怎么理解从库的IO线程

发布时间：2021-12-23 10:48:09 所属栏目：MySql教程来源：互联网

导读：本篇内容介绍了怎么理解从库的IO线程的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！一、流程解析 start_slave -start_slave_threads - if (!mi-inite

本篇内容介绍了“怎么理解从库的IO线程”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

一、流程解析

start_slave
->start_slave_threads
   ->
     if (!mi->inited || !mi->rli->inited)//如果没有初始化
  {
    int error= (!mi->inited ? ER_SLAVE_MI_INIT_REPOSITORY :
                ER_SLAVE_RLI_INIT_REPOSITORY);
   ER_SLAVE_MI_INIT_REPOSITORY
   ER_SLAVE_RLI_INIT_REPOSITORY
   ->
     if (mi->is_auto_position() && (thread_mask & SLAVE_IO) &&
      get_gtid_mode(GTID_MODE_LOCK_NONE) == GTID_MODE_OFF)
      ER_CANT_USE_AUTO_POSITION_WITH_GTID_MODE_OFF eng
      "The replication receiver thread%-.192s cannot start in
      AUTO_POSITION mode: this server uses @@GLOBAL.GTID_MODE = OFF."
  -> 启动IO 线程
       if (thread_mask & SLAVE_IO)
                   is_error= start_slave_thread(
                      #ifdef HAVE_PSI_INTERFACE
                                 key_thread_slave_io,
                      #endif
                                 handle_slave_io, lock_io, lock_cond_io,
                                 cond_io,
                                 &mi->slave_running, &mi->slave_run_id,
                                 mi);
     -> mysql_thread_create 建立线程回调函数handle_slave_io
       ->handle_slave_io
         ->初始化IO线程属性 init_slave_thread
           进入状态THD_STAGE_INFO(thd, stage_waiting_for_master_update);
         ->safe_connect 进行连接主库
           ->connect_to_master
            ->将参数slave_net_timeout设置为IO线程连接超时和IO线程读取Event 超时
              case MYSQL_OPT_CONNECT_TIMEOUT: //MYSQL_OPT_CONNECT_TIMEOUT
               mysql->options.connect_timeout= *(uint*) arg;
               break;
             case MYSQL_OPT_READ_TIMEOUT://MYSQL_OPT_READ_TIMEOUT
               mysql->options.read_timeout= *(uint*) arg;
               break;
            ->循环实现连接和重新连接
            -> 根据用户名、密码、IP、端口建立连接
              mysql_real_connect(mysql, mi->host, user, password, 0, mi->port, 0, client_flag)
            ->如果连接失败循环重连
              每次打印日志
              mi->report(ERROR_LEVEL, last_errno,
               "error %s to master '%s@%s:%d'"
               " - retry-time: %d retries: %lu",
               (reconnect ? "reconnecting" : "connecting"),
               mi->get_user(), mi->host, mi->port,
               mi->connect_retry, err_count + 1);
             if (++err_count == mi->retry_count)
              {
                slave_was_killed=1;
                break;
              }
              slave_sleep(thd, mi->connect_retry, io_slave_killed, mi); //睡眠时间
              每次睡眠时间为MASTER_CONNECT_RETRY设置的时间，默认60秒，循环次数由MASTER_RETRY_COUNT指定
              默认86400次
         ->get_master_version_and_clock
           ->比较版本
           ->发起命令SELECT UNIX_TIMESTAMP() 获取主库时间
             mysql_real_query(mysql, STRING_WITH_LEN("SELECT UNIX_TIMESTAMP()
             计算差值用于延迟计算
             mi->clock_diff_with_master= (long) (time((time_t*) 0) - strtoul(master_row[0], 0, 10));
             也就是说差值计算是在start slave命令发起的时候进行计算的，后面如果修改slave的服务器时间
             那么延迟计算将出现问题
           ->发起命令SELECT @@GLOBAL.SERVER_ID 获取主库server id
             比较主库的server id和本从库是否相同，如果相同则报错
             The slave I/O thread stops because master and slave have equal
             MySQL server ids; these ids must be different for replication to work (or
             the --replicate-same-server-id option must be used on slave but this does
             not always make sense; please check the manual before using it).
           ->发起命令SELECT @@GLOBAL.COLLATION_SERVER
             如果主库的这个值和备库不一致将会报错
             The slave I/O thread stops because master and slave have
             different values for the COLLATION_SERVER global variable. The values must
             be equal for the Statement-format replication to work
           ->发起命令SELECT @@GLOBAL.TIME_ZONE 老版本检测
             比较主库和从库的时区，如果不一致
             The slave I/O thread stops because master and slave have
             different values for the TIME_ZONE global variable. The values must
             be equal for the Statement-format replication to work
           ->发起命令SELECT @@GLOBAL.GTID_MODE
             比较主库和从库的GTID MODE是否兼容
                 if ((slave_gtid_mode == GTID_MODE_OFF &&
                      master_gtid_mode >= GTID_MODE_ON_PERMISSIVE) ||
                     (slave_gtid_mode == GTID_MODE_ON &&
                      master_gtid_mode <= GTID_MODE_OFF_PERMISSIVE))
                 {
                   mi->report(ERROR_LEVEL, ER_SLAVE_FATAL_ERROR,
                              "The replication receiver thread cannot start because "
                              "the master has GTID_MODE = %.192s and this server has "
                              "GTID_MODE = %.192s.",
