text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  // The following only applies to changes made to this file as part of YugaByte development.
  //
  // Portions Copyright (c) YugaByte, Inc.
  //
  // 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.
  //
  
  // This header file defines the set of trace_event macros without specifying
  // how the events actually get collected and stored. If you need to expose trace
  // events to some other universe, you can copy-and-paste this file as well as
  // trace_event.h, modifying the macros contained there as necessary for the
  // target platform. The end result is that multiple libraries can funnel events
  // through to a shared trace event collector.
  
  // Trace events are for tracking application performance and resource usage.
  // Macros are provided to track:
  //    Begin and end of function calls
  //    Counters
  //
  // Events are issued against categories. Whereas LOG's
  // categories are statically defined, TRACE categories are created
  // implicitly with a string. For example:
  //   TRACE_EVENT_INSTANT0("MY_SUBSYSTEM", "SomeImportantEvent",
  //                        TRACE_EVENT_SCOPE_THREAD)
  //
  // It is often the case that one trace may belong in multiple categories at the
  // same time. The first argument to the trace can be a comma-separated list of
  // categories, forming a category group, like:
  //
  // TRACE_EVENT_INSTANT0("input,views", "OnMouseOver", TRACE_EVENT_SCOPE_THREAD)
  //
  // We can enable/disable tracing of OnMouseOver by enabling/disabling either
  // category.
  //
  // Events can be INSTANT, or can be pairs of BEGIN and END in the same scope:
  //   TRACE_EVENT_BEGIN0("MY_SUBSYSTEM", "SomethingCostly")
  //   doSomethingCostly()
  //   TRACE_EVENT_END0("MY_SUBSYSTEM", "SomethingCostly")
  // Note: our tools can't always determine the correct BEGIN/END pairs unless
  // these are used in the same scope. Use ASYNC_BEGIN/ASYNC_END macros if you
  // need them to be in separate scopes.
  //
  // A common use case is to trace entire function scopes. This
  // issues a trace BEGIN and END automatically:
  //   void doSomethingCostly() {
  //     TRACE_EVENT0("MY_SUBSYSTEM", "doSomethingCostly");
  //     ...
  //   }
  //
  // Additional parameters can be associated with an event:
  //   void doSomethingCostly2(int howMuch) {
  //     TRACE_EVENT1("MY_SUBSYSTEM", "doSomethingCostly",
  //         "howMuch", howMuch);
  //     ...
  //   }
  //
  // The trace system will automatically add to this information the
  // current process id, thread id, and a timestamp in microseconds.
  //
  // To trace an asynchronous procedure such as an IPC send/receive, use
  // ASYNC_BEGIN and ASYNC_END:
  //   [single threaded sender code]
  //     static int send_count = 0;
  //     ++send_count;
  //     TRACE_EVENT_ASYNC_BEGIN0("ipc", "message", send_count);
  //     Send(new MyMessage(send_count));
  //   [receive code]
  //     void OnMyMessage(send_count) {
  //       TRACE_EVENT_ASYNC_END0("ipc", "message", send_count);
  //     }
  // The third parameter is a unique ID to match ASYNC_BEGIN/ASYNC_END pairs.
  // ASYNC_BEGIN and ASYNC_END can occur on any thread of any traced process.
  // Pointers can be used for the ID parameter, and they will be mangled
  // internally so that the same pointer on two different processes will not
  // match. For example:
  //   class MyTracedClass {
  //    public:
  //     MyTracedClass() {
  //       TRACE_EVENT_ASYNC_BEGIN0("category", "MyTracedClass", this);
  //     }
  //     ~MyTracedClass() {
  //       TRACE_EVENT_ASYNC_END0("category", "MyTracedClass", this);
  //     }
  //   }
  //
  // Trace event also supports counters, which is a way to track a quantity
  // as it varies over time. Counters are created with the following macro:
  //   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter", g_myCounterValue);
  //
  // Counters are process-specific. The macro itself can be issued from any
  // thread, however.
  //
  // Sometimes, you want to track two counters at once. You can do this with two
  // counter macros:
  //   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter0", g_myCounterValue[0]);
  //   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter1", g_myCounterValue[1]);
  // Or you can do it with a combined macro:
  //   TRACE_COUNTER2("MY_SUBSYSTEM", "myCounter",
  //       "bytesPinned", g_myCounterValue[0],
  //       "bytesAllocated", g_myCounterValue[1]);
  // This indicates to the tracing UI that these counters should be displayed
  // in a single graph, as a summed area chart.
  //
  // Since counters are in a global namespace, you may want to disambiguate with a
  // unique ID, by using the TRACE_COUNTER_ID* variations.
  //
  // By default, trace collection is compiled in, but turned off at runtime.
  // Collecting trace data is the responsibility of the embedding
  // application. In Chrome's case, navigating to about:tracing will turn on
  // tracing and display data collected across all active processes.
  //
  //
  // Memory scoping note:
  // Tracing copies the pointers, not the string content, of the strings passed
  // in for category_group, name, and arg_names.  Thus, the following code will
  // cause problems:
  //     char* str = strdup("importantName");
  //     TRACE_EVENT_INSTANT0("SUBSYSTEM", str);  // BAD!
  //     free(str);                   // Trace system now has dangling pointer
  //
  // To avoid this issue with the |name| and |arg_name| parameters, use the
  // TRACE_EVENT_COPY_XXX overloads of the macros at additional runtime overhead.
  // Notes: The category must always be in a long-lived char* (i.e. static const).
  //        The |arg_values|, when used, are always deep copied with the _COPY
  //        macros.
  //
  // When are string argument values copied:
  // const char* arg_values are only referenced by default:
  //     TRACE_EVENT1("category", "name",
  //                  "arg1", "literal string is only referenced");
  // Use TRACE_STR_COPY to force copying of a const char*:
  //     TRACE_EVENT1("category", "name",
  //                  "arg1", TRACE_STR_COPY("string will be copied"));
  // std::string arg_values are always copied:
  //     TRACE_EVENT1("category", "name",
  //                  "arg1", std::string("string will be copied"));
  //
  //
  // Convertable notes:
  // Converting a large data type to a string can be costly. To help with this,
  // the trace framework provides an interface ConvertableToTraceFormat. If you
  // inherit from it and implement the AppendAsTraceFormat method the trace
  // framework will call back to your object to convert a trace output time. This
  // means, if the category for the event is disabled, the conversion will not
  // happen.
  //
  //   class MyData : public yb::debug::ConvertableToTraceFormat {
  //    public:
  //     MyData() {}
  //     virtual void AppendAsTraceFormat(std::string* out) const override {
  //       out->append("{\"foo\":1}");
  //     }
  //    private:
  //     virtual ~MyData() {}
  //     DISALLOW_COPY_AND_ASSIGN(MyData);
  //   };
  //
  //   TRACE_EVENT1("foo", "bar", "data",
  //                scoped_refptr<ConvertableToTraceFormat>(new MyData()));
  //
  // The trace framework will take ownership if the passed pointer and it will
  // be free'd when the trace buffer is flushed.
  //
  // Note, we only do the conversion when the buffer is flushed, so the provided
  // data object should not be modified after it's passed to the trace framework.
  //
  //
  // Thread Safety:
  // A thread safe singleton and mutex are used for thread safety. Category
  // enabled flags are used to limit the performance impact when the system
  // is not enabled.
  //
  // TRACE_EVENT macros first cache a pointer to a category. The categories are
  // statically allocated and safe at all times, even after exit. Fetching a
  // category is protected by the TraceLog::lock_. Multiple threads initializing
  // the static variable is safe, as they will be serialized by the lock and
  // multiple calls will return the same pointer to the category.
  //
  // Then the category_group_enabled flag is checked. This is a unsigned char, and
  // not intended to be multithread safe. It optimizes access to AddTraceEvent
  // which is threadsafe internally via TraceLog::lock_. The enabled flag may
  // cause some threads to incorrectly call or skip calling AddTraceEvent near
  // the time of the system being enabled or disabled. This is acceptable as
  // we tolerate some data loss while the system is being enabled/disabled and
  // because AddTraceEvent is threadsafe internally and checks the enabled state
  // again under lock.
  //
  // Without the use of these static category pointers and enabled flags all
  // trace points would carry a significant performance cost of acquiring a lock
  // and resolving the category.
  
