mirror of https://gitee.com/bigwinds/arangodb
130 lines
4.6 KiB
C++
130 lines
4.6 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2017 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 Jan Steemann
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGOD_REPLICATION_REPLICATION_CLIENTS_H
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#define ARANGOD_REPLICATION_REPLICATION_CLIENTS_H 1
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#include "Basics/Common.h"
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#include "Basics/ReadWriteLock.h"
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#include "Replication/SyncerId.h"
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namespace arangodb {
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namespace velocypack {
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class Builder;
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}
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/// @brief struct representing how far a replication client (syncer)
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/// has come in terms of WAL tailing
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struct ReplicationClientProgress {
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/// @brief timestamp of when client last contacted us
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double lastSeenStamp;
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/// @brief timestamp of when this entry will be considered expired
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double expireStamp;
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/// @brief last log tick/WAL tick that was served for this client
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uint64_t lastServedTick;
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/// @brief syncer id of the client
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SyncerId const syncerId;
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/// @brief server id of the client
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std::string const clientId;
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ReplicationClientProgress(double lastSeenStamp, double expireStamp, uint64_t lastServedTick,
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SyncerId syncerId, std::string clientId)
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: lastSeenStamp(lastSeenStamp),
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expireStamp(expireStamp),
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lastServedTick(lastServedTick),
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syncerId(syncerId),
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clientId(std::move(clientId)) {}
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static double steadyClockToSystemClock(double steadyTimestamp);
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};
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/// @brief class to track progress of individual replication clients (syncers)
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/// for a particular database
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class ReplicationClientsProgressTracker {
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public:
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ReplicationClientsProgressTracker() = default;
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#ifndef ARANGODB_ENABLE_MAINTAINER_MODE
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~ReplicationClientsProgressTracker() = default;
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#else
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~ReplicationClientsProgressTracker();
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#endif
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ReplicationClientsProgressTracker(ReplicationClientsProgressTracker const&) = delete;
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ReplicationClientsProgressTracker& operator=(ReplicationClientsProgressTracker const&) = delete;
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/// @brief simply extend the lifetime of a specific syncer, so that its entry
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/// does not expire does not update the syncer's lastServedTick value
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void extend(SyncerId syncerId, std::string const& clientId, double ttl);
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/// @brief simply update the progress of a specific syncer, so that its entry
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/// does not expire this will update the syncer's lastServedTick value
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void track(SyncerId syncerId, std::string const& clientId,
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uint64_t lastServedTick, double ttl);
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/// @brief remove a specific syncer's entry
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void untrack(SyncerId syncerId, std::string const& clientId);
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/// @brief serialize the existing syncers to a VelocyPack builder
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void toVelocyPack(velocypack::Builder& builder) const;
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/// @brief garbage-collect the existing list of syncers
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/// thresholdStamp is the timestamp before all older entries will
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/// be collected
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void garbageCollect(double thresholdStamp);
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/// @brief return the lowest lastServedTick value for all syncers
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/// returns UINT64_MAX in case no syncers are registered
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uint64_t lowestServedValue() const;
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private:
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static inline std::string getKey(SyncerId syncerId, std::string const& clientId) {
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// For backwards compatible APIs, we might not have a syncer ID;
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// fall back to the clientId in that case. SyncerId was introduced in 3.5.0.
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// The only public API using this, /_api/wal/tail, marked the serverId
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// parameter (corresponding to clientId here) as deprecated in 3.5.0.
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// Also, so these values cannot interfere with each other, prefix them to
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// make them disjoint.
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if (syncerId.value != 0) {
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return std::string{"syncerId:"} + syncerId.toString();
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}
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if (!clientId.empty() && clientId != "none") {
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return std::string{"clientId:"} + clientId;
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}
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return std::string{};
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}
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private:
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mutable basics::ReadWriteLock _lock;
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/// @brief mapping from SyncerId -> progress
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std::unordered_map<std::string, ReplicationClientProgress> _clients;
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};
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} // namespace arangodb
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#endif
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