                              get_gtid_mode_string(master_gtid_mode),
                              get_gtid_mode_string(slave_gtid_mode));
                   DBUG_RETURN(1);
                 }
                 if (mi->is_auto_position() && master_gtid_mode != GTID_MODE_ON)
                 {
                   mi->report(ERROR_LEVEL, ER_SLAVE_FATAL_ERROR,
                              "The replication receiver thread cannot start in "
                              "AUTO_POSITION mode: the master has GTID_MODE = %.192s "
                              "instead of ON.",
                              get_gtid_mode_string(master_gtid_mode));
                   DBUG_RETURN(1);
                 }
           ->回到handle_slave_io
         ->get_master_uuid   获取主句UUID 比较UUID
           发起命令SELECT @@GLOBAL.SERVER_UUID
           比较主库和备库的UUID如果相同报错
           "The slave I/O thread stops because master and slave have equal "
                         "MySQL server UUIDs; these UUIDs must be different for "
                         "replication to work."
         ->io_thread_init_commands
           SET @slave_uuid= '%s' 是什么意思
         ->register_slave_on_master 进行注册
           主库调用register_slave进行注册
           注册完成后 show slave hosts就能查询到了主库show slave会调用
           show_slave_hosts 函数
         ->request_dump 发送需要读取的GTID或者位点信息给主库。
           如果是AUTO com_binlog_dump_gtid
           - restirve_gtid+execute_gtid
            if (gtid_executed.add_gtid_set(mi->rli->get_gtid_set()) != RETURN_STATUS_OK ||
             gtid_executed.add_gtid_set(gtid_state->get_executed_gtids()) !=
             RETURN_STATUS_OK)
           - server_id
        主库读取
          (gdb) p gtid_string
            $17 = 0x7ffee400ef20 "010fde77-2075-11e9-ba07-5254009862c0:1,ncb7ea36e-670f-11e9-b483-5254008138e4:1-16"
          (gdb) p name
          $18 = '00' <repeats 16 times>, "v000000a00000000t003443761770000340252U3543771770000242kL01000000000200000000000000346?01000000000200000000000000346?0100000000300252U3543771770000L?01n000000ЪU3543771770000L?0100000000360252U3543771770000240343221010000000000253U3543771770000340b00344376177000020253U3543771770000"I353010000000000t003443761770000240255U354377177000060253U3543771770000272~3560000000000v00000005000000240255U354377177000000256U3543771770000246323M0100000000221333/020000000030=00344376177", '00' <repeats 18 times>, "0200000000000000346?010000000016202360200000000250"...
        (gdb) p pos
         $19 = 4
          不是AUTO
          - server_id
          - MASTER INFO 表的读取位点
          - MASTER INFO 表的读取binlog文件名
          主库读取 com_binlog_dump
            (gdb) p pos
           $1 = 3587
          (gdb) p packet + 10
           $3 = 0x7ffedc00a88b "binlog.000005"
          我们可以看到即便开启了GTID不开启AUTO也不会根据GTID来读取。
         ->循环读取event
           进入状态 stage_waiting_for_master_to_send_event
         ->将读取的event写入到 relay log
           进入状态Queueing master event to the relay log
           ->queue_event 读取的event写入到 relay log
             检测GTID event的合法性
             Cannot replicate GTID-transaction when @@GLOBAL.GTID_MODE = OFF, at file %.512s, position %lld.
             Cannot replicate anonymous transaction when AUTO_POSITION = 1, at file %.512s, position %lld.
             Cannot replicate anonymous transaction when @@GLOBAL.GTID_MODE = ON, at file %.512s, position %lld.
             ->rli->relay_log.append_buffer 进行relay log写入
               ->MYSQL_BIN_LOG::after_append_to_relay_log //进行写入后处理
                ->flush_and_sync 函数根据relay log sync参数设置决定是否做sync操作单位是event个数
                 ->MYSQL_BIN_LOG::sync_binlog_file 判断是否进行刷盘
                ->can_rotate 根据这个值决定是否计入Retrieved_Gtid_Set     边界分析器
                ->进行relay log切换
             ->更改相关被变量
                 master 位置/master 文件
                 增加容量log_space_total
               mi->set_master_log_pos(mi->get_master_log_pos() + inc_pos);//增加master 位置
               rli->relay_log.harvest_bytes_written(&rli->log_space_total);
               /*
                 If this event is GTID_LOG_EVENT we store its GTID to add to the
                 Retrieved_Gtid_Set later, when the last event of the transaction be
                 queued.
               */
               if (event_type == binary_log::GTID_LOG_EVENT)
               {
                 mi->set_last_gtid_queued(gtid);
               }
         ->flush_master_info(mi, FALSE)
          ->Rpl_info_table::do_flush_info
            通过参数sync_master设置决定多少个event 进行写table
            handler->set_sync_period(sync_masterinfo_period);
            if (!(force || (sync_period &&
                  ++(sync_counter) >= sync_period)))//如果没有达到 sync的次数(sync_master_info 或者 sync_relay_log_info次数不做flush 不写表直接返回)
                DBUG_RETURN(0);//但是relay_log_info依赖于是否是table模式如果是table模式则会在commit的时候做相应的flush Slave_worker::flush_info
二、证明sync_master_info单位是Event
设置sync_master_info=1