  #ifndef YB_UTIL_DEBUG_TRACE_EVENT_H_
  #define YB_UTIL_DEBUG_TRACE_EVENT_H_
  
  #include <string>
  
  #include "yb/gutil/atomicops.h"
  #include "yb/gutil/walltime.h"
  
  #include "yb/util/debug/trace_event_impl.h"
  #include "yb/util/debug/trace_event_memory.h" // For INTERNAL_TRACE_MEMORY
  
  // By default, const char* argument values are assumed to have long-lived scope
  // and will not be copied. Use this macro to force a const char* to be copied.
  #define TRACE_STR_COPY(str) \
      trace_event_internal::TraceStringWithCopy(str)
  
  // This will mark the trace event as disabled by default. The user will need
  // to explicitly enable the event.
  #define TRACE_DISABLED_BY_DEFAULT(name) "disabled-by-default-" name
  
  // By default, uint64 ID argument values are not mangled with the Process ID in
  // TRACE_EVENT_ASYNC macros. Use this macro to force Process ID mangling.
  #define TRACE_ID_MANGLE(id) \
      trace_event_internal::TraceID::ForceMangle(id)
  
  // By default, pointers are mangled with the Process ID in TRACE_EVENT_ASYNC
  // macros. Use this macro to prevent Process ID mangling.
  #define TRACE_ID_DONT_MANGLE(id) \
      trace_event_internal::TraceID::DontMangle(id)
  
  // Records a pair of begin and end events called "name" for the current
  // scope, with 0, 1 or 2 associated arguments. If the category is not
  // enabled, then this does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT0(category_group, name) \
      INTERNAL_TRACE_MEMORY(category_group, name) \
      INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name)
  #define TRACE_EVENT1(category_group, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_MEMORY(category_group, name) \
      INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name, arg1_name, arg1_val)
  #define TRACE_EVENT2( \
      category_group, name, arg1_name, arg1_val, arg2_name, arg2_val) \
    INTERNAL_TRACE_MEMORY(category_group, name) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED( \
        category_group, name, arg1_name, arg1_val, arg2_name, arg2_val)
  
  // Records events like TRACE_EVENT2 but uses |memory_tag| for memory tracing.
  // Use this where |name| is too generic to accurately aggregate allocations.
  #define TRACE_EVENT_WITH_MEMORY_TAG2( \
      category, name, memory_tag, arg1_name, arg1_val, arg2_name, arg2_val) \
    INTERNAL_TRACE_MEMORY(category, memory_tag) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED( \
        category, name, arg1_name, arg1_val, arg2_name, arg2_val)
  
  // UNSHIPPED_TRACE_EVENT* are like TRACE_EVENT* except that they are not
  // included in official builds.
  
  #if OFFICIAL_BUILD
  #undef TRACING_IS_OFFICIAL_BUILD
  #define TRACING_IS_OFFICIAL_BUILD 1
  #elif !defined(TRACING_IS_OFFICIAL_BUILD)
  #define TRACING_IS_OFFICIAL_BUILD 0
  #endif
  
  #if TRACING_IS_OFFICIAL_BUILD
  #define UNSHIPPED_TRACE_EVENT0(category_group, name) (void)0
  #define UNSHIPPED_TRACE_EVENT1(category_group, name, arg1_name, arg1_val) \
      (void)0
  #define UNSHIPPED_TRACE_EVENT2(category_group, name, arg1_name, arg1_val, \
                                 arg2_name, arg2_val) (void)0
  #define UNSHIPPED_TRACE_EVENT_INSTANT0(category_group, name, scope) (void)0
  #define UNSHIPPED_TRACE_EVENT_INSTANT1(category_group, name, scope, \
                                         arg1_name, arg1_val) (void)0
  #define UNSHIPPED_TRACE_EVENT_INSTANT2(category_group, name, scope, \
                                         arg1_name, arg1_val, \
                                         arg2_name, arg2_val) (void)0
  #else
  #define UNSHIPPED_TRACE_EVENT0(category_group, name) \
      TRACE_EVENT0(category_group, name)
  #define UNSHIPPED_TRACE_EVENT1(category_group, name, arg1_name, arg1_val) \
      TRACE_EVENT1(category_group, name, arg1_name, arg1_val)
  #define UNSHIPPED_TRACE_EVENT2(category_group, name, arg1_name, arg1_val, \
                                 arg2_name, arg2_val) \
      TRACE_EVENT2(category_group, name, arg1_name, arg1_val, arg2_name, arg2_val)
  #define UNSHIPPED_TRACE_EVENT_INSTANT0(category_group, name, scope) \
      TRACE_EVENT_INSTANT0(category_group, name, scope)
  #define UNSHIPPED_TRACE_EVENT_INSTANT1(category_group, name, scope, \
                                         arg1_name, arg1_val) \
      TRACE_EVENT_INSTANT1(category_group, name, scope, arg1_name, arg1_val)
  #define UNSHIPPED_TRACE_EVENT_INSTANT2(category_group, name, scope, \
                                         arg1_name, arg1_val, \
                                         arg2_name, arg2_val) \
      TRACE_EVENT_INSTANT2(category_group, name, scope, arg1_name, arg1_val, \
                           arg2_name, arg2_val)
  #endif
  
  // Records a single event called "name" immediately, with 0, 1 or 2
  // associated arguments. If the category is not enabled, then this
  // does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT_INSTANT0(category_group, name, scope) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category_group, name, TRACE_EVENT_FLAG_NONE | scope)
  #define TRACE_EVENT_INSTANT1(category_group, name, scope, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category_group, name, TRACE_EVENT_FLAG_NONE | scope, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_INSTANT2(category_group, name, scope, arg1_name, arg1_val, \
                               arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category_group, name, TRACE_EVENT_FLAG_NONE | scope, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_INSTANT0(category_group, name, scope) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category_group, name, TRACE_EVENT_FLAG_COPY | scope)
  #define TRACE_EVENT_COPY_INSTANT1(category_group, name, scope, \
                                    arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category_group, name, TRACE_EVENT_FLAG_COPY | scope, arg1_name, \
          arg1_val)
  #define TRACE_EVENT_COPY_INSTANT2(category_group, name, scope, \
                                    arg1_name, arg1_val, \
                                    arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category_group, name, TRACE_EVENT_FLAG_COPY | scope, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  
  // Sets the current sample state to the given category and name (both must be
  // constant strings). These states are intended for a sampling profiler.
  // Implementation note: we store category and name together because we don't
  // want the inconsistency/expense of storing two pointers.
  // |thread_bucket| is [0..2] and is used to statically isolate samples in one
  // thread from others.
  #define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET( \
      bucket_number, category, name)                 \
          trace_event_internal::                     \
          TraceEventSamplingStateScope<bucket_number>::Set(category "\0" name)
  
