Added integration support for DataDog APM Tracing

vendor/gopkg.in/DataDog/dd-trace-go.v1/LICENSE

@@ -0,0 +1,24 @@
+Copyright (c) 2016, Datadog <info@datadoghq.com>
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+    * Neither the name of Datadog nor the
+      names of its contributors may be used to endorse or promote products
+      derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/gopkg.in/DataDog/dd-trace-go.v1/LICENSE-3rdparty.csv

@@ -0,0 +1,2 @@
+Component,Origin,License,Copyright
+import,io.opentracing,Apache-2.0,Copyright 2016-2017 The OpenTracing Authors

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ddtrace.go

@@ -0,0 +1,108 @@
+// Package ddtrace contains the interfaces that specify the implementations of Datadog's
+// tracing library, as well as a set of sub-packages containing various implementations:
+// our native implementation ("tracer"), a wrapper that can be used with Opentracing
+// ("opentracer") and a mock tracer to be used for testing ("mocktracer"). Additionally,
+// package "ext" provides a set of tag names and values specific to Datadog's APM product.
+//
+// To get started, visit the documentation for any of the packages you'd like to begin
+// with by accessing the subdirectories of this package: https://godoc.org/gopkg.in/DataDog/dd-trace-go.v1/ddtrace#pkg-subdirectories.
+package ddtrace // import "gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+
+import "time"
+
+// Tracer specifies an implementation of the Datadog tracer which allows starting
+// and propagating spans. The official implementation if exposed as functions
+// within the "tracer" package.
+type Tracer interface {
+	// StartSpan starts a span with the given operation name and options.
+	StartSpan(operationName string, opts ...StartSpanOption) Span
+
+	// Extract extracts a span context from a given carrier. Note that baggage item
+	// keys will always be lower-cased to maintain consistency. It is impossible to
+	// maintain the original casing due to MIME header canonicalization standards.
+	Extract(carrier interface{}) (SpanContext, error)
+
+	// Inject injects a span context into the given carrier.
+	Inject(context SpanContext, carrier interface{}) error
+
+	// Stop stops the active tracer and sets the global tracer to a no-op. Calls to
+	// Stop should be idempotent.
+	Stop()
+}
+
+// Span represents a chunk of computation time. Spans have names, durations,
+// timestamps and other metadata. A Tracer is used to create hierarchies of
+// spans in a request, buffer and submit them to the server.
+type Span interface {
+	// SetTag sets a key/value pair as metadata on the span.
+	SetTag(key string, value interface{})
+
+	// SetOperationName sets the operation name for this span. An operation name should be
+	// a representative name for a group of spans (e.g. "grpc.server" or "http.request").
+	SetOperationName(operationName string)
+
+	// BaggageItem returns the baggage item held by the given key.
+	BaggageItem(key string) string
+
+	// SetBaggageItem sets a new baggage item at the given key. The baggage
+	// item should propagate to all descendant spans, both in- and cross-process.
+	SetBaggageItem(key, val string)
+
+	// Finish finishes the current span with the given options. Finish calls should be idempotent.
+	Finish(opts ...FinishOption)
+
+	// Context returns the SpanContext of this Span.
+	Context() SpanContext
+}
+
+// SpanContext represents a span state that can propagate to descendant spans
+// and across process boundaries. It contains all the information needed to
+// spawn a direct descendant of the span that it belongs to. It can be used
+// to create distributed tracing by propagating it using the provided interfaces.
+type SpanContext interface {
+	// SpanID returns the span ID that this context is carrying.
+	SpanID() uint64
+
+	// TraceID returns the trace ID that this context is carrying.
+	TraceID() uint64
+
+	// ForeachBaggageItem provides an iterator over the key/value pairs set as
+	// baggage within this context. Iteration stops when the handler returns
+	// false.
+	ForeachBaggageItem(handler func(k, v string) bool)
+}
+
+// StartSpanOption is a configuration option that can be used with a Tracer's StartSpan method.
+type StartSpanOption func(cfg *StartSpanConfig)
+
+// FinishOption is a configuration option that can be used with a Span's Finish method.
+type FinishOption func(cfg *FinishConfig)
+
+// FinishConfig holds the configuration for finishing a span. It is usually passed around by
+// reference to one or more FinishOption functions which shape it into its final form.
+type FinishConfig struct {
+	// FinishTime represents the time that should be set as finishing time for the
+	// span. Implementations should use the current time when FinishTime.IsZero().
+	FinishTime time.Time
+
+	// Error holds an optional error that should be set on the span before
+	// finishing.
+	Error error
+}
+
+// StartSpanConfig holds the configuration for starting a new span. It is usually passed
+// around by reference to one or more StartSpanOption functions which shape it into its
+// final form.
+type StartSpanConfig struct {
+	// Parent holds the SpanContext that should be used as a parent for the
+	// new span. If nil, implementations should return a root span.
+	Parent SpanContext
+
+	// StartTime holds the time that should be used as the start time of the span.
+	// Implementations should use the current time when StartTime.IsZero().
+	StartTime time.Time
+
+	// Tags holds a set of key/value pairs that should be set as metadata on the
+	// new span.
+	Tags map[string]interface{}
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext/app_types.go

@@ -0,0 +1,19 @@
+package ext // import "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
+
+const (
+	// AppTypeWeb specifies the Web span type and can be used as a tag value
+	// for a span's SpanType tag.
+	AppTypeWeb = "web"
+
+	// AppTypeDB specifies the DB span type and can be used as a tag value
+	// for a span's SpanType tag.
+	AppTypeDB = "db"
+
+	// AppTypeCache specifies the Cache span type and can be used as a tag value
+	// for a span's SpanType tag.
+	AppTypeCache = "cache"
+
+	// AppTypeRPC specifies the RPC span type and can be used as a tag value
+	// for a span's SpanType tag.
+	AppTypeRPC = "rpc"
+)

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext/cassandra.go

@@ -0,0 +1,21 @@
+package ext
+
+const (
+	// CassandraQuery is the tag name used for cassandra queries.
+	CassandraQuery = "cassandra.query"
+
+	// CassandraConsistencyLevel is the tag name to set for consitency level.
+	CassandraConsistencyLevel = "cassandra.consistency_level"
+
+	// CassandraCluster specifies the tag name that is used to set the cluster.
+	CassandraCluster = "cassandra.cluster"
+
+	// CassandraRowCount specifies the tag name to use when settings the row count.
+	CassandraRowCount = "cassandra.row_count"
+
+	// CassandraKeyspace is used as tag name for setting the key space.
+	CassandraKeyspace = "cassandra.keyspace"
+
+	// CassandraPaginated specifies the tag name for paginated queries.
+	CassandraPaginated = "cassandra.paginated"
+)

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext/priority.go

@@ -0,0 +1,22 @@
+package ext
+
+// Priority is a hint given to the backend so that it knows which traces to reject or kept.
+// In a distributed context, it should be set before any context propagation (fork, RPC calls) to be effective.
+
+const (
+	// PriorityUserReject informs the backend that a trace should be rejected and not stored.
+	// This should be used by user code overriding default priority.
+	PriorityUserReject = -1
+
+	// PriorityAutoReject informs the backend that a trace should be rejected and not stored.
+	// This is used by the builtin sampler.
+	PriorityAutoReject = 0
+
+	// PriorityAutoKeep informs the backend that a trace should be kept and not stored.
+	// This is used by the builtin sampler.
+	PriorityAutoKeep = 1
+
+	// PriorityUserKeep informs the backend that a trace should be kept and not stored.
+	// This should be used by user code overriding default priority.
+	PriorityUserKeep = 2
+)

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext/system.go

@@ -0,0 +1,7 @@
+package ext
+
+// Standard system metadata names
+const (
+	// The pid of the traced process
+	Pid = "system.pid"
+)

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext/tags.go

@@ -0,0 +1,50 @@
+// Package ext contains a set of Datadog-specific constants. Most of them are used
+// for setting span metadata.
+package ext
+
+const (
+	// TargetHost sets the target host address.
+	TargetHost = "out.host"
+
+	// TargetPort sets the target host port.
+	TargetPort = "out.port"
+
+	// SamplingPriority is the tag that marks the sampling priority of a span.
+	SamplingPriority = "sampling.priority"
+
+	// SQLType sets the sql type tag.
+	SQLType = "sql"
+
+	// SQLQuery sets the sql query tag on a span.
+	SQLQuery = "sql.query"
+
+	// HTTPMethod specifies the HTTP method used in a span.
+	HTTPMethod = "http.method"
+
+	// HTTPCode sets the HTTP status code as a tag.
+	HTTPCode = "http.status_code"
+
+	// HTTPURL sets the HTTP URL for a span.
+	HTTPURL = "http.url"
+
+	// SpanType defines the Span type (web, db, cache).
+	SpanType = "span.type"
+
+	// ServiceName defines the Service name for this Span.
+	ServiceName = "service.name"
+
+	// ResourceName defines the Resource name for the Span.
+	ResourceName = "resource.name"
+
+	// Error specifies the error tag. It's value is usually of type "error".
+	Error = "error"
+
+	// ErrorMsg specifies the error message.
+	ErrorMsg = "error.msg"
+
+	// ErrorType specifies the error type.
+	ErrorType = "error.type"
+
+	// ErrorStack specifies the stack dump.
+	ErrorStack = "error.stack"
+)

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal/globaltracer.go

@@ -0,0 +1,94 @@
+package internal // import "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
+
+import (
+	"sync"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+)
+
+var (
+	mu           sync.RWMutex   // guards globalTracer
+	globalTracer ddtrace.Tracer = &NoopTracer{}
+)
+
+// SetGlobalTracer sets the global tracer to t.
+func SetGlobalTracer(t ddtrace.Tracer) {
+	mu.Lock()
+	defer mu.Unlock()
+	globalTracer = t
+}
+
+// GetGlobalTracer returns the currently active tracer.
+func GetGlobalTracer() ddtrace.Tracer {
+	mu.RLock()
+	defer mu.RUnlock()
+	return globalTracer
+}
+
+// Testing is set to true when the mock tracer is active. It usually signifies that we are in a test
+// environment. This value is used by tracer.Start to prevent overriding the GlobalTracer in tests.
+var Testing = false
+
+var _ ddtrace.Tracer = (*NoopTracer)(nil)
+
+// NoopTracer is an implementation of ddtrace.Tracer that is a no-op.
+type NoopTracer struct{}
+
+// StartSpan implements ddtrace.Tracer.
+func (NoopTracer) StartSpan(operationName string, opts ...ddtrace.StartSpanOption) ddtrace.Span {
+	return NoopSpan{}
+}
+
+// SetServiceInfo implements ddtrace.Tracer.
+func (NoopTracer) SetServiceInfo(name, app, appType string) {}
+
+// Extract implements ddtrace.Tracer.
+func (NoopTracer) Extract(carrier interface{}) (ddtrace.SpanContext, error) {
+	return NoopSpanContext{}, nil
+}
+
+// Inject implements ddtrace.Tracer.
+func (NoopTracer) Inject(context ddtrace.SpanContext, carrier interface{}) error { return nil }
+
+// Stop implements ddtrace.Tracer.
+func (NoopTracer) Stop() {}
+
+var _ ddtrace.Span = (*NoopSpan)(nil)
+
+// NoopSpan is an implementation of ddtrace.Span that is a no-op.
+type NoopSpan struct{}
+
+// SetTag implements ddtrace.Span.
+func (NoopSpan) SetTag(key string, value interface{}) {}
+
+// SetOperationName implements ddtrace.Span.
+func (NoopSpan) SetOperationName(operationName string) {}
+
+// BaggageItem implements ddtrace.Span.
+func (NoopSpan) BaggageItem(key string) string { return "" }
+
+// SetBaggageItem implements ddtrace.Span.
+func (NoopSpan) SetBaggageItem(key, val string) {}
+
+// Finish implements ddtrace.Span.
+func (NoopSpan) Finish(opts ...ddtrace.FinishOption) {}
+
+// Tracer implements ddtrace.Span.
+func (NoopSpan) Tracer() ddtrace.Tracer { return NoopTracer{} }
+
+// Context implements ddtrace.Span.
+func (NoopSpan) Context() ddtrace.SpanContext { return NoopSpanContext{} }
+
+var _ ddtrace.SpanContext = (*NoopSpanContext)(nil)
+
+// NoopSpanContext is an implementation of ddtrace.SpanContext that is a no-op.
+type NoopSpanContext struct{}
+
+// SpanID implements ddtrace.SpanContext.
+func (NoopSpanContext) SpanID() uint64 { return 0 }
+
+// TraceID implements ddtrace.SpanContext.
+func (NoopSpanContext) TraceID() uint64 { return 0 }
+
+// ForeachBaggageItem implements ddtrace.SpanContext.
+func (NoopSpanContext) ForeachBaggageItem(handler func(k, v string) bool) {}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer/option.go

