mirror of https://gitee.com/bigwinds/arangodb
369 lines
10 KiB
C++
369 lines
10 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2016 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 Kaveh Vahedipour
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGOD_CONSENSUS_AGENT_H
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#define ARANGOD_CONSENSUS_AGENT_H 1
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#include "Agency/AgencyCommon.h"
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#include "Agency/AgentActivator.h"
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#include "Agency/AgentCallback.h"
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#include "Agency/AgentConfiguration.h"
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#include "Agency/AgentInterface.h"
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#include "Agency/Compactor.h"
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#include "Agency/Constituent.h"
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#include "Agency/Inception.h"
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#include "Agency/State.h"
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#include "Agency/Store.h"
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#include "Agency/Supervision.h"
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struct TRI_vocbase_t;
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namespace arangodb {
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namespace consensus {
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class Agent : public arangodb::Thread,
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public AgentInterface {
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public:
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/// @brief Construct with program options
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explicit Agent(config_t const&);
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/// @brief Clean up
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~Agent();
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/// @brief Get current term
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term_t term() const;
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/// @brief Get current term
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std::string id() const;
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/// @brief Vote request
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priv_rpc_ret_t requestVote(term_t, std::string const&, index_t, index_t,
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query_t const&);
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/// @brief Provide configuration
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config_t const config() const;
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/// @brief Start thread
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bool start();
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/// @brief My endpoint
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std::string endpoint() const;
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/// @brief Verbose print of myself
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void print(arangodb::LoggerStream&) const;
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/// @brief Are we fit to run?
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bool fitness() const;
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/// @brief Leader ID
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std::pair<index_t, index_t> lastCommitted() const;
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/// @brief Leader ID
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std::string leaderID() const;
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/// @brief Are we leading?
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bool leading() const;
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/// @brief Pick up leadership tasks
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void lead();
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/// @brief Prepare leadership
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bool prepareLead();
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/// @brief Load persistent state
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void load();
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/// @brief Unpersisted key-value-store
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trans_ret_t transient(query_t const&) override;
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/// @brief Attempt write
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/// Startup flag should NEVER be discarded solely for purpose of
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/// persisting the agency configuration
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write_ret_t write(query_t const&, bool discardStartup = false) override;
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/// @brief Read from agency
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read_ret_t read(query_t const&);
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/// @brief Inquire success of logs given clientIds
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inquire_ret_t inquire(query_t const&);
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/// @brief Attempt read/write transaction
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trans_ret_t transact(query_t const&) override;
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/// @brief Put trxs into list of ongoing ones.
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void addTrxsOngoing(Slice trxs);
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/// @brief Remove trxs from list of ongoing ones.
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void removeTrxsOngoing(Slice trxs);
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/// @brief Check whether a trx is ongoing.
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bool isTrxOngoing(std::string& id);
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/// @brief Received by followers to replicate log entries ($5.3);
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/// also used as heartbeat ($5.2).
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bool recvAppendEntriesRPC(term_t term, std::string const& leaderId,
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index_t prevIndex, term_t prevTerm,
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index_t leaderCommitIndex, query_t const& queries);
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/// @brief Invoked by leader to replicate log entries ($5.3);
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/// also used as heartbeat ($5.2).
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void sendAppendEntriesRPC();
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/// @brief 1. Deal with appendEntries to slaves.
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/// 2. Report success of write processes.
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void run() override final;
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/// @brief Are we still booting?
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bool booting();
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/// @brief Gossip in
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query_t gossip(query_t const&, bool callback = false, size_t version = 0);
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/// @brief Persisted agents
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bool persistedAgents();
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/// @brief Activate new agent in pool to replace failed
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void reportActivated(std::string const&, std::string const&, query_t);
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/// @brief Activate new agent in pool to replace failed
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void failedActivation(std::string const&, std::string const&);
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/// @brief Gossip in
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bool activeAgency();
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/// @brief Start orderly shutdown of threads
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void beginShutdown() override final;
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/// @brief Report appended entries from AgentCallback
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void reportIn(std::string const&, index_t, size_t = 0);
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/// @brief Wait for slaves to confirm appended entries
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AgentInterface::raft_commit_t waitFor(index_t last_entry, double timeout = 2.0) override;
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/// @brief Convencience size of agency
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size_t size() const;
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/// @brief Rebuild DBs by applying state log to empty DB
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index_t rebuildDBs();
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/// @brief Rebuild DBs by applying state log to empty DB
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void compact();
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/// @brief Last log entry
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log_t lastLog() const;
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/// @brief State machine
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State const& state() const;
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/// @brief Get read store and compaction index
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index_t readDB(Node&) const;
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/// @brief Get read store
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Store const& readDB() const;
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/// @brief Get spearhead store
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Store const& spearhead() const;
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/// @brief Get transient store
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Store const& transient() const;
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/// @brief Serve active agent interface
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bool serveActiveAgent();
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/// @brief Start constituent
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void startConstituent();
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/// @brief Get notification as inactive pool member
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void notify(query_t const&);
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/// @brief Detect active agent failures
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void detectActiveAgentFailures();
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/// @brief All there is in the state machine
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query_t allLogs() const;
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/// @brief Last contact with followers
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query_t lastAckedAgo() const;
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/// @brief Am I active agent
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bool active() const;
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/// @brief Become active agent
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query_t activate(query_t const&);
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/// @brief Report measured round trips to inception
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void reportMeasurement(query_t const&);
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/// @brief Are we ready for RAFT?
