Refactored CL for moving the output to a separate thread.

webrtc/call/rtc_event_log_helper_thread.cc

Index: webrtc/call/rtc_event_log_helper_thread.cc
diff --git a/webrtc/call/rtc_event_log_helper_thread.cc b/webrtc/call/rtc_event_log_helper_thread.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5d90256a0ede01861d91b09faf10d70da22ae64e
--- /dev/null
+++ b/webrtc/call/rtc_event_log_helper_thread.cc
@@ -0,0 +1,286 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/call/rtc_event_log_helper_thread.h"
+
+#include <algorithm>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/system_wrappers/include/logging.h"
+
+#ifdef ENABLE_RTC_EVENT_LOG
+
+namespace webrtc {
+
+namespace {
+const int kEventsInHistory = 10000;
+
+bool IsConfigEvent(const rtclog::Event& event) {
+  rtclog::Event_EventType event_type = event.type();
+  return event_type == rtclog::Event::VIDEO_RECEIVER_CONFIG_EVENT ||
+         event_type == rtclog::Event::VIDEO_SENDER_CONFIG_EVENT ||
+         event_type == rtclog::Event::AUDIO_RECEIVER_CONFIG_EVENT ||
+         event_type == rtclog::Event::AUDIO_SENDER_CONFIG_EVENT;
+}
+}  // namespace
+
+// RtcEventLogImpl member functions.
+RtcEventLogHelperThread::RtcEventLogHelperThread(
+    SwapQueue<ControlMessage>* message_queue,
+    SwapQueue<std::unique_ptr<rtclog::Event>>* event_queue,
+    rtc::Event* wake_up,
+    rtc::Event* stopped,
+    const Clock* const clock)
+    : message_queue_(message_queue),
+      event_queue_(event_queue),
+      history_(kEventsInHistory),
+      config_history_(),
+      file_(FileWrapper::Create()),
+      thread_(&ThreadOutputFunction, this, "RtcEventLog thread"),
+      max_size_bytes_(std::numeric_limits<int64_t>::max()),
+      written_bytes_(0),
+      start_time_(0),
+      stop_time_(std::numeric_limits<int64_t>::max()),
+      has_recent_event_(false),
+      most_recent_event_(),
+      output_string_(),
+      wake_up_(wake_up),
+      stopped_(stopped),
+      clock_(clock) {
+  RTC_DCHECK(message_queue_);
+  RTC_DCHECK(event_queue_);
+  RTC_DCHECK(wake_up_);
+  RTC_DCHECK(stopped_);
+  RTC_DCHECK(clock_);
+  thread_.Start();
+}
+
+RtcEventLogHelperThread::~RtcEventLogHelperThread() {
+  ControlMessage message;
+  message.message_type = ControlMessage::TERMINATE_THREAD;
+  message.stop_time = clock_->TimeInMicroseconds();
+  while (!message_queue_->Insert(&message)) {
+    // We can't destroy the event log until we have stopped the thread,
+    // so clear the message queue and try again. Note that if we clear
+    // any STOP_FILE events, then the threads calling StopLogging would likely
+    // wait indefinitely. However, there should not be any such calls as we
+    // are executing the destructor.
+    LOG(LS_WARNING) << "Clearing message queue to terminate thread.";
+    message_queue_->Clear();
+  }
+  wake_up_->Set();  // Wake up the output thread.
+  thread_.Stop();   // Wait for the thread to terminate.
+}
+
+bool RtcEventLogHelperThread::AppendEventToString(rtclog::Event* event) {
+  rtclog::EventStream event_stream;
+  event_stream.add_stream();
+  event_stream.mutable_stream(0)->Swap(event);
+  // We create a new event stream per event but because of the way protobufs
+  // are encoded, events can be merged by concatenating them. Therefore,
+  // it will look like a single stream when we read it back from file.
+  bool stop = true;
+  if (written_bytes_ + static_cast<int64_t>(output_string_.size()) +
+          event_stream.ByteSize() <=
+      max_size_bytes_) {
+    event_stream.AppendToString(&output_string_);
+    stop = false;
+  }
+  // Swap the event back so that we don't mix event types in the queues.
+  event_stream.mutable_stream(0)->Swap(event);
+  return stop;
+}
+
+// Traverses the SwapQueues in timestamp order and copies all events earlier

[the sun, 2016/04/20 11:30:15]

nit: "SwapQueues" isn't strictly true

[terelius, 2016/04/21 08:10:41]

Ack. Since this function basically consists of two if-statements that are called
from LogToMemory and LogToFile respectively, I inlined the relevant parts and
removed this function. The total line count is essentially the same (+1 or 2
lines), but we get less nested if-statements and the logic is spread out between
fewer functions.

+// than |time_limit| either to the history or to a string that will be
+// written to disc.
+bool RtcEventLogHelperThread::ProcessInOrder(bool memory, int64_t time_limit) {
+  if (!has_recent_event_) {
+    has_recent_event_ = event_queue_->Remove(&most_recent_event_);
+  }
+
+  while (has_recent_event_ &&
+         most_recent_event_->timestamp_us() <= time_limit) {
+    if (memory) {
+      if (IsConfigEvent(*most_recent_event_)) {
+        config_history_.push_back(std::move(most_recent_event_));

[the sun, 2016/04/20 11:30:15]

Is it really ok that config_history_ will grow without bounds? I don't see where
it is emptied.

[terelius, 2016/04/21 08:10:41]

You are right; it is never emptied. This is the same behavior as the current
implementation, however.

(The problem is that there is no good way to know when a stream configuration is
no longer needed. Even if we have no packets on a particular SSRC in the history
right now, we still need to keep the config in case we receive packets again
later.)

