[Vendor] Update go-redis to v8.5.0 (#13749)

* Update go-redis to v8.4.0

* github.com/go-redis/redis/v8  v8.4.0 -> v8.5.0

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

* TODO

* Use the Queue termination channel as the default context for pushes

Signed-off-by: Andrew Thornton <art27@cantab.net>

* missed one

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>

vendor/go.opentelemetry.io/otel/trace/config.go

@@ -0,0 +1,196 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"time"
+
+	"go.opentelemetry.io/otel/label"
+)
+
+// TracerConfig is a group of options for a Tracer.
+type TracerConfig struct {
+	// InstrumentationVersion is the version of the library providing
+	// instrumentation.
+	InstrumentationVersion string
+}
+
+// NewTracerConfig applies all the options to a returned TracerConfig.
+func NewTracerConfig(options ...TracerOption) *TracerConfig {
+	config := new(TracerConfig)
+	for _, option := range options {
+		option.ApplyTracer(config)
+	}
+	return config
+}
+
+// TracerOption applies an option to a TracerConfig.
+type TracerOption interface {
+	ApplyTracer(*TracerConfig)
+}
+
+// SpanConfig is a group of options for a Span.
+type SpanConfig struct {
+	// Attributes describe the associated qualities of a Span.
+	Attributes []label.KeyValue
+	// Timestamp is a time in a Span life-cycle.
+	Timestamp time.Time
+	// Links are the associations a Span has with other Spans.
+	Links []Link
+	// Record is the recording state of a Span.
+	Record bool
+	// NewRoot identifies a Span as the root Span for a new trace. This is
+	// commonly used when an existing trace crosses trust boundaries and the
+	// remote parent span context should be ignored for security.
+	NewRoot bool
+	// SpanKind is the role a Span has in a trace.
+	SpanKind SpanKind
+}
+
+// NewSpanConfig applies all the options to a returned SpanConfig.
+// No validation is performed on the returned SpanConfig (e.g. no uniqueness
+// checking or bounding of data), it is left to the SDK to perform this
+// action.
+func NewSpanConfig(options ...SpanOption) *SpanConfig {
+	c := new(SpanConfig)
+	for _, option := range options {
+		option.ApplySpan(c)
+	}
+	return c
+}
+
+// SpanOption applies an option to a SpanConfig.
+type SpanOption interface {
+	ApplySpan(*SpanConfig)
+}
+
+// NewEventConfig applies all the EventOptions to a returned SpanConfig. If no
+// timestamp option is passed, the returned SpanConfig will have a Timestamp
+// set to the call time, otherwise no validation is performed on the returned
+// SpanConfig.
+func NewEventConfig(options ...EventOption) *SpanConfig {
+	c := new(SpanConfig)
+	for _, option := range options {
+		option.ApplyEvent(c)
+	}
+	if c.Timestamp.IsZero() {
+		c.Timestamp = time.Now()
+	}
+	return c
+}
+
+// EventOption applies span event options to a SpanConfig.
+type EventOption interface {
+	ApplyEvent(*SpanConfig)
+}
+
+// LifeCycleOption applies span life-cycle options to a SpanConfig. These
+// options set values releated to events in a spans life-cycle like starting,
+// ending, experiencing an error and other user defined notable events.
+type LifeCycleOption interface {
+	SpanOption
+	EventOption
+}
+
+type attributeSpanOption []label.KeyValue
+
+func (o attributeSpanOption) ApplySpan(c *SpanConfig)  { o.apply(c) }
+func (o attributeSpanOption) ApplyEvent(c *SpanConfig) { o.apply(c) }
+func (o attributeSpanOption) apply(c *SpanConfig) {
+	c.Attributes = append(c.Attributes, []label.KeyValue(o)...)
+}
+
+// WithAttributes adds the attributes related to a span life-cycle event.
+// These attributes are used to describe the work a Span represents when this
+// option is provided to a Span's start or end events. Otherwise, these
+// attributes provide additional information about the event being recorded
+// (e.g. error, state change, processing progress, system event).
+//
+// If multiple of these options are passed the attributes of each successive
+// option will extend the attributes instead of overwriting. There is no
+// guarantee of uniqueness in the resulting attributes.
+func WithAttributes(attributes ...label.KeyValue) LifeCycleOption {
+	return attributeSpanOption(attributes)
+}
+
+type timestampSpanOption time.Time
+
+func (o timestampSpanOption) ApplySpan(c *SpanConfig)  { o.apply(c) }
+func (o timestampSpanOption) ApplyEvent(c *SpanConfig) { o.apply(c) }
+func (o timestampSpanOption) apply(c *SpanConfig)      { c.Timestamp = time.Time(o) }
+
+// WithTimestamp sets the time of a Span life-cycle moment (e.g. started,
+// stopped, errored).
+func WithTimestamp(t time.Time) LifeCycleOption {
+	return timestampSpanOption(t)
+}
+
+type linksSpanOption []Link
+
+func (o linksSpanOption) ApplySpan(c *SpanConfig) { c.Links = append(c.Links, []Link(o)...) }
+
+// WithLinks adds links to a Span. The links are added to the existing Span
+// links, i.e. this does not overwrite.
+func WithLinks(links ...Link) SpanOption {
+	return linksSpanOption(links)
+}
+
+type recordSpanOption bool
+
+func (o recordSpanOption) ApplySpan(c *SpanConfig) { c.Record = bool(o) }
+
+// WithRecord specifies that the span should be recorded. It is important to
+// note that implementations may override this option, i.e. if the span is a
+// child of an un-sampled trace.
+func WithRecord() SpanOption {
+	return recordSpanOption(true)
+}
+
+type newRootSpanOption bool
+
+func (o newRootSpanOption) ApplySpan(c *SpanConfig) { c.NewRoot = bool(o) }
+
+// WithNewRoot specifies that the Span should be treated as a root Span. Any
+// existing parent span context will be ignored when defining the Span's trace
+// identifiers.
+func WithNewRoot() SpanOption {
+	return newRootSpanOption(true)
+}
+
+type spanKindSpanOption SpanKind
+
+func (o spanKindSpanOption) ApplySpan(c *SpanConfig) { c.SpanKind = SpanKind(o) }
+
+// WithSpanKind sets the SpanKind of a Span.
+func WithSpanKind(kind SpanKind) SpanOption {
+	return spanKindSpanOption(kind)
+}
+
+// InstrumentationOption is an interface for applying instrumentation specific
+// options.
+type InstrumentationOption interface {
+	TracerOption
+}
+
+// WithInstrumentationVersion sets the instrumentation version.
+func WithInstrumentationVersion(version string) InstrumentationOption {
+	return instrumentationVersionOption(version)
+}
+
+type instrumentationVersionOption string
+
+func (i instrumentationVersionOption) ApplyTracer(config *TracerConfig) {
+	config.InstrumentationVersion = string(i)
+}

