text: ////////////////////////////////////////////////////////////////////////////////
  /// DISCLAIMER
  ///
  /// Copyright 2014-2021 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 Michael Hackstein
  ////////////////////////////////////////////////////////////////////////////////
  
  #include "ShortestPathFinder.h"
  
  #include "ApplicationFeatures/ApplicationServer.h"
  #include "Aql/Query.h"
  #include "Basics/StringUtils.h"
  #include "Cluster/ServerState.h"
  #include "Graph/ClusterTraverserCache.h"
  #include "Graph/ShortestPathOptions.h"
  #include "Logger/LogMacros.h"
  #include "Network/Methods.h"
  #include "Network/NetworkFeature.h"
  #include "Network/Utils.h"
  #include "Transaction/Methods.h"
  
  using namespace arangodb;
  using namespace arangodb::graph;
  
  ShortestPathFinder::ShortestPathFinder(ShortestPathOptions& options)
      : _options(options), _httpRequests(0) {}
  
  void ShortestPathFinder::destroyEngines() {
    if (!ServerState::instance()->isCoordinator()) {
      return;
    }
    NetworkFeature const& nf =
        _options.query().vocbase().server().getFeature<NetworkFeature>();
    network::ConnectionPool* pool = nf.pool();
    // We have to clean up the engines in Coordinator Case.
    if (pool == nullptr) {
      return;
    }
    // nullptr only happens on controlled server shutdown
  
    auto ch = reinterpret_cast<ClusterTraverserCache*>(_options.cache());
  
    network::RequestOptions options;
    options.database = _options.trx()->vocbase().name();
    options.timeout = network::Timeout(30.0);
    options.skipScheduler = true;  // hack to speed up future.get()
  
    for (auto const& it : *ch->engines()) {
      incHttpRequests(1);
  
      auto res = network::sendRequestRetry(
                     pool, "server:" + it.first, fuerte::RestVerb::Delete,
                     "/_internal/traverser/" +
                         arangodb::basics::StringUtils::itoa(it.second),
                     VPackBuffer<uint8_t>(), options)
                     .get();
  
      if (res.error != fuerte::Error::NoError) {
        // Note If there was an error on server side we do not have
        // CL_COMM_SENT
        LOG_TOPIC("d31a4", ERR, arangodb::Logger::GRAPHS)
            << "Could not destroy all traversal engines: "
            << TRI_errno_string(network::fuerteToArangoErrorCode(res));
      }
    }
  }
  
  ShortestPathOptions& ShortestPathFinder::options() const { return _options; }
  