components/drive/event_logger.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef COMPONENTS_DRIVE_EVENT_LOGGER_H_
   6 #define COMPONENTS_DRIVE_EVENT_LOGGER_H_
   7
   8 #include <deque>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/basictypes.h"
  13 #include "base/compiler_specific.h"
  14 #include "base/logging.h"
  15 #include "base/synchronization/lock.h"
  16 #include "base/time/time.h"
  17
  18 namespace drive {
  19
  20 // The default history size used by EventLogger.
  21 const int kDefaultHistorySize = 1000;
  22
  23 // EventLogger is used to collect and expose text messages for diagnosing
  24 // behaviors of Google APIs stuff. For instance, the collected messages are
  25 // exposed to chrome:drive-internals.
  26 class EventLogger {
  27  public:
  28   // Represents a single event log.
  29   struct Event {
  30     Event(int id, logging::LogSeverity severity, const std::string& what);
  31     int id;  // Monotonically increasing ID starting from 0.
  32     logging::LogSeverity severity;  // Severity of the event.
  33     base::Time when;  // When the event occurred.
  34     std::string what;  // What happened.
  35   };
  36
  37   // Creates an event logger that keeps the latest kDefaultHistorySize events.
  38   EventLogger();
  39   ~EventLogger();
  40
  41   // Logs a message and its severity.
  42   // Can be called from any thread as long as the object is alive.
  43   void LogRawString(logging::LogSeverity severity, const std::string& what);
  44
  45   // Logs a message with formatting.
  46   // Can be called from any thread as long as the object is alive.
  47   void Log(logging::LogSeverity severity, const char* format, ...)
  48       PRINTF_FORMAT(3, 4);
  49
  50   // Sets the history size. The existing history is cleared.
  51   // Can be called from any thread as long as the object is alive.
  52   void SetHistorySize(size_t history_size);
  53
  54   // Gets the list of latest events (the oldest event comes first).
  55   // Can be called from any thread as long as the object is alive.
  56   std::vector<Event> GetHistory();
  57
  58  private:
  59   std::deque<Event> history_;  // guarded by lock_.
  60   size_t history_size_;  // guarded by lock_.
  61   int next_event_id_;  // guarded by lock_.
  62   base::Lock lock_;
  63
  64   DISALLOW_COPY_AND_ASSIGN(EventLogger);
  65 };
  66
  67 }  // namespace drive
  68
  69 #endif  // COMPONENTS_DRIVE_EVENT_LOGGER_H_