  // Returns a current sampling state of the given bucket.
  #define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
      trace_event_internal::TraceEventSamplingStateScope<bucket_number>::Current()
  
  // Creates a scope of a sampling state of the given bucket.
  //
  // {  // The sampling state is set within this scope.
  //    TRACE_EVENT_SAMPLING_STATE_SCOPE_FOR_BUCKET(0, "category", "name");
  //    ...;
  // }
  #define TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(                   \
      bucket_number, category, name)                                      \
      trace_event_internal::TraceEventSamplingStateScope<bucket_number>   \
          traceEventSamplingScope(category "\0" name);
  
  // Syntactic sugars for the sampling tracing in the main thread.
  #define TRACE_EVENT_SCOPED_SAMPLING_STATE(category, name) \
      TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(0, category, name)
  #define TRACE_EVENT_GET_SAMPLING_STATE() \
      TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(0)
  #define TRACE_EVENT_SET_SAMPLING_STATE(category, name) \
      TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(0, category, name)
  
  
  // Records a single BEGIN event called "name" immediately, with 0, 1 or 2
  // associated arguments. If the category is not enabled, then this
  // does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT_BEGIN0(category_group, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category_group, name, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_BEGIN1(category_group, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category_group, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_BEGIN2(category_group, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category_group, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_BEGIN0(category_group, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category_group, name, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_BEGIN1(category_group, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category_group, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_BEGIN2(category_group, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category_group, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  
  // Similar to TRACE_EVENT_BEGINx but with a custom |at| timestamp provided.
  // - |id| is used to match the _BEGIN event with the _END event.
  //   Events are considered to match if their category_group, name and id values
  //   all match. |id| must either be a pointer or an integer value up to 64 bits.
  //   If it's a pointer, the bits will be xored with a hash of the process ID so
  //   that the same pointer on two different processes will not collide.
  #define TRACE_EVENT_BEGIN_WITH_ID_TID_AND_TIMESTAMP0(category_group, \
          name, id, thread_id, timestamp) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP( \
          TRACE_EVENT_PHASE_ASYNC_BEGIN, category_group, name, id, thread_id, \
          timestamp, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_COPY_BEGIN_WITH_ID_TID_AND_TIMESTAMP0( \
          category_group, name, id, thread_id, timestamp) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP( \
          TRACE_EVENT_PHASE_ASYNC_BEGIN, category_group, name, id, thread_id, \
          timestamp, TRACE_EVENT_FLAG_COPY)
  
  // Records a single END event for "name" immediately. If the category
  // is not enabled, then this does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT_END0(category_group, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category_group, name, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_END1(category_group, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category_group, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_END2(category_group, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category_group, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_END0(category_group, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category_group, name, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_END1(category_group, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category_group, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_END2(category_group, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category_group, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  
  // Similar to TRACE_EVENT_ENDx but with a custom |at| timestamp provided.
  // - |id| is used to match the _BEGIN event with the _END event.
  //   Events are considered to match if their category_group, name and id values
  //   all match. |id| must either be a pointer or an integer value up to 64 bits.
  //   If it's a pointer, the bits will be xored with a hash of the process ID so
  //   that the same pointer on two different processes will not collide.
  #define TRACE_EVENT_END_WITH_ID_TID_AND_TIMESTAMP0(category_group, \
          name, id, thread_id, timestamp) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP( \
          TRACE_EVENT_PHASE_ASYNC_END, category_group, name, id, thread_id, \
          timestamp, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_COPY_END_WITH_ID_TID_AND_TIMESTAMP0( \
          category_group, name, id, thread_id, timestamp) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP( \
          TRACE_EVENT_PHASE_ASYNC_END, category_group, name, id, thread_id, \
          timestamp, TRACE_EVENT_FLAG_COPY)
  
  // Records the value of a counter called "name" immediately. Value
  // must be representable as a 32 bit integer.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_COUNTER1(category_group, name, value) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, TRACE_EVENT_FLAG_NONE, \
          "value", static_cast<int>(value))
  #define TRACE_COPY_COUNTER1(category_group, name, value) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, TRACE_EVENT_FLAG_COPY, \
          "value", static_cast<int>(value))
  
  // Records the values of a multi-parted counter called "name" immediately.
  // The UI will treat value1 and value2 as parts of a whole, displaying their
  // values as a stacked-bar chart.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_COUNTER2(category_group, name, value1_name, value1_val, \
          value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, TRACE_EVENT_FLAG_NONE, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  #define TRACE_COPY_COUNTER2(category_group, name, value1_name, value1_val, \
          value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, TRACE_EVENT_FLAG_COPY, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  
  // Records the value of a counter called "name" immediately. Value
  // must be representable as a 32 bit integer.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  // - |id| is used to disambiguate counters with the same name. It must either
  //   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
  //   will be xored with a hash of the process ID so that the same pointer on
  //   two different processes will not collide.
  #define TRACE_COUNTER_ID1(category_group, name, id, value) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, \
          "value", static_cast<int>(value))
  #define TRACE_COPY_COUNTER_ID1(category_group, name, id, value) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          "value", static_cast<int>(value))
  
  // Records the values of a multi-parted counter called "name" immediately.
  // The UI will treat value1 and value2 as parts of a whole, displaying their
  // values as a stacked-bar chart.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  // - |id| is used to disambiguate counters with the same name. It must either
  //   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
  //   will be xored with a hash of the process ID so that the same pointer on
  //   two different processes will not collide.
  #define TRACE_COUNTER_ID2(category_group, name, id, value1_name, value1_val, \
          value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  #define TRACE_COPY_COUNTER_ID2(category_group, name, id, value1_name, \
          value1_val, value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  
  
