chrome/browser/metrics/tracking_synchronizer.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 CHROME_BROWSER_METRICS_TRACKING_SYNCHRONIZER_H_
   6 #define CHROME_BROWSER_METRICS_TRACKING_SYNCHRONIZER_H_
   7
   8 #include <map>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/basictypes.h"
  13 #include "base/lazy_instance.h"
  14 #include "base/memory/ref_counted.h"
  15 #include "base/memory/weak_ptr.h"
  16 #include "content/public/browser/profiler_subscriber.h"
  17
  18 // This class maintains state that is used to upload profiler data from the
  19 // various processes, into the browser process. Such transactions are usually
  20 // instigated by the browser. In general, a process will respond by gathering
  21 // profiler data, and transmitting the pickled profiler data. We collect the
  22 // data in asynchronous mode that doesn't block the UI thread.
  23 //
  24 // To assure that all the processes have responded, a counter is maintained
  25 // to indicate the number of pending (not yet responsive) processes. We tag
  26 // each group of requests with a sequence number. For each group of requests, we
  27 // create RequestContext object which stores the sequence number, pending
  28 // processes and the callback_object that needs to be notified when we receive
  29 // an update from processes. When an update arrives we find the RequestContext
  30 // associated with sequence number and send the unpickled profiler data to the
  31 // |callback_object_|.
  32
  33 namespace chrome_browser_metrics {
  34
  35 class TrackingSynchronizerObserver;
  36
  37 class TrackingSynchronizer
  38     : public content::ProfilerSubscriber,
  39       public base::RefCountedThreadSafe<TrackingSynchronizer> {
  40  public:
  41   // Construction also sets up the global singleton instance. This instance is
  42   // used to communicate between the IO and UI thread, and is destroyed only as
  43   // the main thread (browser_main) terminates, which means the IO thread has
  44   // already completed, and will not need this instance any further.
  45   TrackingSynchronizer();
  46
  47   // Contact all processes, and get them to upload to the browser any/all
  48   // changes to profiler data. It calls |callback_object|'s SetData method with
  49   // the data received from each sub-process.
  50   // This method is accessible on UI thread.
  51   static void FetchProfilerDataAsynchronously(
  52       const base::WeakPtr<TrackingSynchronizerObserver>& callback_object);
  53
  54   // ------------------------------------------------------
  55   // ProfilerSubscriber methods for browser child processes
  56   // ------------------------------------------------------
  57
  58   // Update the number of pending processes for the given |sequence_number|.
  59   // This is called on UI thread.
  60   virtual void OnPendingProcesses(int sequence_number,
  61                                   int pending_processes,
  62                                   bool end) OVERRIDE;
  63
  64  private:
  65   friend class base::RefCountedThreadSafe<TrackingSynchronizer>;
  66
  67   class RequestContext;
  68
  69   virtual ~TrackingSynchronizer();
  70
  71   // Send profiler_data back to callback_object_ by calling
  72   // DecrementPendingProcessesAndSendData which records that we are waiting
  73   // for one less profiler data from renderer or browser child process for the
  74   // given sequence number. This method is accessible on UI thread.
  75   virtual void OnProfilerDataCollected(
  76       int sequence_number,
  77       const tracked_objects::ProcessDataSnapshot& profiler_data,
  78       int process_type) OVERRIDE;
  79
  80   // Establish a new sequence_number_, and use it to notify all the processes of
  81   // the need to supply, to the browser, their tracking data. It also registers
  82   // |callback_object| in |outstanding_requests_| map. Return the
  83   // sequence_number_ that was used. This method is accessible on UI thread.
  84   int RegisterAndNotifyAllProcesses(
  85       const base::WeakPtr<TrackingSynchronizerObserver>& callback_object);
  86
  87   // It finds the RequestContext for the given |sequence_number| and notifies
  88   // the RequestContext's |callback_object_| about the |value|. This is called
  89   // whenever we receive profiler data from processes. It also records that we
  90   // are waiting for one less profiler data from a process for the given
  91   // sequence number. If we have received a response from all renderers and
  92   // browser processes, then it calls RequestContext's DeleteIfAllDone to delete
  93   // the entry for sequence_number. This method is accessible on UI thread.
  94   void DecrementPendingProcessesAndSendData(
  95       int sequence_number,
  96       const tracked_objects::ProcessDataSnapshot& profiler_data,
  97       int process_type);
  98
  99   // Get a new sequence number to be sent to processes from browser process.
 100   // This method is accessible on UI thread.
 101   int GetNextAvailableSequenceNumber();
 102
 103   // We don't track the actual processes that are contacted for an update, only
 104   // the count of the number of processes, and we can sometimes time-out and
 105   // give up on a "slow to respond" process.  We use a sequence_number to be
 106   // sure a response from a process is associated with the current round of
 107   // requests. All sequence numbers used are non-negative.
 108   // last_used_sequence_number_ is the most recently used number (used to avoid
 109   // reuse for a long time).
 110   int last_used_sequence_number_;
 111
 112   DISALLOW_COPY_AND_ASSIGN(TrackingSynchronizer);
 113 };
 114
 115 }  // namespace chrome_browser_metrics
 116
 117 #endif  // CHROME_BROWSER_METRICS_TRACKING_SYNCHRONIZER_H_