@@ -0,0 +1,24 @@
+package opentracer // import "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer"
+
+import (
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
+
+	opentracing "github.com/opentracing/opentracing-go"
+)
+
+// ServiceName can be used with opentracing.StartSpan to set the
+// service name of a span.
+func ServiceName(name string) opentracing.StartSpanOption {
+	return opentracing.Tag{Key: ext.ServiceName, Value: name}
+}
+
+// ResourceName can be used with opentracing.StartSpan to set the
+// resource name of a span.
+func ResourceName(name string) opentracing.StartSpanOption {
+	return opentracing.Tag{Key: ext.ResourceName, Value: name}
+}
+
+// SpanType can be used with opentracing.StartSpan to set the type of a span.
+func SpanType(name string) opentracing.StartSpanOption {
+	return opentracing.Tag{Key: ext.SpanType, Value: name}
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer/span.go

@@ -0,0 +1,83 @@
+package opentracer
+
+import (
+	"fmt"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
+
+	opentracing "github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/log"
+)
+
+var _ opentracing.Span = (*span)(nil)
+
+// span implements opentracing.Span on top of ddtrace.Span.
+type span struct {
+	ddtrace.Span
+	*opentracer
+}
+
+func (s *span) Context() opentracing.SpanContext                      { return s.Span.Context() }
+func (s *span) Finish()                                               { s.Span.Finish() }
+func (s *span) Tracer() opentracing.Tracer                            { return s.opentracer }
+func (s *span) LogEvent(event string)                                 { /* deprecated */ }
+func (s *span) LogEventWithPayload(event string, payload interface{}) { /* deprecated */ }
+func (s *span) Log(data opentracing.LogData)                          { /* deprecated */ }
+
+func (s *span) FinishWithOptions(opts opentracing.FinishOptions) {
+	for _, lr := range opts.LogRecords {
+		if len(lr.Fields) > 0 {
+			s.LogFields(lr.Fields...)
+		}
+	}
+	s.Span.Finish(tracer.FinishTime(opts.FinishTime))
+}
+
+func (s *span) LogFields(fields ...log.Field) {
+	// catch standard opentracing keys and adjust to internal ones as per spec:
+	// https://github.com/opentracing/specification/blob/master/semantic_conventions.md#log-fields-table
+	for _, f := range fields {
+		switch f.Key() {
+		case "event":
+			if v, ok := f.Value().(string); ok && v == "error" {
+				s.SetTag("error", true)
+			}
+		case "error", "error.object":
+			if err, ok := f.Value().(error); ok {
+				s.SetTag("error", err)
+			}
+		case "message":
+			s.SetTag(ext.ErrorMsg, fmt.Sprint(f.Value()))
+		case "stack":
+			s.SetTag(ext.ErrorStack, fmt.Sprint(f.Value()))
+		default:
+			// not implemented
+		}
+	}
+}
+
+func (s *span) LogKV(keyVals ...interface{}) {
+	fields, err := log.InterleavedKVToFields(keyVals...)
+	if err != nil {
+		// TODO(gbbr): create a log package
+		return
+	}
+	s.LogFields(fields...)
+}
+
+func (s *span) SetBaggageItem(key, val string) opentracing.Span {
+	s.Span.SetBaggageItem(key, val)
+	return s
+}
+
+func (s *span) SetOperationName(operationName string) opentracing.Span {
+	s.Span.SetOperationName(operationName)
+	return s
+}
+
+func (s *span) SetTag(key string, value interface{}) opentracing.Span {
+	s.Span.SetTag(key, value)
+	return s
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer/tracer.go

@@ -0,0 +1,81 @@
+// Package opentracer provides a wrapper on top of the Datadog tracer that can be used with Opentracing.
+// It also provides a set of opentracing.StartSpanOption that are specific to Datadog's APM product.
+// To use it, simply call "New".
+//
+// Note that there are currently some small incompatibilities between the Opentracing spec and the Datadog
+// APM product, which we are in the process of addressing on the long term. When using Datadog, the
+// Opentracing operation name is what is called resource in Datadog's terms and the Opentracing "component"
+// tag is Datadog's operation name. Meaning that in order to define (in Opentracing terms) a span that
+// has the operation name "/user/profile" and the component "http.request", one would do:
+//  opentracing.StartSpan("http.request", opentracer.ResourceName("/user/profile"))
+//
+// Some libraries and frameworks are supported out-of-the-box by using our integrations. You can see a list
+// of supported integrations here: https://godoc.org/gopkg.in/DataDog/dd-trace-go.v1/contrib. They are fully
+// compatible with the Opentracing implementation.
+package opentracer
+
+import (
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
+
+	opentracing "github.com/opentracing/opentracing-go"
+)
+
+// New creates, instantiates and returns an Opentracing compatible version of the
+// Datadog tracer using the provided set of options.
+func New(opts ...tracer.StartOption) opentracing.Tracer {
+	tracer.Start(opts...)
+	return &opentracer{internal.GetGlobalTracer()}
+}
+
+var _ opentracing.Tracer = (*opentracer)(nil)
+
+// opentracer implements opentracing.Tracer on top of ddtrace.Tracer.
+type opentracer struct{ ddtrace.Tracer }
+
+// StartSpan implements opentracing.Tracer.
+func (t *opentracer) StartSpan(operationName string, options ...opentracing.StartSpanOption) opentracing.Span {
+	var sso opentracing.StartSpanOptions
+	for _, o := range options {
+		o.Apply(&sso)
+	}
+	opts := []ddtrace.StartSpanOption{tracer.StartTime(sso.StartTime)}
+	for _, ref := range sso.References {
+		if v, ok := ref.ReferencedContext.(ddtrace.SpanContext); ok && ref.Type == opentracing.ChildOfRef {
+			opts = append(opts, tracer.ChildOf(v))
+			break // can only have one parent
+		}
+	}
+	for k, v := range sso.Tags {
+		opts = append(opts, tracer.Tag(k, v))
+	}
+	return &span{
+		Span:       t.Tracer.StartSpan(operationName, opts...),
+		opentracer: t,
+	}
+}
+
+// Inject implements opentracing.Tracer.
+func (t *opentracer) Inject(ctx opentracing.SpanContext, format interface{}, carrier interface{}) error {
+	sctx, ok := ctx.(ddtrace.SpanContext)
+	if !ok {
+		return opentracing.ErrUnsupportedFormat
+	}
+	switch format {
+	case opentracing.TextMap, opentracing.HTTPHeaders:
+		return t.Tracer.Inject(sctx, carrier)
+	default:
+		return opentracing.ErrUnsupportedFormat
+	}
+}
+
+// Extract implements opentracing.Tracer.
+func (t *opentracer) Extract(format interface{}, carrier interface{}) (opentracing.SpanContext, error) {
+	switch format {
+	case opentracing.TextMap, opentracing.HTTPHeaders:
+		return t.Tracer.Extract(carrier)
+	default:
+		return nil, opentracing.ErrUnsupportedFormat
+	}
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/context.go

@@ -0,0 +1,42 @@
+package tracer
+
+import (
+	"context"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
+)
+
+type contextKey struct{}
+
+var activeSpanKey = contextKey{}
+
+// ContextWithSpan returns a copy of the given context which includes the span s.
+func ContextWithSpan(ctx context.Context, s Span) context.Context {
+	return context.WithValue(ctx, activeSpanKey, s)
+}
+
+// SpanFromContext returns the span contained in the given context. A second return
+// value indicates if a span was found in the context. If no span is found, a no-op
+// span is returned.
+func SpanFromContext(ctx context.Context) (Span, bool) {
+	if ctx == nil {
+		return &internal.NoopSpan{}, false
+	}
+	v := ctx.Value(activeSpanKey)
+	if s, ok := v.(ddtrace.Span); ok {
+		return s, true
+	}
+	return &internal.NoopSpan{}, false
+}
+
+// StartSpanFromContext returns a new span with the given operation name and options. If a span
+// is found in the context, it will be used as the parent of the resulting span. If the ChildOf
+// option is passed, the span from context will take precedence over it as the parent span.
+func StartSpanFromContext(ctx context.Context, operationName string, opts ...StartSpanOption) (Span, context.Context) {
+	if s, ok := SpanFromContext(ctx); ok {
+		opts = append(opts, ChildOf(s.Context()))
+	}
+	s := StartSpan(operationName, opts...)
+	return s, ContextWithSpan(ctx, s)
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/doc.go

@@ -0,0 +1,50 @@
+// Package tracer contains Datadog's core tracing client. It is used to trace
+// requests as they flow across web servers, databases and microservices, giving
+// developers visibility into bottlenecks and troublesome requests. To start the
+// tracer, simply call the start method along with an optional set of options.
+// By default, the trace agent is considered to be found at "localhost:8126". In a
+// setup where this would be different (let's say 127.0.0.1:1234), we could do:
+// 	tracer.Start(tracer.WithAgentAddr("127.0.0.1:1234"))
+// 	defer tracer.Stop()
+//
+// The tracing client can perform trace sampling. While the trace agent
+// already samples traces to reduce bandwidth usage, client sampling reduces
+// performance overhead. To make use of it, the package comes with a ready-to-use
+// rate sampler that can be passed to the tracer. To use it and keep only 30% of the
+// requests, one would do:
+//   s := tracer.NewRateSampler(0.3)
+//   tracer.Start(tracer.WithSampler(s))
+//
+// All spans created by the tracer contain a context hereby referred to as the span
+// context. Note that this is different from Go's context. The span context is used
+// to package essential information from a span, which is needed when creating child
+// spans that inherit from it. Thus, a child span is created from a span's span context.
+// The span context can originate from within the same process, but also a
+// different process or even a different machine in the case of distributed tracing.
+//
+// To make use of distributed tracing, a span's context may be injected via a carrier
+// into a transport (HTTP, RPC, etc.) to be extracted on the other end and used to
+// create spans that are direct descendants of it. A couple of carrier interfaces
+// which should cover most of the use-case scenarios are readily provided, such as
+// HTTPCarrier and TextMapCarrier. Users are free to create their own, which will work
+// with our propagation algorithm as long as they implement the TextMapReader and TextMapWriter
+// interfaces. An example alternate implementation is the MDCarrier in our gRPC integration.
+//
+// As an example, injecting a span's context into an HTTP request would look like this:
+//  req, err := http.NewRequest("GET", "http://example.com", nil)
+//  // ...
+//  err := tracer.Inject(span.Context(), tracer.HTTPHeadersCarrier(req.Header))
+//  // ...
+//  http.DefaultClient.Do(req)
+// Then, on the server side, to continue the trace one would do:
+//  sctx, err := tracer.Extract(tracer.HTTPHeadersCarrier(req.Header))
+//  // ...
+//  span := tracer.StartSpan("child.span", tracer.ChildOf(sctx))
+// In the same manner, any means can be used as a carrier to inject a context into a transport. Go's
+// context can also be used as a means to transport spans within the same process. The methods
+// StartSpanFromContext, ContextWithSpan and SpanFromContext exist for this reason.
+//
+// Some libraries and frameworks are supported out-of-the-box by using one
+// of our integrations. You can see a list of supported integrations here:
+// https://godoc.org/gopkg.in/DataDog/dd-trace-go.v1/contrib
+package tracer // import "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/errors.go