  // Records a single ASYNC_BEGIN event called "name" immediately, with 0, 1 or 2
  // associated arguments. If the category is not enabled, then this
  // does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  // - |id| is used to match the ASYNC_BEGIN event with the ASYNC_END event. ASYNC
  //   events are considered to match if their category_group, name and id values
  //   all match. |id| must either be a pointer or an integer value up to 64 bits.
  //   If it's a pointer, the bits will be xored with a hash of the process ID so
  //   that the same pointer on two different processes will not collide.
  //
  // An asynchronous operation can consist of multiple phases. The first phase is
  // defined by the ASYNC_BEGIN calls. Additional phases can be defined using the
  // ASYNC_STEP_INTO or ASYNC_STEP_PAST macros. The ASYNC_STEP_INTO macro will
  // annotate the block following the call. The ASYNC_STEP_PAST macro will
  // annotate the block prior to the call. Note that any particular event must use
  // only STEP_INTO or STEP_PAST macros; they can not mix and match. When the
  // operation completes, call ASYNC_END.
  //
  // An ASYNC trace typically occurs on a single thread (if not, they will only be
  // drawn on the thread defined in the ASYNC_BEGIN event), but all events in that
  // operation must use the same |name| and |id|. Each step can have its own
  // args.
  #define TRACE_EVENT_ASYNC_BEGIN0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_ASYNC_BEGIN1(category_group, name, id, arg1_name, \
          arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_ASYNC_BEGIN2(category_group, name, id, arg1_name, \
          arg1_val, arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_ASYNC_BEGIN0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_ASYNC_BEGIN1(category_group, name, id, arg1_name, \
          arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_ASYNC_BEGIN2(category_group, name, id, arg1_name, \
          arg1_val, arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  
  // Records a single ASYNC_STEP_INTO event for |step| immediately. If the
  // category is not enabled, then this does nothing. The |name| and |id| must
  // match the ASYNC_BEGIN event above. The |step| param identifies this step
  // within the async event. This should be called at the beginning of the next
  // phase of an asynchronous operation. The ASYNC_BEGIN event must not have any
  // ASYNC_STEP_PAST events.
  #define TRACE_EVENT_ASYNC_STEP_INTO0(category_group, name, id, step) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_INTO, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step)
  #define TRACE_EVENT_ASYNC_STEP_INTO1(category_group, name, id, step, \
                                       arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_INTO, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
          arg1_name, arg1_val)
  
  // Records a single ASYNC_STEP_PAST event for |step| immediately. If the
  // category is not enabled, then this does nothing. The |name| and |id| must
  // match the ASYNC_BEGIN event above. The |step| param identifies this step
  // within the async event. This should be called at the beginning of the next
  // phase of an asynchronous operation. The ASYNC_BEGIN event must not have any
  // ASYNC_STEP_INTO events.
  #define TRACE_EVENT_ASYNC_STEP_PAST0(category_group, name, id, step) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_PAST, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step)
  #define TRACE_EVENT_ASYNC_STEP_PAST1(category_group, name, id, step, \
                                       arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_PAST, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
          arg1_name, arg1_val)
  
  // Records a single ASYNC_END event for "name" immediately. If the category
  // is not enabled, then this does nothing.
  #define TRACE_EVENT_ASYNC_END0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_ASYNC_END1(category_group, name, id, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_ASYNC_END2(category_group, name, id, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_ASYNC_END0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_ASYNC_END1(category_group, name, id, arg1_name, \
          arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_ASYNC_END2(category_group, name, id, arg1_name, \
          arg1_val, arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  
  
  // Records a single FLOW_BEGIN event called "name" immediately, with 0, 1 or 2
  // associated arguments. If the category is not enabled, then this
  // does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  // - |id| is used to match the FLOW_BEGIN event with the FLOW_END event. FLOW
  //   events are considered to match if their category_group, name and id values
  //   all match. |id| must either be a pointer or an integer value up to 64 bits.
  //   If it's a pointer, the bits will be xored with a hash of the process ID so
  //   that the same pointer on two different processes will not collide.
  // FLOW events are different from ASYNC events in how they are drawn by the
  // tracing UI. A FLOW defines asynchronous data flow, such as posting a task
  // (FLOW_BEGIN) and later executing that task (FLOW_END). Expect FLOWs to be
  // drawn as lines or arrows from FLOW_BEGIN scopes to FLOW_END scopes. Similar
  // to ASYNC, a FLOW can consist of multiple phases. The first phase is defined
  // by the FLOW_BEGIN calls. Additional phases can be defined using the FLOW_STEP
  // macros. When the operation completes, call FLOW_END. An async operation can
  // span threads and processes, but all events in that operation must use the
  // same |name| and |id|. Each event can have its own args.
  #define TRACE_EVENT_FLOW_BEGIN0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_FLOW_BEGIN1(category_group, name, id, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_FLOW_BEGIN2(category_group, name, id, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_FLOW_BEGIN0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_FLOW_BEGIN1(category_group, name, id, arg1_name, \
          arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_FLOW_BEGIN2(category_group, name, id, arg1_name, \
          arg1_val, arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_BEGIN, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  
  // Records a single FLOW_STEP event for |step| immediately. If the category
  // is not enabled, then this does nothing. The |name| and |id| must match the
  // FLOW_BEGIN event above. The |step| param identifies this step within the
  // async event. This should be called at the beginning of the next phase of an
  // asynchronous operation.
  #define TRACE_EVENT_FLOW_STEP0(category_group, name, id, step) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_STEP, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step)
  #define TRACE_EVENT_FLOW_STEP1(category_group, name, id, step, \
          arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_STEP, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_FLOW_STEP0(category_group, name, id, step) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_STEP, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, "step", step)
  #define TRACE_EVENT_COPY_FLOW_STEP1(category_group, name, id, step, \
          arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_STEP, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, "step", step, \
          arg1_name, arg1_val)
  
  // Records a single FLOW_END event for "name" immediately. If the category
  // is not enabled, then this does nothing.
  #define TRACE_EVENT_FLOW_END0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_FLOW_END1(category_group, name, id, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_FLOW_END2(category_group, name, id, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_FLOW_END0(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_FLOW_END1(category_group, name, id, arg1_name, \
          arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_FLOW_END2(category_group, name, id, arg1_name, \
          arg1_val, arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
          category_group, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  
  // Macros to track the life time and value of arbitrary client objects.
  // See also TraceTrackableObject.
  #define TRACE_EVENT_OBJECT_CREATED_WITH_ID(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_CREATE_OBJECT, \
          category_group, name, TRACE_ID_DONT_MANGLE(id), TRACE_EVENT_FLAG_NONE)
  
  #define TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(category_group, name, id, snapshot) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_SNAPSHOT_OBJECT, \
          category_group, name, TRACE_ID_DONT_MANGLE(id), TRACE_EVENT_FLAG_NONE, \
          "snapshot", snapshot)
  
  #define TRACE_EVENT_OBJECT_DELETED_WITH_ID(category_group, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_DELETE_OBJECT, \
          category_group, name, TRACE_ID_DONT_MANGLE(id), TRACE_EVENT_FLAG_NONE)
  
  #define INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE() \
      PREDICT_FALSE(*INTERNAL_TRACE_EVENT_UID(category_group_enabled) & \
          (yb::debug::TraceLog::ENABLED_FOR_RECORDING | \
           yb::debug::TraceLog::ENABLED_FOR_EVENT_CALLBACK))
  
  // Macro to efficiently determine if a given category group is enabled.
  #define TRACE_EVENT_CATEGORY_GROUP_ENABLED(category_group, ret) \
      do { \
        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
        if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
          *ret = true; \
        } else { \
          *ret = false; \
        } \
      } while (0)
  
  // Macro to efficiently determine, through polling, if a new trace has begun.
  #define TRACE_EVENT_IS_NEW_TRACE(ret) \
      do { \
        static int INTERNAL_TRACE_EVENT_UID(lastRecordingNumber) = 0; \
        int num_traces_recorded = TRACE_EVENT_API_GET_NUM_TRACES_RECORDED(); \
        if (num_traces_recorded != -1 && \
            num_traces_recorded != \
            INTERNAL_TRACE_EVENT_UID(lastRecordingNumber)) { \
          INTERNAL_TRACE_EVENT_UID(lastRecordingNumber) = \
              num_traces_recorded; \
          *ret = true; \
        } else { \
          *ret = false; \
        } \
      } while (0)
  
  ////////////////////////////////////////////////////////////////////////////////
  // Implementation specific tracing API definitions.
  
