base/trace_event/trace_log.h

// Copyright 2015 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.

#ifndef BASE_TRACE_EVENT_TRACE_LOG_H_
#define BASE_TRACE_EVENT_TRACE_LOG_H_

#include <stddef.h>
#include <stdint.h>

#include <atomic>
#include <memory>
#include <string>
#include <unordered_map>
#include <vector>

#include "base/atomicops.h"
#include "base/containers/stack.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/memory/scoped_refptr.h"
#include "base/single_thread_task_runner.h"
#include "base/time/time_override.h"
#include "base/trace_event/category_registry.h"
#include "base/trace_event/memory_dump_provider.h"
#include "base/trace_event/trace_config.h"
#include "base/trace_event/trace_event_impl.h"
#include "build/build_config.h"

namespace base {
class RefCountedString;

template <typename T>
class NoDestructor;

namespace trace_event {

struct TraceCategory;
class TraceBuffer;
class TraceBufferChunk;
class TraceEvent;
class TraceEventFilter;
class TraceEventMemoryOverhead;

struct BASE_EXPORT TraceLogStatus {
  TraceLogStatus();
  ~TraceLogStatus();
  uint32_t event_capacity;
  uint32_t event_count;
};

class BASE_EXPORT TraceLog : public MemoryDumpProvider {
 public:
  // Argument passed to TraceLog::SetEnabled.
  enum Mode : uint8_t {
    // Enables normal tracing (recording trace events in the trace buffer).
    RECORDING_MODE = 1 << 0,

    // Trace events are enabled just for filtering but not for recording. Only
    // event filters config of |trace_config| argument is used.
    FILTERING_MODE = 1 << 1
  };

  static TraceLog* GetInstance();

  // Retrieves a copy (for thread-safety) of the current TraceConfig.
  TraceConfig GetCurrentTraceConfig() const;

  // Initializes the thread-local event buffer, if not already initialized and
  // if the current thread supports that (has a message loop).
  void InitializeThreadLocalEventBufferIfSupported();

  // See TraceConfig comments for details on how to control which categories
  // will be traced. SetDisabled must be called distinctly for each mode that is
  // enabled. If tracing has already been enabled for recording, category filter
  // (enabled and disabled categories) will be merged into the current category
  // filter. Enabling RECORDING_MODE does not enable filters. Trace event
  // filters will be used only if FILTERING_MODE is set on |modes_to_enable|.
  // Conversely to RECORDING_MODE, FILTERING_MODE doesn't support upgrading,
  // i.e. filters can only be enabled if not previously enabled.
  void SetEnabled(const TraceConfig& trace_config, uint8_t modes_to_enable);

  // TODO(ssid): Remove the default SetEnabled and IsEnabled. They should take
  // Mode as argument.

  // Disables tracing for all categories for the specified |modes_to_disable|
  // only. Only RECORDING_MODE is taken as default |modes_to_disable|.
  void SetDisabled();
  void SetDisabled(uint8_t modes_to_disable);

  // Returns true if TraceLog is enabled on recording mode.
  // Note: Returns false even if FILTERING_MODE is enabled.
  bool IsEnabled() { return enabled_modes_ & RECORDING_MODE; }

  // Returns a bitmap of enabled modes from TraceLog::Mode.
  uint8_t enabled_modes() { return enabled_modes_; }

  // The number of times we have begun recording traces. If tracing is off,
  // returns -1. If tracing is on, then it returns the number of times we have
  // recorded a trace. By watching for this number to increment, you can
  // passively discover when a new trace has begun. This is then used to
  // implement the TRACE_EVENT_IS_NEW_TRACE() primitive.
  int GetNumTracesRecorded();

#if defined(OS_ANDROID)
  void StartATrace();
  void StopATrace();
  void AddClockSyncMetadataEvent();
#endif

  // Enabled state listeners give a callback when tracing is enabled or
  // disabled. This can be used to tie into other library's tracing systems
  // on-demand.
  class BASE_EXPORT EnabledStateObserver {
   public:
    virtual ~EnabledStateObserver() = default;

    // Called just after the tracing system becomes enabled, outside of the
    // |lock_|. TraceLog::IsEnabled() is true at this point.
    virtual void OnTraceLogEnabled() = 0;