主库做一个大事务，观察slave_master_info表如下：

mysql> select * from slave_master_info G;
*************************** 1. row ***************************
       Number_of_lines: 25
       Master_log_name: binlog.000002
        Master_log_pos: 1222540
主库执行：

/mysqldata/mysql3340/bin/mysqlbinlog binlog.000002   --base64-output='decode-rows'|grep -C 10 -E "BEGIN|COMMIT"
主库event 可以看到在中间

BEGIN
/*!*/;
# at 992468
#190519 13:07:26 server id 413340 end_log_pos 992520 CRC32 0x5d85ea03 Table_map: `testmts`.`testio` mapped to number 111
# at 992520
#190519 13:07:26 server id 413340 end_log_pos 1000735 CRC32 0xfceb6697         Write_rows: table id 111
# at 1000735
#190519 13:07:26 server id 413340 end_log_pos 1008950 CRC32 0x0ca6515c         Write_rows: table id 111
# at 1008950
#190519 13:07:26 server id 413340 end_log_pos 1017165 CRC32 0x21d7b17d         Write_rows: table id 111
# at 1017165
--
# at 2939475
#190519 13:07:26 server id 413340 end_log_pos 2947690 CRC32 0xcb553fab         Write_rows: table id 111
# at 2947690
#190519 13:07:26 server id 413340 end_log_pos 2955905 CRC32 0xd42382c9         Write_rows: table id 111
# at 2955905
#190519 13:07:26 server id 413340 end_log_pos 2964120 CRC32 0xe516b98a         Write_rows: table id 111
# at 2964120
#190519 13:07:26 server id 413340 end_log_pos 2967035 CRC32 0x9cbfbc0a         Write_rows: table id 111 flags: STMT_END_F
# at 2967035
#190519 13:07:26 server id 413340 end_log_pos 2967066 CRC32 0xb907da17         Xid = 45
COMMIT/*!*/;
SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
DELIMITER ;
# End of log file
/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;
You have mail in /var/spool/mail/root
三、测试AUTO_POSITION=1和POSTION模式下MysqlD异常重启的恢复过程
下面是 recover_relay_log=0 的情况 POS和GTID AUTO_POSITION=1不同的处理。