@@ -0,0 +1,69 @@
+package tracer
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+)
+
+var errorPrefix = fmt.Sprintf("Datadog Tracer Error (%s): ", tracerVersion)
+
+type traceEncodingError struct{ context error }
+
+func (e *traceEncodingError) Error() string {
+	return fmt.Sprintf("error encoding trace: %s", e.context)
+}
+
+type spanBufferFullError struct{}
+
+func (e *spanBufferFullError) Error() string {
+	return fmt.Sprintf("trace span cap (%d) reached, dropping trace", traceMaxSize)
+}
+
+type dataLossError struct {
+	count   int   // number of items lost
+	context error // any context error, if available
+}
+
+func (e *dataLossError) Error() string {
+	return fmt.Sprintf("lost traces (count: %d), error: %v", e.count, e.context)
+}
+
+type errorSummary struct {
+	Count   int
+	Example string
+}
+
+func aggregateErrors(errChan <-chan error) map[string]errorSummary {
+	errs := make(map[string]errorSummary, len(errChan))
+	for {
+		select {
+		case err := <-errChan:
+			if err == nil {
+				break
+			}
+			key := fmt.Sprintf("%T", err)
+			summary := errs[key]
+			summary.Count++
+			summary.Example = err.Error()
+			errs[key] = summary
+		default: // stop when there's no more data
+			return errs
+		}
+	}
+}
+
+// logErrors logs the errors, preventing log file flooding, when there
+// are many messages, it caps them and shows a quick summary.
+// As of today it only logs using standard golang log package, but
+// later we could send those stats to agent // TODO(ufoot).
+func logErrors(errChan <-chan error) {
+	errs := aggregateErrors(errChan)
+	for _, v := range errs {
+		var repeat string
+		if v.Count > 1 {
+			repeat = " (repeated " + strconv.Itoa(v.Count) + " times)"
+		}
+		log.Println(errorPrefix + v.Example + repeat)
+	}
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/option.go

@@ -0,0 +1,163 @@
+package tracer
+
+import (
+	"os"
+	"path/filepath"
+	"time"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
+)
+
+// config holds the tracer configuration.
+type config struct {
+	// debug, when true, writes details to logs.
+	debug bool
+
+	// serviceName specifies the name of this application.
+	serviceName string
+
+	// sampler specifies the sampler that will be used for sampling traces.
+	sampler Sampler
+
+	// agentAddr specifies the hostname and  of the agent where the traces
+	// are sent to.
+	agentAddr string
+
+	// globalTags holds a set of tags that will be automatically applied to
+	// all spans.
+	globalTags map[string]interface{}
+
+	// transport specifies the Transport interface which will be used to send data to the agent.
+	transport transport
+
+	// propagator propagates span context cross-process
+	propagator Propagator
+}
+
+// StartOption represents a function that can be provided as a parameter to Start.
+type StartOption func(*config)
+
+// defaults sets the default values for a config.
+func defaults(c *config) {
+	c.serviceName = filepath.Base(os.Args[0])
+	c.sampler = NewAllSampler()
+	c.agentAddr = defaultAddress
+}
+
+// WithDebugMode enables debug mode on the tracer, resulting in more verbose logging.
+func WithDebugMode(enabled bool) StartOption {
+	return func(c *config) {
+		c.debug = enabled
+	}
+}
+
+// WithPropagator sets an alternative propagator to be used by the tracer.
+func WithPropagator(p Propagator) StartOption {
+	return func(c *config) {
+		c.propagator = p
+	}
+}
+
+// WithServiceName sets the default service name to be used with the tracer.
+func WithServiceName(name string) StartOption {
+	return func(c *config) {
+		c.serviceName = name
+	}
+}
+
+// WithAgentAddr sets the address where the agent is located. The default is
+// localhost:8126. It should contain both host and port.
+func WithAgentAddr(addr string) StartOption {
+	return func(c *config) {
+		c.agentAddr = addr
+	}
+}
+
+// WithGlobalTag sets a key/value pair which will be set as a tag on all spans
+// created by tracer. This option may be used multiple times.
+func WithGlobalTag(k string, v interface{}) StartOption {
+	return func(c *config) {
+		if c.globalTags == nil {
+			c.globalTags = make(map[string]interface{})
+		}
+		c.globalTags[k] = v
+	}
+}
+
+// WithSampler sets the given sampler to be used with the tracer. By default
+// an all-permissive sampler is used.
+func WithSampler(s Sampler) StartOption {
+	return func(c *config) {
+		c.sampler = s
+	}
+}
+
+// StartSpanOption is a configuration option for StartSpan. It is aliased in order
+// to help godoc group all the functions returning it together. It is considered
+// more correct to refer to it as the type as the origin, ddtrace.StartSpanOption.
+type StartSpanOption = ddtrace.StartSpanOption
+
+// Tag sets the given key/value pair as a tag on the started Span.
+func Tag(k string, v interface{}) StartSpanOption {
+	return func(cfg *ddtrace.StartSpanConfig) {
+		if cfg.Tags == nil {
+			cfg.Tags = map[string]interface{}{}
+		}
+		cfg.Tags[k] = v
+	}
+}
+
+// ServiceName sets the given service name on the started span. For example "http.server".
+func ServiceName(name string) StartSpanOption {
+	return Tag(ext.ServiceName, name)
+}
+
+// ResourceName sets the given resource name on the started span. A resource could
+// be an SQL query, a URL, an RPC method or something else.
+func ResourceName(name string) StartSpanOption {
+	return Tag(ext.ResourceName, name)
+}
+
+// SpanType sets the given span type on the started span. Some examples in the case of
+// the Datadog APM product could be "web", "db" or "cache".
+func SpanType(name string) StartSpanOption {
+	return Tag(ext.SpanType, name)
+}
+
+// ChildOf tells StartSpan to use the given span context as a parent for the
+// created span.
+func ChildOf(ctx ddtrace.SpanContext) StartSpanOption {
+	return func(cfg *ddtrace.StartSpanConfig) {
+		cfg.Parent = ctx
+	}
+}
+
+// StartTime sets a custom time as the start time for the created span. By
+// default a span is started using the creation time.
+func StartTime(t time.Time) StartSpanOption {
+	return func(cfg *ddtrace.StartSpanConfig) {
+		cfg.StartTime = t
+	}
+}
+
+// FinishOption is a configuration option for FinishSpan. It is aliased in order
+// to help godoc group all the functions returning it together. It is considered
+// more correct to refer to it as the type as the origin, ddtrace.FinishOption.
+type FinishOption = ddtrace.FinishOption
+
+// FinishTime sets the given time as the finishing time for the span. By default,
+// the current time is used.
+func FinishTime(t time.Time) FinishOption {
+	return func(cfg *ddtrace.FinishConfig) {
+		cfg.FinishTime = t
+	}
+}
+
+// WithError adds the given error to the span before marking it as finished. If it is
+// nil it will be disregarded.
+func WithError(err error) FinishOption {
+	return func(cfg *ddtrace.FinishConfig) {
+		cfg.Error = err
+	}
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/payload.go

@@ -0,0 +1,116 @@
+package tracer
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+
+	"github.com/tinylib/msgp/msgp"
+)
+
+// payload is a wrapper on top of the msgpack encoder which allows constructing an
+// encoded array by pushing its entries sequentially, one at a time. It basically
+// allows us to encode as we would with a stream, except that the contents of the stream
+// can be read as a slice by the msgpack decoder at any time. It follows the guidelines
+// from the msgpack array spec:
+// https://github.com/msgpack/msgpack/blob/master/spec.md#array-format-family
+//
+// payload implements io.Reader and can be used with the decoder directly. To create
+// a new payload use the newPayload method.
+//
+// payload is not safe for concurrent use.
+//
+// This structure basically allows us to push traces into the payload one at a time
+// in order to always have knowledge of the payload size, but also making it possible
+// for the agent to decode it as an array.
+type payload struct {
+	// header specifies the first few bytes in the msgpack stream
+	// indicating the type of array (fixarray, array16 or array32)
+	// and the number of items contained in the stream.
+	header []byte
+
+	// off specifies the current read position on the header.
+	off int
+
+	// count specifies the number of items in the stream.
+	count uint64
+
+	// buf holds the sequence of msgpack-encoded items.
+	buf bytes.Buffer
+}
+
+var _ io.Reader = (*payload)(nil)
+
+// newPayload returns a ready to use payload.
+func newPayload() *payload {
+	p := &payload{
+		header: make([]byte, 8),
+		off:    8,
+	}
+	return p
+}
+
+// push pushes a new item into the stream.
+func (p *payload) push(t spanList) error {
+	if err := msgp.Encode(&p.buf, t); err != nil {
+		return err
+	}
+	p.count++
+	p.updateHeader()
+	return nil
+}
+
+// itemCount returns the number of items available in the srteam.
+func (p *payload) itemCount() int {
+	return int(p.count)
+}
+
+// size returns the payload size in bytes. After the first read the value becomes
+// inaccurate by up to 8 bytes.
+func (p *payload) size() int {
+	return p.buf.Len() + len(p.header) - p.off
+}
+
+// reset resets the internal buffer, counter and read offset.
+func (p *payload) reset() {
+	p.off = 8
+	p.count = 0
+	p.buf.Reset()
+}
+
+// https://github.com/msgpack/msgpack/blob/master/spec.md#array-format-family
+const (
+	msgpackArrayFix byte = 144  // up to 15 items
+	msgpackArray16       = 0xdc // up to 2^16-1 items, followed by size in 2 bytes
+	msgpackArray32       = 0xdd // up to 2^32-1 items, followed by size in 4 bytes
+)
+
+// updateHeader updates the payload header based on the number of items currently
+// present in the stream.
+func (p *payload) updateHeader() {
+	n := p.count
+	switch {
+	case n <= 15:
+		p.header[7] = msgpackArrayFix + byte(n)
+		p.off = 7
+	case n <= 1<<16-1:
+		binary.BigEndian.PutUint64(p.header, n) // writes 2 bytes
+		p.header[5] = msgpackArray16
+		p.off = 5
+	default: // n <= 1<<32-1
+		binary.BigEndian.PutUint64(p.header, n) // writes 4 bytes
+		p.header[3] = msgpackArray32
+		p.off = 3
+	}
+}
+
+// Read implements io.Reader. It reads from the msgpack-encoded stream.
+func (p *payload) Read(b []byte) (n int, err error) {
+	if p.off < len(p.header) {
+		// reading header
+		n = copy(b, p.header[p.off:])
+		p.off += n
+		return n, nil
+	}
+	return p.buf.Read(b)
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/propagator.go

