github.com/facebookincubator/go-belt@v0.0.0-20230703220935-39cd348f1a38/tool/experimental/tracer/span.go

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package tracer

import (
	"time"

	"github.com/facebookincubator/go-belt"
	"github.com/facebookincubator/go-belt/pkg/field"
)

// Span is a single time interval.
type Span interface {
	// ID is the ID for the Span. It may have different types, depending
	// on specific implementation of the Tracer.
	//
	// Not all tracing systems may support that.
	ID() any

	// TraceIDs are the set if unique IDs associated with the current context.
	//
	// See the description of belt.TraceIDs.
	//
	// Not all tracing systems may support that.
	TraceIDs() belt.TraceIDs

	// Name is the name of the Span. Usually it explains what happens within
	// this span.
	Name() string

	// StartTS returns the timestamp of the beginning of the Span.
	//
	// Can be zero value if unknown. For example it could
	// happen due sampling, or it could just be not supported
	// byt a specific implementation.
	StartTS() time.Time

	// Fields is the set of structured data attached to the Span.
	Fields() field.AbstractFields

	// Parent is the parent Span. If there is no parent then an untyped nil is returned.
	Parent() Span

	// SetName sets the Name (see the description of method Name).
	SetName(string)

	// Annotate adds an event with the specified timestamp and description to the Span.
	//
	// Not all tracing systems may support that.
	Annotate(ts time.Time, description string)

	// SetField sets a structured field in the Span.
	//
	// Not all tracing systems may support that.
	SetField(field.Key, field.Value)

	// SetField set multiple structured fields at once in the Span.
	//
	// Not all tracing systems may support that.
	SetFields(field.AbstractFields)

	// Finish closes the Span using time.Now() as the ending timestamp and sends it.
	Finish()

	// FinishWithDuration closes the Span using startTS+duration as the ending timestamp and sends it.
	FinishWithDuration(duration time.Duration)

	// Flush forces to immediatelly empty all the buffers (send if something was delayed and so on).
	Flush()
}

var _ belt.Artifact = (Span)(nil)

// Spans is a collection of Span-s.
type Spans []Span

// Earliest returns the Span with the lowest start timestamp.
func (s Spans) Earliest() Span {
	if len(s) == 0 {
		return nil
	}
	earliest := s[0]
	for _, span := range s {
		if span.StartTS().Before(earliest.StartTS()) {
			earliest = span
		}
	}
	return earliest
}