
+	if len(h) != 3 {
+		t.Errorf("Unexpected header length: %v", len(h))
+	}
+	// The prefix comes from just above; the suffix comes from
+	// testTracer.Inject().
+	if h.Get("testprefix-fakeid") != strconv.Itoa(fakeID) {
+		t.Errorf("Could not find fakeid at expected key")
+	}
+}
+
+func TestHTTPHeaderExtract(t *testing.T) {
+	h := http.Header{}
+	h.Add("NotOT", "blah")
+	h.Add("opname", "AlsoNotOT")
+	h.Add("testprefix-fakeid", "42")
+	tracer := testTracer{}
+
+	// Use HTTPHeadersCarrier to wrap around `h`.
+	carrier := HTTPHeadersCarrier(h)
+	spanContext, err := tracer.Extract(HTTPHeaders, carrier)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if spanContext.(testSpanContext).FakeID != 42 {
+		t.Errorf("Failed to read testprefix-fakeid correctly")
+	}
+}

vendor/src/github.com/opentracing/opentracing-go/span.go

@@ -0,0 +1,185 @@
+package opentracing
+
+import (
+	"time"
+
+	"github.com/opentracing/opentracing-go/log"
+)
+
+// SpanContext represents Span state that must propagate to descendant Spans and across process
+// boundaries (e.g., a <trace_id, span_id, sampled> tuple).
+type SpanContext interface {
+	// ForeachBaggageItem grants access to all baggage items stored in the
+	// SpanContext.
+	// The handler function will be called for each baggage key/value pair.
+	// The ordering of items is not guaranteed.
+	//
+	// The bool return value indicates if the handler wants to continue iterating
+	// through the rest of the baggage items; for example if the handler is trying to
+	// find some baggage item by pattern matching the name, it can return false
+	// as soon as the item is found to stop further iterations.
+	ForeachBaggageItem(handler func(k, v string) bool)
+}
+
+// Span represents an active, un-finished span in the OpenTracing system.
+//
+// Spans are created by the Tracer interface.
+type Span interface {
+	// Sets the end timestamp and finalizes Span state.
+	//
+	// With the exception of calls to Context() (which are always allowed),
+	// Finish() must be the last call made to any span instance, and to do
+	// otherwise leads to undefined behavior.
+	Finish()
+	// FinishWithOptions is like Finish() but with explicit control over
+	// timestamps and log data.
+	FinishWithOptions(opts FinishOptions)
+
+	// Context() yields the SpanContext for this Span. Note that the return
+	// value of Context() is still valid after a call to Span.Finish(), as is
+	// a call to Span.Context() after a call to Span.Finish().
+	Context() SpanContext
+
+	// Sets or changes the operation name.
+	SetOperationName(operationName string) Span
+
+	// Adds a tag to the span.
+	//
+	// If there is a pre-existing tag set for `key`, it is overwritten.
+	//
+	// Tag values can be numeric types, strings, or bools. The behavior of
+	// other tag value types is undefined at the OpenTracing level. If a
+	// tracing system does not know how to handle a particular value type, it
+	// may ignore the tag, but shall not panic.
+	SetTag(key string, value interface{}) Span
+
+	// LogFields is an efficient and type-checked way to record key:value
+	// logging data about a Span, though the programming interface is a little
+	// more verbose than LogKV(). Here's an example:
+	//
+	//    span.LogFields(
+	//        log.String("event", "soft error"),
+	//        log.String("type", "cache timeout"),
+	//        log.Int("waited.millis", 1500))
+	//
+	// Also see Span.FinishWithOptions() and FinishOptions.BulkLogData.