    // Called just after the tracing system disables, outside of the |lock_|.
    // TraceLog::IsEnabled() is false at this point.
    virtual void OnTraceLogDisabled() = 0;
  };
  // Adds an observer. Cannot be called from within the observer callback.
  void AddEnabledStateObserver(EnabledStateObserver* listener);
  // Removes an observer. Cannot be called from within the observer callback.
  void RemoveEnabledStateObserver(EnabledStateObserver* listener);
  // Adds an observer that is owned by TraceLog. This is useful for agents that
  // implement tracing feature that needs to stay alive as long as TraceLog
  // does.
  void AddOwnedEnabledStateObserver(
      std::unique_ptr<EnabledStateObserver> listener);
  bool HasEnabledStateObserver(EnabledStateObserver* listener) const;

  // Asynchronous enabled state listeners. When tracing is enabled or disabled,
  // for each observer, a task for invoking its appropriate callback is posted
  // to the thread from which AddAsyncEnabledStateObserver() was called. This
  // allows the observer to be safely destroyed, provided that it happens on the
  // same thread that invoked AddAsyncEnabledStateObserver().
  class BASE_EXPORT AsyncEnabledStateObserver {
   public:
    virtual ~AsyncEnabledStateObserver() = default;

    // Posted just after the tracing system becomes enabled, outside |lock_|.
    // TraceLog::IsEnabled() is true at this point.
    virtual void OnTraceLogEnabled() = 0;

    // Posted just after the tracing system becomes disabled, outside |lock_|.
    // TraceLog::IsEnabled() is false at this point.
    virtual void OnTraceLogDisabled() = 0;
  };
  void AddAsyncEnabledStateObserver(
      WeakPtr<AsyncEnabledStateObserver> listener);
  void RemoveAsyncEnabledStateObserver(AsyncEnabledStateObserver* listener);
  bool HasAsyncEnabledStateObserver(AsyncEnabledStateObserver* listener) const;

  TraceLogStatus GetStatus() const;
  bool BufferIsFull() const;

  // Computes an estimate of the size of the TraceLog including all the retained
  // objects.
  void EstimateTraceMemoryOverhead(TraceEventMemoryOverhead* overhead);

  void SetArgumentFilterPredicate(
      const ArgumentFilterPredicate& argument_filter_predicate);

  // Flush all collected events to the given output callback. The callback will
  // be called one or more times either synchronously or asynchronously from
  // the current thread with IPC-bite-size chunks. The string format is
  // undefined. Use TraceResultBuffer to convert one or more trace strings to
  // JSON. The callback can be null if the caller doesn't want any data.
  // Due to the implementation of thread-local buffers, flush can't be
  // done when tracing is enabled. If called when tracing is enabled, the
  // callback will be called directly with (empty_string, false) to indicate
  // the end of this unsuccessful flush. Flush does the serialization
  // on the same thread if the caller doesn't set use_worker_thread explicitly.
  typedef base::Callback<void(const scoped_refptr<base::RefCountedString>&,
                              bool has_more_events)> OutputCallback;
  void Flush(const OutputCallback& cb, bool use_worker_thread = false);

  // Cancels tracing and discards collected data.
  void CancelTracing(const OutputCallback& cb);

  using AddTraceEventOverrideCallback = void (*)(TraceEvent*,
                                                 bool thread_will_flush,
                                                 TraceEventHandle* handle);
  using OnFlushCallback = void (*)();
  using UpdateDurationCallback = void (*)(TraceEventHandle handle,
                                          const TimeTicks& now,
                                          const ThreadTicks& thread_now);
  // The callbacks will be called up until the point where the flush is
  // finished, i.e. must be callable until OutputCallback is called with
  // has_more_events==false.
  void SetAddTraceEventOverrides(
      const AddTraceEventOverrideCallback& add_event_override,
      const OnFlushCallback& on_flush_callback,
      const UpdateDurationCallback& update_duration_callback);

  // Called by TRACE_EVENT* macros, don't call this directly.
  // The name parameter is a category group for example:
  // TRACE_EVENT0("renderer,webkit", "WebViewImpl::HandleInputEvent")
  static const unsigned char* GetCategoryGroupEnabled(const char* name);
  static const char* GetCategoryGroupName(
      const unsigned char* category_group_enabled);
  static constexpr const unsigned char* GetBuiltinCategoryEnabled(
      const char* name) {
    TraceCategory* builtin_category =
        CategoryRegistry::GetBuiltinCategoryByName(name);
    if (builtin_category)
      return builtin_category->state_ptr();
    return nullptr;
  }