vendor/go.opentelemetry.io/otel/trace/doc.go

@@ -0,0 +1,70 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/*
+Package trace provides an implementation of the tracing part of the
+OpenTelemetry API.
+
+This package is currently in a pre-GA phase. Backwards incompatible changes
+may be introduced in subsequent minor version releases as we work to track the
+evolving OpenTelemetry specification and user feedback.
+
+To participate in distributed traces a Span needs to be created for the
+operation being performed as part of a traced workflow. It its simplest form:
+
+	var tracer trace.Tracer
+
+	func init() {
+		tracer = otel.Tracer("instrumentation/package/name")
+	}
+
+	func operation(ctx context.Context) {
+		var span trace.Span
+		ctx, span = tracer.Start(ctx, "operation")
+		defer span.End()
+		// ...
+	}
+
+A Tracer is unique to the instrumentation and is used to create Spans.
+Instrumentation should be designed to accept a TracerProvider from which it
+can create its own unique Tracer. Alternatively, the registered global
+TracerProvider from the go.opentelemetry.io/otel package can be used as
+a default.
+
+	const (
+		name    = "instrumentation/package/name"
+		version = "0.1.0"
+	)
+
+	type Instrumentation struct {
+		tracer trace.Tracer
+	}
+
+	func NewInstrumentation(tp trace.TracerProvider) *Instrumentation {
+		if tp == nil {
+			tp = otel.TracerProvider()
+		}
+		return &Instrumentation{
+			tracer: tp.Tracer(name, trace.WithInstrumentationVersion(version)),
+		}
+	}
+
+	func operation(ctx context.Context, inst *Instrumentation) {
+		var span trace.Span
+		ctx, span = inst.tracer.Start(ctx, "operation")
+		defer span.End()
+		// ...
+	}
+*/
+package trace // import "go.opentelemetry.io/otel/trace"

