tracer.h

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// Copyright 2026 The A11 Authors.
 
#ifndef A11_OBS_TRACER_H_
#define A11_OBS_TRACER_H_
 
#include <string_view>
 
#include "a11/obs/span.h"
#include "a11/obs/trace_context.h"
 
namespace a11::obs {
 
class Tracer {
 public:
  // Starts a span continuing a remote parent recovered from headers. When
  // `parent` is null (or points at an empty context), the span begins a fresh
  // root trace. Baggage carried by the parent is retained for propagation.
  static Span StartSpan(std::string_view name, SpanKind kind,
                        const TraceContext* parent);
 
  // Starts a span parented to an in-process span, inheriting its baggage.
  static Span StartChildSpan(std::string_view name, SpanKind kind,
                             const Span& parent);
 
  // Starts a root span for a session or stream, optionally pinning the trace
  // id (32 lowercase hex chars). An empty `preassigned_trace_id` lets the SDK
  // generate one. This is the implementation-level hook for preassigning trace
  // ids without widening any public transport interface.
  static Span StartRootSpan(std::string_view name, SpanKind kind,
                            std::string_view preassigned_trace_id = {});
};
 
}  // namespace a11::obs
 
#endif  // A11_OBS_TRACER_H_