chrome/browser/sync/glue/shared_change_processor.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_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_H_
   6 #define CHROME_BROWSER_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_H_
   7
   8 #include "base/location.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "base/memory/weak_ptr.h"
  11 #include "base/message_loop_proxy.h"
  12 #include "base/synchronization/lock.h"
  13 #include "chrome/browser/sync/glue/data_type_error_handler.h"
  14 #include "sync/api/sync_change_processor.h"
  15 #include "sync/api/sync_error.h"
  16 #include "sync/api/sync_error_factory.h"
  17 #include "sync/api/sync_merge_result.h"
  18 #include "sync/internal_api/public/engine/model_safe_worker.h"
  19
  20 class ProfileSyncComponentsFactory;
  21 class ProfileSyncService;
  22
  23 namespace syncer {
  24 class SyncData;
  25 class SyncableService;
  26
  27 typedef std::vector<syncer::SyncData> SyncDataList;
  28 }  // namespace
  29
  30 namespace browser_sync {
  31
  32 class GenericChangeProcessor;
  33 class DataTypeErrorHandler;
  34
  35 // A ref-counted wrapper around a GenericChangeProcessor for use with datatypes
  36 // that don't live on the UI thread.
  37 //
  38 // We need to make it refcounted as the ownership transfer from the
  39 // DataTypeController is dependent on threading, and hence racy. The
  40 // SharedChangeProcessor should be created on the UI thread, but should only be
  41 // connected and used on the same thread as the datatype it interacts with.
  42 //
  43 // The only thread-safe method is Disconnect, which will disconnect from the
  44 // generic change processor, letting us shut down the syncer/datatype without
  45 // waiting for non-UI threads.
  46 //
  47 // Note: since we control the work being done while holding the lock, we ensure
  48 // no I/O or other intensive work is done while blocking the UI thread (all
  49 // the work is in-memory sync interactions).
  50 //
  51 // We use virtual methods so that we can use mock's in testing.
  52 class SharedChangeProcessor
  53     : public base::RefCountedThreadSafe<SharedChangeProcessor> {
  54  public:
  55   // Create an uninitialized SharedChangeProcessor (to be later connected).
  56   SharedChangeProcessor();
  57
  58   // Connect to the Syncer and prepare to handle changes for |type|. Will
  59   // create and store a new GenericChangeProcessor and return a weak pointer to
  60   // the syncer::SyncableService associated with |type|.
  61   // Note: If this SharedChangeProcessor has been disconnected, or the
  62   // syncer::SyncableService was not alive, will return a null weak pointer.
  63   virtual base::WeakPtr<syncer::SyncableService> Connect(
  64     ProfileSyncComponentsFactory* sync_factory,
  65     ProfileSyncService* sync_service,
  66     DataTypeErrorHandler* error_handler,
  67     syncer::ModelType type,
  68     const base::WeakPtr<syncer::SyncMergeResult>& merge_result);
  69
  70   // Disconnects from the generic change processor. May be called from any
  71   // thread. After this, all attempts to interact with the change processor by
  72   // |local_service_| are dropped and return errors. The syncer will be safe to
  73   // shut down from the point of view of this datatype.
  74   // Note: Once disconnected, you cannot reconnect without creating a new
  75   // SharedChangeProcessor.
  76   // Returns: true if we were previously succesfully connected, false if we were
  77   // already disconnected.
  78   virtual bool Disconnect();
  79
  80   // GenericChangeProcessor stubs (with disconnect support).
  81   // Should only be called on the same thread the datatype resides.
  82   virtual syncer::SyncError GetSyncData(
  83       syncer::SyncDataList* current_sync_data);
  84   virtual int GetSyncCount();
  85   virtual syncer::SyncError ProcessSyncChanges(
  86       const tracked_objects::Location& from_here,
  87       const syncer::SyncChangeList& change_list);
  88   virtual bool SyncModelHasUserCreatedNodes(bool* has_nodes);
  89   virtual bool CryptoReadyIfNecessary();
  90
  91   // Register |generic_change_processor_| as the change processor for the
  92   // current type on |model_safe_group|.
  93   // Does nothing if |disconnected_| is true.
  94   virtual void ActivateDataType(syncer::ModelSafeGroup model_safe_group);
  95
  96   virtual syncer::SyncError CreateAndUploadError(
  97       const tracked_objects::Location& location,
  98       const std::string& message);
  99
 100  protected:
 101   friend class base::RefCountedThreadSafe<SharedChangeProcessor>;
 102   virtual ~SharedChangeProcessor();
 103
 104  private:
 105   // Monitor lock for this object. All methods that interact with the change
 106   // processor must aquire this lock and check whether we're disconnected or
 107   // not. Once disconnected, all attempted changes to or loads from the change
 108   // processor return errors. This enables us to shut down the syncer without
 109   // having to wait for possibly non-UI thread datatypes to complete work.
 110   mutable base::Lock monitor_lock_;
 111   bool disconnected_;
 112
 113   // The sync datatype we were last connected to.
 114   syncer::ModelType type_;
 115
 116   // The ProfileSyncService we're currently connected to.
 117   ProfileSyncService* sync_service_;
 118
 119   // The loop that all methods except the constructor, destructor, and
 120   // Disconnect() should be called on.  Set in Connect().
 121   scoped_refptr<base::MessageLoopProxy> backend_loop_;
 122
 123   // Used only on |backend_loop_|.
 124   GenericChangeProcessor* generic_change_processor_;
 125
 126   DataTypeErrorHandler* error_handler_;
 127
 128   DISALLOW_COPY_AND_ASSIGN(SharedChangeProcessor);
 129 };
 130
 131 }  // namespace browser_sync
 132
 133 #endif  // CHROME_BROWSER_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_H_