vendor/go.opentelemetry.io/otel/trace/trace.go

@@ -0,0 +1,549 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace // import "go.opentelemetry.io/otel/trace"
+
+import (
+	"bytes"
+	"context"
+	"encoding/hex"
+	"encoding/json"
+	"regexp"
+	"strings"
+
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/label"
+)
+
+const (
+	// FlagsSampled is a bitmask with the sampled bit set. A SpanContext
+	// with the sampling bit set means the span is sampled.
+	FlagsSampled = byte(0x01)
+	// FlagsDeferred is a bitmask with the deferred bit set. A SpanContext
+	// with the deferred bit set means the sampling decision has been
+	// defered to the receiver.
+	FlagsDeferred = byte(0x02)
+	// FlagsDebug is a bitmask with the debug bit set.
+	FlagsDebug = byte(0x04)
+
+	errInvalidHexID errorConst = "trace-id and span-id can only contain [0-9a-f] characters, all lowercase"
+
+	errInvalidTraceIDLength errorConst = "hex encoded trace-id must have length equals to 32"
+	errNilTraceID           errorConst = "trace-id can't be all zero"
+
+	errInvalidSpanIDLength errorConst = "hex encoded span-id must have length equals to 16"
+	errNilSpanID           errorConst = "span-id can't be all zero"
+
+	// based on the W3C Trace Context specification, see https://www.w3.org/TR/trace-context-1/#tracestate-header
+	traceStateKeyFormat                      = `[a-z][_0-9a-z\-\*\/]{0,255}`
+	traceStateKeyFormatWithMultiTenantVendor = `[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}`
+	traceStateValueFormat                    = `[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]`
+
+	traceStateMaxListMembers = 32
+
+	errInvalidTraceStateKeyValue errorConst = "provided key or value is not valid according to the" +
+		" W3C Trace Context specification"
+	errInvalidTraceStateMembersNumber errorConst = "trace state would exceed the maximum limit of members (32)"
+	errInvalidTraceStateDuplicate     errorConst = "trace state key/value pairs with duplicate keys provided"
+)
+
+type errorConst string
+
+func (e errorConst) Error() string {
+	return string(e)
+}
+
+// TraceID is a unique identity of a trace.
+// nolint:golint
+type TraceID [16]byte
+
+var nilTraceID TraceID
+var _ json.Marshaler = nilTraceID
+
+// IsValid checks whether the trace TraceID is valid. A valid trace ID does
+// not consist of zeros only.
+func (t TraceID) IsValid() bool {
+	return !bytes.Equal(t[:], nilTraceID[:])
+}
+
+// MarshalJSON implements a custom marshal function to encode TraceID
+// as a hex string.
+func (t TraceID) MarshalJSON() ([]byte, error) {
+	return json.Marshal(t.String())
+}
+
+// String returns the hex string representation form of a TraceID
+func (t TraceID) String() string {
+	return hex.EncodeToString(t[:])
+}
+
+// SpanID is a unique identity of a span in a trace.
+type SpanID [8]byte
+
+var nilSpanID SpanID
+var _ json.Marshaler = nilSpanID
+
+// IsValid checks whether the SpanID is valid. A valid SpanID does not consist
+// of zeros only.
+func (s SpanID) IsValid() bool {
+	return !bytes.Equal(s[:], nilSpanID[:])
+}
+
+// MarshalJSON implements a custom marshal function to encode SpanID
+// as a hex string.
+func (s SpanID) MarshalJSON() ([]byte, error) {
+	return json.Marshal(s.String())
+}
+
+// String returns the hex string representation form of a SpanID
+func (s SpanID) String() string {
+	return hex.EncodeToString(s[:])
+}
+
+// TraceIDFromHex returns a TraceID from a hex string if it is compliant with
+// the W3C trace-context specification.  See more at
+// https://www.w3.org/TR/trace-context/#trace-id
+// nolint:golint
+func TraceIDFromHex(h string) (TraceID, error) {
+	t := TraceID{}
+	if len(h) != 32 {
+		return t, errInvalidTraceIDLength
+	}
+
+	if err := decodeHex(h, t[:]); err != nil {
+		return t, err
+	}
+
+	if !t.IsValid() {
+		return t, errNilTraceID
+	}
+	return t, nil
+}
+
+// SpanIDFromHex returns a SpanID from a hex string if it is compliant
+// with the w3c trace-context specification.
+// See more at https://www.w3.org/TR/trace-context/#parent-id
+func SpanIDFromHex(h string) (SpanID, error) {
+	s := SpanID{}
+	if len(h) != 16 {
+		return s, errInvalidSpanIDLength
+	}
+
+	if err := decodeHex(h, s[:]); err != nil {
+		return s, err
+	}
+
+	if !s.IsValid() {
+		return s, errNilSpanID
+	}
+	return s, nil
+}
+
+func decodeHex(h string, b []byte) error {
+	for _, r := range h {
+		switch {
+		case 'a' <= r && r <= 'f':
+			continue