@@ -0,0 +1,52 @@
+package tracer
+
+import (
+	"errors"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+)
+
+// Propagator implementations should be able to inject and extract
+// SpanContexts into an implementation specific carrier.
+type Propagator interface {
+	// Inject takes the SpanContext and injects it into the carrier.
+	Inject(context ddtrace.SpanContext, carrier interface{}) error
+
+	// Extract returns the SpanContext from the given carrier.
+	Extract(carrier interface{}) (ddtrace.SpanContext, error)
+}
+
+// TextMapWriter allows setting key/value pairs of strings on the underlying
+// data structure. Carriers implementing TextMapWriter are compatible to be
+// used with Datadog's TextMapPropagator.
+type TextMapWriter interface {
+	// Set sets the given key/value pair.
+	Set(key, val string)
+}
+
+// TextMapReader allows iterating over sets of key/value pairs. Carriers implementing
+// TextMapReader are compatible to be used with Datadog's TextMapPropagator.
+type TextMapReader interface {
+	// ForeachKey iterates over all keys that exist in the underlying
+	// carrier. It takes a callback function which will be called
+	// using all key/value pairs as arguments. ForeachKey will return
+	// the first error returned by the handler.
+	ForeachKey(handler func(key, val string) error) error
+}
+
+var (
+	// ErrInvalidCarrier is returned when the carrier provided to the propagator
+	// does not implemented the correct interfaces.
+	ErrInvalidCarrier = errors.New("invalid carrier")
+
+	// ErrInvalidSpanContext is returned when the span context found in the
+	// carrier is not of the expected type.
+	ErrInvalidSpanContext = errors.New("invalid span context")
+
+	// ErrSpanContextCorrupted is returned when there was a problem parsing
+	// the information found in the carrier.
+	ErrSpanContextCorrupted = errors.New("span context corrupted")
+
+	// ErrSpanContextNotFound represents missing information in the given carrier.
+	ErrSpanContextNotFound = errors.New("span context not found")
+)

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/rand.go

@@ -0,0 +1,50 @@
+package tracer
+
+import (
+	cryptorand "crypto/rand"
+	"log"
+	"math"
+	"math/big"
+	"math/rand"
+	"sync"
+	"time"
+)
+
+// random holds a thread-safe source of random numbers.
+var random *rand.Rand
+
+func init() {
+	var seed int64
+	n, err := cryptorand.Int(cryptorand.Reader, big.NewInt(math.MaxInt64))
+	if err == nil {
+		seed = n.Int64()
+	} else {
+		log.Printf("%scannot generate random seed: %v; using current time\n", errorPrefix, err)
+		seed = time.Now().UnixNano()
+	}
+	random = rand.New(&safeSource{
+		source: rand.NewSource(seed),
+	})
+}
+
+// safeSource holds a thread-safe implementation of rand.Source64.
+type safeSource struct {
+	source rand.Source
+	sync.Mutex
+}
+
+func (rs *safeSource) Int63() int64 {
+	rs.Lock()
+	n := rs.source.Int63()
+	rs.Unlock()
+
+	return n
+}
+
+func (rs *safeSource) Uint64() uint64 { return uint64(rs.Int63()) }
+
+func (rs *safeSource) Seed(seed int64) {
+	rs.Lock()
+	rs.Seed(seed)
+	rs.Unlock()
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/sampler.go

@@ -0,0 +1,72 @@
+package tracer
+
+import (
+	"math"
+	"sync"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+)
+
+// Sampler is the generic interface of any sampler. It must be safe for concurrent use.
+type Sampler interface {
+	// Sample returns true if the given span should be sampled.
+	Sample(span Span) bool
+}
+
+// RateSampler is a sampler implementation which randomly selects spans using a
+// provided rate. For example, a rate of 0.75 will permit 75% of the spans.
+// RateSampler implementations should be safe for concurrent use.
+type RateSampler interface {
+	Sampler
+
+	// Rate returns the current sample rate.
+	Rate() float64
+
+	// SetRate sets a new sample rate.
+	SetRate(rate float64)
+}
+
+// rateSampler samples from a sample rate.
+type rateSampler struct {
+	sync.RWMutex
+	rate float64
+}
+
+// NewAllSampler is a short-hand for NewRateSampler(1). It is all-permissive.
+func NewAllSampler() RateSampler { return NewRateSampler(1) }
+
+// NewRateSampler returns an initialized RateSampler with a given sample rate.
+func NewRateSampler(rate float64) RateSampler {
+	return &rateSampler{rate: rate}
+}
+
+// Rate returns the current rate of the sampler.
+func (r *rateSampler) Rate() float64 {
+	r.RLock()
+	defer r.RUnlock()
+	return r.rate
+}
+
+// SetRate sets a new sampling rate.
+func (r *rateSampler) SetRate(rate float64) {
+	r.Lock()
+	r.rate = rate
+	r.Unlock()
+}
+
+// constants used for the Knuth hashing, same as agent.
+const knuthFactor = uint64(1111111111111111111)
+
+// Sample returns true if the given span should be sampled.
+func (r *rateSampler) Sample(spn ddtrace.Span) bool {
+	s, ok := spn.(*span)
+	if !ok {
+		return false
+	}
+	r.RLock()
+	defer r.RUnlock()
+	if r.rate < 1 {
+		return s.TraceID*knuthFactor < uint64(r.rate*math.MaxUint64)
+	}
+	return true
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/span.go

@@ -0,0 +1,231 @@
+//go:generate msgp -unexported -marshal=false -o=span_msgp.go -tests=false
+
+package tracer
+
+import (
+	"fmt"
+	"reflect"
+	"runtime/debug"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/tinylib/msgp/msgp"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
+)
+
+type (
+	// spanList implements msgp.Encodable on top of a slice of spans.
+	spanList []*span
+
+	// spanLists implements msgp.Decodable on top of a slice of spanList.
+	// This type is only used in tests.
+	spanLists []spanList
+)
+
+var (
+	_ ddtrace.Span   = (*span)(nil)
+	_ msgp.Encodable = (*spanList)(nil)
+	_ msgp.Decodable = (*spanLists)(nil)
+)
+
+// span represents a computation. Callers must call Finish when a span is
+// complete to ensure it's submitted.
+type span struct {
+	sync.RWMutex `msg:"-"`
+
+	Name     string             `msg:"name"`              // operation name
+	Service  string             `msg:"service"`           // service name (i.e. "grpc.server", "http.request")
+	Resource string             `msg:"resource"`          // resource name (i.e. "/user?id=123", "SELECT * FROM users")
+	Type     string             `msg:"type"`              // protocol associated with the span (i.e. "web", "db", "cache")
+	Start    int64              `msg:"start"`             // span start time expressed in nanoseconds since epoch
+	Duration int64              `msg:"duration"`          // duration of the span expressed in nanoseconds
+	Meta     map[string]string  `msg:"meta,omitempty"`    // arbitrary map of metadata
+	Metrics  map[string]float64 `msg:"metrics,omitempty"` // arbitrary map of numeric metrics
+	SpanID   uint64             `msg:"span_id"`           // identifier of this span
+	TraceID  uint64             `msg:"trace_id"`          // identifier of the root span
+	ParentID uint64             `msg:"parent_id"`         // identifier of the span's direct parent
+	Error    int32              `msg:"error"`             // error status of the span; 0 means no errors
+
+	finished bool         `msg:"-"` // true if the span has been submitted to a tracer.
+	context  *spanContext `msg:"-"` // span propagation context
+}
+
+// Context yields the SpanContext for this Span. Note that the return
+// value of Context() is still valid after a call to Finish(). This is
+// called the span context and it is different from Go's context.
+func (s *span) Context() ddtrace.SpanContext { return s.context }
+
+// SetBaggageItem sets a key/value pair as baggage on the span. Baggage items
+// are propagated down to descendant spans and injected cross-process. Use with
+// care as it adds extra load onto your tracing layer.
+func (s *span) SetBaggageItem(key, val string) {
+	s.context.setBaggageItem(key, val)
+}
+
+// BaggageItem gets the value for a baggage item given its key. Returns the
+// empty string if the value isn't found in this Span.
+func (s *span) BaggageItem(key string) string {
+	return s.context.baggageItem(key)
+}
+
+// SetTag adds a set of key/value metadata to the span.
+func (s *span) SetTag(key string, value interface{}) {
+	s.Lock()
+	defer s.Unlock()
+	// We don't lock spans when flushing, so we could have a data race when
+	// modifying a span as it's being flushed. This protects us against that
+	// race, since spans are marked `finished` before we flush them.
+	if s.finished {
+		return
+	}
+	if key == ext.Error {
+		s.setTagError(value)
+		return
+	}
+	if v, ok := value.(string); ok {
+		s.setTagString(key, v)
+		return
+	}
+	if v, ok := toFloat64(value); ok {
+		s.setTagNumeric(key, v)
+		return
+	}
+	// not numeric, not a string and not an error, the likelihood of this
+	// happening is close to zero, but we should nevertheless account for it.
+	s.Meta[key] = fmt.Sprint(value)
+}
+
+// setTagError sets the error tag. It accounts for various valid scenarios.
+// This method is not safe for concurrent use.
+func (s *span) setTagError(value interface{}) {
+	switch v := value.(type) {
+	case bool:
+		// bool value as per Opentracing spec.
+		if !v {
+			s.Error = 0
+		} else {
+			s.Error = 1
+		}
+	case error:
+		// if anyone sets an error value as the tag, be nice here
+		// and provide all the benefits.
+		s.Error = 1
+		s.Meta[ext.ErrorMsg] = v.Error()
+		s.Meta[ext.ErrorType] = reflect.TypeOf(v).String()
+		s.Meta[ext.ErrorStack] = string(debug.Stack())
+	case nil:
+		// no error
+		s.Error = 0
+	default:
+		// in all other cases, let's assume that setting this tag
+		// is the result of an error.
+		s.Error = 1
+	}
+}
+
+// setTagString sets a string tag. This method is not safe for concurrent use.
+func (s *span) setTagString(key, v string) {
+	switch key {
+	case ext.ServiceName:
+		s.Service = v
+	case ext.ResourceName:
+		s.Resource = v
+	case ext.SpanType:
+		s.Type = v
+	default:
+		s.Meta[key] = v
+	}
+}
+
+// setTagNumeric sets a numeric tag, in our case called a metric. This method
+// is not safe for concurrent use.
+func (s *span) setTagNumeric(key string, v float64) {
+	switch key {
+	case ext.SamplingPriority:
+		// setting sampling priority per spec
+		s.Metrics[samplingPriorityKey] = v
+		s.context.setSamplingPriority(int(v))
+	default:
+		s.Metrics[key] = v
+	}
+}
+
+// Finish closes this Span (but not its children) providing the duration
+// of its part of the tracing session.
+func (s *span) Finish(opts ...ddtrace.FinishOption) {
+	var cfg ddtrace.FinishConfig
+	for _, fn := range opts {
+		fn(&cfg)
+	}
+	var t int64
+	if cfg.FinishTime.IsZero() {
+		t = now()
+	} else {
+		t = cfg.FinishTime.UnixNano()
+	}
+	if cfg.Error != nil {
+		s.SetTag(ext.Error, cfg.Error)
+	}
+	s.finish(t)
+}
+
+// SetOperationName sets or changes the operation name.
+func (s *span) SetOperationName(operationName string) {
+	s.Lock()
+	defer s.Unlock()
+
+	s.Name = operationName
+}
+
+func (s *span) finish(finishTime int64) {
+	s.Lock()
+	defer s.Unlock()
+	// We don't lock spans when flushing, so we could have a data race when
+	// modifying a span as it's being flushed. This protects us against that
+	// race, since spans are marked `finished` before we flush them.
+	if s.finished {
+		// already finished
+		return
+	}
+	if s.Duration == 0 {
+		s.Duration = finishTime - s.Start
+	}
+	s.finished = true
+
+	if !s.context.sampled {
+		// not sampled
+		return
+	}
+	s.context.finish()
+}
+
+// String returns a human readable representation of the span. Not for
+// production, just debugging.
+func (s *span) String() string {
+	lines := []string{
+		fmt.Sprintf("Name: %s", s.Name),
+		fmt.Sprintf("Service: %s", s.Service),
+		fmt.Sprintf("Resource: %s", s.Resource),
+		fmt.Sprintf("TraceID: %d", s.TraceID),
+		fmt.Sprintf("SpanID: %d", s.SpanID),
+		fmt.Sprintf("ParentID: %d", s.ParentID),
+		fmt.Sprintf("Start: %s", time.Unix(0, s.Start)),
+		fmt.Sprintf("Duration: %s", time.Duration(s.Duration)),
+		fmt.Sprintf("Error: %d", s.Error),
+		fmt.Sprintf("Type: %s", s.Type),
+		"Tags:",
+	}
+	s.RLock()
+	for key, val := range s.Meta {
+		lines = append(lines, fmt.Sprintf("\t%s:%s", key, val))
+	}
+	for key, val := range s.Metrics {
+		lines = append(lines, fmt.Sprintf("\t%s:%f", key, val))
+	}
+	s.RUnlock()
+	return strings.Join(lines, "\n")
+}
+
+const samplingPriorityKey = "_sampling_priority_v1"

