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170 lines
6.0 KiB
170 lines
6.0 KiB
5 months ago
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/* Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program 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, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#ifndef RPL_APPLIER_READER_INCLUDED
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#define RPL_APPLIER_READER_INCLUDED
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#include "mysqld.h"
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#include "sql/binlog.h"
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#include "sql/binlog_reader.h"
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class Relay_log_info;
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/**
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This class provides the feature to read events from relay log files.
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- Open() function just opens the first relay log file
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(rli->get_group_relay_log_name()) which need to be applied by slave.
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- read_next_event() just returns the events one by one. It will close()
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current relay log and open next relay log file automatically when reaching
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the end of current relay log. Internally each relay log file is opened and
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read by using a Relaylog_file_reader.
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- It will purge the applied relay logs accordingly when moving to next relay
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log.
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- When reaching the end of active relay log file, it will wait for new events
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coming and make MTS checkpoints accordingly while waiting for events.
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*/
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class Rpl_applier_reader {
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public:
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/**
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@param[in] rli relay log info is used in the function. So rli should be
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initialized before initializing Rpl_applier_reader object.
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*/
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Rpl_applier_reader(Relay_log_info *rli);
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Rpl_applier_reader(const Rpl_applier_reader &) = delete;
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Rpl_applier_reader &operator=(const Rpl_applier_reader &) = delete;
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~Rpl_applier_reader();
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/**
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Open the first relay log file which will be read by applier and
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seek to correct position. The file name and position are read from
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rli->get_group_master_log_name() and rli->get_group_relay_log_pos().
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@param[out] errmsg Set the error message to it if any error happens.
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@retval false Success
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@retval true Error
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*/
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bool open(const char **errmsg);
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void close();
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/**
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Read next event from relay log.
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- It will wait until the receiver writes some events to relay log in case
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where there are no more events left to read from the active relay log.
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- The caller must hold m_rli->data_lock. The lock will be released
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temporarily while waiting and required after waking up.
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- The wait is protected by relay_log.lock_binlog_end_pos().
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@retval Log_event* A valid Log_event object.
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@retval nullptr Error happened or sql thread was killed.
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*/
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Log_event *read_next_event();
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private:
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Relaylog_file_reader m_relaylog_file_reader;
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Relay_log_info *m_rli = nullptr;
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/** Stores the error message which is used internally */
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const char *m_errmsg = nullptr;
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bool m_reading_active_log = true;
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/**
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Stores active log's end position. Thus avoids to call
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relay_log.get_binlog_log_pos() for each event.
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*/
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my_off_t m_log_end_pos = 0;
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/*
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It stores offset of relay log index to speed up finding next relay log
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files.
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*/
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LOG_INFO m_linfo;
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bool m_relay_log_purge = relay_log_purge;
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class Stage_controller;
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/**
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When reaching the end of current relay log file, close it and open next
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relay log. purge old relay logs if necessary.
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@retval false Success
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@retval true Error
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*/
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bool move_to_next_log();
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/**
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It reads the coordinates up to which the receiver thread has written and
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check whether there is any event to be read.
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@retval false The applier has read all events.
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@retval true The applier is behind the receiver.
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*/
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bool read_active_log_end_pos();
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/**
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In the case receiver thread says master skipped some events, it will
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generate a Rotate_log_event for applier to advance executed master log
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position.
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*/
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Rotate_log_event *generate_rotate_event();
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/**
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Purge relay log files prior to m_rli->group_relay_log_name.
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It is used to be called MYSQL_BIN_LOG::purge_first_log
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@retval false Success
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@retval true Error
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*/
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bool purge_applied_logs();
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/**
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Waits for new events coming. Returning successfully just means it gets a
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signal. That doesn't guarantee that any new event came.
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@retval false Success
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@retval true Error. The thread is killed or flush failed while
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executing mts_checkpoint_routine.
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@note the The caller must hold m_rli->data_lock and
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relaylog.lock_binlog_end_pos().
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*/
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bool wait_for_new_event();
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/**
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It checks if the relaylog file reader should be reopened and then reopens
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the reader if receiver thread truncated some data from active relay log.
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The caller must hold m_rli->data_lock
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@retval false Success
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@retval true Error
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*/
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bool reopen_log_reader_if_needed();
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/* reset seconds_behind_master when starting to wait for events coming */
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void reset_seconds_behind_master();
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/* relay_log_space_limit should be disabled temporarily in some cases. */
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void disable_relay_log_space_limit_if_needed();
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#ifndef DBUG_OFF
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void debug_print_next_event_positions();
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#endif
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};
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#endif // RPL_APPLIER_READER_INCLUDED
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