  // Get a pointer to the enabled state of the given trace category. Only
  // long-lived literal strings should be given as the category group. The
  // returned pointer can be held permanently in a local static for example. If
  // the unsigned char is non-zero, tracing is enabled. If tracing is enabled,
  // TRACE_EVENT_API_ADD_TRACE_EVENT can be called. It's OK if tracing is disabled
  // between the load of the tracing state and the call to
  // TRACE_EVENT_API_ADD_TRACE_EVENT, because this flag only provides an early out
  // for best performance when tracing is disabled.
  // const unsigned char*
  //     TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(const char* category_group)
  #define TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED \
      yb::debug::TraceLog::GetCategoryGroupEnabled
  
  // Get the number of times traces have been recorded. This is used to implement
  // the TRACE_EVENT_IS_NEW_TRACE facility.
  // unsigned int TRACE_EVENT_API_GET_NUM_TRACES_RECORDED()
  #define TRACE_EVENT_API_GET_NUM_TRACES_RECORDED \
      yb::debug::TraceLog::GetInstance()->GetNumTracesRecorded
  
  // Add a trace event to the platform tracing system.
  // yb::debug::TraceEventHandle TRACE_EVENT_API_ADD_TRACE_EVENT(
  //                    char phase,
  //                    const unsigned char* category_group_enabled,
  //                    const char* name,
  //                    uint64_t id,
  //                    int num_args,
  //                    const char** arg_names,
  //                    const unsigned char* arg_types,
  //                    const uint64_t* arg_values,
  //                    unsigned char flags)
  #define TRACE_EVENT_API_ADD_TRACE_EVENT \
      yb::debug::TraceLog::GetInstance()->AddTraceEvent
  
  // Add a trace event to the platform tracing system.
  // yb::debug::TraceEventHandle TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_TIMESTAMP(
  //                    char phase,
  //                    const unsigned char* category_group_enabled,
  //                    const char* name,
  //                    uint64_t id,
  //                    int thread_id,
  //                    const MicrosecondsInt64& timestamp,
  //                    int num_args,
  //                    const char** arg_names,
  //                    const unsigned char* arg_types,
  //                    const uint64_t* arg_values,
  //                    unsigned char flags)
  #define TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP \
      yb::debug::TraceLog::GetInstance()->AddTraceEventWithThreadIdAndTimestamp
  
  // Set the duration field of a COMPLETE trace event.
  // void TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
  //     const unsigned char* category_group_enabled,
  //     const char* name,
  //     yb::debug::TraceEventHandle id)
  #define TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION \
      yb::debug::TraceLog::GetInstance()->UpdateTraceEventDuration
  
  // Defines atomic operations used internally by the tracing system.
  #define TRACE_EVENT_API_ATOMIC_WORD AtomicWord
  #define TRACE_EVENT_API_ATOMIC_LOAD(var) base::subtle::NoBarrier_Load(&(var))
  #define TRACE_EVENT_API_ATOMIC_STORE(var, value) \
      base::subtle::NoBarrier_Store(&(var), (value))
  
  // Defines visibility for classes in trace_event.h
  #define TRACE_EVENT_API_CLASS_EXPORT BASE_EXPORT
  
  // The thread buckets for the sampling profiler.
  TRACE_EVENT_API_CLASS_EXPORT extern \
      TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
  
  #define TRACE_EVENT_API_THREAD_BUCKET(thread_bucket)                           \
      g_trace_state[thread_bucket]
  
  ////////////////////////////////////////////////////////////////////////////////
  
  // Implementation detail: trace event macros create temporary variables
  // to keep instrumentation overhead low. These macros give each temporary
  // variable a unique name based on the line number to prevent name collisions.
  #define INTERNAL_TRACE_EVENT_UID3(a, b) \
      trace_event_unique_##a##b
  #define INTERNAL_TRACE_EVENT_UID2(a, b) \
      INTERNAL_TRACE_EVENT_UID3(a, b)
  #define INTERNAL_TRACE_EVENT_UID(name_prefix) \
      INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
  
  // Implementation detail: internal macro to create static category.
  // No barriers are needed, because this code is designed to operate safely
  // even when the unsigned char* points to garbage data (which may be the case
  // on processors without cache coherency).
  #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES( \
      category_group, atomic, category_group_enabled) \
      category_group_enabled = \
          reinterpret_cast<const unsigned char*>(TRACE_EVENT_API_ATOMIC_LOAD( \
              atomic)); \
      if (PREDICT_FALSE(!category_group_enabled)) { \
        category_group_enabled = \
            TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group); \
        TRACE_EVENT_API_ATOMIC_STORE(atomic, \
            reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>( \
                category_group_enabled)); \
      }
  
  #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group) \
      static TRACE_EVENT_API_ATOMIC_WORD INTERNAL_TRACE_EVENT_UID(atomic) = 0; \
      const unsigned char* INTERNAL_TRACE_EVENT_UID(category_group_enabled); \
      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES(category_group, \
          INTERNAL_TRACE_EVENT_UID(atomic), \
          INTERNAL_TRACE_EVENT_UID(category_group_enabled));
  
  // Implementation detail: internal macro to create static category and add
  // event if the category is enabled.
  #define INTERNAL_TRACE_EVENT_ADD(phase, category_group, name, flags, ...) \
      do { \
        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
        if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
          trace_event_internal::AddTraceEvent( \
              phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
              trace_event_internal::kNoEventId, flags, ##__VA_ARGS__); \
        } \
      } while (0)
  
  // Implementation detail: internal macro to create static category and add begin
  // event if the category is enabled. Also adds the end event when the scope
  // ends.
  #define INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name, ...) \
      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
      trace_event_internal::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer); \
      if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
        yb::debug::TraceEventHandle h = trace_event_internal::AddTraceEvent( \
            TRACE_EVENT_PHASE_COMPLETE, \
            INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
            name, trace_event_internal::kNoEventId, \
            TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
        INTERNAL_TRACE_EVENT_UID(tracer).Initialize( \
            INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, h); \
      }
  
  // Implementation detail: internal macro to create static category and add
  // event if the category is enabled.
  #define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category_group, name, id, \
                                           flags, ...) \
      do { \
        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
        if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
          unsigned char trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID; \
          trace_event_internal::TraceID trace_event_trace_id( \
              id, &trace_event_flags); \
          trace_event_internal::AddTraceEvent( \
              phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
              name, trace_event_trace_id.data(), trace_event_flags, \
              ##__VA_ARGS__); \
        } \
      } while (0)
  
  // Implementation detail: internal macro to create static category and add
  // event if the category is enabled.
  #define INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(phase, \
          category_group, name, id, thread_id, timestamp, flags, ...) \
      do { \
        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
        if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
          unsigned char trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID; \
          trace_event_internal::TraceID trace_event_trace_id( \
              id, &trace_event_flags); \
          trace_event_internal::AddTraceEventWithThreadIdAndTimestamp( \
              phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
              name, trace_event_trace_id.data(), \
              thread_id, timestamp, \
              trace_event_flags, ##__VA_ARGS__); \
        } \
      } while (0)
  
  // Notes regarding the following definitions:
  // New values can be added and propagated to third party libraries, but existing
  // definitions must never be changed, because third party libraries may use old
  // definitions.
  