断点

Master_info::set_master_log_pos 设置master info io thread 读取主库的binlog pos
Relay_log_info::set_group_relay_log_pos 设置relay info sql thread 从库读取relay pos的位置
GTID
AUTO_POSITION binlog recover_relay_log=0的情况下：
DUMP线程会重新发送最后一个事务给从库，从库使用Crash前的Relay_Log_Pos进行读取。relay log可能出现不完整的事务。这种情况会触发回滚机制。单线程会在GTID event 中回滚，MTS会由协调线程调用coord_handle_partial_binlogged_transaction回滚
change master to
master_host='192.168.99.41',
master_user='repl',
master_password='gelc123',
master_port=3340,
AUTO_POSITION=1;
start slave;
主库：

# at 912
#190519 21:22:16 server id 413340 end_log_pos 977 CRC32 0x5840ca71     GTID    last_committed=1        sequence_number=2       rbr_only=yes
/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;
SET @@SESSION.GTID_NEXT= 'cb7ea36e-670f-11e9-b483-5254008138e4:2'/*!*/;
# at 977
#190519 21:22:16 server id 413340 end_log_pos 1052 CRC32 0xcd8345de    Query   thread_id=3     exec_time=13    error_code=0
SET TIMESTAMP=1558272136/*!*/;
BEGIN
/*!*/;
# at 1052
#190519 21:22:16 server id 413340 end_log_pos 1104 CRC32 0x782391dd    Table_map: `testmts`.`testgp` mapped to number 108
# at 1104
#190519 21:22:16 server id 413340 end_log_pos 9319 CRC32 0x8de0fbdd    Write_rows: table id 108
# at 9319
#190519 21:22:16 server id 413340 end_log_pos 17534 CRC32 0xae798162   Write_rows: table id 108
# at 17534
#190519 21:22:16 server id 413340 end_log_pos 25749 CRC32 0x683b9e95   Write_rows: table id 108
# at 25749
--
# at 477574
#190519 21:22:16 server id 413340 end_log_pos 485789 CRC32 0x44e99850 Write_rows: table id 108
# at 485789
#190519 21:22:16 server id 413340 end_log_pos 494004 CRC32 0x280300fd Write_rows: table id 108
# at 494004
#190519 21:22:16 server id 413340 end_log_pos 502219 CRC32 0x075c8ff8 Write_rows: table id 108
# at 502219
#190519 21:22:16 server id 413340 end_log_pos 503274 CRC32 0x08c3f96c Write_rows: table id 108 flags: STMT_END_F
# at 503274
#190519 21:22:16 server id 413340 end_log_pos 503305 CRC32 0x3b6dd31c Xid = 26
COMMIT/*!*/;
SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
DELIMITER ;
mysql> show slave status G
*************************** 1. row ***************************
               Slave_IO_State: Queueing master event to the relay log
                  Master_Host: 192.168.99.41
                  Master_User: repl
                  Master_Port: 3340
                Connect_Retry: 60
              Master_Log_File: binlog.000001
          Read_Master_Log_Pos: 165404
               Relay_Log_File: relay.000002
                Relay_Log_Pos: 1119
        Relay_Master_Log_File: binlog.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
crash 后

mysql> show slave status G
*************************** 1. row ***************************
               Slave_IO_State:
                  Master_Host: 192.168.99.41
                  Master_User: repl
                  Master_Port: 3340
                Connect_Retry: 60
              Master_Log_File: binlog.000001
          Read_Master_Log_Pos: 190049
               Relay_Log_File: relay.000002
                Relay_Log_Pos: 1119
        Relay_Master_Log_File: binlog.000001
不完整的事物日志如下：

# at 1119
#190519 21:22:16 server id 413340 end_log_pos 977 CRC32 0x5840ca71     GTID    last_committed=1        sequence_number=2       rbr_only=yes
/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;
SET @@SESSION.GTID_NEXT= 'cb7ea36e-670f-11e9-b483-5254008138e4:2'/*!*/;
# at 1184
#190519 21:22:16 server id 413340 end_log_pos 1052 CRC32 0xcd8345de    Query   thread_id=3     exec_time=13    error_code=0
SET TIMESTAMP=1558272136/*!*/;
BEGIN
/*!*/;
# at 1259
#190519 21:22:16 server id 413340 end_log_pos 1104 CRC32 0x782391dd    Table_map: `testmts`.`testgp` mapped to number 108
# at 1311
#190519 21:22:16 server id 413340 end_log_pos 9319 CRC32 0x8de0fbdd    Write_rows: table id 108
# at 9526
#190519 21:22:16 server id 413340 end_log_pos 17534 CRC32 0xae798162   Write_rows: table id 108
# at 17741
#190519 21:22:16 server id 413340 end_log_pos 25749 CRC32 0x683b9e95   Write_rows: table id 108
# at 25956
WARNING: The range of printed events ends with a row event or a table map event that does not have
the STMT_END_F flag set. This might be because the last statement was not fully written to the log,
or because you are using a --stop-position or --stop-datetime that refers to an event in the middle of a statement.
The event(s) from the partial statement have not been written to output.
启动后 IO_THREAD