+		case '0' <= r && r <= '9':
+			continue
+		default:
+			return errInvalidHexID
+		}
+	}
+
+	decoded, err := hex.DecodeString(h)
+	if err != nil {
+		return err
+	}
+
+	copy(b, decoded)
+	return nil
+}
+
+// TraceState provides additional vendor-specific trace identification information
+// across different distributed tracing systems. It represents an immutable list consisting
+// of key/value pairs. There can be a maximum of 32 entries in the list.
+//
+// Key and value of each list member must be valid according to the W3C Trace Context specification
+// (see https://www.w3.org/TR/trace-context-1/#key and https://www.w3.org/TR/trace-context-1/#value
+// respectively).
+//
+// Trace state must be valid according to the W3C Trace Context specification at all times. All
+// mutating operations validate their input and, in case of valid parameters, return a new TraceState.
+type TraceState struct { //nolint:golint
+	// TODO @matej-g: Consider implementing this as label.Set, see
+	// comment https://github.com/open-telemetry/opentelemetry-go/pull/1340#discussion_r540599226
+	kvs []label.KeyValue
+}
+
+var _ json.Marshaler = TraceState{}
+var keyFormatRegExp = regexp.MustCompile(
+	`^((` + traceStateKeyFormat + `)|(` + traceStateKeyFormatWithMultiTenantVendor + `))$`,
+)
+var valueFormatRegExp = regexp.MustCompile(`^(` + traceStateValueFormat + `)$`)
+
+// MarshalJSON implements a custom marshal function to encode trace state.
+func (ts TraceState) MarshalJSON() ([]byte, error) {
+	return json.Marshal(ts.kvs)
+}
+
+// String returns trace state as a string valid according to the
+// W3C Trace Context specification.
+func (ts TraceState) String() string {
+	var sb strings.Builder
+
+	for i, kv := range ts.kvs {
+		sb.WriteString((string)(kv.Key))
+		sb.WriteByte('=')
+		sb.WriteString(kv.Value.Emit())
+
+		if i != len(ts.kvs)-1 {
+			sb.WriteByte(',')
+		}
+	}
+
+	return sb.String()
+}
+
+// Get returns a value for given key from the trace state.
+// If no key is found or provided key is invalid, returns an empty value.
+func (ts TraceState) Get(key label.Key) label.Value {
+	if !isTraceStateKeyValid(key) {
+		return label.Value{}
+	}
+
+	for _, kv := range ts.kvs {
+		if kv.Key == key {
+			return kv.Value
+		}
+	}
+
+	return label.Value{}
+}
+
+// Insert adds a new key/value, if one doesn't exists; otherwise updates the existing entry.
+// The new or updated entry is always inserted at the beginning of the TraceState, i.e.
+// on the left side, as per the W3C Trace Context specification requirement.
+func (ts TraceState) Insert(entry label.KeyValue) (TraceState, error) {
+	if !isTraceStateKeyValueValid(entry) {
+		return ts, errInvalidTraceStateKeyValue
+	}
+
+	ckvs := ts.copyKVsAndDeleteEntry(entry.Key)
+	if len(ckvs)+1 > traceStateMaxListMembers {
+		return ts, errInvalidTraceStateMembersNumber
+	}
+
+	ckvs = append(ckvs, label.KeyValue{})
+	copy(ckvs[1:], ckvs)
+	ckvs[0] = entry
+
+	return TraceState{ckvs}, nil
+}
+
+// Delete removes specified entry from the trace state.
+func (ts TraceState) Delete(key label.Key) (TraceState, error) {
+	if !isTraceStateKeyValid(key) {
+		return ts, errInvalidTraceStateKeyValue
+	}
+
+	return TraceState{ts.copyKVsAndDeleteEntry(key)}, nil
+}
+
+// IsEmpty returns true if the TraceState does not contain any entries
+func (ts TraceState) IsEmpty() bool {
+	return len(ts.kvs) == 0
+}
+
+func (ts TraceState) copyKVsAndDeleteEntry(key label.Key) []label.KeyValue {
+	ckvs := make([]label.KeyValue, len(ts.kvs))
+	copy(ckvs, ts.kvs)
+	for i, kv := range ts.kvs {
+		if kv.Key == key {
+			ckvs = append(ckvs[:i], ckvs[i+1:]...)
+			break
+		}
+	}
+
+	return ckvs
+}
+
+// TraceStateFromKeyValues is a convenience method to create a new TraceState from
+// provided key/value pairs.
+func TraceStateFromKeyValues(kvs ...label.KeyValue) (TraceState, error) { //nolint:golint
+	if len(kvs) == 0 {
+		return TraceState{}, nil
+	}
+
+	if len(kvs) > traceStateMaxListMembers {
+		return TraceState{}, errInvalidTraceStateMembersNumber
+	}
+
+	km := make(map[label.Key]bool)
+	for _, kv := range kvs {
+		if !isTraceStateKeyValueValid(kv) {
+			return TraceState{}, errInvalidTraceStateKeyValue
+		}
+		_, ok := km[kv.Key]
+		if ok {
+			return TraceState{}, errInvalidTraceStateDuplicate
+		}
+		km[kv.Key] = true
+	}
+
+	ckvs := make([]label.KeyValue, len(kvs))
+	copy(ckvs, kvs)
+	return TraceState{ckvs}, nil
+}