  // Phase indicates the nature of an event entry. E.g. part of a begin/end pair.
  #define TRACE_EVENT_PHASE_BEGIN    ('B')
  #define TRACE_EVENT_PHASE_END      ('E')
  #define TRACE_EVENT_PHASE_COMPLETE ('X')
  #define TRACE_EVENT_PHASE_INSTANT  ('i')
  #define TRACE_EVENT_PHASE_ASYNC_BEGIN ('S')
  #define TRACE_EVENT_PHASE_ASYNC_STEP_INTO  ('T')
  #define TRACE_EVENT_PHASE_ASYNC_STEP_PAST  ('p')
  #define TRACE_EVENT_PHASE_ASYNC_END   ('F')
  #define TRACE_EVENT_PHASE_FLOW_BEGIN ('s')
  #define TRACE_EVENT_PHASE_FLOW_STEP  ('t')
  #define TRACE_EVENT_PHASE_FLOW_END   ('f')
  #define TRACE_EVENT_PHASE_METADATA ('M')
  #define TRACE_EVENT_PHASE_COUNTER  ('C')
  #define TRACE_EVENT_PHASE_SAMPLE  ('P')
  #define TRACE_EVENT_PHASE_CREATE_OBJECT ('N')
  #define TRACE_EVENT_PHASE_SNAPSHOT_OBJECT ('O')
  #define TRACE_EVENT_PHASE_DELETE_OBJECT ('D')
  
  // Flags for changing the behavior of TRACE_EVENT_API_ADD_TRACE_EVENT.
  #define TRACE_EVENT_FLAG_NONE         (static_cast<unsigned char>(0))
  #define TRACE_EVENT_FLAG_COPY         (static_cast<unsigned char>(1 << 0))
  #define TRACE_EVENT_FLAG_HAS_ID       (static_cast<unsigned char>(1 << 1))
  #define TRACE_EVENT_FLAG_MANGLE_ID    (static_cast<unsigned char>(1 << 2))
  #define TRACE_EVENT_FLAG_SCOPE_OFFSET (static_cast<unsigned char>(1 << 3))
  
  #define TRACE_EVENT_FLAG_SCOPE_MASK   (static_cast<unsigned char>( \
      TRACE_EVENT_FLAG_SCOPE_OFFSET | (TRACE_EVENT_FLAG_SCOPE_OFFSET << 1)))
  
  // Type values for identifying types in the TraceValue union.
  #define TRACE_VALUE_TYPE_BOOL         (static_cast<unsigned char>(1))
  #define TRACE_VALUE_TYPE_UINT         (static_cast<unsigned char>(2))
  #define TRACE_VALUE_TYPE_INT          (static_cast<unsigned char>(3))
  #define TRACE_VALUE_TYPE_DOUBLE       (static_cast<unsigned char>(4))
  #define TRACE_VALUE_TYPE_POINTER      (static_cast<unsigned char>(5))
  #define TRACE_VALUE_TYPE_STRING       (static_cast<unsigned char>(6))
  #define TRACE_VALUE_TYPE_COPY_STRING  (static_cast<unsigned char>(7))
  #define TRACE_VALUE_TYPE_CONVERTABLE  (static_cast<unsigned char>(8))
  
  // Enum reflecting the scope of an INSTANT event. Must fit within
  // TRACE_EVENT_FLAG_SCOPE_MASK.
  #define TRACE_EVENT_SCOPE_GLOBAL  (static_cast<unsigned char>(0 << 3))
  #define TRACE_EVENT_SCOPE_PROCESS (static_cast<unsigned char>(1 << 3))
  #define TRACE_EVENT_SCOPE_THREAD  (static_cast<unsigned char>(2 << 3))
  
  #define TRACE_EVENT_SCOPE_NAME_GLOBAL  ('g')
  #define TRACE_EVENT_SCOPE_NAME_PROCESS ('p')
  #define TRACE_EVENT_SCOPE_NAME_THREAD  ('t')
  
  namespace trace_event_internal {
  
  // Specify these values when the corresponding argument of AddTraceEvent is not
  // used.
  const int kZeroNumArgs = 0;
  const uint64_t kNoEventId = 0;
  
  // TraceID encapsulates an ID that can either be an integer or pointer. Pointers
  // are by default mangled with the Process ID so that they are unlikely to
  // collide when the same pointer is used on different processes.
  class TraceID {
   public:
    class DontMangle {
     public:
      explicit DontMangle(const void* id)
          : data_(static_cast<uint64_t>(
                reinterpret_cast<unsigned long>(id))) {}  // NOLINT(runtime/int)
      explicit DontMangle(uint64_t id) : data_(id) {}
      explicit DontMangle(unsigned int id) : data_(id) {}
      explicit DontMangle(unsigned short id) : data_(id) {}  // NOLINT(runtime/int)
      explicit DontMangle(unsigned char id) : data_(id) {}
      explicit DontMangle(long long id)  // NOLINT(runtime/int)
          : data_(static_cast<uint64_t>(id)) {}
      explicit DontMangle(long id)  // NOLINT(runtime/int)
          : data_(static_cast<uint64_t>(id)) {}
      explicit DontMangle(int id)
          : data_(static_cast<uint64_t>(id)) {}
      explicit DontMangle(short id)  // NOLINT(runtime/int)
          : data_(static_cast<uint64_t>(id)) {}
      explicit DontMangle(signed char id)
          : data_(static_cast<uint64_t>(id)) {}
      uint64_t data() const { return data_; }
     private:
      uint64_t data_;
    };
  
    class ForceMangle {
     public:
      explicit ForceMangle(uint64_t id) : data_(id) {}
      explicit ForceMangle(unsigned int id) : data_(id) {}
      explicit ForceMangle(unsigned short id) : data_(id) {}  // NOLINT(runtime/int)
      explicit ForceMangle(unsigned char id) : data_(id) {}
      explicit ForceMangle(long long id)  // NOLINT(runtime/int)
          : data_(static_cast<uint64_t>(id)) {}
      explicit ForceMangle(long id)  // NOLINT(runtime/int)
          : data_(static_cast<uint64_t>(id)) {}
      explicit ForceMangle(int id)
          : data_(static_cast<uint64_t>(id)) {}
      explicit ForceMangle(short id)  // NOLINT(runtime/int)
          : data_(static_cast<uint64_t>(id)) {}
      explicit ForceMangle(signed char id)
          : data_(static_cast<uint64_t>(id)) {}
      uint64_t data() const { return data_; }
     private:
      uint64_t data_;
    };
  
    TraceID(const void* id, unsigned char* flags)
        : data_(static_cast<uint64_t>(
                reinterpret_cast<unsigned long>(id))) {  // NOLINT(runtime/int)
      *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
    }
    TraceID(ForceMangle id, unsigned char* flags) : data_(id.data()) {
      *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
    }
    TraceID(DontMangle id, unsigned char* flags) : data_(id.data()) {
    }
    TraceID(uint64_t id, unsigned char* flags)
        : data_(id) { (void)flags; }
    TraceID(unsigned int id, unsigned char* flags)
        : data_(id) { (void)flags; }
    TraceID(unsigned short id, unsigned char* flags)  // NOLINT(runtime/int)
        : data_(id) { (void)flags; }
    TraceID(unsigned char id, unsigned char* flags)
        : data_(id) { (void)flags; }
    TraceID(long long id, unsigned char* flags)  // NOLINT(runtime/int)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(long id, unsigned char* flags)  // NOLINT(runtime/int)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(int id, unsigned char* flags)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(short id, unsigned char* flags)  // NOLINT(runtime/int)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(signed char id, unsigned char* flags)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
  
    uint64_t data() const { return data_; }
  
   private:
    uint64_t data_;
  };
  
