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Diffstat (limited to 'vendor/github.com/opentracing/opentracing-go/tracer.go')
| -rw-r--r-- | vendor/github.com/opentracing/opentracing-go/tracer.go | 304 |
1 files changed, 304 insertions, 0 deletions
diff --git a/vendor/github.com/opentracing/opentracing-go/tracer.go b/vendor/github.com/opentracing/opentracing-go/tracer.go new file mode 100644 index 00000000..715f0ced --- /dev/null +++ b/vendor/github.com/opentracing/opentracing-go/tracer.go @@ -0,0 +1,304 @@ +package opentracing + +import "time" + +// Tracer is a simple, thin interface for Span creation and SpanContext +// propagation. +type Tracer interface { + + // Create, start, and return a new Span with the given `operationName` and + // incorporate the given StartSpanOption `opts`. (Note that `opts` borrows + // from the "functional options" pattern, per + // http://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis) + // + // A Span with no SpanReference options (e.g., opentracing.ChildOf() or + // opentracing.FollowsFrom()) becomes the root of its own trace. + // + // Examples: + // + // var tracer opentracing.Tracer = ... + // + // // The root-span case: + // sp := tracer.StartSpan("GetFeed") + // + // // The vanilla child span case: + // sp := tracer.StartSpan( + // "GetFeed", + // opentracing.ChildOf(parentSpan.Context())) + // + // // All the bells and whistles: + // sp := tracer.StartSpan( + // "GetFeed", + // opentracing.ChildOf(parentSpan.Context()), + // opentracing.Tag{"user_agent", loggedReq.UserAgent}, + // opentracing.StartTime(loggedReq.Timestamp), + // ) + // + StartSpan(operationName string, opts ...StartSpanOption) Span + + // Inject() takes the `sm` SpanContext instance and injects it for + // propagation within `carrier`. The actual type of `carrier` depends on + // the value of `format`. + // + // OpenTracing defines a common set of `format` values (see BuiltinFormat), + // and each has an expected carrier type. + // + // Other packages may declare their own `format` values, much like the keys + // used by `context.Context` (see https://godoc.org/context#WithValue). + // + // Example usage (sans error handling): + // + // carrier := opentracing.HTTPHeadersCarrier(httpReq.Header) + // err := tracer.Inject( + // span.Context(), + // opentracing.HTTPHeaders, + // carrier) + // + // NOTE: All opentracing.Tracer implementations MUST support all + // BuiltinFormats. + // + // Implementations may return opentracing.ErrUnsupportedFormat if `format` + // is not supported by (or not known by) the implementation. + // + // Implementations may return opentracing.ErrInvalidCarrier or any other + // implementation-specific error if the format is supported but injection + // fails anyway. + // + // See Tracer.Extract(). + Inject(sm SpanContext, format interface{}, carrier interface{}) error + + // Extract() returns a SpanContext instance given `format` and `carrier`. + // + // OpenTracing defines a common set of `format` values (see BuiltinFormat), + // and each has an expected carrier type. + // + // Other packages may declare their own `format` values, much like the keys + // used by `context.Context` (see + // https://godoc.org/golang.org/x/net/context#WithValue). + // + // Example usage (with StartSpan): + // + // + // carrier := opentracing.HTTPHeadersCarrier(httpReq.Header) + // clientContext, err := tracer.Extract(opentracing.HTTPHeaders, carrier) + // + // // ... assuming the ultimate goal here is to resume the trace with a + // // server-side Span: + // var serverSpan opentracing.Span + // if err == nil { + // span = tracer.StartSpan( + // rpcMethodName, ext.RPCServerOption(clientContext)) + // } else { + // span = tracer.StartSpan(rpcMethodName) + // } + // + // + // NOTE: All opentracing.Tracer implementations MUST support all + // BuiltinFormats. + // + // Return values: + // - A successful Extract returns a SpanContext instance and a nil error + // - If there was simply no SpanContext to extract in `carrier`, Extract() + // returns (nil, opentracing.ErrSpanContextNotFound) + // - If `format` is unsupported or unrecognized, Extract() returns (nil, + // opentracing.ErrUnsupportedFormat) + // - If there are more fundamental problems with the `carrier` object, + // Extract() may return opentracing.ErrInvalidCarrier, + // opentracing.ErrSpanContextCorrupted, or implementation-specific + // errors. + // + // See Tracer.Inject(). + Extract(format interface{}, carrier interface{}) (SpanContext, error) +} + +// StartSpanOptions allows Tracer.StartSpan() callers and implementors a +// mechanism to override the start timestamp, specify Span References, and make +// a single Tag or multiple Tags available at Span start time. +// +// StartSpan() callers should look at the StartSpanOption interface and +// implementations available in this package. +// +// Tracer implementations can convert a slice of `StartSpanOption` instances +// into a `StartSpanOptions` struct like so: +// +// func StartSpan(opName string, opts ...opentracing.StartSpanOption) { +// sso := opentracing.StartSpanOptions{} +// for _, o := range opts { +// o.Apply(&sso) +// } +// ... +// } +// +type StartSpanOptions struct { + // Zero or more causal references to other Spans (via their SpanContext). + // If empty, start a "root" Span (i.e., start a new trace). + References []SpanReference + + // StartTime overrides the Span's start time, or implicitly becomes + // time.Now() if StartTime.IsZero(). + StartTime time.Time + + // Tags may have zero or more entries; the restrictions on map values are + // identical to those for Span.SetTag(). May be nil. + // + // If specified, the caller hands off ownership of Tags at + // StartSpan() invocation time. + Tags map[string]interface{} +} + +// StartSpanOption instances (zero or more) may be passed to Tracer.StartSpan. +// +// StartSpanOption borrows from the "functional options" pattern, per +// http://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis +type StartSpanOption interface { + Apply(*StartSpanOptions) +} + +// SpanReferenceType is an enum type describing different categories of +// relationships between two Spans. If Span-2 refers to Span-1, the +// SpanReferenceType describes Span-1 from Span-2's perspective. For example, +// ChildOfRef means that Span-1 created Span-2. +// +// NOTE: Span-1 and Span-2 do *not* necessarily depend on each other for +// completion; e.g., Span-2 may be part of a background job enqueued by Span-1, +// or Span-2 may be sitting in a distributed queue behind Span-1. +type SpanReferenceType int + +const ( + // ChildOfRef refers to a parent Span that caused *and* somehow depends + // upon the new child Span. Often (but not always), the parent Span cannot + // finish until the child Span does. + // + // An timing diagram for a ChildOfRef that's blocked on the new Span: + // + // [-Parent Span---------] + // [-Child Span----] + // + // See http://opentracing.io/spec/ + // + // See opentracing.ChildOf() + ChildOfRef SpanReferenceType = iota + + // FollowsFromRef refers to a parent Span that does not depend in any way + // on the result of the new child Span. For instance, one might use + // FollowsFromRefs to describe pipeline stages separated by queues, + // or a fire-and-forget cache insert at the tail end of a web request. + // + // A FollowsFromRef Span is part of the same logical trace as the new Span: + // i.e., the new Span is somehow caused by the work of its FollowsFromRef. + // + // All of the following could be valid timing diagrams for children that + // "FollowFrom" a parent. + // + // [-Parent Span-] [-Child Span-] + // + // + // [-Parent Span--] + // [-Child Span-] + // + // + // [-Parent Span-] + // [-Child Span-] + // + // See http://opentracing.io/spec/ + // + // See opentracing.FollowsFrom() + FollowsFromRef +) + +// SpanReference is a StartSpanOption that pairs a SpanReferenceType and a +// referenced SpanContext. See the SpanReferenceType documentation for +// supported relationships. If SpanReference is created with +// ReferencedContext==nil, it has no effect. Thus it allows for a more concise +// syntax for starting spans: +// +// sc, _ := tracer.Extract(someFormat, someCarrier) +// span := tracer.StartSpan("operation", opentracing.ChildOf(sc)) +// +// The `ChildOf(sc)` option above will not panic if sc == nil, it will just +// not add the parent span reference to the options. +type SpanReference struct { + Type SpanReferenceType + ReferencedContext SpanContext +} + +// Apply satisfies the StartSpanOption interface. +func (r SpanReference) Apply(o *StartSpanOptions) { + if r.ReferencedContext != nil { + o.References = append(o.References, r) + } +} + +// ChildOf returns a StartSpanOption pointing to a dependent parent span. +// If sc == nil, the option has no effect. +// +// See ChildOfRef, SpanReference +func ChildOf(sc SpanContext) SpanReference { + return SpanReference{ + Type: ChildOfRef, + ReferencedContext: sc, + } +} + +// FollowsFrom returns a StartSpanOption pointing to a parent Span that caused +// the child Span but does not directly depend on its result in any way. +// If sc == nil, the option has no effect. +// +// See FollowsFromRef, SpanReference +func FollowsFrom(sc SpanContext) SpanReference { + return SpanReference{ + Type: FollowsFromRef, + ReferencedContext: sc, + } +} + +// StartTime is a StartSpanOption that sets an explicit start timestamp for the +// new Span. +type StartTime time.Time + +// Apply satisfies the StartSpanOption interface. +func (t StartTime) Apply(o *StartSpanOptions) { + o.StartTime = time.Time(t) +} + +// Tags are a generic map from an arbitrary string key to an opaque value type. +// The underlying tracing system is responsible for interpreting and +// serializing the values. +type Tags map[string]interface{} + +// Apply satisfies the StartSpanOption interface. +func (t Tags) Apply(o *StartSpanOptions) { + if o.Tags == nil { + o.Tags = make(map[string]interface{}) + } + for k, v := range t { + o.Tags[k] = v + } +} + +// Tag may be passed as a StartSpanOption to add a tag to new spans, +// or its Set method may be used to apply the tag to an existing Span, +// for example: +// +// tracer.StartSpan("opName", Tag{"Key", value}) +// +// or +// +// Tag{"key", value}.Set(span) +type Tag struct { + Key string + Value interface{} +} + +// Apply satisfies the StartSpanOption interface. +func (t Tag) Apply(o *StartSpanOptions) { + if o.Tags == nil { + o.Tags = make(map[string]interface{}) + } + o.Tags[t.Key] = t.Value +} + +// Set applies the tag to an existing Span. +func (t Tag) Set(s Span) { + s.SetTag(t.Key, t.Value) +} |