+
+func isTraceStateKeyValid(key label.Key) bool {
+	return keyFormatRegExp.MatchString(string(key))
+}
+
+func isTraceStateKeyValueValid(kv label.KeyValue) bool {
+	return isTraceStateKeyValid(kv.Key) &&
+		valueFormatRegExp.MatchString(kv.Value.Emit())
+}
+
+// SpanContext contains identifying trace information about a Span.
+type SpanContext struct {
+	TraceID    TraceID
+	SpanID     SpanID
+	TraceFlags byte
+	TraceState TraceState
+}
+
+// IsValid returns if the SpanContext is valid. A valid span context has a
+// valid TraceID and SpanID.
+func (sc SpanContext) IsValid() bool {
+	return sc.HasTraceID() && sc.HasSpanID()
+}
+
+// HasTraceID checks if the SpanContext has a valid TraceID.
+func (sc SpanContext) HasTraceID() bool {
+	return sc.TraceID.IsValid()
+}
+
+// HasSpanID checks if the SpanContext has a valid SpanID.
+func (sc SpanContext) HasSpanID() bool {
+	return sc.SpanID.IsValid()
+}
+
+// IsDeferred returns if the deferred bit is set in the trace flags.
+func (sc SpanContext) IsDeferred() bool {
+	return sc.TraceFlags&FlagsDeferred == FlagsDeferred
+}
+
+// IsDebug returns if the debug bit is set in the trace flags.
+func (sc SpanContext) IsDebug() bool {
+	return sc.TraceFlags&FlagsDebug == FlagsDebug
+}
+
+// IsSampled returns if the sampling bit is set in the trace flags.
+func (sc SpanContext) IsSampled() bool {
+	return sc.TraceFlags&FlagsSampled == FlagsSampled
+}
+
+type traceContextKeyType int
+
+const (
+	currentSpanKey traceContextKeyType = iota
+	remoteContextKey
+)
+
+// ContextWithSpan returns a copy of parent with span set to current.
+func ContextWithSpan(parent context.Context, span Span) context.Context {
+	return context.WithValue(parent, currentSpanKey, span)
+}
+
+// SpanFromContext returns the current span from ctx, or noop span if none set.
+func SpanFromContext(ctx context.Context) Span {
+	if span, ok := ctx.Value(currentSpanKey).(Span); ok {
+		return span
+	}
+	return noopSpan{}
+}
+
+// SpanContextFromContext returns the current SpanContext from ctx, or an empty SpanContext if none set.
+func SpanContextFromContext(ctx context.Context) SpanContext {
+	if span := SpanFromContext(ctx); span != nil {
+		return span.SpanContext()
+	}
+	return SpanContext{}
+}
+
+// ContextWithRemoteSpanContext returns a copy of parent with a remote set as
+// the remote span context.
+func ContextWithRemoteSpanContext(parent context.Context, remote SpanContext) context.Context {
+	return context.WithValue(parent, remoteContextKey, remote)
+}
+
+// RemoteSpanContextFromContext returns the remote span context from ctx.
+func RemoteSpanContextFromContext(ctx context.Context) SpanContext {
+	if sc, ok := ctx.Value(remoteContextKey).(SpanContext); ok {
+		return sc
+	}
+	return SpanContext{}
+}
+
+// Span is the individual component of a trace. It represents a single named
+// and timed operation of a workflow that is traced. A Tracer is used to
+// create a Span and it is then up to the operation the Span represents to
+// properly end the Span when the operation itself ends.
+type Span interface {
+	// Tracer returns the Tracer that created the Span. Tracer MUST NOT be
+	// nil.
+	Tracer() Tracer
+
+	// End completes the Span. The Span is considered complete and ready to be
+	// delivered through the rest of the telemetry pipeline after this method
+	// is called. Therefore, updates to the Span are not allowed after this
+	// method has been called.
+	End(options ...SpanOption)
+
+	// AddEvent adds an event with the provided name and options.
+	AddEvent(name string, options ...EventOption)
+
+	// IsRecording returns the recording state of the Span. It will return
+	// true if the Span is active and events can be recorded.
+	IsRecording() bool
+
+	// RecordError records an error as a Span event.
+	RecordError(err error, options ...EventOption)
+
+	// SpanContext returns the SpanContext of the Span. The returned
+	// SpanContext is usable even after the End has been called for the Span.
+	SpanContext() SpanContext
+
+	// SetStatus sets the status of the Span in the form of a code and a
+	// message. SetStatus overrides the value of previous calls to SetStatus
+	// on the Span.
+	SetStatus(code codes.Code, msg string)
+
+	// SetName sets the Span name.
+	SetName(name string)
+
+	// SetAttributes sets kv as attributes of the Span. If a key from kv
+	// already exists for an attribute of the Span it will be overwritten with