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/span_msgp.go

@@ -0,0 +1,448 @@
+package tracer
+
+// NOTE: THIS FILE WAS PRODUCED BY THE
+// MSGP CODE GENERATION TOOL (github.com/tinylib/msgp)
+// DO NOT EDIT
+
+import (
+	"github.com/tinylib/msgp/msgp"
+)
+
+// DecodeMsg implements msgp.Decodable
+func (z *span) DecodeMsg(dc *msgp.Reader) (err error) {
+	var field []byte
+	_ = field
+	var zb0001 uint32
+	zb0001, err = dc.ReadMapHeader()
+	if err != nil {
+		return
+	}
+	for zb0001 > 0 {
+		zb0001--
+		field, err = dc.ReadMapKeyPtr()
+		if err != nil {
+			return
+		}
+		switch msgp.UnsafeString(field) {
+		case "name":
+			z.Name, err = dc.ReadString()
+			if err != nil {
+				return
+			}
+		case "service":
+			z.Service, err = dc.ReadString()
+			if err != nil {
+				return
+			}
+		case "resource":
+			z.Resource, err = dc.ReadString()
+			if err != nil {
+				return
+			}
+		case "type":
+			z.Type, err = dc.ReadString()
+			if err != nil {
+				return
+			}
+		case "start":
+			z.Start, err = dc.ReadInt64()
+			if err != nil {
+				return
+			}
+		case "duration":
+			z.Duration, err = dc.ReadInt64()
+			if err != nil {
+				return
+			}
+		case "meta":
+			var zb0002 uint32
+			zb0002, err = dc.ReadMapHeader()
+			if err != nil {
+				return
+			}
+			if z.Meta == nil && zb0002 > 0 {
+				z.Meta = make(map[string]string, zb0002)
+			} else if len(z.Meta) > 0 {
+				for key, _ := range z.Meta {
+					delete(z.Meta, key)
+				}
+			}
+			for zb0002 > 0 {
+				zb0002--
+				var za0001 string
+				var za0002 string
+				za0001, err = dc.ReadString()
+				if err != nil {
+					return
+				}
+				za0002, err = dc.ReadString()
+				if err != nil {
+					return
+				}
+				z.Meta[za0001] = za0002
+			}
+		case "metrics":
+			var zb0003 uint32
+			zb0003, err = dc.ReadMapHeader()
+			if err != nil {
+				return
+			}
+			if z.Metrics == nil && zb0003 > 0 {
+				z.Metrics = make(map[string]float64, zb0003)
+			} else if len(z.Metrics) > 0 {
+				for key, _ := range z.Metrics {
+					delete(z.Metrics, key)
+				}
+			}
+			for zb0003 > 0 {
+				zb0003--
+				var za0003 string
+				var za0004 float64
+				za0003, err = dc.ReadString()
+				if err != nil {
+					return
+				}
+				za0004, err = dc.ReadFloat64()
+				if err != nil {
+					return
+				}
+				z.Metrics[za0003] = za0004
+			}
+		case "span_id":
+			z.SpanID, err = dc.ReadUint64()
+			if err != nil {
+				return
+			}
+		case "trace_id":
+			z.TraceID, err = dc.ReadUint64()
+			if err != nil {
+				return
+			}
+		case "parent_id":
+			z.ParentID, err = dc.ReadUint64()
+			if err != nil {
+				return
+			}
+		case "error":
+			z.Error, err = dc.ReadInt32()
+			if err != nil {
+				return
+			}
+		default:
+			err = dc.Skip()
+			if err != nil {
+				return
+			}
+		}
+	}
+	return
+}
+
+// EncodeMsg implements msgp.Encodable
+func (z *span) EncodeMsg(en *msgp.Writer) (err error) {
+	// map header, size 12
+	// write "name"
+	err = en.Append(0x8c, 0xa4, 0x6e, 0x61, 0x6d, 0x65)
+	if err != nil {
+		return
+	}
+	err = en.WriteString(z.Name)
+	if err != nil {
+		return
+	}
+	// write "service"
+	err = en.Append(0xa7, 0x73, 0x65, 0x72, 0x76, 0x69, 0x63, 0x65)
+	if err != nil {
+		return
+	}
+	err = en.WriteString(z.Service)
+	if err != nil {
+		return
+	}
+	// write "resource"
+	err = en.Append(0xa8, 0x72, 0x65, 0x73, 0x6f, 0x75, 0x72, 0x63, 0x65)
+	if err != nil {
+		return
+	}
+	err = en.WriteString(z.Resource)
+	if err != nil {
+		return
+	}
+	// write "type"
+	err = en.Append(0xa4, 0x74, 0x79, 0x70, 0x65)
+	if err != nil {
+		return
+	}
+	err = en.WriteString(z.Type)
+	if err != nil {
+		return
+	}
+	// write "start"
+	err = en.Append(0xa5, 0x73, 0x74, 0x61, 0x72, 0x74)
+	if err != nil {
+		return
+	}
+	err = en.WriteInt64(z.Start)
+	if err != nil {
+		return
+	}
+	// write "duration"
+	err = en.Append(0xa8, 0x64, 0x75, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e)
+	if err != nil {
+		return
+	}
+	err = en.WriteInt64(z.Duration)
+	if err != nil {
+		return
+	}
+	// write "meta"
+	err = en.Append(0xa4, 0x6d, 0x65, 0x74, 0x61)
+	if err != nil {
+		return
+	}
+	err = en.WriteMapHeader(uint32(len(z.Meta)))
+	if err != nil {
+		return
+	}
+	for za0001, za0002 := range z.Meta {
+		err = en.WriteString(za0001)
+		if err != nil {
+			return
+		}
+		err = en.WriteString(za0002)
+		if err != nil {
+			return
+		}
+	}
+	// write "metrics"
+	err = en.Append(0xa7, 0x6d, 0x65, 0x74, 0x72, 0x69, 0x63, 0x73)
+	if err != nil {
+		return
+	}
+	err = en.WriteMapHeader(uint32(len(z.Metrics)))
+	if err != nil {
+		return
+	}
+	for za0003, za0004 := range z.Metrics {
+		err = en.WriteString(za0003)
+		if err != nil {
+			return
+		}
+		err = en.WriteFloat64(za0004)
+		if err != nil {
+			return
+		}
+	}
+	// write "span_id"
+	err = en.Append(0xa7, 0x73, 0x70, 0x61, 0x6e, 0x5f, 0x69, 0x64)
+	if err != nil {
+		return
+	}
+	err = en.WriteUint64(z.SpanID)
+	if err != nil {
+		return
+	}
+	// write "trace_id"
+	err = en.Append(0xa8, 0x74, 0x72, 0x61, 0x63, 0x65, 0x5f, 0x69, 0x64)
+	if err != nil {
+		return
+	}
+	err = en.WriteUint64(z.TraceID)
+	if err != nil {
+		return
+	}
+	// write "parent_id"
+	err = en.Append(0xa9, 0x70, 0x61, 0x72, 0x65, 0x6e, 0x74, 0x5f, 0x69, 0x64)
+	if err != nil {
+		return
+	}
+	err = en.WriteUint64(z.ParentID)
+	if err != nil {
+		return
+	}
+	// write "error"
+	err = en.Append(0xa5, 0x65, 0x72, 0x72, 0x6f, 0x72)
+	if err != nil {
+		return
+	}
+	err = en.WriteInt32(z.Error)
+	if err != nil {
+		return
+	}
+	return
+}
+
+// Msgsize returns an upper bound estimate of the number of bytes occupied by the serialized message
+func (z *span) Msgsize() (s int) {
+	s = 1 + 5 + msgp.StringPrefixSize + len(z.Name) + 8 + msgp.StringPrefixSize + len(z.Service) + 9 + msgp.StringPrefixSize + len(z.Resource) + 5 + msgp.StringPrefixSize + len(z.Type) + 6 + msgp.Int64Size + 9 + msgp.Int64Size + 5 + msgp.MapHeaderSize
+	if z.Meta != nil {
+		for za0001, za0002 := range z.Meta {
+			_ = za0002
+			s += msgp.StringPrefixSize + len(za0001) + msgp.StringPrefixSize + len(za0002)
+		}
+	}
+	s += 8 + msgp.MapHeaderSize
+	if z.Metrics != nil {
+		for za0003, za0004 := range z.Metrics {
+			_ = za0004
+			s += msgp.StringPrefixSize + len(za0003) + msgp.Float64Size
+		}
+	}
+	s += 8 + msgp.Uint64Size + 9 + msgp.Uint64Size + 10 + msgp.Uint64Size + 6 + msgp.Int32Size
+	return
+}
+
+// DecodeMsg implements msgp.Decodable
+func (z *spanList) DecodeMsg(dc *msgp.Reader) (err error) {
+	var zb0002 uint32
+	zb0002, err = dc.ReadArrayHeader()
+	if err != nil {
+		return
+	}
+	if cap((*z)) >= int(zb0002) {
+		(*z) = (*z)[:zb0002]
+	} else {
+		(*z) = make(spanList, zb0002)
+	}
+	for zb0001 := range *z {
+		if dc.IsNil() {
+			err = dc.ReadNil()
+			if err != nil {
+				return
+			}
+			(*z)[zb0001] = nil
+		} else {
+			if (*z)[zb0001] == nil {
+				(*z)[zb0001] = new(span)
+			}
+			err = (*z)[zb0001].DecodeMsg(dc)
+			if err != nil {
+				return
+			}
+		}
+	}
+	return
+}
+
+// EncodeMsg implements msgp.Encodable
+func (z spanList) EncodeMsg(en *msgp.Writer) (err error) {
+	err = en.WriteArrayHeader(uint32(len(z)))
+	if err != nil {
+		return
+	}
+	for zb0003 := range z {
+		if z[zb0003] == nil {
+			err = en.WriteNil()
+			if err != nil {
+				return
+			}
+		} else {
+			err = z[zb0003].EncodeMsg(en)
+			if err != nil {
+				return
+			}
+		}
+	}
+	return
+}
+
+// Msgsize returns an upper bound estimate of the number of bytes occupied by the serialized message
+func (z spanList) Msgsize() (s int) {
+	s = msgp.ArrayHeaderSize
+	for zb0003 := range z {
+		if z[zb0003] == nil {
+			s += msgp.NilSize
+		} else {
+			s += z[zb0003].Msgsize()
+		}
+	}
+	return
+}
+
+// DecodeMsg implements msgp.Decodable
+func (z *spanLists) DecodeMsg(dc *msgp.Reader) (err error) {
+	var zb0003 uint32
+	zb0003, err = dc.ReadArrayHeader()
+	if err != nil {
+		return
+	}
+	if cap((*z)) >= int(zb0003) {
+		(*z) = (*z)[:zb0003]
+	} else {
+		(*z) = make(spanLists, zb0003)
+	}
+	for zb0001 := range *z {
+		var zb0004 uint32
+		zb0004, err = dc.ReadArrayHeader()
+		if err != nil {
+			return
+		}
+		if cap((*z)[zb0001]) >= int(zb0004) {
+			(*z)[zb0001] = ((*z)[zb0001])[:zb0004]
+		} else {
+			(*z)[zb0001] = make(spanList, zb0004)
+		}
+		for zb0002 := range (*z)[zb0001] {
+			if dc.IsNil() {
+				err = dc.ReadNil()
+				if err != nil {
+					return
+				}
+				(*z)[zb0001][zb0002] = nil
+			} else {
+				if (*z)[zb0001][zb0002] == nil {
+					(*z)[zb0001][zb0002] = new(span)
+				}
+				err = (*z)[zb0001][zb0002].DecodeMsg(dc)
+				if err != nil {
+					return
+				}
+			}
+		}
+	}
+	return
+}
+
+// EncodeMsg implements msgp.Encodable
+func (z spanLists) EncodeMsg(en *msgp.Writer) (err error) {
+	err = en.WriteArrayHeader(uint32(len(z)))
+	if err != nil {
+		return
+	}
+	for zb0005 := range z {
+		err = en.WriteArrayHeader(uint32(len(z[zb0005])))
+		if err != nil {
+			return
+		}
+		for zb0006 := range z[zb0005] {
+			if z[zb0005][zb0006] == nil {
+				err = en.WriteNil()
+				if err != nil {
+					return
+				}
+			} else {
+				err = z[zb0005][zb0006].EncodeMsg(en)
+				if err != nil {
+					return
+				}
+			}
+		}
+	}
+	return
+}
+
+// Msgsize returns an upper bound estimate of the number of bytes occupied by the serialized message
+func (z spanLists) Msgsize() (s int) {
+	s = msgp.ArrayHeaderSize
+	for zb0005 := range z {
+		s += msgp.ArrayHeaderSize
+		for zb0006 := range z[zb0005] {
+			if z[zb0005][zb0006] == nil {
+				s += msgp.NilSize
+			} else {
+				s += z[zb0005][zb0006].Msgsize()
+			}
+		}
+	}
+	return
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/spancontext.go

