MySQL GTID 错误处理汇总

刺骨的言语ヽ痛彻心扉 2022-07-16 07:07 454阅读 0赞

> MySQL GTID是在传统的mysql主从复制的基础之上演化而来的产物，即通过UUID加上事务ID的方式来确保每一个事物的唯一性。这样的操作方式使得我们不再需要关心所谓的log\_file和log\_Pos，只是简单的告诉从库，从哪个服务器上去找主库就OK了。简化了主从的搭建以及failover的过程，同时比传统的复制更加安全可靠。由于GTID是连续没有空洞的，因此主从库出现数据冲突时，可以通过注入空事物的方式进行跳过。本文主要讲述GTID主从架构的错误处理方式。

## 一、GTID的相关特性 ##

[配置MySQL GTID 主从复制][MySQL GTID]  
[基于mysqldump搭建gtid主从][mysqldump_gtid]

## 二、GTID如何跳过事务冲突 ##

很多无法预料的情形导致mysql主从发生事务冲突，主从失败或停止的情形，即需要修复主从
        对于GTID方式的主从架构而言，更多的是处理事务冲突来修复主从
        GTID不支持通过传统设置sql_slave_skip_counter方法来跳过事务
        方法：通过注入空事务来填补事务空洞，等同于传统复制的(set global sql_slave_skip_counter = 1)
        步骤：
                stop slave；
                set gtid_next='xxxxxxx:N'; --指定下一个事务执行的版本，即想要跳过的GTID
                begin;
                commit;  --注入一个空事物
                set gtid_next='AUTOMATIC' --自动的寻找GTID事务。
                start slave; --开始同步

## 三、GTID事务冲突的几种常见类型 ##

1、主库新增记录，从库提示主键冲突
        2、主库对象可更新，从库无对应的对象可更新
        3、主库对象可删除，从库无对应的对象可删除
        4、通过延迟从修复主库意外删除的对象
        5、主库日志被purged的情形

# 四、示例演示 #

### 1、从库报主键重复(Errno: 1062) ###

(root@Master)[tempdb]>create table t1 ( -> id tinyint not null primary key,ename varchar(20),blog varchar(50));
    
    (root@Master)[tempdb]>insert into t1 -> values(1,'leshami','http://blog.csdn.net/leshami');
    
    (root@Master)[tempdb]>insert into t1 -> values(2,'robin','http://blog.csdn.net/robinson_0612');
    
    (root@Master)[tempdb]>set sql_log_bin=off;
    
    (root@Master)[tempdb]>delete from t1 where ename='robin';
    
    (root@Master)[tempdb]>set sql_log_bin=on;
    
    (root@Master)[tempdb]>insert into t1 -> values(2,'robin','http://blog.csdn.net/robinson_0612');
    
    -- 从库状态报错，提示重复的primary key
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
    Last_Errno: 1062
    Last_Error: Could not execute Write_rows event on table tempdb.t1; Duplicate entry '2' for key 'PRIMARY', 
                            Error_code: 1062; handler error HA_ERR_FOUND_DUPP_KEY; 
                            the event's master log node233-binlog.000004, end_log_pos 4426 Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-90 Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-89 Auto_Position: 1 -- 如下解决方案，可以通过删除重库的这条记录 (root@Slave)[tempdb]>stop slave; (root@Slave)[tempdb]>delete from t1 where ename='robin'; (root@Slave)[tempdb]>start slave; (root@Slave)[tempdb]>show slave status \G *************************** 1. row *************************** Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-90 Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-90, 78336cdc-8cfb-11e6-ba9f-000c29328504:1 --这里多了一个GTID，注意这个是从库上执行的，这里的UUID跟IP 245的UUID一致 Auto_Position: 1 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version: (root@Slave)[tempdb]>show variables like '%uuid%'; +---------------+--------------------------------------+ | Variable_name | Value | +---------------+--------------------------------------+ | server_uuid | 78336cdc-8cfb-11e6-ba9f-000c29328504 | +---------------+--------------------------------------+