+	// the value contained in kv.
+	SetAttributes(kv ...label.KeyValue)
+}
+
+// Link is the relationship between two Spans. The relationship can be within
+// the same Trace or across different Traces.
+//
+// For example, a Link is used in the following situations:
+//
+//   1. Batch Processing: A batch of operations may contain operations
+//      associated with one or more traces/spans. Since there can only be one
+//      parent SpanContext, a Link is used to keep reference to the
+//      SpanContext of all operations in the batch.
+//   2. Public Endpoint: A SpanContext for an in incoming client request on a
+//      public endpoint should be considered untrusted. In such a case, a new
+//      trace with its own identity and sampling decision needs to be created,
+//      but this new trace needs to be related to the original trace in some
+//      form. A Link is used to keep reference to the original SpanContext and
+//      track the relationship.
+type Link struct {
+	SpanContext
+	Attributes []label.KeyValue
+}
+
+// SpanKind is the role a Span plays in a Trace.
+type SpanKind int
+
+// As a convenience, these match the proto definition, see
+// https://github.com/open-telemetry/opentelemetry-proto/blob/30d237e1ff3ab7aa50e0922b5bebdd93505090af/opentelemetry/proto/trace/v1/trace.proto#L101-L129
+//
+// The unspecified value is not a valid `SpanKind`. Use `ValidateSpanKind()`
+// to coerce a span kind to a valid value.
+const (
+	// SpanKindUnspecified is an unspecified SpanKind and is not a valid
+	// SpanKind. SpanKindUnspecified should be replaced with SpanKindInternal
+	// if it is received.
+	SpanKindUnspecified SpanKind = 0
+	// SpanKindInternal is a SpanKind for a Span that represents an internal
+	// operation within an application.
+	SpanKindInternal SpanKind = 1
+	// SpanKindServer is a SpanKind for a Span that represents the operation
+	// of handling a request from a client.
+	SpanKindServer SpanKind = 2
+	// SpanKindClient is a SpanKind for a Span that represents the operation
+	// of client making a request to a server.
+	SpanKindClient SpanKind = 3
+	// SpanKindProducer is a SpanKind for a Span that represents the operation
+	// of a producer sending a message to a message broker. Unlike
+	// SpanKindClient and SpanKindServer, there is often no direct
+	// relationship between this kind of Span and a SpanKindConsumer kind. A
+	// SpanKindProducer Span will end once the message is accepted by the
+	// message broker which might not overlap with the processing of that
+	// message.
+	SpanKindProducer SpanKind = 4
+	// SpanKindConsumer is a SpanKind for a Span that represents the operation
+	// of a consumer receiving a message from a message broker. Like
+	// SpanKindProducer Spans, there is often no direct relationship between
+	// this Span and the Span that produced the message.
+	SpanKindConsumer SpanKind = 5
+)
+
+// ValidateSpanKind returns a valid span kind value.  This will coerce
+// invalid values into the default value, SpanKindInternal.
+func ValidateSpanKind(spanKind SpanKind) SpanKind {
+	switch spanKind {
+	case SpanKindInternal,
+		SpanKindServer,
+		SpanKindClient,
+		SpanKindProducer,
+		SpanKindConsumer:
+		// valid
+		return spanKind
+	default:
+		return SpanKindInternal
+	}
+}
+
+// String returns the specified name of the SpanKind in lower-case.
+func (sk SpanKind) String() string {
+	switch sk {
+	case SpanKindInternal:
+		return "internal"
+	case SpanKindServer:
+		return "server"
+	case SpanKindClient:
+		return "client"
+	case SpanKindProducer:
+		return "producer"
+	case SpanKindConsumer:
+		return "consumer"
+	default:
+		return "unspecified"
+	}
+}
+
+// Tracer is the creator of Spans.
+type Tracer interface {
+	// Start creates a span.
+	Start(ctx context.Context, spanName string, opts ...SpanOption) (context.Context, Span)
+}
+
+// TracerProvider provides access to instrumentation Tracers.
+type TracerProvider interface {
+	// Tracer creates an implementation of the Tracer interface.
+	// The instrumentationName must be the name of the library providing
+	// instrumentation. This name may be the same as the instrumented code
+	// only if that code provides built-in instrumentation. If the
+	// instrumentationName is empty, then a implementation defined default
+	// name will be used instead.
+	Tracer(instrumentationName string, opts ...TracerOption) Tracer
+}