mysql> show slave status G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.99.41
                  Master_User: repl
                  Master_Port: 3340
                Connect_Retry: 60
              Master_Log_File: binlog.000001
          Read_Master_Log_Pos: 503305
               Relay_Log_File: relay.000002
                Relay_Log_Pos: 1119
        Relay_Master_Log_File: binlog.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: No
启动IO TRHEAD后重新传输了，但是老的没有完全传输完成的日志还在relay log
新的日志已经有了，老的也还在。

# at 445
#190519 21:22:16 server id 413340 end_log_pos 977 CRC32 0x5840ca71     GTID    last_committed=1        sequence_number=2       rbr_only=yes
/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;
SET @@SESSION.GTID_NEXT= 'cb7ea36e-670f-11e9-b483-5254008138e4:2'/*!*/;
# at 510
#190519 21:22:16 server id 413340 end_log_pos 1052 CRC32 0xcd8345de    Query   thread_id=3     exec_time=13    error_code=0
SET TIMESTAMP=1558272136/*!*/;
SET @@session.pseudo_thread_id=3/*!*/;
SET @@session.foreign_key_checks=1, @@session.sql_auto_is_null=0, @@session.unique_checks=1, @@session.autocommit=1/*!*/;
SET @@session.sql_mode=1075838976/*!*/;
SET @@session.auto_increment_increment=1, @@session.auto_increment_offset=1/*!*/;
/*!C utf8 *//*!*/;
SET @@session.character_set_client=83,@@session.collation_connection=83,@@session.collation_server=33/*!*/;
SET @@session.lc_time_names=0/*!*/;
SET @@session.collation_database=DEFAULT/*!*/;
BEGIN
/*!*/;
# at 585
#190519 21:22:16 server id 413340 end_log_pos 1104 CRC32 0x782391dd    Table_map: `testmts`.`testgp` mapped to number 108
# at 637
#190519 21:22:16 server id 413340 end_log_pos 9319 CRC32 0x8de0fbdd    Write_rows: table id 108
# at 8852
#190519 21:22:16 server id 413340 end_log_pos 17534 CRC32 0xae798162   Write_rows: table id 108
# at 17067
#190519 21:22:16 server id 413340 end_log_pos 25749 CRC32 0x683b9e95   Write_rows: table id 108 (以上本来已经传输了)
# at 25282
--
# at 477107
#190519 21:22:16 server id 413340 end_log_pos 485789 CRC32 0x44e99850 Write_rows: table id 108
# at 485322
#190519 21:22:16 server id 413340 end_log_pos 494004 CRC32 0x280300fd Write_rows: table id 108
# at 493537
#190519 21:22:16 server id 413340 end_log_pos 502219 CRC32 0x075c8ff8 Write_rows: table id 108
# at 501752
#190519 21:22:16 server id 413340 end_log_pos 503274 CRC32 0x08c3f96c Write_rows: table id 108 flags: STMT_END_F
# at 502807
#190519 21:22:16 server id 413340 end_log_pos 503305 CRC32 0x3b6dd31c Xid = 26
COMMIT/*!*/;
POSITION
在 recover_relay_log=0的情况下从库会从Read_Master_Log_Pos的位置接着拉取replay log，一旦Read_Master_Log_Pos和replay log出现问题那么将会导致从库异常。主库只需要从Relay_Log_Pos的位置应用即可。因此参数
sync_relay_log=1
sync_master_info=1
是必须的。
change master to
master_host='192.168.99.41',
master_user='repl',
master_password='gelc123',
master_port=3340,
MASTER_LOG_FILE='binlog.000001',
MASTER_LOG_POS=154;
start slave;
mysql> show slave status G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.99.41
                  Master_User: repl
                  Master_Port: 3340
                Connect_Retry: 60
              Master_Log_File: binlog.000001
          Read_Master_Log_Pos: 912
               Relay_Log_File: relay.000002
                Relay_Log_Pos: 1075
        Relay_Master_Log_File: binlog.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
写入途中：

