[Sync] Store the past 10 traffic records in memory.

sync/engine/traffic_recorder.cc

Index: sync/engine/traffic_recorder.cc
diff --git a/sync/engine/traffic_recorder.cc b/sync/engine/traffic_recorder.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e9ea716c03b0076e170c6c2ffbb7678c34d315a4
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+++ b/sync/engine/traffic_recorder.cc
@@ -0,0 +1,81 @@
+// 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.
+
+#include "sync/engine/traffic_recorder.h"
+
+#include "base/json/json_writer.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/values.h"
+#include "sync/protocol/proto_value_conversions.h"
+#include "sync/protocol/sync.pb.h"
+#include "sync/sessions/sync_session.h"
+
+namespace browser_sync {
+
+TrafficRecorder::TrafficRecord::TrafficRecord(const std::string& message,
+                                              TrafficMessageType message_type,
+                                              bool truncated) :
+    message(message),
+    message_type(message_type),
+    truncated(truncated) {
+}
+
+TrafficRecorder::TrafficRecord::TrafficRecord()
+    : message_type(UNKNOWN_MESSAGE_TYPE),
+      truncated(false) {
+}
+
+TrafficRecorder::TrafficRecord::~TrafficRecord() {
+}
+
+TrafficRecorder::TrafficRecorder(unsigned int max_messages,
+    unsigned int max_message_size)
+    : max_messages_(max_messages),
+      max_message_size_(max_message_size) {
+}
+
+TrafficRecorder::~TrafficRecorder() {
+}
+
+
+void TrafficRecorder::AddTrafficToQueue(TrafficRecord* record) {
+  records_.resize(records_.size() + 1);
+  std::swap(records_.back(), *record);
+
+  // We might have more records than our limit.
+  // Maintain the size invariant by deleting items.
+  while (records_.size() > max_messages_) {
+    records_.pop_front();
+  }
+}
+
+void TrafficRecorder::StoreProtoInQueue(
+    const ::google::protobuf::MessageLite& msg,
+    TrafficMessageType type) {
+  bool truncated = false;
+  std::string message;
+  if (static_cast<unsigned int>(msg.ByteSize()) >= max_message_size_) {
+    // TODO(lipalani): Trim the specifics to fit in size.
+    truncated = true;
+  } else {
+    msg.SerializeToString(&message);
+  }
+
+  TrafficRecord record(message, type, truncated);
+  AddTrafficToQueue(&record);
+}
+
+void TrafficRecorder::RecordClientToServerMessage(
+    const sync_pb::ClientToServerMessage& msg) {
+  StoreProtoInQueue(msg, CLIENT_TO_SERVER_MESSAGE);
+}
+
+void TrafficRecorder::RecordClientToServerResponse(
+    const sync_pb::ClientToServerResponse& response) {
+  StoreProtoInQueue(response, CLIENT_TO_SERVER_RESPONSE);
+}
+
+}  // namespace browser_sync
+