Implementing Distributed Tracing

exp, _ := otlptracegrpc.New(ctx)
tp := sdktrace.NewTracerProvider(
    sdktrace.WithBatcher(exp),
    sdktrace.WithResource(resource.NewSchemaless(
        semconv.ServiceName("user-service"),
    )),
)
otel.SetTracerProvider(tp)
otel.SetTextMapPropagator(propagation.TraceContext{})

import "go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
conn, _ := grpc.NewClient(addr,
    grpc.WithStatsHandler(otelgrpc.NewClientHandler()),
    grpc.WithTransportCredentials(creds),
)

srv := grpc.NewServer(grpc.StatsHandler(otelgrpc.NewServerHandler()))

ctx, span := otel.Tracer("user").Start(ctx, "LoadFromDB")
defer span.End()

span.SetAttributes(
    attribute.String("user.id", id),
    attribute.Int("db.rows", n),
)

span.AddEvent("cache.miss", trace.WithAttributes(attribute.String("key", k)))
if err != nil {
    span.RecordError(err)
    span.SetStatus(otelcodes.Error, err.Error())
}

sc := trace.SpanContextFromContext(ctx)
slog.InfoContext(ctx, "processed",
    slog.String("trace_id", sc.TraceID().String()),
    slog.String("span_id", sc.SpanID().String()),
)