+	LogFields(fields ...log.Field)
+
+	// LogKV is a concise, readable way to record key:value logging data about
+	// a Span, though unfortunately this also makes it less efficient and less
+	// type-safe than LogFields(). Here's an example:
+	//
+	//    span.LogKV(
+	//        "event", "soft error",
+	//        "type", "cache timeout",
+	//        "waited.millis", 1500)
+	//
+	// For LogKV (as opposed to LogFields()), the parameters must appear as
+	// key-value pairs, like
+	//
+	//    span.LogKV(key1, val1, key2, val2, key3, val3, ...)
+	//
+	// The keys must all be strings. The values may be strings, numeric types,
+	// bools, Go error instances, or arbitrary structs.
+	//
+	// (Note to implementors: consider the log.InterleavedKVToFields() helper)
+	LogKV(alternatingKeyValues ...interface{})
+
+	// SetBaggageItem sets a key:value pair on this Span and its SpanContext
+	// that also propagates to descendants of this Span.
+	//
+	// SetBaggageItem() enables powerful functionality given a full-stack
+	// opentracing integration (e.g., arbitrary application data from a mobile
+	// app can make it, transparently, all the way into the depths of a storage
+	// system), and with it some powerful costs: use this feature with care.
+	//
+	// IMPORTANT NOTE #1: SetBaggageItem() will only propagate baggage items to
+	// *future* causal descendants of the associated Span.
+	//
+	// IMPORTANT NOTE #2: Use this thoughtfully and with care. Every key and
+	// value is copied into every local *and remote* child of the associated
+	// Span, and that can add up to a lot of network and cpu overhead.
+	//
+	// Returns a reference to this Span for chaining.
+	SetBaggageItem(restrictedKey, value string) Span
+
+	// Gets the value for a baggage item given its key. Returns the empty string
+	// if the value isn't found in this Span.
+	BaggageItem(restrictedKey string) string
+
+	// Provides access to the Tracer that created this Span.
+	Tracer() Tracer
+
+	// Deprecated: use LogFields or LogKV
+	LogEvent(event string)
+	// Deprecated: use LogFields or LogKV
+	LogEventWithPayload(event string, payload interface{})
+	// Deprecated: use LogFields or LogKV
+	Log(data LogData)
+}
+
+// LogRecord is data associated with a single Span log. Every LogRecord
+// instance must specify at least one Field.
+type LogRecord struct {
+	Timestamp time.Time
+	Fields    []log.Field
+}
+
+// FinishOptions allows Span.FinishWithOptions callers to override the finish
+// timestamp and provide log data via a bulk interface.
+type FinishOptions struct {
+	// FinishTime overrides the Span's finish time, or implicitly becomes
+	// time.Now() if FinishTime.IsZero().
+	//
+	// FinishTime must resolve to a timestamp that's >= the Span's StartTime
+	// (per StartSpanOptions).
+	FinishTime time.Time
+
+	// LogRecords allows the caller to specify the contents of many LogFields()
+	// calls with a single slice. May be nil.
+	//
+	// None of the LogRecord.Timestamp values may be .IsZero() (i.e., they must
+	// be set explicitly). Also, they must be >= the Span's start timestamp and
+	// <= the FinishTime (or time.Now() if FinishTime.IsZero()). Otherwise the
+	// behavior of FinishWithOptions() is undefined.
+	//
+	// If specified, the caller hands off ownership of LogRecords at
+	// FinishWithOptions() invocation time.
+	//
+	// If specified, the (deprecated) BulkLogData must be nil or empty.
+	LogRecords []LogRecord
+
+	// BulkLogData is DEPRECATED.