### 2、从库报找不到对应的被更新的记录(Errno: 1032) ###

--首先在从库上删除leshami这条记录
    (root@Slave)[tempdb]>delete from t1 where ename='leshami';
    
    --接下来再主库尝试更新leshami这条记录
    (root@Master)[tempdb]>update t1 set 
     -> blog='http://blog.csdn.net/robinson_0612' where ename='leshami';
    
    Query OK, 1 row affected (0.02 sec)
    Rows matched: 1  Changed: 1  Warnings: 0
    
    -- 查看从库状态
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
    Last_SQL_Errno: 1032
    Last_SQL_Error: Could not execute Update_rows event on table tempdb.t1; Can't find record in 't1',
     Error_code: 1032; handler error HA_ERR_KEY_NOT_FOUND;
     the event's master log node233-binlog.000004, end_log_pos 4769
    Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-91
    Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-90,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-2
    
    -- 通过mysqlbinlog在主服务器上寻找报错的binglog日志文件及位置，找到对应的SQL语句，如下所示
    -- update中的where后面的部分为更新前的数据，set部分为更新后的数据，因此可以将更新前的数据插入到从库
    # mysqlbinlog --no-defaults -v -v --base64-output=DECODE-ROWS /data/node233-binlog.000004|grep -A '10' 4769
    #161009 13:46:34 server id 233 end_log_pos 4769 CRC32 0xb60df74e Update_rows: table id 147 flags: STMT_END_F
    ### UPDATE `tempdb`.`t1`
    ### WHERE
    ### @1=1 /* TINYINT meta=0 nullable=0 is_null=0 */
    ### @2='leshami' /* VARSTRING(20) meta=20 nullable=1 is_null=0 */
    ### @3='http://blog.csdn.net/leshami' /* VARSTRING(50) meta=50 nullable=1 is_null=0 */
    ### SET
    ### @1=1 /* TINYINT meta=0 nullable=0 is_null=0 */
    ### @2='leshami' /* VARSTRING(20) meta=20 nullable=1 is_null=0 */
    ### @3='http://blog.csdn.net/robinson_0612' /* VARSTRING(50) meta=50 nullable=1 is_null=0 */
    # at 4769
    #161009 13:46:34 server id 233 end_log_pos 4800 CRC32 0xa9669811 Xid = 1749
    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*/;   
    
    (root@Slave)[tempdb]>select * from t1;
    +----+-------+------------------------------------+
    | id | ename | blog                               |
    +----+-------+------------------------------------+
    |  2 | robin | http://blog.csdn.net/robinson_0612 |
    +----+-------+------------------------------------+
    
    (root@Slave)[tempdb]>stop slave sql_thread;
    
    (root@Slave)[tempdb]>insert into t1 values(1,'leshami','http://blog.csdn.net/leshami');
    
    (root@Slave)[tempdb]>start slave sql_thread;
    
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
     Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-91
     Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-91,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-3
     Auto_Position: 1

### 3、从库找不到对应的被删除的记录(Errno: 1032) ###

-- 如果是在主库上删除记录，而从库上找不到对应的记录，则可以直接跳过该事务
    -- 下面我们首选在从库上删除一条记录
    (root@Slave)[tempdb]>delete from t1 where ename='robin';
    
    -- 接下来在主库上删除该记录
    (root@Master)[tempdb]>delete from t1 where ename='robin';
    
    -- 从库端提示无法找到对应的记录
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
    Last_SQL_Error: Could not execute Delete_rows event on table tempdb.t1; Can't find record in 't1',
     Error_code: 1032; handler error HA_ERR_KEY_NOT_FOUND; 
     the event's master log node233-binlog.000004, end_log_pos 5070
    Last_SQL_Error_Timestamp: 161009 15:08:06
     Master_SSL_Crl: 
    Master_SSL_Crlpath: 
    Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-92
     Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-91,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-4
     Auto_Position: 1 
    
    -- 下面通过注入空事务来跳过
    (root@Slave)[tempdb]>stop slave sql_thread;
    
    (root@Slave)[tempdb]>set gtid_next='1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:92';
    
    (root@Slave)[tempdb]>begin;commit;
    
    (root@Slave)[tempdb]>set gtid_next='AUTOMATIC';
    
