sync: make scheduling logic and job ownership more obvious.

sync/sessions/sync_session.h

 // 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.
 
 // A class representing an attempt to synchronize the local syncable data
 // store with a sync server. A SyncSession instance is passed as a stateful
 // bundle to and from various SyncerCommands with the goal of converging the
 // client view of data with that of the server. The commands twiddle with
 // session status in response to events and hiccups along the way, set and
 // query session progress with regards to conflict resolution and applying
@@ skipping 94 matching lines @@
   // Builds a thread-safe and read-only copy of the current session state.
   SyncSessionSnapshot TakeSnapshot() const;
 
   // Builds and sends a snapshot to the session context's listeners.
   void SendEventNotification(SyncEngineEvent::EventCause cause);
 
   // Returns true if this session contains data that should go through the sync
   // engine again.
   bool HasMoreToSync() const;
 
-  // Returns true if we completely ran the session without errors.
-  //
-  // There are many errors that could prevent a sync cycle from succeeding.
-  // These include invalid local state, inability to contact the server,
-  // inability to authenticate with the server, and server errors.  What they
-  // have in common is that the we either need to take some action and then
-  // retry the sync cycle or, in the case of transient errors, retry after some
-  // backoff timer has expired.  Most importantly, the SyncScheduler should not
-  // assume that the original action that triggered the sync cycle (ie. a nudge
-  // or a notification) has been properly serviced.
-  //
-  // This function also returns false if SyncShare has not been called on this
-  // session yet, or if ResetTransientState() has been called on this session
-  // since the last call to SyncShare.
-  bool Succeeded() const;
-
-  // Returns true if we reached the server successfully and the server did not
-  // return any error codes. Returns false if no connection was attempted.
-  bool SuccessfullyReachedServer() const;
+  // Returns true if we reached the server. Note that "reaching the server"
+  // here means that from an HTTP perspective, we succeeded (HTTP 200).  The
+  // server **MAY** have returned a sync protocol error.
+  // See SERVER_RETURN_* in the SyncerError enum for values.
+  bool DidReachServer() const;
 
   // Collects all state pertaining to how and why |s| originated and unions it
   // with corresponding state in |this|, leaving |s| unchanged.  Allows |this|
   // to take on the responsibilities |s| had (e.g. certain data types) in the
   // next SyncShare operation using |this|, rather than needed two separate
   // sessions.
   void Coalesce(const SyncSession& session);
 
-  // Compares the routing_info_, workers and payload map with the passed in
-  // session. Purges types from the above 3 which are not in session. Useful
+  // Compares the routing_info_, workers and payload map with those passed in.
+  // Purges types from the above 3 which are not present in latest. Useful
   // to update the sync session when the user has disabled some types from
   // syncing.
-  void RebaseRoutingInfoWithLatest(const SyncSession& session);
+  void RebaseRoutingInfoWithLatest(
+      const ModelSafeRoutingInfo& routing_info,
+      const std::vector<ModelSafeWorker*>& workers);
 
   // Should be called any time |this| is being re-used in a new call to
   // SyncShare (e.g., HasMoreToSync returned true).
   void PrepareForAnotherSyncCycle();
 
   // TODO(akalin): Split this into context() and mutable_context().
   SyncSessionContext* context() const { return context_; }
   Delegate* delegate() const { return delegate_; }
   syncable::WriteTransaction* write_transaction() { return write_transaction_; }
   const StatusController& status_controller() const {
@@ skipping 16 matching lines @@
 
   // Returns the set of groups which have enabled types.
   const std::set<ModelSafeGroup>& GetEnabledGroups() const;
 
   // Returns the set of enabled groups that have conflicts.
   std::set<ModelSafeGroup> GetEnabledGroupsWithConflicts() const;
 
   // Returns the set of enabled groups that have verified updates.
   std::set<ModelSafeGroup> GetEnabledGroupsWithVerifiedUpdates() const;
 
-  // Mark the session has having finished all the sync steps it needed.
-  void SetFinished();
-
  private:
   // Extend the encapsulation boundary to utilities for internal member
   // assignments. This way, the scope of these actions is explicit, they can't
   // be overridden, and assigning is always accompanied by unassigning.
   friend class ScopedSetSessionWriteTransaction;
 
   // The context for this session, guaranteed to outlive |this|.
   SyncSessionContext* const context_;
 
   // The source for initiating this sync session.
@@ skipping 17 matching lines @@
 
   // The routing info for the duration of this session, dictating which
   // datatypes should be synced and which workers should be used when working
   // on those datatypes.
   ModelSafeRoutingInfo routing_info_;
 
   // The set of groups with enabled types.  Computed from
   // |routing_info_|.
   std::set<ModelSafeGroup> enabled_groups_;
 
-  // Whether this session has reached its last step or not. Gets reset on each
-  // new cycle (via PrepareForAnotherSyncCycle).
-  bool finished_;
-
   DISALLOW_COPY_AND_ASSIGN(SyncSession);
 };
 
 // Installs a WriteTransaction to a given session and later clears it when the
 // utility falls out of scope. Transactions are not nestable, so it is an error
 // to try and use one of these if the session already has a transaction.
 class ScopedSetSessionWriteTransaction {
  public:
   ScopedSetSessionWriteTransaction(SyncSession* session,
                                    syncable::WriteTransaction* trans)
       : session_(session) {
     DCHECK(!session_->write_transaction_);
     session_->write_transaction_ = trans;
   }
   ~ScopedSetSessionWriteTransaction() { session_->write_transaction_ = NULL; }
 
  private:
   SyncSession* session_;
   DISALLOW_COPY_AND_ASSIGN(ScopedSetSessionWriteTransaction);
 };
 
 }  // namespace sessions
 }  // namespace syncer
 
 #endif  // SYNC_SESSIONS_SYNC_SESSION_H_