@@ -0,0 +1,193 @@
+package tracer
+
+import (
+	"sync"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
+)
+
+var _ ddtrace.SpanContext = (*spanContext)(nil)
+
+// SpanContext represents a span state that can propagate to descendant spans
+// and across process boundaries. It contains all the information needed to
+// spawn a direct descendant of the span that it belongs to. It can be used
+// to create distributed tracing by propagating it using the provided interfaces.
+type spanContext struct {
+	// the below group should propagate only locally
+
+	trace   *trace // reference to the trace that this span belongs too
+	span    *span  // reference to the span that hosts this context
+	sampled bool   // whether this span will be sampled or not
+
+	// the below group should propagate cross-process
+
+	traceID uint64
+	spanID  uint64
+
+	mu          sync.RWMutex // guards below fields
+	baggage     map[string]string
+	priority    int
+	hasPriority bool
+}
+
+// newSpanContext creates a new SpanContext to serve as context for the given
+// span. If the provided parent is not nil, the context will inherit the trace,
+// baggage and other values from it. This method also pushes the span into the
+// new context's trace and as a result, it should not be called multiple times
+// for the same span.
+func newSpanContext(span *span, parent *spanContext) *spanContext {
+	context := &spanContext{
+		traceID: span.TraceID,
+		spanID:  span.SpanID,
+		sampled: true,
+		span:    span,
+	}
+	if v, ok := span.Metrics[samplingPriorityKey]; ok {
+		context.hasPriority = true
+		context.priority = int(v)
+	}
+	if parent != nil {
+		context.trace = parent.trace
+		context.sampled = parent.sampled
+		context.hasPriority = parent.hasSamplingPriority()
+		context.priority = parent.samplingPriority()
+		parent.ForeachBaggageItem(func(k, v string) bool {
+			context.setBaggageItem(k, v)
+			return true
+		})
+	}
+	if context.trace == nil {
+		context.trace = newTrace()
+	}
+	// put span in context's trace
+	context.trace.push(span)
+	return context
+}
+
+// SpanID implements ddtrace.SpanContext.
+func (c *spanContext) SpanID() uint64 { return c.spanID }
+
+// TraceID implements ddtrace.SpanContext.
+func (c *spanContext) TraceID() uint64 { return c.traceID }
+
+// ForeachBaggageItem implements ddtrace.SpanContext.
+func (c *spanContext) ForeachBaggageItem(handler func(k, v string) bool) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	for k, v := range c.baggage {
+		if !handler(k, v) {
+			break
+		}
+	}
+}
+
+func (c *spanContext) setSamplingPriority(p int) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.priority = p
+	c.hasPriority = true
+}
+
+func (c *spanContext) samplingPriority() int {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.priority
+}
+
+func (c *spanContext) hasSamplingPriority() bool {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.hasPriority
+}
+
+func (c *spanContext) setBaggageItem(key, val string) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.baggage == nil {
+		c.baggage = make(map[string]string, 1)
+	}
+	c.baggage[key] = val
+}
+
+func (c *spanContext) baggageItem(key string) string {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.baggage[key]
+}
+
+// finish marks this span as finished in the trace.
+func (c *spanContext) finish() { c.trace.ackFinish() }
+
+// trace holds information about a specific trace. This structure is shared
+// between all spans in a trace.
+type trace struct {
+	mu       sync.RWMutex // guards below fields
+	spans    []*span      // all the spans that are part of this trace
+	finished int          // the number of finished spans
+	full     bool         // signifies that the span buffer is full
+}
+
+var (
+	// traceStartSize is the initial size of our trace buffer,
+	// by default we allocate for a handful of spans within the trace,
+	// reasonable as span is actually way bigger, and avoids re-allocating
+	// over and over. Could be fine-tuned at runtime.
+	traceStartSize = 10
+	// traceMaxSize is the maximum number of spans we keep in memory.
+	// This is to avoid memory leaks, if above that value, spans are randomly
+	// dropped and ignore, resulting in corrupted tracing data, but ensuring
+	// original program continues to work as expected.
+	traceMaxSize = int(1e5)
+)
+
+// newTrace creates a new trace using the given callback which will be called
+// upon completion of the trace.
+func newTrace() *trace {
+	return &trace{spans: make([]*span, 0, traceStartSize)}
+}
+
+// push pushes a new span into the trace. If the buffer is full, it returns
+// a errBufferFull error.
+func (t *trace) push(sp *span) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.full {
+		return
+	}
+	if len(t.spans) >= traceMaxSize {
+		// capacity is reached, we will not be able to complete this trace.
+		t.full = true
+		t.spans = nil // GC
+		if tr, ok := internal.GetGlobalTracer().(*tracer); ok {
+			// we have a tracer we can submit errors too.
+			tr.pushError(&spanBufferFullError{})
+		}
+		return
+	}
+	t.spans = append(t.spans, sp)
+}
+
+// ackFinish aknowledges that another span in the trace has finished, and checks
+// if the trace is complete, in which case it calls the onFinish function.
+func (t *trace) ackFinish() {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.full {
+		// capacity has been reached, the buffer is no longer tracking
+		// all the spans in the trace, so the below conditions will not
+		// be accurate and would trigger a pre-mature flush, exposing us
+		// to a race condition where spans can be modified while flushing.
+		return
+	}
+	t.finished++
+	if len(t.spans) != t.finished {
+		return
+	}
+	if tr, ok := internal.GetGlobalTracer().(*tracer); ok {
+		// we have a tracer that can receive completed traces.
+		tr.pushTrace(t.spans)
+	}
+	t.spans = nil
+	t.finished = 0 // important, because a buffer can be used for several flushes
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/textmap.go