  // Simple union to store various types as uint64_t.
  union TraceValueUnion {
    bool as_bool;
    uint64_t as_uint;
    long long as_int;  // NOLINT(runtime/int)
    double as_double;
    const void* as_pointer;
    const char* as_string;
  };
  
  // Simple container for const char* that should be copied instead of retained.
  class TraceStringWithCopy {
   public:
    explicit TraceStringWithCopy(const char* str) : str_(str) {}
    const char* str() const { return str_; }
   private:
    const char* str_;
  };
  
  // Define SetTraceValue for each allowed type. It stores the type and
  // value in the return arguments. This allows this API to avoid declaring any
  // structures so that it is portable to third_party libraries.
  #define INTERNAL_DECLARE_SET_TRACE_VALUE(actual_type, \
                                           arg_expression, \
                                           union_member, \
                                           value_type_id) \
      static inline void SetTraceValue( \
          actual_type arg, \
          unsigned char* type, \
          uint64_t* value) { \
        TraceValueUnion type_value; \
        type_value.union_member = arg_expression; \
        *type = value_type_id; \
        *value = type_value.as_uint; \
      }
  // Simpler form for int types that can be safely casted.
  #define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actual_type, \
                                               value_type_id) \
      static inline void SetTraceValue( \
          actual_type arg, \
          unsigned char* type, \
          uint64_t* value) { \
        *type = value_type_id; \
        *value = static_cast<uint64_t>(arg); \
      }
  
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(uint64_t, TRACE_VALUE_TYPE_UINT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned int, TRACE_VALUE_TYPE_UINT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned short, TRACE_VALUE_TYPE_UINT)  // NOLINT(runtime/int)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long long, TRACE_VALUE_TYPE_INT)  // NOLINT(runtime/int)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long, TRACE_VALUE_TYPE_INT)  // NOLINT(runtime/int)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(short, TRACE_VALUE_TYPE_INT)  // NOLINT(runtime/int)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
  INTERNAL_DECLARE_SET_TRACE_VALUE(bool, arg, as_bool, TRACE_VALUE_TYPE_BOOL)
  INTERNAL_DECLARE_SET_TRACE_VALUE(double, arg, as_double,
                                   TRACE_VALUE_TYPE_DOUBLE)
  INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, arg, as_pointer,
                                   TRACE_VALUE_TYPE_POINTER)
  INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, arg, as_string,
                                   TRACE_VALUE_TYPE_STRING)
  INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, arg.str(),
                                   as_string, TRACE_VALUE_TYPE_COPY_STRING)
  #if defined(__APPLE__)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(size_t, TRACE_VALUE_TYPE_UINT)
  #endif
  
  #undef INTERNAL_DECLARE_SET_TRACE_VALUE
  #undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT
  
  // std::string version of SetTraceValue so that trace arguments can be strings.
  static inline void SetTraceValue(const std::string& arg,
                                   unsigned char* type,
                                   uint64_t* value) {
    TraceValueUnion type_value;
    type_value.as_string = arg.c_str();
    *type = TRACE_VALUE_TYPE_COPY_STRING;
    *value = type_value.as_uint;
  }
  
  // These AddTraceEvent and AddTraceEventWithThreadIdAndTimestamp template
  // functions are defined here instead of in the macro, because the arg_values
  // could be temporary objects, such as std::string. In order to store
  // pointers to the internal c_str and pass through to the tracing API,
  // the arg_values must live throughout these procedures.
  
  static inline yb::debug::TraceEventHandle
  AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      int thread_id,
      const MicrosecondsInt64& timestamp,
      unsigned char flags,
      const char* arg1_name,
      const scoped_refptr<yb::debug::ConvertableToTraceFormat>& arg1_val) {
    const int num_args = 1;
    unsigned char arg_types[1] = { TRACE_VALUE_TYPE_CONVERTABLE };
    return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
        phase, category_group_enabled, name, id, thread_id, timestamp,
        num_args, &arg1_name, arg_types, NULL, &arg1_val, flags);
  }
  
  template<class ARG1_TYPE>
  static inline yb::debug::TraceEventHandle
  AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      int thread_id,
      const MicrosecondsInt64& timestamp,
      unsigned char flags,
      const char* arg1_name,
      const ARG1_TYPE& arg1_val,
      const char* arg2_name,
      const scoped_refptr<yb::debug::ConvertableToTraceFormat>& arg2_val) {
    const int num_args = 2;
    const char* arg_names[2] = { arg1_name, arg2_name };
  
    unsigned char arg_types[2];
    uint64_t arg_values[2];
    SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
    arg_types[1] = TRACE_VALUE_TYPE_CONVERTABLE;
  
    scoped_refptr<yb::debug::ConvertableToTraceFormat> convertable_values[2];
    convertable_values[1] = arg2_val;
  
    return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
        phase, category_group_enabled, name, id, thread_id, timestamp,
        num_args, arg_names, arg_types, arg_values, convertable_values, flags);
  }
  
  template<class ARG2_TYPE>
  static inline yb::debug::TraceEventHandle
  AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      int thread_id,
      const MicrosecondsInt64& timestamp,
      unsigned char flags,
      const char* arg1_name,
      const scoped_refptr<yb::debug::ConvertableToTraceFormat>& arg1_val,
      const char* arg2_name,
      const ARG2_TYPE& arg2_val) {
    const int num_args = 2;
    const char* arg_names[2] = { arg1_name, arg2_name };
  
    unsigned char arg_types[2];
    uint64_t arg_values[2];
    arg_types[0] = TRACE_VALUE_TYPE_CONVERTABLE;
    arg_values[0] = 0;
    SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
  
    scoped_refptr<yb::debug::ConvertableToTraceFormat> convertable_values[2];
    convertable_values[0] = arg1_val;
  
    return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
        phase, category_group_enabled, name, id, thread_id, timestamp,
        num_args, arg_names, arg_types, arg_values, convertable_values, flags);
  }
  
  static inline yb::debug::TraceEventHandle
  AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      int thread_id,
      const MicrosecondsInt64& timestamp,
      unsigned char flags,
      const char* arg1_name,
      const scoped_refptr<yb::debug::ConvertableToTraceFormat>& arg1_val,
      const char* arg2_name,
      const scoped_refptr<yb::debug::ConvertableToTraceFormat>& arg2_val) {
    const int num_args = 2;
    const char* arg_names[2] = { arg1_name, arg2_name };
    unsigned char arg_types[2] =
        { TRACE_VALUE_TYPE_CONVERTABLE, TRACE_VALUE_TYPE_CONVERTABLE };
    scoped_refptr<yb::debug::ConvertableToTraceFormat> convertable_values[2] =
        { arg1_val, arg2_val };
  
    return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
        phase, category_group_enabled, name, id, thread_id, timestamp,
        num_args, arg_names, arg_types, NULL, convertable_values, flags);
  }
  
