frostfs-api-go/pkg/tracing/propagator.go

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package tracing
import (
"context"
"fmt"
"strconv"
"go.opentelemetry.io/otel/propagation"
"go.opentelemetry.io/otel/trace"
)
const (
traceIDHeader = "x-frostfs-trace-id"
spanIDHeader = "x-frostfs-span-id"
flagsHeader = "x-frostfs-trace-flags"
)
const (
flagsSampled = 1 << iota
)
// propagator serializes SpanContext to/from headers.
// x-frostfs-trace-id - TraceID, 16 bytes, hex-string (32 bytes).
// x-frostfs-span-id - SpanID, 8 bytes, hexstring (16 bytes).
// x-frostfs-trace-flags - trace flags (now sampled only).
type propagator struct{}
// Propagator is propagation.TextMapPropagator instance, used to extract/inject trace info from/to remote context.
var Propagator propagation.TextMapPropagator = &propagator{}
// Inject injects tracing info to carrier.
func (p *propagator) Inject(ctx context.Context, carrier propagation.TextMapCarrier) {
sc := trace.SpanFromContext(ctx).SpanContext()
if !sc.TraceID().IsValid() || !sc.SpanID().IsValid() {
return
}
var flags int
if sc.IsSampled() {
flags = flags | flagsSampled
}
carrier.Set(traceIDHeader, sc.TraceID().String())
carrier.Set(spanIDHeader, sc.SpanID().String())
carrier.Set(flagsHeader, fmt.Sprintf("%x", flags))
}
// Extract extracts tracing info from carrier and returns context with tracing info.
// In case of error returns ctx.
func (p *propagator) Extract(ctx context.Context, carrier propagation.TextMapCarrier) context.Context {
spanConfig := trace.SpanContextConfig{}
var err error
traceIDStr := carrier.Get(traceIDHeader)
traceIDDefined := false
if traceIDStr != "" {
traceIDDefined = true
spanConfig.TraceID, err = trace.TraceIDFromHex(traceIDStr)
if err != nil {
return ctx
}
}
spanIDstr := carrier.Get(spanIDHeader)
spanIDDefined := false
if spanIDstr != "" {
spanIDDefined = true
spanConfig.SpanID, err = trace.SpanIDFromHex(spanIDstr)
if err != nil {
return ctx
}
}
if traceIDDefined != spanIDDefined {
return ctx //traceID + spanID must be defined OR no traceID and no spanID
}
flagsStr := carrier.Get(flagsHeader)
if flagsStr != "" {
var v int64
v, err = strconv.ParseInt(flagsStr, 16, 32)
if err != nil {
return ctx
}
if v&flagsSampled == flagsSampled {
spanConfig.TraceFlags = trace.FlagsSampled
}
}
return trace.ContextWithRemoteSpanContext(ctx, trace.NewSpanContext(spanConfig))
}
// Fields returns the keys whose values are set with Inject.
func (p *propagator) Fields() []string {
return []string{traceIDHeader, spanIDHeader, flagsHeader}
}