components/sync_driver/shared_change_processor.h

   1 // Copyright 2014 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_SYNC_DRIVER_SHARED_CHANGE_PROCESSOR_H_
   6 #define COMPONENTS_SYNC_DRIVER_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/single_thread_task_runner.h"
  12 #include "base/synchronization/lock.h"
  13 #include "components/sync_driver/data_type_error_handler.h"
  14 #include "sync/api/sync_change_processor.h"
  15 #include "sync/api/sync_data.h"
  16 #include "sync/api/sync_error.h"
  17 #include "sync/api/sync_error_factory.h"
  18 #include "sync/api/sync_merge_result.h"
  19 #include "sync/internal_api/public/engine/model_safe_worker.h"
  20
  21 namespace syncer {
  22 class SyncableService;
  23 struct UserShare;
  24 }  // namespace syncer
  25
  26 namespace sync_driver {
  27
  28 class ChangeProcessor;
  29 class GenericChangeProcessor;
  30 class GenericChangeProcessorFactory;
  31 class DataTypeErrorHandler;
  32 class SyncApiComponentFactory;
  33
  34 // A ref-counted wrapper around a GenericChangeProcessor for use with datatypes
  35 // that don't live on the UI thread.
  36 //
  37 // We need to make it refcounted as the ownership transfer from the
  38 // DataTypeController is dependent on threading, and hence racy. The
  39 // SharedChangeProcessor should be created on the UI thread, but should only be
  40 // connected and used on the same thread as the datatype it interacts with.
  41 //
  42 // The only thread-safe method is Disconnect, which will disconnect from the
  43 // generic change processor, letting us shut down the syncer/datatype without
  44 // waiting for non-UI threads.
  45 //
  46 // Note: since we control the work being done while holding the lock, we ensure
  47 // no I/O or other intensive work is done while blocking the UI thread (all
  48 // the work is in-memory sync interactions).
  49 //
  50 // We use virtual methods so that we can use mock's in testing.
  51 class SharedChangeProcessor
  52     : public base::RefCountedThreadSafe<SharedChangeProcessor> {
  53  public:
  54   // Create an uninitialized SharedChangeProcessor.
  55   SharedChangeProcessor();
  56
  57   // Connect to the Syncer and prepare to handle changes for |type|. Will
  58   // create and store a new GenericChangeProcessor and return a weak pointer to
  59   // the syncer::SyncableService associated with |type|.
  60   // Note: If this SharedChangeProcessor has been disconnected, or the
  61   // syncer::SyncableService was not alive, will return a null weak pointer.
  62   virtual base::WeakPtr<syncer::SyncableService> Connect(
  63       SyncApiComponentFactory* sync_factory,
  64       GenericChangeProcessorFactory* processor_factory,
  65       syncer::UserShare* user_share,
  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 int GetSyncCount();
  83   virtual syncer::SyncError ProcessSyncChanges(
  84       const tracked_objects::Location& from_here,
  85       const syncer::SyncChangeList& change_list);
  86   virtual syncer::SyncDataList GetAllSyncData(syncer::ModelType type) const;
  87   virtual syncer::SyncError GetAllSyncDataReturnError(
  88       syncer::ModelType type,
  89       syncer::SyncDataList* data) const;
  90   virtual syncer::SyncError UpdateDataTypeContext(
  91       syncer::ModelType type,
  92       syncer::SyncChangeProcessor::ContextRefreshStatus refresh_status,
  93       const std::string& context);
  94   virtual bool SyncModelHasUserCreatedNodes(bool* has_nodes);
  95   virtual bool CryptoReadyIfNecessary();
  96
  97   // If a datatype context associated with the current type exists, fills
  98   // |context| and returns true. Otheriwse, if there has not been a context
  99   // set, returns false.
 100   virtual bool GetDataTypeContext(std::string* context) const;
 101
 102   virtual syncer::SyncError CreateAndUploadError(
 103       const tracked_objects::Location& location,
 104       const std::string& message);
 105
 106   ChangeProcessor* generic_change_processor();
 107
 108  protected:
 109   friend class base::RefCountedThreadSafe<SharedChangeProcessor>;
 110   virtual ~SharedChangeProcessor();
 111
 112  private:
 113   // Monitor lock for this object. All methods that interact with the change
 114   // processor must aquire this lock and check whether we're disconnected or
 115   // not. Once disconnected, all attempted changes to or loads from the change
 116   // processor return errors. This enables us to shut down the syncer without
 117   // having to wait for possibly non-UI thread datatypes to complete work.
 118   mutable base::Lock monitor_lock_;
 119   bool disconnected_;
 120
 121   // The sync datatype we were last connected to.
 122   syncer::ModelType type_;
 123
 124   // The frontend / UI MessageLoop this object is constructed on. May also be
 125   // destructed and/or disconnected on this loop, see ~SharedChangeProcessor.
 126   const scoped_refptr<const base::SingleThreadTaskRunner> frontend_task_runner_;
 127
 128   // The loop that all methods except the constructor, destructor, and
 129   // Disconnect() should be called on.  Set in Connect().
 130   scoped_refptr<base::SingleThreadTaskRunner> backend_task_runner_;
 131
 132   // Used only on |backend_loop_|.
 133   GenericChangeProcessor* generic_change_processor_;
 134
 135   DataTypeErrorHandler* error_handler_;
 136
 137   DISALLOW_COPY_AND_ASSIGN(SharedChangeProcessor);
 138 };
 139
 140 }  // namespace sync_driver
 141
 142 #endif  // COMPONENTS_SYNC_DRIVER_SHARED_CHANGE_PROCESSOR_H_