mysql> show slave status G;
*************************** 1. row ***************************
               Slave_IO_State: Queueing master event to the relay log
                  Master_Host: 192.168.99.41
                  Master_User: repl
                  Master_Port: 3340
                Connect_Retry: 60
              Master_Log_File: binlog.000001
          Read_Master_Log_Pos: 124329
               Relay_Log_File: relay.000002
                Relay_Log_Pos: 1075
        Relay_Master_Log_File: binlog.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
主库binlog：

BEGIN
/*!*/;
# at 1052
#190519 16:43:43 server id 413340 end_log_pos 1104 CRC32 0x1b959719    Table_map: `testmts`.`testgp` mapped to number 108
# at 1104
#190519 16:43:43 server id 413340 end_log_pos 9319 CRC32 0x98ff5e73    Write_rows: table id 108
# at 9319
#190519 16:43:43 server id 413340 end_log_pos 17534 CRC32 0xbb6624cc   Write_rows: table id 108
# at 17534
#190519 16:43:43 server id 413340 end_log_pos 25749 CRC32 0x7d243b3b   Write_rows: table id 108
# at 25749
--
# at 477574
#190519 16:43:43 server id 413340 end_log_pos 485789 CRC32 0x51f63dfe Write_rows: table id 108
# at 485789
#190519 16:43:43 server id 413340 end_log_pos 494004 CRC32 0x3d1ca553 Write_rows: table id 108
# at 494004
#190519 16:43:43 server id 413340 end_log_pos 502219 CRC32 0x12432a56 Write_rows: table id 108
# at 502219
#190519 16:43:43 server id 413340 end_log_pos 503274 CRC32 0x4373f461 Write_rows: table id 108 flags: STMT_END_F
# at 503274
#190519 16:43:43 server id 413340 end_log_pos 503305 CRC32 0xe33a6266 Xid = 60
COMMIT/*!*/;
Crash启动后日志如下：

