In my golang application, I've instrumented OTEL tracing middleware with otelmux
middleware and ddotel
tracer provider:
package tracing
import (
"github.com/gorilla/mux"
"go.opentelemetry.io/contrib/instrumentation/github.com/gorilla/mux/otelmux"
ddotel "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentelemetry"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
)
// Middleware returns a tracing middleware that will add a span for each request.
func Middleware(t *TraceProvider) mux.MiddlewareFunc {
sampler := tracer.NewRateSampler(0.1)
provider := ddotel.NewTracerProvider(
tracer.WithSampler(sampler),
tracer.WithRuntimeMetrics(),
)
return otelmux.Middleware("my-service", otelmux.WithTracerProvider(provider))
}
Whenever a trace is attached to a request (considering the sampling rate), I'd like to pull the trace ID from the root span, so I can inject it into a logging API in order to correlate the log from that request with the trace from same request.
So far, I didn't find a straightforward to get the trace ID from the request context.
How can I extract the trace ID?
Thanks for best solution as commented by @hamed-n:
Here is a function to extract the trace ID from the span context using the trace package: "go.opentelemetry.io/otel/trace":
func GetTraceID(ctx context.Context) string {
spanCtx := trace.SpanContextFromContext(ctx)
if spanCtx.HasTraceID() {
traceID := spanCtx.TraceID()
return traceID.String()
}
return ""
}
In my case, since the provider I'm using is DataDog, I had to convert the trace ID to uint64 big endian:
func GetTraceID(ctx context.Context) string {
spanCtx := trace.SpanContextFromContext(ctx)
if spanCtx.HasTraceID() {
// Since datadog trace provider (ddtrace) uses big endian uint64 for the trace ID, we must first to first convert it back to uint64.
traceID := spanCtx.TraceID()
traceIDRaw := [16]byte(traceID)
traceIDUint64 := byteArrToUint64(traceIDRaw[8:])
traceIDStr := strconv.FormatUint(traceIDUint64, 10)
return traceIDStr
}
return ""
}
func byteArrToUint64(buf []byte) uint64 {
var x uint64
for i, b := range buf {
x = x<<8 + uint64(b)
if i == 7 {
return x
}
}
return x
}