+	BulkLogData []LogData
+}
+
+// LogData is DEPRECATED
+type LogData struct {
+	Timestamp time.Time
+	Event     string
+	Payload   interface{}
+}
+
+// ToLogRecord converts a deprecated LogData to a non-deprecated LogRecord
+func (ld *LogData) ToLogRecord() LogRecord {
+	var literalTimestamp time.Time
+	if ld.Timestamp.IsZero() {
+		literalTimestamp = time.Now()
+	} else {
+		literalTimestamp = ld.Timestamp
+	}
+	rval := LogRecord{
+		Timestamp: literalTimestamp,
+	}
+	if ld.Payload == nil {
+		rval.Fields = []log.Field{
+			log.String("event", ld.Event),
+		}
+	} else {
+		rval.Fields = []log.Field{
+			log.String("event", ld.Event),
+			log.Object("payload", ld.Payload),
+		}
+	}
+	return rval
+}

vendor/src/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
+}

vendor/src/github.com/opentracing/opentracing-go/tracer.go

@@ -0,0 +1,305 @@
+package opentracing
+
+import "time"
+
+// Tracer is a simple, thin interface for Span creation and SpanContext
+// propagation.
+type Tracer interface {
+
+	// Create, start, and return a new Span with the given `operationName` and
+	// incorporate the given StartSpanOption `opts`. (Note that `opts` borrows
+	// from the "functional options" pattern, per
+	// http://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis)
+	//
+	// A Span with no SpanReference options (e.g., opentracing.ChildOf() or
+	// opentracing.FollowsFrom()) becomes the root of its own trace.
+	//
+	// Examples:
+	//
+	//     var tracer opentracing.Tracer = ...
+	//
+	//     // The root-span case:
+	//     sp := tracer.StartSpan("GetFeed")
+	//
+	//     // The vanilla child span case:
+	//     sp := tracer.StartSpan(
+	//         "GetFeed",
+	//         opentracing.ChildOf(parentSpan.Context()))
+	//
+	//     // All the bells and whistles:
+	//     sp := tracer.StartSpan(
+	//         "GetFeed",
+	//         opentracing.ChildOf(parentSpan.Context()),
+	//         opentracing.Tag{"user_agent", loggedReq.UserAgent},
+	//         opentracing.StartTime(loggedReq.Timestamp),
+	//     )
+	//
+	StartSpan(operationName string, opts ...StartSpanOption) Span
+
+	// Inject() takes the `sm` SpanContext instance and injects it for
+	// propagation within `carrier`. The actual type of `carrier` depends on
+	// the value of `format`.
+	//
+	// OpenTracing defines a common set of `format` values (see BuiltinFormat),
+	// and each has an expected carrier type.
+	//
+	// Other packages may declare their own `format` values, much like the keys
+	// used by `context.Context` (see
+	// https://godoc.org/golang.org/x/net/context#WithValue).
+	//
+	// Example usage (sans error handling):
+	//
+	//     carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
+	//     err := tracer.Inject(
+	//         span.Context(),
+	//         opentracing.HTTPHeaders,
+	//         carrier)
+	//
+	// NOTE: All opentracing.Tracer implementations MUST support all
+	// BuiltinFormats.
+	//
+	// Implementations may return opentracing.ErrUnsupportedFormat if `format`
+	// is not supported by (or not known by) the implementation.
+	//
+	// Implementations may return opentracing.ErrInvalidCarrier or any other
+	// implementation-specific error if the format is supported but injection
+	// fails anyway.
+	//
+	// See Tracer.Extract().
+	Inject(sm SpanContext, format interface{}, carrier interface{}) error
+
+	// Extract() returns a SpanContext instance given `format` and `carrier`.
+	//
+	// OpenTracing defines a common set of `format` values (see BuiltinFormat),
+	// and each has an expected carrier type.
+	//
+	// Other packages may declare their own `format` values, much like the keys
+	// used by `context.Context` (see
+	// https://godoc.org/golang.org/x/net/context#WithValue).
+	//
+	// Example usage (with StartSpan):
+	//
+	//
+	//     carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
+	//     clientContext, err := tracer.Extract(opentracing.HTTPHeaders, carrier)
+	//
+	//     // ... assuming the ultimate goal here is to resume the trace with a
+	//     // server-side Span:
+	//     var serverSpan opentracing.Span
+	//     if err == nil {
+	//         span = tracer.StartSpan(
+	//             rpcMethodName, ext.RPCServerOption(clientContext))
+	//     } else {
+	//         span = tracer.StartSpan(rpcMethodName)
+	//     }
+	//
+	//
+	// NOTE: All opentracing.Tracer implementations MUST support all
+	// BuiltinFormats.
