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096b5c5c7a
This patch removes log_position from streaming_context. The log_position was meant for keeping track of the database specific position corresponding to the changes that have been already replicated by a streaming transaction. In reality, things may be more complex in the DBMS side and a size_t may be unsufficient to keep track of the progress of a streaming transaction. For example, in MariaDB, it may be necessary to keep track of positions in both transaction and statement caches. Suggesting that the responsibility of tracking these position(s) should be delegated to client_service. The log_position was also used to do sanity checks in streaming_step(). Those sanity checks are preserved by simply keeping track of the number of bytes that were certified by the streaming transaction.
220 lines
6.8 KiB
C++
220 lines
6.8 KiB
C++
/*
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* Copyright (C) 2018 Codership Oy <info@codership.com>
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*
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* This file is part of wsrep-lib.
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*
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* Wsrep-lib is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* Wsrep-lib is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with wsrep-lib. If not, see <https://www.gnu.org/licenses/>.
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*/
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/** @file client_service.hpp
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*
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* This file will define a `callback` abstract interface for a
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* DBMS client session service. The interface will define methods
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* which will be called by the wsrep-lib.
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*/
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#ifndef WSREP_CLIENT_SERVICE_HPP
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#define WSREP_CLIENT_SERVICE_HPP
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#include "buffer.hpp"
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#include "provider.hpp"
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#include "mutex.hpp"
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#include "lock.hpp"
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namespace wsrep
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{
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class client_service
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{
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public:
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client_service() { }
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virtual ~client_service() { }
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/**
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* Return true if the current transaction has been interrupted
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* by the DBMS. The lock which is passed to interrupted call
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* will always have underlying mutex locked.
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*
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* @param lock Lock object grabbed by the client_state
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*/
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virtual bool interrupted(wsrep::unique_lock<wsrep::mutex>& lock) const = 0;
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/**
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* Reset possible global or thread local parameters associated
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* to the thread.
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*/
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virtual void reset_globals() = 0;
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/**
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* Store possible global or thread local parameters associated
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* to the thread.
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*/
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virtual void store_globals() = 0;
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/**
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* Set up a data for replication.
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*/
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virtual int prepare_data_for_replication() = 0;
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/**
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* Clean up after transcation has been terminated.
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*/
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virtual void cleanup_transaction() = 0;
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//
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// Streaming
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//
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/**
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* Return true if current statement is allowed for streaming,
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* otherwise false.
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*/
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virtual bool statement_allowed_for_streaming() const = 0;
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/**
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* Return the total number of bytes generated by the transaction
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* context.
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*/
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virtual size_t bytes_generated() const = 0;
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/**
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* Prepare a buffer containing data for the next fragment to replicate.
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*
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* @return Zero in case of success, non-zero on failure.
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* If there is no data to replicate, the method shall return
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* zero and leave the buffer empty.
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*/
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virtual int
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prepare_fragment_for_replication(wsrep::mutable_buffer& buffer) = 0;
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/**
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* Remove fragments from the storage within current transaction.
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* Fragment removal will be committed once the current transaction
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* commits.
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*
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* @return Zero in case of success, non-zero on failure.
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*/
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virtual int remove_fragments() = 0;
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//
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// Rollback
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//
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/**
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* Perform brute force rollback.
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*
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* This method may be called from two contexts, either from
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* client state methods when the BF abort condition is detected,
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* or from the background rollbacker thread. The task for this
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* method is to release all reasources held by the client
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* after BF abort so that the high priority thread can continue
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* applying.
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*/
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virtual int bf_rollback() = 0;
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//
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// Interface to global server state
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//
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/**
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* Forcefully shut down the DBMS process or replication system.
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* This may be called in situations where
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* the process may encounter a situation where data integrity
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* may not be guaranteed or other unrecoverable condition is
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* encontered.
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*/
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virtual void emergency_shutdown() = 0;
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// Replaying
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/**
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* Notify that the client will replay.
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*
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* @todo This should not be visible to DBMS level, should be
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* handled internally by wsrep-lib.
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*/
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virtual void will_replay() = 0;
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/**
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* Signal that replay is done.
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*/
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virtual void signal_replayed() = 0;
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/**
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* Replay the current transaction. The implementation must put
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* the caller Client Context into applying mode and call
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* client_state::replay().
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*
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* @todo This should not be visible to DBMS level, should be
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* handled internally by wsrep-lib.
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*/
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virtual enum wsrep::provider::status replay() = 0;
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/**
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* Replay the current transaction. This is used for replaying
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* prepared XA transactions, which are BF aborted but not
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* while orderding commit / rollback.
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*/
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virtual enum wsrep::provider::status replay_unordered() = 0;
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/**
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* Wait until all replaying transactions have been finished
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* replaying.
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*
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* @todo This should not be visible to DBMS level, should be
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* handled internally by wsrep-lib.
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*/
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virtual void wait_for_replayers(wsrep::unique_lock<wsrep::mutex>&) = 0;
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//
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// XA
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//
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/**
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* Send a commit by xid
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*/
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virtual enum wsrep::provider::status commit_by_xid() = 0;
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/**
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* Returns true if the client has an ongoing XA transaction.
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* This method is used to determine when to cleanup the
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* corresponding wsrep-lib transaction object.
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* This method should return false when the XA transaction
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* is over, and the wsrep-lib transaction object can be
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* cleaned up.
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*/
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virtual bool is_explicit_xa() = 0;
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/**
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* Returns true if the currently executing command is
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* a rollback for XA. This is used to avoid setting a
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* a deadlock error rollback as it may be unexpected
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* by the DBMS.
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*/
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virtual bool is_xa_rollback() = 0;
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//
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// Debug interface
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//
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/**
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* Enter debug sync point.
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*
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* @params sync_point Name of the debug sync point.
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*/
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virtual void debug_sync(const char* sync_point) = 0;
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/**
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* Forcefully kill the process if the crash_point has
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* been enabled.
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*/
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virtual void debug_crash(const char* crash_point) = 0;
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};
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}
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#endif // WSREP_CLIENT_SERVICE_HPP
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