text: /**
  *    Copyright (C) 2013 10gen Inc.
  *
  *    This program is free software: you can redistribute it and/or  modify
  *    it under the terms of the GNU Affero General Public License, version 3,
  *    as published by the Free Software Foundation.
  *
  *    This program is distributed in the hope that it will be useful,
  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *    GNU Affero General Public License for more details.
  *
  *    You should have received a copy of the GNU Affero General Public License
  *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
  
  
  #pragma once
  
  #include "mongo/db/repl/oplogreader.h"
  #include "mongo/util/background.h"
  
  
  namespace mongo {
  
      class Member;
  
      class SyncSourceFeedback : public BackgroundJob {
      public:
          SyncSourceFeedback() : BackgroundJob(false /*don't selfdelete*/),
                                _syncTarget(NULL),
                                _oplogReader(new OplogReader()),
                                _supportsUpdater(false),
                                _positionChanged(false),
                                _handshakeNeeded(false) {}
  
          ~SyncSourceFeedback() {
              delete _oplogReader;
          }
  
          /// Adds an entry to _member for a secondary that has connected to us.
          void associateMember(const BSONObj& id, const int memberId);
  
          /// Ensures local.me is populated and populates it if not.
          void ensureMe();
  
          /// Passes handshake up the replication chain, upon receiving a handshake.
          void forwardSlaveHandshake();
  
          void updateSelfInMap(const OpTime& ot) {
              updateMap(_me["_id"].OID(), ot);
          }
  
          /// Connect to sync target and create OplogReader if needed.
          bool connect(const Member* target);
  
          void resetConnection() {
              LOG(1) << "resetting connection in sync source feedback";
              _connection.reset();
          }
  
          void resetOplogReaderConnection() {
              _oplogReader->resetConnection();
          }
  
          /// Used extensively in bgsync, to see if we need to use the OplogReader syncing method.
          bool supportsUpdater() const {
              // oplogReader will be NULL if new updater is supported
              //boost::unique_lock<boost::mutex> lock(_mtx);
              return _supportsUpdater;
          }
  
          /// Transfers information about a chained node's oplog position from downstream to upstream
          void percolate(const mongo::OID& rid, const OpTime& ot);
  
          /// Updates the _slaveMap to be forwarded to the sync target.
          void updateMap(const mongo::OID& rid, const OpTime& ot);
  
          std::string name() const { return "SyncSourceFeedbackThread"; }
  
          /// Loops forever, passing updates when they are present.
          void run();
  
          /* The below methods just fall through to OplogReader and are only used when our sync target
           * does not support the update command.
           */
          bool connectOplogReader(const std::string& hostName) {
              return _oplogReader->connect(hostName, _me);
          }
  
          bool connect(const mongo::OID& rid, const int from, const string& to) {
              return _oplogReader->connect(rid, from, to);
          }
  
          void ghostQueryGTE(const char *ns, OpTime t) {
              _oplogReader->ghostQueryGTE(ns, t);
          }
  
          bool haveCursor() {
              return _oplogReader->haveCursor();
          }
  
          bool more() {
              return _oplogReader->more();
          }
  
          bool moreInCurrentBatch() {
              return _oplogReader->moreInCurrentBatch();
          }
  
          BSONObj nextSafe() {
              return _oplogReader->nextSafe();
          }
  
          void tailCheck() {
              _oplogReader->tailCheck();
          }
  
          void tailingQueryGTE(const char *ns, OpTime t, const BSONObj* fields=0) {
              _oplogReader->tailingQueryGTE(ns, t, fields);
          }
  
      private:
          /* Generally replAuthenticate will only be called within system threads to fully
           * authenticate connections to other nodes in the cluster that will be used as part of
           * internal operations. If a user-initiated action results in needing to call
           * replAuthenticate, you can call it with skipAuthCheck set to false. Only do this if you
           * are certain that the proper auth checks have already run to ensure that the user is
           * authorized to do everything that this connection will be used for!
           */
          bool replAuthenticate(bool skipAuthCheck);
  
          /* Sends initialization information to our sync target, also determines whether or not they
           * support the updater command.
           */
          bool replHandshake();
  
          /* Inform the sync target of our current position in the oplog, as well as the positions
           * of all secondaries chained through us.
           */
          bool updateUpstream();
  
          bool hasConnection() {
              return _connection.get();
          }
  
          /// Connect to sync target and create OplogReader if needed.
          bool _connect(const std::string& hostName);
  
          // stores our OID to be passed along in commands
          BSONObj _me;
          // the member we are currently syncing from
          const Member* _syncTarget;
          // holds the oplogReader for use when we fall back to old style updates
          OplogReader* _oplogReader;
          // our connection to our sync target
          boost::scoped_ptr<DBClientConnection> _connection;
          // tracks whether we are in fallback mode or not
          bool _supportsUpdater;
          // protects connection
          boost::mutex _connmtx;
          // protects cond and maps and the indicator bools
          boost::mutex _mtx;
          // contains the most recent optime of each member syncing to us
          map<mongo::OID, OpTime> _slaveMap;
          typedef map<mongo::OID, Member*> OIDMemberMap;
          // contains a pointer to each member, which we can look up by oid
          OIDMemberMap _members;
          // used to alert our thread of changes which need to be passed up the chain
          boost::condition _cond;
          // used to indicate a position change which has not yet been pushed along
          bool _positionChanged;
          // used to indicate a connection change which has not yet been shook on
          bool _handshakeNeeded;
      };
  }
  