  static inline yb::debug::TraceEventHandle
  AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      int thread_id,
      const MicrosecondsInt64& timestamp,
      unsigned char flags) {
    return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
        phase, category_group_enabled, name, id, thread_id, timestamp,
        kZeroNumArgs, NULL, NULL, NULL, NULL, flags);
  }
  
  int TraceEventThreadId();
  
  static inline yb::debug::TraceEventHandle AddTraceEvent(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      unsigned char flags) {
    int thread_id = TraceEventThreadId();
    MicrosecondsInt64 now = GetMonoTimeMicros();
    return AddTraceEventWithThreadIdAndTimestamp(phase, category_group_enabled,
                                                 name, id, thread_id, now, flags);
  }
  
  template<class ARG1_TYPE>
  static inline yb::debug::TraceEventHandle
  AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      int thread_id,
      const MicrosecondsInt64& timestamp,
      unsigned char flags,
      const char* arg1_name,
      const ARG1_TYPE& arg1_val) {
    const int num_args = 1;
    unsigned char arg_types[1];
    uint64_t arg_values[1];
    SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
    return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
        phase, category_group_enabled, name, id, thread_id, timestamp,
        num_args, &arg1_name, arg_types, arg_values, NULL, flags);
  }
  
  template<class ARG1_TYPE>
  static inline yb::debug::TraceEventHandle AddTraceEvent(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      unsigned char flags,
      const char* arg1_name,
      const ARG1_TYPE& arg1_val) {
    int thread_id = TraceEventThreadId();
    MicrosecondsInt64 now = GetMonoTimeMicros();
    return AddTraceEventWithThreadIdAndTimestamp(phase, category_group_enabled,
                                                 name, id, thread_id, now, flags,
                                                 arg1_name, arg1_val);
  }
  
  template<class ARG1_TYPE, class ARG2_TYPE>
  static inline yb::debug::TraceEventHandle
  AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      int thread_id,
      const MicrosecondsInt64& timestamp,
      unsigned char flags,
      const char* arg1_name,
      const ARG1_TYPE& arg1_val,
      const char* arg2_name,
      const ARG2_TYPE& arg2_val) {
    const int num_args = 2;
    const char* arg_names[2] = { arg1_name, arg2_name };
    unsigned char arg_types[2];
    uint64_t arg_values[2];
    SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
    SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
    return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
        phase, category_group_enabled, name, id, thread_id, timestamp,
        num_args, arg_names, arg_types, arg_values, NULL, flags);
  }
  
  template<class ARG1_TYPE, class ARG2_TYPE>
  static inline yb::debug::TraceEventHandle AddTraceEvent(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      uint64_t id,
      unsigned char flags,
      const char* arg1_name,
      const ARG1_TYPE& arg1_val,
      const char* arg2_name,
      const ARG2_TYPE& arg2_val) {
    int thread_id = TraceEventThreadId();
    MicrosecondsInt64 now = GetMonoTimeMicros();
    return AddTraceEventWithThreadIdAndTimestamp(phase, category_group_enabled,
                                                 name, id, thread_id, now, flags,
                                                 arg1_name, arg1_val,
                                                 arg2_name, arg2_val);
  }
  
  // Used by TRACE_EVENTx macros. Do not use directly.
  class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
   public:
    // Note: members of data_ intentionally left uninitialized. See Initialize.
    ScopedTracer() : p_data_(NULL) {}
  
    ~ScopedTracer() {
      if (p_data_ && *data_.category_group_enabled)
        TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
            data_.category_group_enabled, data_.name, data_.event_handle);
    }
  
    void Initialize(const unsigned char* category_group_enabled,
                    const char* name,
                    yb::debug::TraceEventHandle event_handle) {
      data_.category_group_enabled = category_group_enabled;
      data_.name = name;
      data_.event_handle = event_handle;
      p_data_ = &data_;
    }
  
   private:
    // This Data struct workaround is to avoid initializing all the members
    // in Data during construction of this object, since this object is always
    // constructed, even when tracing is disabled. If the members of Data were
    // members of this class instead, compiler warnings occur about potential
    // uninitialized accesses.
    struct Data {
      const unsigned char* category_group_enabled = nullptr;
      const char* name = nullptr;
      yb::debug::TraceEventHandle event_handle;
    };
    Data* p_data_;
    Data data_;
  };
  
  // Used by TRACE_EVENT_BINARY_EFFICIENTx macro. Do not use directly.
  class TRACE_EVENT_API_CLASS_EXPORT ScopedTraceBinaryEfficient {
   public:
    ScopedTraceBinaryEfficient(const char* category_group, const char* name);
    ~ScopedTraceBinaryEfficient();
  
   private:
    const unsigned char* category_group_enabled_;
    const char* name_;
    yb::debug::TraceEventHandle event_handle_;
  };
  
  // This macro generates less code then TRACE_EVENT0 but is also
  // slower to execute when tracing is off. It should generally only be
  // used with code that is seldom executed or conditionally executed
  // when debugging.
  // For now the category_group must be "gpu".
  #define TRACE_EVENT_BINARY_EFFICIENT0(category_group, name) \
      trace_event_internal::ScopedTraceBinaryEfficient \
          INTERNAL_TRACE_EVENT_UID(scoped_trace)(category_group, name);
  
  // TraceEventSamplingStateScope records the current sampling state
  // and sets a new sampling state. When the scope exists, it restores
  // the sampling state having recorded.
  template<size_t BucketNumber>
  class TraceEventSamplingStateScope {
   public:
    explicit TraceEventSamplingStateScope(const char* category_and_name) {
      previous_state_ = TraceEventSamplingStateScope<BucketNumber>::Current();
      TraceEventSamplingStateScope<BucketNumber>::Set(category_and_name);
    }
  
    ~TraceEventSamplingStateScope() {
      TraceEventSamplingStateScope<BucketNumber>::Set(previous_state_);
    }
  
    static inline const char* Current() {
      return reinterpret_cast<const char*>(TRACE_EVENT_API_ATOMIC_LOAD(
        g_trace_state[BucketNumber]));
    }
  
    static inline void Set(const char* category_and_name) {
      TRACE_EVENT_API_ATOMIC_STORE(
        g_trace_state[BucketNumber],
        reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>(
          const_cast<char*>(category_and_name)));
    }
  
   private:
    const char* previous_state_;
  };
  
  }  // namespace trace_event_internal
  
  namespace yb {
  namespace debug {
  
  template<typename IDType> class TraceScopedTrackableObject {
   public:
    TraceScopedTrackableObject(const char* category_group, const char* name,
        IDType id)
      : category_group_(category_group),
        name_(name),
        id_(id) {
      TRACE_EVENT_OBJECT_CREATED_WITH_ID(category_group_, name_, id_);
    }
  
    template <typename ArgType> void snapshot(ArgType snapshot) {
      TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(category_group_, name_, id_, snapshot);
    }
  
    ~TraceScopedTrackableObject() {
      TRACE_EVENT_OBJECT_DELETED_WITH_ID(category_group_, name_, id_);
    }
  
   private:
    const char* category_group_;
    const char* name_;
    IDType id_;
  
    DISALLOW_COPY_AND_ASSIGN(TraceScopedTrackableObject);
  };
  
  } // namespace debug
  } // namespace yb
  
  #endif /* YB_UTIL_DEBUG_TRACE_EVENT_H_ */
  