tracing/scoped_tracer_factory.h

// Copyright 2026 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#ifndef THIRD_PARTY_CREDENTIO_TRACING_SCOPED_TRACER_FACTORY_H_
#define THIRD_PARTY_CREDENTIO_TRACING_SCOPED_TRACER_FACTORY_H_

#include <memory>

#include "absl/base/nullability.h"
#include "tracing/tracer_factory.h"

namespace credentio_tracing {

// RAII guard that installs a TracerFactory for the current thread during its
// lifetime and restores the previous one upon destruction.
//
// Installing and clearing a thread-local factory by hand is error prone: the
// two calls must run on the same thread, which is easy to get wrong when the
// work in between hops to a callback or a dispatch queue. This guard makes
// that mistake unrepresentable for synchronous scopes.
//
// It only covers work performed on the calling thread. To scope tracing to an
// asynchronous operation, carry the factory on the operation's
// `credentio::AsyncContext` instead.
class ScopedTracerFactory {
 public:
  // Installs `factory` as the calling thread's factory.
  explicit ScopedTracerFactory(
      absl_nullable std::shared_ptr<TracerFactory> factory);

  // Restores the previously installed thread-local factory.
  ~ScopedTracerFactory();

  ScopedTracerFactory(const ScopedTracerFactory&) = delete;
  ScopedTracerFactory& operator=(const ScopedTracerFactory&) = delete;
  ScopedTracerFactory(ScopedTracerFactory&&) = delete;
  ScopedTracerFactory& operator=(ScopedTracerFactory&&) = delete;

 private:
  absl_nullable std::shared_ptr<TracerFactory> previous_factory_;
};

}  // namespace credentio_tracing

#endif  // THIRD_PARTY_CREDENTIO_TRACING_SCOPED_TRACER_FACTORY_H_