debug/trace.h

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/*
 *
 * Copyright 2015 gRPC authors.
 *
 * 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
 *
 *     http://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 GRPC_CORE_LIB_DEBUG_TRACE_H
#define GRPC_CORE_LIB_DEBUG_TRACE_H
 
#if defined(__has_feature)
#if __has_feature(thread_sanitizer)
#define GRPC_THREADSAFE_TRACER
#endif
#endif
 
#include <grpc/support/port_platform.h>
 
#ifdef GRPC_THREADSAFE_TRACER
#include <atomic>
#endif
 
#include "src/core/lib/gprpp/global_config.h"
#include "src/core/lib/gprpp/memory.h"
 
GPR_GLOBAL_CONFIG_DECLARE_STRING(grpc_trace);
 
// TODO(veblush): Remove this deprecated function once codes depending on this
// function are updated in the internal repo.
void grpc_tracer_init(const char* env_var_name);
 
void grpc_tracer_init();
void grpc_tracer_shutdown(void);
 
namespace grpc_core {
 
class TraceFlag;
class TraceFlagList {
 public:
  static bool Set(const char* name, bool enabled);
  static void Add(TraceFlag* flag);
 
 private:
  static void LogAllTracers();
  static TraceFlag* root_tracer_;
};
 
namespace testing {
void grpc_tracer_enable_flag(TraceFlag* flag);
}
 
class TraceFlag {
 public:
  TraceFlag(bool default_enabled, const char* name);
  // TraceFlag needs to be trivially destructible since it is used as global
  // variable.
  ~TraceFlag() = default;
 
  const char* name() const { return name_; }
 
// Use the symbol GRPC_USE_TRACERS to determine if tracers will be enabled in
// opt builds (tracers are always on in dbg builds). The default in OSS is for
// tracers to be on since we support binary distributions of gRPC for the
// wrapped language (wr don't want to force recompilation to get tracing).
// Internally, however, for performance reasons, we compile them out by
// default, since internal build systems make recompiling trivial.
//
// Prefer GRPC_TRACE_FLAG_ENABLED() macro instead of using enabled() directly.
#define GRPC_USE_TRACERS  // tracers on by default in OSS
#if defined(GRPC_USE_TRACERS) || !defined(NDEBUG)
  bool enabled() {
#ifdef GRPC_THREADSAFE_TRACER
    return value_.load(std::memory_order_relaxed);
#else
    return value_;
#endif  // GRPC_THREADSAFE_TRACER
  }
#else
  bool enabled() { return false; }
#endif /* defined(GRPC_USE_TRACERS) || !defined(NDEBUG) */
 
 private:
  friend void testing::grpc_tracer_enable_flag(TraceFlag* flag);
  friend class TraceFlagList;
 
  void set_enabled(bool enabled) {
#ifdef GRPC_THREADSAFE_TRACER
    value_.store(enabled, std::memory_order_relaxed);
#else
    value_ = enabled;
#endif
  }
 
  TraceFlag* next_tracer_;
  const char* const name_;
#ifdef GRPC_THREADSAFE_TRACER
  std::atomic<bool> value_;
#else
  bool value_;
#endif
};
 
#define GRPC_TRACE_FLAG_ENABLED(f) GPR_UNLIKELY((f).enabled())
 
#ifndef NDEBUG
typedef TraceFlag DebugOnlyTraceFlag;
#else
class DebugOnlyTraceFlag {
 public:
  constexpr DebugOnlyTraceFlag(bool /*default_enabled*/, const char* /*name*/) {
  }
  constexpr bool enabled() const { return false; }
  constexpr const char* name() const { return "DebugOnlyTraceFlag"; }
 
 private:
  void set_enabled(bool /*enabled*/) {}
};
#endif
 
}  // namespace grpc_core
 
#endif /* GRPC_CORE_LIB_DEBUG_TRACE_H */