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bool ready() const;
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/// @brief Set readyness for RAFT
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void ready(bool b);
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/// @brief Reset RAFT timeout intervals
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void resetRAFTTimes(double, double);
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/// @brief Get start time of leadership
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TimePoint const& leaderSince() const;
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/// @brief Update a peers endpoint in my configuration
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void updatePeerEndpoint(query_t const& message);
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/// @brief Update a peers endpoint in my configuration
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void updatePeerEndpoint(std::string const& id, std::string const& ep);
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/// @brief Assemble an agency to commitId
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query_t buildDB(index_t);
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/// @brief Guarding taking over leadership
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void beginPrepareLeadership() { _preparing = true; }
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void endPrepareLeadership() { _preparing = false; }
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// #brief access Inception thread
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Inception const* inception() const;
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/// @brief State reads persisted state and prepares the agent
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friend class State;
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friend class Compactor;
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private:
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/// @brief persist agency configuration in RAFT
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void persistConfiguration(term_t t);
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/// @brief Find out, if we've had acknowledged RPCs recent enough
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bool challengeLeadership();
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/// @brief Notify inactive pool members of changes in configuration
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void notifyInactive() const;
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/// @brief Activate this agent in single agent mode.
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bool activateAgency();
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/// @brief Assignment of persisted state
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Agent& operator=(VPackSlice const&);
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/// @brief Get current term
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bool id(std::string const&);
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/// @brief Get current term
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bool mergeConfiguration(VPackSlice const&);
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/// @brief Leader ID
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void lastCommitted(index_t);
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/// @brief Leader election delegate
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Constituent _constituent;
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/// @brief Cluster supervision module
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Supervision _supervision;
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/// @brief State machine
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State _state;
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/// @brief Configuration of command line options
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config_t _config;
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/// @brief
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/// Leader: Last index that is "committed" in the sense that the leader
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/// has convinced itself that an absolute majority (including the leader)
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/// have written the entry into their log, this variable is only maintained
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/// on the leader.
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/// Follower: this is only kept on followers and indicates what the leader
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/// told them it has last "committed" in the above sense.
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index_t _commitIndex;
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/// @brief Index of highest log entry applied to state achine (initialized
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/// to 0, increases monotonically)
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index_t _lastApplied;
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/// @brief Spearhead (write) kv-store
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Store _spearhead;
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/// @brief Committed (read) kv-store
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Store _readDB;
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/// @brief Committed (read) kv-store for transient data
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Store _transient;
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/// @brief Condition variable for appendEntries
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arangodb::basics::ConditionVariable _appendCV;
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/// @brief Condition variable for waitFor
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arangodb::basics::ConditionVariable _waitForCV;
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/// @brief Confirmed indices of all members of agency
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std::map<std::string, index_t> _confirmed;
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std::map<std::string, index_t> _lastHighest;
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std::map<std::string, TimePoint> _lastAcked;
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std::map<std::string, TimePoint> _lastSent;
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std::map<std::string, TimePoint> _earliestPackage;
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/**< @brief RAFT consistency lock:
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_spearhead
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_read_db
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_lastCommitedIndex (log index)
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_lastAcked
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_confirmed
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_nextCompactionAfter
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*/
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mutable arangodb::Mutex _ioLock;
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// lock for _leaderCommitIndex
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mutable arangodb::Mutex _liLock;
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// @brief guard _activator
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mutable arangodb::Mutex _activatorLock;
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/// @brief Next compaction after
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index_t _nextCompactionAfter;
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/// @brief Inception thread getting an agent up to join RAFT from cmd or persistence
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std::unique_ptr<Inception> _inception;
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/// @brief Activator thread for the leader to wake up a sleeping agent from pool
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std::unique_ptr<AgentActivator> _activator;
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/// @brief Compactor
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Compactor _compactor;
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/// @brief Agent is ready for RAFT
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std::atomic<bool> _ready;
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std::atomic<bool> _preparing;
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/// @brief Keep track of when I last took on leadership
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TimePoint _leaderSince;
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/// @brief Ids of ongoing transactions, used for inquire:
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std::set<std::string> _ongoingTrxs;
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// lock for _ongoingTrxs
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arangodb::Mutex _trxsLock;
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};
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}
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}
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#endif
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