+      } else {
+        history_.push_back(std::move(most_recent_event_));
+      }
+    } else {
+      bool stop = AppendEventToString(most_recent_event_.get());
+      if (stop) {
+        return stop;
+      }
+      if (IsConfigEvent(*most_recent_event_)) {
+        config_history_.push_back(std::move(most_recent_event_));
+      }
+    }
+    has_recent_event_ = event_queue_->Remove(&most_recent_event_);
+  }
+  // We want to stop logging if the remaining events are more recent than the
+  // time limit, or in other words if we have terminated the loop despite
+  // having more events in the queue.
+  return has_recent_event_ && most_recent_event_->timestamp_us() > stop_time_;
+}
+
+void RtcEventLogHelperThread::LogToMemory() {
+  RTC_DCHECK(!file_->Open());
+
+  // Process each event in order and append it to the appropriate history_.
+  int64_t current_time = clock_->TimeInMicroseconds();
+  ProcessInOrder(true, current_time);
+}
+
+void RtcEventLogHelperThread::StartLogFile() {
+  RTC_DCHECK(file_->Open());
+  bool stop = false;
+  output_string_.clear();
+
+  // Create and serialize the LOG_START event.
+  rtclog::Event start_event;
+  start_event.set_timestamp_us(start_time_);
+  start_event.set_type(rtclog::Event::LOG_START);
+  AppendEventToString(&start_event);
+
+  // Serialize the config information for all old streams.
+  for (auto& event : config_history_) {
+    AppendEventToString(event.get());
+  }
+
+  // Serialize the events in the event queue.
+  while (!history_.empty() && !stop) {
+    stop = AppendEventToString(history_.front().get());
+    if (!stop) {
+      history_.pop_front();
+    }
+  }
+
+  // Write to file.
+  file_->Write(output_string_.data(), output_string_.size());
+  written_bytes_ += output_string_.size();
+
+  // Free the allocated memory since we probably won't need this amount of
+  // space again.
+  output_string_.clear();
+  output_string_.shrink_to_fit();
+
+  if (stop) {
+    RTC_DCHECK(file_->Open());
+    StopLogFile();
+  }
+}
+
+void RtcEventLogHelperThread::LogToFile() {
+  RTC_DCHECK(file_->Open());
+  output_string_.clear();
+
+  // Process each event in order and append it to the output_string_.
+  int64_t current_time = clock_->TimeInMicroseconds();
+  bool stop = ProcessInOrder(false, std::min(current_time, stop_time_));
+
+  // Write string to file.
+  file_->Write(output_string_.data(), output_string_.size());
+  written_bytes_ += output_string_.size();
+
+  if (!file_->Open()) {
+    LOG(LS_WARNING) << "WebRTC event log file closed by FileWrapper.";
+  }
+
+  if (stop) {
+    RTC_DCHECK(file_->Open());
+    StopLogFile();
+  }
+}
+
+void RtcEventLogHelperThread::StopLogFile() {
+  RTC_DCHECK(file_->Open());
+  output_string_.clear();
+
+  rtclog::Event end_event;
+  end_event.set_timestamp_us(stop_time_);
+  end_event.set_type(rtclog::Event::LOG_END);
+  AppendEventToString(&end_event);
+
+  if (written_bytes_ + static_cast<int64_t>(output_string_.size()) <=
+      max_size_bytes_) {
+    file_->Write(output_string_.data(), output_string_.size());
+    written_bytes_ += output_string_.size();
+  }
+
+  max_size_bytes_ = std::numeric_limits<int64_t>::max();
+  written_bytes_ = 0;
+  start_time_ = 0;
+  stop_time_ = std::numeric_limits<int64_t>::max();
+  output_string_.clear();
+  file_->CloseFile();
+  RTC_DCHECK(!file_->Open());
+}
+
+void RtcEventLogHelperThread::WriteLog() {
+  ControlMessage message;
+
+  while (true) {
+    // Process control messages.
+    while (message_queue_->Remove(&message)) {
+      switch (message.message_type) {
+        case ControlMessage::START_FILE:
+          if (!file_->Open()) {
+            max_size_bytes_ = message.max_size_bytes;
+            start_time_ = message.start_time;
+            stop_time_ = message.stop_time;
+            file_.swap(message.file);
+            StartLogFile();
+          } else {
+            // Already started. Ignore message and close file handle.
+            message.file->CloseFile();
+          }
+          break;
+        case ControlMessage::STOP_FILE:
+          if (file_->Open()) {
+            stop_time_ = message.stop_time;
+            LogToFile();  // Log remaining events from message queues.
+          }
+          // LogToFile might stop on it's own so we need to recheck the state.
+          if (file_->Open()) {
+            StopLogFile();
+          }
+          stopped_->Set();
+          break;
+        case ControlMessage::TERMINATE_THREAD:
+          if (file_->Open()) {
+            StopLogFile();
+          }
+          return;
+      }
+    }
+
+    // Write events to file or memory
+    if (file_->Open()) {
+      LogToFile();
+    } else {
+      LogToMemory();
+    }
+
+    // Accumulate a new batch of events instead of processing them one at a
+    // time.
+    wake_up_->Wait(50);
+  }
+}
+
+bool RtcEventLogHelperThread::ThreadOutputFunction(void* obj) {
+  RtcEventLogHelperThread* helper = static_cast<RtcEventLogHelperThread*>(obj);
+  helper->WriteLog();
+  return false;
+}
+
+}  // namespace webrtc
+
+#endif  // ENABLE_RTC_EVENT_LOG