@@ -0,0 +1,198 @@
+package tracer
+
+import (
+	"net/http"
+	"strconv"
+	"strings"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+)
+
+// HTTPHeadersCarrier wraps an http.Header as a TextMapWriter and TextMapReader, allowing
+// it to be used using the provided Propagator implementation.
+type HTTPHeadersCarrier http.Header
+
+var _ TextMapWriter = (*HTTPHeadersCarrier)(nil)
+var _ TextMapReader = (*HTTPHeadersCarrier)(nil)
+
+// Set implements TextMapWriter.
+func (c HTTPHeadersCarrier) Set(key, val string) {
+	h := http.Header(c)
+	h.Add(key, val)
+}
+
+// ForeachKey implements TextMapReader.
+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
+}
+
+// TextMapCarrier allows the use of a regular map[string]string as both TextMapWriter
+// and TextMapReader, making it compatible with the provided Propagator.
+type TextMapCarrier map[string]string
+
+var _ TextMapWriter = (*TextMapCarrier)(nil)
+var _ TextMapReader = (*TextMapCarrier)(nil)
+
+// Set implements TextMapWriter.
+func (c TextMapCarrier) Set(key, val string) {
+	c[key] = val
+}
+
+// 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
+}
+
+const (
+	// DefaultBaggageHeaderPrefix specifies the prefix that will be used in
+	// HTTP headers or text maps to prefix baggage keys.
+	DefaultBaggageHeaderPrefix = "ot-baggage-"
+
+	// DefaultTraceIDHeader specifies the key that will be used in HTTP headers
+	// or text maps to store the trace ID.
+	DefaultTraceIDHeader = "x-datadog-trace-id"
+
+	// DefaultParentIDHeader specifies the key that will be used in HTTP headers
+	// or text maps to store the parent ID.
+	DefaultParentIDHeader = "x-datadog-parent-id"
+
+	// DefaultPriorityHeader specifies the key that will be used in HTTP headers
+	// or text maps to store the sampling priority value.
+	DefaultPriorityHeader = "x-datadog-sampling-priority"
+)
+
+// PropagatorConfig defines the configuration for initializing a propagator.
+type PropagatorConfig struct {
+	// BaggagePrefix specifies the prefix that will be used to store baggage
+	// items in a map. It defaults to DefaultBaggageHeaderPrefix.
+	BaggagePrefix string
+
+	// TraceHeader specifies the map key that will be used to store the trace ID.
+	// It defaults to DefaultTraceIDHeader.
+	TraceHeader string
+
+	// ParentHeader specifies the map key that will be used to store the parent ID.
+	// It defaults to DefaultParentIDHeader.
+	ParentHeader string
+
+	// PriorityHeader specifies the map key that will be used to store the sampling priority.
+	// It deafults to DefaultPriorityHeader.
+	PriorityHeader string
+}
+
+// NewPropagator returns a new propagator which uses TextMap to inject
+// and extract values. It propagates trace and span IDs and baggage.
+// To use the defaults, nil may be provided in place of the config.
+func NewPropagator(cfg *PropagatorConfig) Propagator {
+	if cfg == nil {
+		cfg = new(PropagatorConfig)
+	}
+	if cfg.BaggagePrefix == "" {
+		cfg.BaggagePrefix = DefaultBaggageHeaderPrefix
+	}
+	if cfg.TraceHeader == "" {
+		cfg.TraceHeader = DefaultTraceIDHeader
+	}
+	if cfg.ParentHeader == "" {
+		cfg.ParentHeader = DefaultParentIDHeader
+	}
+	if cfg.PriorityHeader == "" {
+		cfg.PriorityHeader = DefaultPriorityHeader
+	}
+	return &propagator{cfg}
+}
+
+// propagator implements a propagator which uses TextMap internally.
+// It propagates the trace and span IDs, as well as the baggage from the
+// context.
+type propagator struct{ cfg *PropagatorConfig }
+
+// Inject defines the Propagator to propagate SpanContext data
+// out of the current process. The implementation propagates the
+// TraceID and the current active SpanID, as well as the Span baggage.
+func (p *propagator) Inject(spanCtx ddtrace.SpanContext, carrier interface{}) error {
+	switch v := carrier.(type) {
+	case TextMapWriter:
+		return p.injectTextMap(spanCtx, v)
+	default:
+		return ErrInvalidCarrier
+	}
+}
+
+func (p *propagator) injectTextMap(spanCtx ddtrace.SpanContext, writer TextMapWriter) error {
+	ctx, ok := spanCtx.(*spanContext)
+	if !ok || ctx.traceID == 0 || ctx.spanID == 0 {
+		return ErrInvalidSpanContext
+	}
+	// propagate the TraceID and the current active SpanID
+	writer.Set(p.cfg.TraceHeader, strconv.FormatUint(ctx.traceID, 10))
+	writer.Set(p.cfg.ParentHeader, strconv.FormatUint(ctx.spanID, 10))
+	if ctx.hasSamplingPriority() {
+		writer.Set(p.cfg.PriorityHeader, strconv.Itoa(ctx.samplingPriority()))
+	}
+	// propagate OpenTracing baggage
+	for k, v := range ctx.baggage {
+		writer.Set(p.cfg.BaggagePrefix+k, v)
+	}
+	return nil
+}
+
+// Extract implements Propagator.
+func (p *propagator) Extract(carrier interface{}) (ddtrace.SpanContext, error) {
+	switch v := carrier.(type) {
+	case TextMapReader:
+		return p.extractTextMap(v)
+	default:
+		return nil, ErrInvalidCarrier
+	}
+}
+
+func (p *propagator) extractTextMap(reader TextMapReader) (ddtrace.SpanContext, error) {
+	var ctx spanContext
+	err := reader.ForeachKey(func(k, v string) error {
+		var err error
+		key := strings.ToLower(k)
+		switch key {
+		case p.cfg.TraceHeader:
+			ctx.traceID, err = strconv.ParseUint(v, 10, 64)
+			if err != nil {
+				return ErrSpanContextCorrupted
+			}
+		case p.cfg.ParentHeader:
+			ctx.spanID, err = strconv.ParseUint(v, 10, 64)
+			if err != nil {
+				return ErrSpanContextCorrupted
+			}
+		case p.cfg.PriorityHeader:
+			ctx.priority, err = strconv.Atoi(v)
+			if err != nil {
+				return ErrSpanContextCorrupted
+			}
+			ctx.hasPriority = true
+		default:
+			if strings.HasPrefix(key, p.cfg.BaggagePrefix) {
+				ctx.setBaggageItem(strings.TrimPrefix(key, p.cfg.BaggagePrefix), v)
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	if ctx.traceID == 0 || ctx.spanID == 0 {
+		return nil, ErrSpanContextNotFound
+	}
+	return &ctx, nil
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/time.go

@@ -0,0 +1,10 @@
+// +build !windows
+
+package tracer
+
+import "time"
+
+// now returns current UTC time in nanos.
+func now() int64 {
+	return time.Now().UTC().UnixNano()
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/time_windows.go

@@ -0,0 +1,35 @@
+package tracer
+
+import (
+	"log"
+	"time"
+
+	"golang.org/x/sys/windows"
+)
+
+// This method is more precise than the go1.8 time.Now on Windows
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/hh706895(v=vs.85).aspx
+// It is however ~10x slower and requires Windows 8+.
+func highPrecisionNow() int64 {
+	var ft windows.Filetime
+	windows.GetSystemTimePreciseAsFileTime(&ft)
+	return ft.Nanoseconds()
+}
+
+func lowPrecisionNow() int64 {
+	return time.Now().UTC().UnixNano()
+}
+
+var now func() int64
+
+// If GetSystemTimePreciseAsFileTime is not available we default to the less
+// precise implementation based on time.Now()
+func init() {
+	if err := windows.LoadGetSystemTimePreciseAsFileTime(); err != nil {
+		log.Printf("Unable to load high precison timer, defaulting to time.Now()")
+		now = lowPrecisionNow
+	} else {
+		log.Printf("Using high precision timer")
+		now = highPrecisionNow
+	}
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/tracer.go