  // Called by TRACE_EVENT* macros, don't call this directly.
  // If |copy| is set, |name|, |arg_name1| and |arg_name2| will be deep copied
  // into the event; see "Memory scoping note" and TRACE_EVENT_COPY_XXX above.
  TraceEventHandle AddTraceEvent(char phase,
                                 const unsigned char* category_group_enabled,
                                 const char* name,
                                 const char* scope,
                                 unsigned long long id,
                                 TraceArguments* args,
                                 unsigned int flags);
  TraceEventHandle AddTraceEventWithBindId(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      const char* scope,
      unsigned long long id,
      unsigned long long bind_id,
      TraceArguments* args,
      unsigned int flags);
  TraceEventHandle AddTraceEventWithProcessId(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      const char* scope,
      unsigned long long id,
      int process_id,
      TraceArguments* args,
      unsigned int flags);
  TraceEventHandle AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      const char* scope,
      unsigned long long id,
      int thread_id,
      const TimeTicks& timestamp,
      TraceArguments* args,
      unsigned int flags);
  TraceEventHandle AddTraceEventWithThreadIdAndTimestamp(
      char phase,
      const unsigned char* category_group_enabled,
      const char* name,
      const char* scope,
      unsigned long long id,
      unsigned long long bind_id,
      int thread_id,
      const TimeTicks& timestamp,
      TraceArguments* args,
      unsigned int flags);

  // Adds a metadata event that will be written when the trace log is flushed.
  void AddMetadataEvent(const unsigned char* category_group_enabled,
                        const char* name,
                        TraceArguments* args,
                        unsigned int flags);

  void UpdateTraceEventDuration(const unsigned char* category_group_enabled,
                                const char* name,
                                TraceEventHandle handle);

  void UpdateTraceEventDurationExplicit(
      const unsigned char* category_group_enabled,
      const char* name,
      TraceEventHandle handle,
      const TimeTicks& now,
      const ThreadTicks& thread_now);

  void EndFilteredEvent(const unsigned char* category_group_enabled,
                        const char* name,
                        TraceEventHandle handle);

  int process_id() const { return process_id_; }

  uint64_t MangleEventId(uint64_t id);

  // Exposed for unittesting:

  // Testing factory for TraceEventFilter.
  typedef std::unique_ptr<TraceEventFilter> (*FilterFactoryForTesting)(
      const std::string& /* predicate_name */);
  void SetFilterFactoryForTesting(FilterFactoryForTesting factory) {
    filter_factory_for_testing_ = factory;
  }

  // Allows clearing up our singleton instance.
  static void ResetForTesting();

  // Allow tests to inspect TraceEvents.
  TraceEvent* GetEventByHandle(TraceEventHandle handle);

  void SetProcessID(int process_id);

  // Process sort indices, if set, override the order of a process will appear
  // relative to other processes in the trace viewer. Processes are sorted first
  // on their sort index, ascending, then by their name, and then tid.
  void SetProcessSortIndex(int sort_index);

  // Sets the name of the process.
  void set_process_name(const std::string& process_name) {
    AutoLock lock(lock_);
    process_name_ = process_name;
  }

  bool IsProcessNameEmpty() const { return process_name_.empty(); }

  // Processes can have labels in addition to their names. Use labels, for
  // instance, to list out the web page titles that a process is handling.
  void UpdateProcessLabel(int label_id, const std::string& current_label);
  void RemoveProcessLabel(int label_id);

  // Thread sort indices, if set, override the order of a thread will appear
  // within its process in the trace viewer. Threads are sorted first on their
  // sort index, ascending, then by their name, and then tid.
  void SetThreadSortIndex(PlatformThreadId thread_id, int sort_index);

  // Allow setting an offset between the current TimeTicks time and the time
  // that should be reported.
  void SetTimeOffset(TimeDelta offset);

  size_t GetObserverCountForTest() const;