vendor/go.opentelemetry.io/otel/trace/trace_noop.go

@@ -0,0 +1,84 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace // import "go.opentelemetry.io/otel/trace"
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/label"
+)
+
+// NewNoopTracerProvider returns an implementation of TracerProvider that
+// performs no operations. The Tracer and Spans created from the returned
+// TracerProvider also perform no operations.
+func NewNoopTracerProvider() TracerProvider {
+	return noopTracerProvider{}
+}
+
+type noopTracerProvider struct{}
+
+var _ TracerProvider = noopTracerProvider{}
+
+// Tracer returns noop implementation of Tracer.
+func (p noopTracerProvider) Tracer(string, ...TracerOption) Tracer {
+	return noopTracer{}
+}
+
+// noopTracer is an implementation of Tracer that preforms no operations.
+type noopTracer struct{}
+
+var _ Tracer = noopTracer{}
+
+// Start starts a noop span.
+func (t noopTracer) Start(ctx context.Context, name string, _ ...SpanOption) (context.Context, Span) {
+	span := noopSpan{}
+	return ContextWithSpan(ctx, span), span
+}
+
+// noopSpan is an implementation of Span that preforms no operations.
+type noopSpan struct{}
+
+var _ noopSpan = noopSpan{}
+
+// SpanContext returns an empty span context.
+func (noopSpan) SpanContext() SpanContext { return SpanContext{} }
+
+// IsRecording always returns false.
+func (noopSpan) IsRecording() bool { return false }
+
+// SetStatus does nothing.
+func (noopSpan) SetStatus(codes.Code, string) {}
+
+// SetError does nothing.
+func (noopSpan) SetError(bool) {}
+
+// SetAttributes does nothing.
+func (noopSpan) SetAttributes(...label.KeyValue) {}
+
+// End does nothing.
+func (noopSpan) End(...SpanOption) {}
+
+// RecordError does nothing.
+func (noopSpan) RecordError(error, ...EventOption) {}
+
+// Tracer returns the Tracer that created this Span.
+func (noopSpan) Tracer() Tracer { return noopTracer{} }
+
+// AddEvent does nothing.
+func (noopSpan) AddEvent(string, ...EventOption) {}
+
+// SetName does nothing.
+func (noopSpan) SetName(string) {}