# at 321652
#190519 16:43:43 server id 413340 end_log_pos 329704 CRC32 0xbf87ced1 Write_rows: table id 108
# at 329867
#190519 16:43:43 server id 413340 end_log_pos 337919 CRC32 0x2f3bd840 Write_rows: table id 108
# at 338082
#190519 16:43:43 server id 413340 end_log_pos 346134 CRC32 0xe317c093 Write_rows: table id 108
# at 346297
#190519 16:43:43 server id 413340 end_log_pos 354349 CRC32 0x81e3ea0d Write_rows: table id 108
# at 354512
#190519 16:43:43 server id 413340 end_log_pos 362564 CRC32 0x7f51fc3a Write_rows: table id 108
# at 362727
#190519 16:25:17 server id 953340 end_log_pos 362770 CRC32 0xb6611a85 Rotate to relay.000003 pos: 4
WARNING: The range of printed events ends with a row event or a table map event that does not have the STMT_END_F flag set. This might be because the last statement was not fully written to the log, or because you are using a --stop-position or --stop-datetime that refers to an event in the middle of a statement. The event(s) from the partial statement have not been written to output.
ROLLBACK /* added by mysqlbinlog */ /*!*/;
SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
DELIMITER ;
# End of log file
/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;
[root@gp1 log]# /mysqldata/mysql3340/bin/mysqlbinlog --base64-output='decode-rows' relay.000003
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
DELIMITER /*!*/;
# at 4
#190519 16:25:17 server id 953340 end_log_pos 123 CRC32 0xe6fd01bf     Start: binlog v 4, server v 5.7.22-22-debug-log created 190519 16:25:17
# This Format_description_event appears in a relay log and was generated by the slave thread.
# at 123
#190519 16:25:17 server id 953340 end_log_pos 154 CRC32 0xde5482b5     Previous-GTIDs
# [empty]
# at 154
#700101 8:00:00 server id 413340 end_log_pos 0 CRC32 0x86e86060       Rotate to binlog.000001 pos: 362564
# at 198
#190519 16:42:31 server id 413340 end_log_pos 0 CRC32 0x5361aca0       Start: binlog v 4, server v 5.7.22-22-debug-log created 190519 16:42:31
# at 317
#190519 16:43:43 server id 413340 end_log_pos 370779 CRC32 0x8b7abae8 Write_rows: table id 108
# at 8532
#190519 16:43:43 server id 413340 end_log_pos 378994 CRC32 0x28e1279c Write_rows: table id 108
# at 16747
#190519 16:43:43 server id 413340 end_log_pos 387209 CRC32 0x278d98ed Write_rows: table id 108
# at 24962
#190519 16:43:43 server id 413340 end_log_pos 395424 CRC32 0x85d21655 Write_rows: table id 108
# at 33177
#190519 16:43:43 server id 413340 end_log_pos 403639 CRC32 0x156e00c4 Write_rows: table id 108
# at 41392
#190519 16:43:43 server id 413340 end_log_pos 411854 CRC32 0xed83b3ac Write_rows: table id 108
# at 49607
#190519 16:43:43 server id 413340 end_log_pos 420069 CRC32 0x465939b4 Write_rows: table id 108
# at 57822
#190519 16:43:43 server id 413340 end_log_pos 428284 CRC32 0xaab146d2 Write_rows: table id 108
# at 66037
#190519 16:43:43 server id 413340 end_log_pos 436499 CRC32 0x97f1428f Write_rows: table id 108
WARNING: The range of printed events ends with a row event or a table map event that does not have the STMT_END_F flag set. This might be because the last statement was not fully written to the log, or because you are using a --stop-position or --stop-datetime that refers to an event in the middle of a statement. The event(s) from the partial statement have not been written to output.
SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
DELIMITER ;
# End of log file
/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;
[root@gp1 log]# /mysqldata/mysql3340/bin/mysqlbinlog --base64-output='decode-rows' relay.000005
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
DELIMITER /*!*/;
# at 4
#190519 16:31:57 server id 953340 end_log_pos 123 CRC32 0xecc598ac     Start: binlog v 4, server v 5.7.22-22-debug-log created 190519 16:31:57
# This Format_description_event appears in a relay log and was generated by the slave thread.
# at 123
#190519 16:31:57 server id 953340 end_log_pos 154 CRC32 0x21c8a43a     Previous-GTIDs
# [empty]
# at 154
#700101 8:00:00 server id 413340 end_log_pos 0 CRC32 0xeed34528       Rotate to binlog.000001 pos: 428284
# at 198
#190519 16:42:31 server id 413340 end_log_pos 0 CRC32 0x5361aca0       Start: binlog v 4, server v 5.7.22-22-debug-log created 190519 16:42:31
# at 317
#190519 16:43:43 server id 413340 end_log_pos 436499 CRC32 0x97f1428f Write_rows: table id 108
# at 8532
#190519 16:43:43 server id 413340 end_log_pos 444714 CRC32 0xfd447f7d Write_rows: table id 108
# at 16747
#190519 16:43:43 server id 413340 end_log_pos 452929 CRC32 0xc4c67bff Write_rows: table id 108
# at 24962
#190519 16:43:43 server id 413340 end_log_pos 461144 CRC32 0x6dbd096a Write_rows: table id 108
# at 33177
#190519 16:43:43 server id 413340 end_log_pos 469359 CRC32 0xb42d58b6 Write_rows: table id 108
# at 41392
#190519 16:43:43 server id 413340 end_log_pos 477574 CRC32 0x7a2e502d Write_rows: table id 108
# at 49607
#190519 16:43:43 server id 413340 end_log_pos 485789 CRC32 0x51f63dfe Write_rows: table id 108
# at 57822
#190519 16:43:43 server id 413340 end_log_pos 494004 CRC32 0x3d1ca553 Write_rows: table id 108
# at 66037
#190519 16:43:43 server id 413340 end_log_pos 502219 CRC32 0x12432a56 Write_rows: table id 108
# at 74252
#190519 16:43:43 server id 413340 end_log_pos 503274 CRC32 0x4373f461 Write_rows: table id 108 flags: STMT_END_F
# at 75307
#190519 16:43:43 server id 413340 end_log_pos 503305 CRC32 0xe33a6266 Xid = 60
COMMIT/*!*/;
SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
从 end_log_pos 可以看到他们凑成了一个完整的事务日志。

“怎么理解从库的IO线程”的内容就介绍到这里了，感谢大家的阅读。

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