text: ////////////////////////////////////////////////////////////////////////////////
  /// DISCLAIMER
  ///
  /// Copyright 2014-2018 ArangoDB GmbH, Cologne, Germany
  /// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
  ///
  /// Licensed under the Apache License, Version 2.0 (the "License");
  /// you may not use this file except in compliance with the License.
  /// You may obtain a copy of the License at
  ///
  ///     http://www.apache.org/licenses/LICENSE-2.0
  ///
  /// Unless required by applicable law or agreed to in writing, software
  /// distributed under the License is distributed on an "AS IS" BASIS,
  /// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  /// See the License for the specific language governing permissions and
  /// limitations under the License.
  ///
  /// Copyright holder is ArangoDB GmbH, Cologne, Germany
  ///
  /// @author Jan Steemann
  ////////////////////////////////////////////////////////////////////////////////
  
  #ifndef ARANGOD_REPLICATION_INITIAL_SYNCER_H
  #define ARANGOD_REPLICATION_INITIAL_SYNCER_H 1
  
  #include "Basics/Common.h"
  #include "Basics/Result.h"
  #include "Replication/ReplicationApplierConfiguration.h"
  #include "Replication/Syncer.h"
  #include "Replication/utilities.h"
  #include "Scheduler/Scheduler.h"
  
  #include <velocypack/Slice.h>
  
  struct TRI_vocbase_t;
  
  namespace arangodb {
  
  struct InitialSyncerDumpStats {
    // total number of requests to /_api/replication/dump
    uint64_t numDumpRequests = 0;
    // total time spent waiting for responses to /_api/replication/dump
    double waitedForDump = 0.0;
    // total time spent for locally applying dump markers
    double waitedForApply = 0.0;
  };
  
  struct InitialSyncerIncrementalSyncStats {
    // total number of requests to /_api/replication/keys?type=keys
    uint64_t numKeysRequests = 0;
    // total number of requests to /_api/replication/keys?type=docs
    uint64_t numDocsRequests = 0;
    // total number of documents that for which document data were requested
    uint64_t numDocsRequested = 0;
    // total number of insert operations performed during sync
    uint64_t numDocsInserted = 0;
    // total number of remove operations performed during sync
    uint64_t numDocsRemoved = 0;
    // total time spent waiting on response for initial call to
    // /_api/replication/keys
    double waitedForInitial = 0.0;
    // total time spent waiting for responses to /_api/replication/keys?type=keys
    double waitedForKeys = 0.0;
    // total time spent waiting for responses to /_api/replication/keys?type=docs
    double waitedForDocs = 0.0;
  };
  
  class InitialSyncer : public Syncer {
   public:
    explicit InitialSyncer(ReplicationApplierConfiguration const&,
                           replutils::ProgressInfo::Setter s = [](std::string const&) -> void {});
  
    ~InitialSyncer();
  
   public:
    virtual Result run(bool incremental) = 0;
  
    /// @brief return the last log tick of the master at start
    TRI_voc_tick_t getLastLogTick() const { return _state.master.lastLogTick; }
  
    /// @brief return the collections that were synced
    std::map<TRI_voc_cid_t, std::string> const& getProcessedCollections() const {
      return _progress.processedCollections;
    }
  
    std::string progress() const { return _progress.message; }
  
   protected:
    /// @brief start a recurring task to extend the batch
    void startRecurringBatchExtension();
  
   protected:
    replutils::BatchInfo _batch;
    replutils::ProgressInfo _progress;
    
    /// recurring task to keep the batch alive
    Scheduler::WorkHandle _batchPingTimer;
  };
  }  // namespace arangodb
  
  #endif
  