  // Call this method if the current thread may block the message loop to
  // prevent the thread from using the thread-local buffer because the thread
  // may not handle the flush request in time causing lost of unflushed events.
  void SetCurrentThreadBlocksMessageLoop();

#if defined(OS_WIN)
  // This function is called by the ETW exporting module whenever the ETW
  // keyword (flags) changes. This keyword indicates which categories should be
  // exported, so whenever it changes, we adjust accordingly.
  void UpdateETWCategoryGroupEnabledFlags();
#endif

  // Replaces |logged_events_| with a new TraceBuffer for testing.
  void SetTraceBufferForTesting(std::unique_ptr<TraceBuffer> trace_buffer);

 private:
  typedef unsigned int InternalTraceOptions;

  FRIEND_TEST_ALL_PREFIXES(TraceEventTestFixture,
                           TraceBufferRingBufferGetReturnChunk);
  FRIEND_TEST_ALL_PREFIXES(TraceEventTestFixture,
                           TraceBufferRingBufferHalfIteration);
  FRIEND_TEST_ALL_PREFIXES(TraceEventTestFixture,
                           TraceBufferRingBufferFullIteration);
  FRIEND_TEST_ALL_PREFIXES(TraceEventTestFixture, TraceBufferVectorReportFull);
  FRIEND_TEST_ALL_PREFIXES(TraceEventTestFixture,
                           ConvertTraceConfigToInternalOptions);
  FRIEND_TEST_ALL_PREFIXES(TraceEventTestFixture,
                           TraceRecordAsMuchAsPossibleMode);
  FRIEND_TEST_ALL_PREFIXES(TraceEventTestFixture, ConfigTraceBufferLimit);

  friend class base::NoDestructor<TraceLog>;

  // MemoryDumpProvider implementation.
  bool OnMemoryDump(const MemoryDumpArgs& args,
                    ProcessMemoryDump* pmd) override;

  // Enable/disable each category group based on the current mode_,
  // category_filter_ and event_filters_enabled_.
  // Enable the category group in the recording mode if category_filter_ matches
  // the category group, is not null. Enable category for filtering if any
  // filter in event_filters_enabled_ enables it.
  void UpdateCategoryRegistry();
  void UpdateCategoryState(TraceCategory* category);

  void CreateFiltersForTraceConfig();

  InternalTraceOptions GetInternalOptionsFromTraceConfig(
      const TraceConfig& config);

  class ThreadLocalEventBuffer;
  class OptionalAutoLock;
  struct RegisteredAsyncObserver;

  TraceLog();
  ~TraceLog() override;
  void AddMetadataEventsWhileLocked();
  template <typename T>
  void AddMetadataEventWhileLocked(int thread_id,
                                   const char* metadata_name,
                                   const char* arg_name,
                                   const T& value);

  InternalTraceOptions trace_options() const {
    return static_cast<InternalTraceOptions>(
        subtle::NoBarrier_Load(&trace_options_));
  }

  TraceBuffer* trace_buffer() const { return logged_events_.get(); }
  TraceBuffer* CreateTraceBuffer();

  std::string EventToConsoleMessage(unsigned char phase,
                                    const TimeTicks& timestamp,
                                    TraceEvent* trace_event);

  TraceEvent* AddEventToThreadSharedChunkWhileLocked(TraceEventHandle* handle,
                                                     bool check_buffer_is_full);
  void CheckIfBufferIsFullWhileLocked();
  void SetDisabledWhileLocked(uint8_t modes);

  TraceEvent* GetEventByHandleInternal(TraceEventHandle handle,
                                       OptionalAutoLock* lock);

  void FlushInternal(const OutputCallback& cb,
                     bool use_worker_thread,
                     bool discard_events);

  // |generation| is used in the following callbacks to check if the callback
  // is called for the flush of the current |logged_events_|.
  void FlushCurrentThread(int generation, bool discard_events);
  // Usually it runs on a different thread.
  static void ConvertTraceEventsToTraceFormat(
      std::unique_ptr<TraceBuffer> logged_events,
      const TraceLog::OutputCallback& flush_output_callback,
      const ArgumentFilterPredicate& argument_filter_predicate);
  void FinishFlush(int generation, bool discard_events);
  void OnFlushTimeout(int generation, bool discard_events);

  int generation() const {
    return static_cast<int>(subtle::NoBarrier_Load(&generation_));
  }
  bool CheckGeneration(int generation) const {
    return generation == this->generation();
  }
  void UseNextTraceBuffer();