+	//
+	// Return values:
+	//  - A successful Extract returns a SpanContext instance and a nil error
+	//  - If there was simply no SpanContext to extract in `carrier`, Extract()
+	//    returns (nil, opentracing.ErrSpanContextNotFound)
+	//  - If `format` is unsupported or unrecognized, Extract() returns (nil,
+	//    opentracing.ErrUnsupportedFormat)
+	//  - If there are more fundamental problems with the `carrier` object,
+	//    Extract() may return opentracing.ErrInvalidCarrier,
+	//    opentracing.ErrSpanContextCorrupted, or implementation-specific
+	//    errors.
+	//
+	// See Tracer.Inject().
+	Extract(format interface{}, carrier interface{}) (SpanContext, error)
+}
+
+// StartSpanOptions allows Tracer.StartSpan() callers and implementors a
+// mechanism to override the start timestamp, specify Span References, and make
+// a single Tag or multiple Tags available at Span start time.
+//
+// StartSpan() callers should look at the StartSpanOption interface and
+// implementations available in this package.
+//
+// Tracer implementations can convert a slice of `StartSpanOption` instances
+// into a `StartSpanOptions` struct like so:
+//
+//     func StartSpan(opName string, opts ...opentracing.StartSpanOption) {
+//         sso := opentracing.StartSpanOptions{}
+//         for _, o := range opts {
+//             o.Apply(&sso)
+//         }
+//         ...
+//     }
+//
+type StartSpanOptions struct {
+	// Zero or more causal references to other Spans (via their SpanContext).
+	// If empty, start a "root" Span (i.e., start a new trace).
+	References []SpanReference
+
+	// StartTime overrides the Span's start time, or implicitly becomes
+	// time.Now() if StartTime.IsZero().
+	StartTime time.Time
+
+	// Tags may have zero or more entries; the restrictions on map values are
+	// identical to those for Span.SetTag(). May be nil.
+	//
+	// If specified, the caller hands off ownership of Tags at
+	// StartSpan() invocation time.
+	Tags map[string]interface{}
+}
+
+// StartSpanOption instances (zero or more) may be passed to Tracer.StartSpan.
+//
+// StartSpanOption borrows from the "functional options" pattern, per
+// http://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis
+type StartSpanOption interface {
+	Apply(*StartSpanOptions)
+}
+
+// SpanReferenceType is an enum type describing different categories of
+// relationships between two Spans. If Span-2 refers to Span-1, the
+// SpanReferenceType describes Span-1 from Span-2's perspective. For example,
+// ChildOfRef means that Span-1 created Span-2.
+//
+// NOTE: Span-1 and Span-2 do *not* necessarily depend on each other for
+// completion; e.g., Span-2 may be part of a background job enqueued by Span-1,
+// or Span-2 may be sitting in a distributed queue behind Span-1.
+type SpanReferenceType int
+
+const (
+	// ChildOfRef refers to a parent Span that caused *and* somehow depends
+	// upon the new child Span. Often (but not always), the parent Span cannot
+	// finish until the child Span does.
+	//
+	// An timing diagram for a ChildOfRef that's blocked on the new Span:
+	//
+	//     [-Parent Span---------]
+	//          [-Child Span----]
+	//
+	// See http://opentracing.io/spec/
+	//
+	// See opentracing.ChildOf()
+	ChildOfRef SpanReferenceType = iota
+
+	// FollowsFromRef refers to a parent Span that does not depend in any way
+	// on the result of the new child Span. For instance, one might use
+	// FollowsFromRefs to describe pipeline stages separated by queues,
+	// or a fire-and-forget cache insert at the tail end of a web request.
