mirror of https://gitee.com/bigwinds/arangodb
116 lines
4.4 KiB
C++
116 lines
4.4 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2018 ArangoDB GmbH, Cologne, Germany
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/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Max Neunhoeffer
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/// @author Andreas Streichardt
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGOD_CLUSTER_FOLLOWER_INFO_H
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#define ARANGOD_CLUSTER_FOLLOWER_INFO_H 1
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#include "ClusterInfo.h"
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namespace arangodb {
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////////////////////////////////////////////////////////////////////////////////
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/// @brief a class to track followers that are in sync for a shard
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////////////////////////////////////////////////////////////////////////////////
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class FollowerInfo {
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std::shared_ptr<std::vector<ServerID> const> _followers;
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mutable Mutex _mutex;
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arangodb::LogicalCollection* _docColl;
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std::string _theLeader;
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// if the latter is empty, then we are leading
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bool _theLeaderTouched;
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public:
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explicit FollowerInfo(arangodb::LogicalCollection* d)
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: _followers(new std::vector<ServerID>()), _docColl(d), _theLeaderTouched(false) {}
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//////////////////////////////////////////////////////////////////////////////
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/// @brief get information about current followers of a shard.
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//////////////////////////////////////////////////////////////////////////////
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std::shared_ptr<std::vector<ServerID> const> get() const;
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//////////////////////////////////////////////////////////////////////////////
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/// @brief add a follower to a shard, this is only done by the server side
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/// of the "get-in-sync" capabilities. This reports to the agency under
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/// `/Current` but in asynchronous "fire-and-forget" way. The method
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/// fails silently, if the follower information has since been dropped
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/// (see `dropFollowerInfo` below).
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//////////////////////////////////////////////////////////////////////////////
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void add(ServerID const& s);
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//////////////////////////////////////////////////////////////////////////////
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/// @brief remove a follower from a shard, this is only done by the
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/// server if a synchronous replication request fails. This reports to
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/// the agency under `/Current` but in an asynchronous "fire-and-forget"
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/// way.
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//////////////////////////////////////////////////////////////////////////////
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bool remove(ServerID const& s);
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//////////////////////////////////////////////////////////////////////////////
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/// @brief clear follower list, no changes in agency necesary
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//////////////////////////////////////////////////////////////////////////////
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void clear();
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//////////////////////////////////////////////////////////////////////////////
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/// @brief check whether the given server is a follower
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//////////////////////////////////////////////////////////////////////////////
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bool contains(ServerID const& s) const;
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//////////////////////////////////////////////////////////////////////////////
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/// @brief set leadership
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//////////////////////////////////////////////////////////////////////////////
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void setTheLeader(std::string const& who) {
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MUTEX_LOCKER(locker, _mutex);
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_theLeader = who;
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_theLeaderTouched = true;
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}
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//////////////////////////////////////////////////////////////////////////////
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/// @brief get the leader
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//////////////////////////////////////////////////////////////////////////////
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std::string getLeader() const {
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MUTEX_LOCKER(locker, _mutex);
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return _theLeader;
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}
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//////////////////////////////////////////////////////////////////////////////
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/// @brief see if leader was explicitly set
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//////////////////////////////////////////////////////////////////////////////
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bool getLeaderTouched() const {
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MUTEX_LOCKER(locker, _mutex);
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return _theLeaderTouched;
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}
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};
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} // end namespace arangodb
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#endif
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