  TimeTicks OffsetNow() const {
    // This should be TRACE_TIME_TICKS_NOW but include order makes that hard.
    return OffsetTimestamp(base::subtle::TimeTicksNowIgnoringOverride());
  }
  TimeTicks OffsetTimestamp(const TimeTicks& timestamp) const {
    return timestamp - time_offset_;
  }

  // Internal representation of trace options since we store the currently used
  // trace option as an AtomicWord.
  static const InternalTraceOptions kInternalNone;
  static const InternalTraceOptions kInternalRecordUntilFull;
  static const InternalTraceOptions kInternalRecordContinuously;
  static const InternalTraceOptions kInternalEchoToConsole;
  static const InternalTraceOptions kInternalRecordAsMuchAsPossible;
  static const InternalTraceOptions kInternalEnableArgumentFilter;

  // This lock protects TraceLog member accesses (except for members protected
  // by thread_info_lock_) from arbitrary threads.
  mutable Lock lock_;
  // This lock protects accesses to thread_names_, thread_event_start_times_
  // and thread_colors_.
  Lock thread_info_lock_;
  uint8_t enabled_modes_;  // See TraceLog::Mode.
  int num_traces_recorded_;
  std::unique_ptr<TraceBuffer> logged_events_;
  std::vector<std::unique_ptr<TraceEvent>> metadata_events_;

  // The lock protects observers access.
  mutable Lock observers_lock_;
  bool dispatching_to_observers_ = false;
  std::vector<EnabledStateObserver*> enabled_state_observers_;
  std::map<AsyncEnabledStateObserver*, RegisteredAsyncObserver>
      async_observers_;
  // Manages ownership of the owned observers. The owned observers will also be
  // added to |enabled_state_observers_|.
  std::vector<std::unique_ptr<EnabledStateObserver>>
      owned_enabled_state_observer_copy_;

  std::string process_name_;
  std::unordered_map<int, std::string> process_labels_;
  int process_sort_index_;
  std::unordered_map<int, int> thread_sort_indices_;
  std::unordered_map<int, std::string> thread_names_;
  base::Time process_creation_time_;

  // The following two maps are used only when ECHO_TO_CONSOLE.
  std::unordered_map<int, base::stack<TimeTicks>> thread_event_start_times_;
  std::unordered_map<std::string, int> thread_colors_;

  TimeTicks buffer_limit_reached_timestamp_;

  // XORed with TraceID to make it unlikely to collide with other processes.
  unsigned long long process_id_hash_;

  int process_id_;

  TimeDelta time_offset_;

  subtle::AtomicWord /* Options */ trace_options_;

  TraceConfig trace_config_;
  TraceConfig::EventFilters enabled_event_filters_;

  ThreadLocalPointer<ThreadLocalEventBuffer> thread_local_event_buffer_;
  ThreadLocalBoolean thread_blocks_message_loop_;
  ThreadLocalBoolean thread_is_in_trace_event_;

  // Contains task runners for the threads that have had at least one event
  // added into the local event buffer.
  std::unordered_map<int, scoped_refptr<SingleThreadTaskRunner>>
      thread_task_runners_;

  // For events which can't be added into the thread local buffer, e.g. events
  // from threads without a message loop.
  std::unique_ptr<TraceBufferChunk> thread_shared_chunk_;
  size_t thread_shared_chunk_index_;

  // Set when asynchronous Flush is in progress.
  OutputCallback flush_output_callback_;
  scoped_refptr<SequencedTaskRunner> flush_task_runner_;
  ArgumentFilterPredicate argument_filter_predicate_;
  subtle::AtomicWord generation_;
  bool use_worker_thread_;
  std::atomic<AddTraceEventOverrideCallback> add_trace_event_override_;
  std::atomic<OnFlushCallback> on_flush_callback_;
  std::atomic<UpdateDurationCallback> update_duration_callback_;

  FilterFactoryForTesting filter_factory_for_testing_;

  DISALLOW_COPY_AND_ASSIGN(TraceLog);
};

}  // namespace trace_event
}  // namespace base

#endif  // BASE_TRACE_EVENT_TRACE_LOG_H_