@@ -0,0 +1,378 @@
+package tracer
+
+import (
+	"errors"
+	"log"
+	"os"
+	"strconv"
+	"time"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
+)
+
+var _ ddtrace.Tracer = (*tracer)(nil)
+
+// tracer creates, buffers and submits Spans which are used to time blocks of
+// computation. They are accumulated and streamed into an internal payload,
+// which is flushed to the agent whenever its size exceeds a specific threshold
+// or when a certain interval of time has passed, whichever happens first.
+//
+// tracer operates based on a worker loop which responds to various request
+// channels. It additionally holds two buffers which accumulates error and trace
+// queues to be processed by the payload encoder.
+type tracer struct {
+	*config
+	*payload
+
+	flushAllReq    chan chan<- struct{}
+	flushTracesReq chan struct{}
+	flushErrorsReq chan struct{}
+	exitReq        chan struct{}
+
+	payloadQueue chan []*span
+	errorBuffer  chan error
+
+	// stopped is a channel that will be closed when the worker has exited.
+	stopped chan struct{}
+
+	// syncPush is used for testing. When non-nil, it causes pushTrace to become
+	// a synchronous (blocking) operation, meaning that it will only return after
+	// the trace has been fully processed and added onto the payload.
+	syncPush chan struct{}
+}
+
+const (
+	// flushInterval is the interval at which the payload contents will be flushed
+	// to the transport.
+	flushInterval = 2 * time.Second
+
+	// payloadMaxLimit is the maximum payload size allowed and should indicate the
+	// maximum size of the package that the agent can receive.
+	payloadMaxLimit = 9.5 * 1024 * 1024 // 9.5 MB
+
+	// payloadSizeLimit specifies the maximum allowed size of the payload before
+	// it will trigger a flush to the transport.
+	payloadSizeLimit = payloadMaxLimit / 2
+)
+
+// Start starts the tracer with the given set of options. It will stop and replace
+// any running tracer, meaning that calling it several times will result in a restart
+// of the tracer by replacing the current instance with a new one.
+func Start(opts ...StartOption) {
+	if internal.Testing {
+		return // mock tracer active
+	}
+	t := internal.GetGlobalTracer()
+	internal.SetGlobalTracer(newTracer(opts...))
+	t.Stop()
+}
+
+// Stop stops the started tracer. Subsequent calls are valid but become no-op.
+func Stop() {
+	internal.SetGlobalTracer(&internal.NoopTracer{})
+}
+
+// Span is an alias for ddtrace.Span. It is here to allow godoc to group methods returning
+// ddtrace.Span. It is recommended and is considered more correct to refer to this type as
+// ddtrace.Span instead.
+type Span = ddtrace.Span
+
+// StartSpan starts a new span with the given operation name and set of options.
+// If the tracer is not started, calling this function is a no-op.
+func StartSpan(operationName string, opts ...StartSpanOption) Span {
+	return internal.GetGlobalTracer().StartSpan(operationName, opts...)
+}
+
+// Extract extracts a SpanContext from the carrier. The carrier is expected
+// to implement TextMapReader, otherwise an error is returned.
+// If the tracer is not started, calling this function is a no-op.
+func Extract(carrier interface{}) (ddtrace.SpanContext, error) {
+	return internal.GetGlobalTracer().Extract(carrier)
+}
+
+// Inject injects the given SpanContext into the carrier. The carrier is
+// expected to implement TextMapWriter, otherwise an error is returned.
+// If the tracer is not started, calling this function is a no-op.
+func Inject(ctx ddtrace.SpanContext, carrier interface{}) error {
+	return internal.GetGlobalTracer().Inject(ctx, carrier)
+}
+
+const (
+	// payloadQueueSize is the buffer size of the trace channel.
+	payloadQueueSize = 1000
+
+	// errorBufferSize is the buffer size of the error channel.
+	errorBufferSize = 200
+)
+
+func newTracer(opts ...StartOption) *tracer {
+	c := new(config)
+	defaults(c)
+	for _, fn := range opts {
+		fn(c)
+	}
+	if c.transport == nil {
+		c.transport = newTransport(c.agentAddr)
+	}
+	if c.propagator == nil {
+		c.propagator = NewPropagator(nil)
+	}
+	t := &tracer{
+		config:         c,
+		payload:        newPayload(),
+		flushAllReq:    make(chan chan<- struct{}),
+		flushTracesReq: make(chan struct{}, 1),
+		flushErrorsReq: make(chan struct{}, 1),
+		exitReq:        make(chan struct{}),
+		payloadQueue:   make(chan []*span, payloadQueueSize),
+		errorBuffer:    make(chan error, errorBufferSize),
+		stopped:        make(chan struct{}),
+	}
+
+	go t.worker()
+
+	return t
+}
+
+// worker receives finished traces to be added into the payload, as well
+// as periodically flushes traces to the transport.
+func (t *tracer) worker() {
+	defer close(t.stopped)
+	ticker := time.NewTicker(flushInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case trace := <-t.payloadQueue:
+			t.pushPayload(trace)
+
+		case <-ticker.C:
+			t.flush()
+
+		case done := <-t.flushAllReq:
+			t.flush()
+			done <- struct{}{}
+
+		case <-t.flushTracesReq:
+			t.flushTraces()
+
+		case <-t.flushErrorsReq:
+			t.flushErrors()
+
+		case <-t.exitReq:
+			t.flush()
+			return
+		}
+	}
+}
+
+func (t *tracer) pushTrace(trace []*span) {
+	select {
+	case <-t.stopped:
+		return
+	default:
+	}
+	select {
+	case t.payloadQueue <- trace:
+	default:
+		t.pushError(&dataLossError{
+			context: errors.New("payload queue full, dropping trace"),
+			count:   len(trace),
+		})
+	}
+	if t.syncPush != nil {
+		// only in tests
+		<-t.syncPush
+	}
+}
+
+func (t *tracer) pushError(err error) {
+	select {
+	case <-t.stopped:
+		return
+	default:
+	}
+	if len(t.errorBuffer) >= cap(t.errorBuffer)/2 { // starts being full, anticipate, try and flush soon
+		select {
+		case t.flushErrorsReq <- struct{}{}:
+		default: // a flush was already requested, skip
+		}
+	}
+	select {
+	case t.errorBuffer <- err:
+	default:
+		// OK, if we get this, our error error buffer is full,
+		// we can assume it is filled with meaningful messages which
+		// are going to be logged and hopefully read, nothing better
+		// we can do, blocking would make things worse.
+	}
+}
+
+// StartSpan creates, starts, and returns a new Span with the given `operationName`.
+func (t *tracer) StartSpan(operationName string, options ...ddtrace.StartSpanOption) ddtrace.Span {
+	var opts ddtrace.StartSpanConfig
+	for _, fn := range options {
+		fn(&opts)
+	}
+	var startTime int64
+	if opts.StartTime.IsZero() {
+		startTime = now()
+	} else {
+		startTime = opts.StartTime.UnixNano()
+	}
+	var context *spanContext
+	if opts.Parent != nil {
+		if ctx, ok := opts.Parent.(*spanContext); ok {
+			context = ctx
+		}
+	}
+	id := random.Uint64()
+	// span defaults
+	span := &span{
+		Name:     operationName,
+		Service:  t.config.serviceName,
+		Resource: operationName,
+		Meta:     map[string]string{},
+		Metrics:  map[string]float64{},
+		SpanID:   id,
+		TraceID:  id,
+		ParentID: 0,
+		Start:    startTime,
+	}
+	if context != nil {
+		// this is a child span
+		span.TraceID = context.traceID
+		span.ParentID = context.spanID
+		if context.hasSamplingPriority() {
+			span.Metrics[samplingPriorityKey] = float64(context.samplingPriority())
+		}
+		if context.span != nil {
+			context.span.RLock()
+			span.Service = context.span.Service
+			context.span.RUnlock()
+		}
+	}
+	span.context = newSpanContext(span, context)
+	if context == nil || context.span == nil {
+		// this is either a global root span or a process-level root span
+		span.SetTag(ext.Pid, strconv.Itoa(os.Getpid()))
+		t.sample(span)
+	}
+	// add tags from options
+	for k, v := range opts.Tags {
+		span.SetTag(k, v)
+	}
+	// add global tags
+	for k, v := range t.config.globalTags {
+		span.SetTag(k, v)
+	}
+	return span
+}
+
+// Stop stops the tracer.
+func (t *tracer) Stop() {
+	select {
+	case <-t.stopped:
+		return
+	default:
+		t.exitReq <- struct{}{}
+		<-t.stopped
+	}
+}
+
+// Inject uses the configured or default TextMap Propagator.
+func (t *tracer) Inject(ctx ddtrace.SpanContext, carrier interface{}) error {
+	return t.config.propagator.Inject(ctx, carrier)
+}
+
+// Extract uses the configured or default TextMap Propagator.
+func (t *tracer) Extract(carrier interface{}) (ddtrace.SpanContext, error) {
+	return t.config.propagator.Extract(carrier)
+}
+
+// flushTraces will push any currently buffered traces to the server.
+func (t *tracer) flushTraces() {
+	if t.payload.itemCount() == 0 {
+		return
+	}
+	size, count := t.payload.size(), t.payload.itemCount()
+	if t.config.debug {
+		log.Printf("Sending payload: size: %d traces: %d\n", size, count)
+	}
+	err := t.config.transport.send(t.payload)
+	if err != nil && size > payloadMaxLimit {
+		// we couldn't send the payload and it is getting too big to be
+		// accepted by the agent, we have to drop it.
+		t.payload.reset()
+		t.pushError(&dataLossError{context: err, count: count})
+	}
+	if err == nil {
+		// send succeeded
+		t.payload.reset()
+	}
+}
+
+// flushErrors will process log messages that were queued
+func (t *tracer) flushErrors() {
+	logErrors(t.errorBuffer)
+}
+
+func (t *tracer) flush() {
+	t.flushTraces()
+	t.flushErrors()
+}
+
+// forceFlush forces a flush of data (traces and services) to the agent.
+// Flushes are done by a background task on a regular basis, so you never
+// need to call this manually, mostly useful for testing and debugging.
+func (t *tracer) forceFlush() {
+	done := make(chan struct{})
+	t.flushAllReq <- done
+	<-done
+}
+
+// pushPayload pushes the trace onto the payload. If the payload becomes
+// larger than the threshold as a result, it sends a flush request.
+func (t *tracer) pushPayload(trace []*span) {
+	if err := t.payload.push(trace); err != nil {
+		t.pushError(&traceEncodingError{context: err})
+	}
+	if t.payload.size() > payloadSizeLimit {
+		// getting large
+		select {
+		case t.flushTracesReq <- struct{}{}:
+		default:
+			// flush already queued
+		}
+	}
+	if t.syncPush != nil {
+		// only in tests
+		t.syncPush <- struct{}{}
+	}
+}
+
+// sampleRateMetricKey is the metric key holding the applied sample rate. Has to be the same as the Agent.
+const sampleRateMetricKey = "_sample_rate"
+
+// Sample samples a span with the internal sampler.
+func (t *tracer) sample(span *span) {
+	sampler := t.config.sampler
+	sampled := sampler.Sample(span)
+	span.context.sampled = sampled
+	if !sampled {
+		return
+	}
+	if rs, ok := sampler.(RateSampler); ok && rs.Rate() < 1 {
+		// the span was sampled using a rate sampler which wasn't all permissive,
+		// so we make note of the sampling rate.
+		span.Lock()
+		defer span.Unlock()
+		if span.finished {
+			// we don't touch finished span as they might be flushing
+			return
+		}
+		span.Metrics[sampleRateMetricKey] = rs.Rate()
+	}
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/transport.go

@@ -0,0 +1,120 @@
+package tracer
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"runtime"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var tracerVersion = "v1.0"
+
+const (
+	defaultHostname    = "localhost"
+	defaultPort        = "8126"
+	defaultAddress     = defaultHostname + ":" + defaultPort
+	defaultHTTPTimeout = time.Second             // defines the current timeout before giving up with the send process
+	traceCountHeader   = "X-Datadog-Trace-Count" // header containing the number of traces in the payload
+)
+
+// Transport is an interface for span submission to the agent.
+type transport interface {
+	send(p *payload) error
+}
+
+// newTransport returns a new Transport implementation that sends traces to a
+// trace agent running on the given hostname and port. If the zero values for
+// hostname and port are provided, the default values will be used ("localhost"
+// for hostname, and "8126" for port).
+//
+// In general, using this method is only necessary if you have a trace agent
+// running on a non-default port or if it's located on another machine.
+func newTransport(addr string) transport {
+	return newHTTPTransport(addr)
+}
+
+// newDefaultTransport return a default transport for this tracing client
+func newDefaultTransport() transport {
+	return newHTTPTransport(defaultAddress)
+}
+
+type httpTransport struct {
+	traceURL string            // the delivery URL for traces
+	client   *http.Client      // the HTTP client used in the POST
+	headers  map[string]string // the Transport headers
+}
+
+// newHTTPTransport returns an httpTransport for the given endpoint
+func newHTTPTransport(addr string) *httpTransport {
+	// initialize the default EncoderPool with Encoder headers
+	defaultHeaders := map[string]string{
+		"Datadog-Meta-Lang":             "go",
+		"Datadog-Meta-Lang-Version":     strings.TrimPrefix(runtime.Version(), "go"),
+		"Datadog-Meta-Lang-Interpreter": runtime.Compiler + "-" + runtime.GOARCH + "-" + runtime.GOOS,
+		"Datadog-Meta-Tracer-Version":   tracerVersion,
+		"Content-Type":                  "application/msgpack",
+	}
+	host, port, _ := net.SplitHostPort(addr)
+	if host == "" {
+		host = defaultHostname
+	}
+	if port == "" {
+		port = defaultPort
+	}
+	addr = fmt.Sprintf("%s:%s", host, port)
+	return &httpTransport{
+		traceURL: fmt.Sprintf("http://%s/v0.3/traces", addr),
+		client: &http.Client{
+			// We copy the transport to avoid using the default one, as it might be
+			// augmented with tracing and we don't want these calls to be recorded.
+			// See https://golang.org/pkg/net/http/#DefaultTransport .
+			Transport: &http.Transport{
+				Proxy: http.ProxyFromEnvironment,
+				DialContext: (&net.Dialer{
+					Timeout:   30 * time.Second,
+					KeepAlive: 30 * time.Second,
+					DualStack: true,
+				}).DialContext,
+				MaxIdleConns:          100,
+				IdleConnTimeout:       90 * time.Second,
+				TLSHandshakeTimeout:   10 * time.Second,
+				ExpectContinueTimeout: 1 * time.Second,
+			},
+			Timeout: defaultHTTPTimeout,
+		},
+		headers: defaultHeaders,
+	}
+}
+
+func (t *httpTransport) send(p *payload) error {
+	// prepare the client and send the payload
+	req, err := http.NewRequest("POST", t.traceURL, p)
+	if err != nil {
+		return fmt.Errorf("cannot create http request: %v", err)
+	}
+	for header, value := range t.headers {
+		req.Header.Set(header, value)
+	}
+	req.Header.Set(traceCountHeader, strconv.Itoa(p.itemCount()))
+	req.Header.Set("Content-Length", strconv.Itoa(p.size()))
+	response, err := t.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+	if code := response.StatusCode; code >= 400 {
+		// error, check the body for context information and
+		// return a nice error.
+		msg := make([]byte, 1000)
+		n, _ := response.Body.Read(msg)
+		txt := http.StatusText(code)
+		if n > 0 {
+			return fmt.Errorf("%s (Status: %s)", msg[:n], txt)
+		}
+		return fmt.Errorf("%s", txt)
+	}
+	return nil
+}

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/util.go

@@ -0,0 +1,32 @@
+package tracer
+
+// toFloat64 attempts to convert value into a float64. If it succeeds it returns
+// the value and true, otherwise 0 and false.
+func toFloat64(value interface{}) (f float64, ok bool) {
+	switch i := value.(type) {
+	case byte:
+		return float64(i), true
+	case float32:
+		return float64(i), true
+	case float64:
+		return i, true
+	case int:
+		return float64(i), true
+	case int16:
+		return float64(i), true
+	case int32:
+		return float64(i), true
+	case int64:
+		return float64(i), true
+	case uint:
+		return float64(i), true
+	case uint16:
+		return float64(i), true
+	case uint32:
+		return float64(i), true
+	case uint64:
+		return float64(i), true
+	default:
+		return 0, false
+	}
+}