+	//
+	// A FollowsFromRef Span is part of the same logical trace as the new Span:
+	// i.e., the new Span is somehow caused by the work of its FollowsFromRef.
+	//
+	// All of the following could be valid timing diagrams for children that
+	// "FollowFrom" a parent.
+	//
+	//     [-Parent Span-]  [-Child Span-]
+	//
+	//
+	//     [-Parent Span--]
+	//      [-Child Span-]
+	//
+	//
+	//     [-Parent Span-]
+	//                 [-Child Span-]
+	//
+	// See http://opentracing.io/spec/
+	//
+	// See opentracing.FollowsFrom()
+	FollowsFromRef
+)
+
+// SpanReference is a StartSpanOption that pairs a SpanReferenceType and a
+// referenced SpanContext. See the SpanReferenceType documentation for
+// supported relationships.  If SpanReference is created with
+// ReferencedContext==nil, it has no effect. Thus it allows for a more concise
+// syntax for starting spans:
+//
+//     sc, _ := tracer.Extract(someFormat, someCarrier)
+//     span := tracer.StartSpan("operation", opentracing.ChildOf(sc))
+//
+// The `ChildOf(sc)` option above will not panic if sc == nil, it will just
+// not add the parent span reference to the options.
+type SpanReference struct {
+	Type              SpanReferenceType
+	ReferencedContext SpanContext
+}
+
+// Apply satisfies the StartSpanOption interface.
+func (r SpanReference) Apply(o *StartSpanOptions) {
+	if r.ReferencedContext != nil {
+		o.References = append(o.References, r)
+	}
+}
+
+// ChildOf returns a StartSpanOption pointing to a dependent parent span.
+// If sc == nil, the option has no effect.
+//
+// See ChildOfRef, SpanReference
+func ChildOf(sc SpanContext) SpanReference {
+	return SpanReference{
+		Type:              ChildOfRef,
+		ReferencedContext: sc,
+	}
+}
+
+// FollowsFrom returns a StartSpanOption pointing to a parent Span that caused
+// the child Span but does not directly depend on its result in any way.
+// If sc == nil, the option has no effect.
+//
+// See FollowsFromRef, SpanReference
+func FollowsFrom(sc SpanContext) SpanReference {
+	return SpanReference{
+		Type:              FollowsFromRef,
+		ReferencedContext: sc,
+	}
+}
+
+// StartTime is a StartSpanOption that sets an explicit start timestamp for the
+// new Span.
+type StartTime time.Time
+
+// Apply satisfies the StartSpanOption interface.
+func (t StartTime) Apply(o *StartSpanOptions) {
+	o.StartTime = time.Time(t)
+}
+
+// Tags are a generic map from an arbitrary string key to an opaque value type.
+// The underlying tracing system is responsible for interpreting and
+// serializing the values.
+type Tags map[string]interface{}
+
+// Apply satisfies the StartSpanOption interface.
+func (t Tags) Apply(o *StartSpanOptions) {
+	if o.Tags == nil {
+		o.Tags = make(map[string]interface{})
+	}
+	for k, v := range t {
+		o.Tags[k] = v
+	}
+}
+
+// Tag may be passed as a StartSpanOption to add a tag to new spans,
+// or its Set method may be used to apply the tag to an existing Span,
+// for example:
+//
+// tracer.StartSpan("opName", Tag{"Key", value})
+//
+//   or
+//
+// Tag{"key", value}.Set(span)
+type Tag struct {
+	Key   string
+	Value interface{}
+}
+
+// Apply satisfies the StartSpanOption interface.
+func (t Tag) Apply(o *StartSpanOptions) {
+	if o.Tags == nil {
+		o.Tags = make(map[string]interface{})
+	}
+	o.Tags[t.Key] = t.Value
+}
+
+// Set applies the tag to an existing Span.
+func (t Tag) Set(s Span) {
+	s.SetTag(t.Key, t.Value)
+}