    (root@Slave)[tempdb]>start slave sql_thread;
    
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
     Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-92
     Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-92,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-4
     Auto_Position: 1
     Replicate_Rewrite_DB: 
     Channel_Name: 
     Master_TLS_Version:

### 4、延迟从修复主库意外truncate ###

-- 主库上面新增表及记录             
    (root@Master)[tempdb]>create table t2 (id tinyint not null primary key, 
     -> ename varchar(20),blog varchar(50));
    
    (root@Master)[tempdb]>insert into t2  
     -> values(1,'leshami','http://blog.csdn.net/leshami');
    
    (root@Master)[tempdb]>insert into t2  
     -> values(2,'robin','http://blog.csdn.net/robinson_0612');
    
    (root@Master)[tempdb]>select * from t2;
    +----+---------+------------------------------------+
    | id | ename   | blog                               |
    +----+---------+------------------------------------+
    |  1 | leshami | http://blog.csdn.net/leshami       |
    |  2 | robin   | http://blog.csdn.net/robinson_0612 |
    +----+---------+------------------------------------+
    
    --先将从库配置为延迟从
    (root@Slave)[tempdb]>stop slave sql_thread;
    Query OK, 0 rows affected (0.01 sec)
    
    (root@Slave)[tempdb]>CHANGE MASTER TO MASTER_DELAY = 300;
    Query OK, 0 rows affected (0.00 sec)
    
    (root@Slave)[tempdb]>start slave sql_thread;
    Query OK, 0 rows affected (0.02 sec)
    
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
     Slave_IO_Running: Yes
     Slave_SQL_Running: Yes
     SQL_Delay: 300 
    
    root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
     Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-99
     Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-99,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-4
     Auto_Position: 1
    
    --查看主库上的binglog gtid
    (root@Master)[tempdb]>show master status\G
    *************************** 1. row ***************************
     File: node233-binlog.000004
     Position: 6970
     Binlog_Do_DB: 
     Binlog_Ignore_DB: 
    Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-99
    1 row in set (0.00 sec)
    
    --在主库上truncate t2
    (root@Master)[tempdb]>truncate table t2;
    Query OK, 0 rows affected (0.03 sec)
    
    --再次查看主库上的binglog gtid，有99变成了100，这个100即是我们需要跳过的ID
    (root@Master)[tempdb]>show master status\G
    *************************** 1. row ***************************
     File: node233-binlog.000004
     Position: 7121
     Binlog_Do_DB: 
     Binlog_Ignore_DB: 
    Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-100
    1 row in set (0.00 sec)
    
    --从库上跳过被意外truncate的事务
    (root@Slave)[tempdb]>stop slave sql_thread;
    Query OK, 0 rows affected (0.01 sec)
    
    (root@Slave)[tempdb]>set gtid_next='1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:100';
    Query OK, 0 rows affected (0.00 sec)
    
    (root@Slave)[tempdb]>begin;commit;
    Query OK, 0 rows affected (0.00 sec)
    
    Query OK, 0 rows affected (0.01 sec)
    
    (root@Slave)[tempdb]>set gtid_next='AUTOMATIC';
    Query OK, 0 rows affected (0.00 sec)
    
    (root@Slave)[tempdb]>start slave sql_thread;
    Query OK, 0 rows affected (0.02 sec)
    
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
     Slave_IO_State: Waiting for master to send event
     Master_Host: Master
     Master_User: repl
     Master_Port: 3306
     Connect_Retry: 60
     Master_Log_File: node233-binlog.000004
     Read_Master_Log_Pos: 7121
     Relay_Log_File: node245-relay-bin.000003
     Relay_Log_Pos: 2982
     Relay_Master_Log_File: node233-binlog.000004
     Slave_IO_Running: Yes
     Slave_SQL_Running: Yes
     ........................... 
     Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-100
     Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-100,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-4
     Auto_Position: 1
    
    -- 很多时候我们并不知道表何时被truncate，因此可以从binlog日志得到其gtid
    -- 如下所示，可以得到这串 SET @@SESSION.GTID_NEXT= '1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:100'
    -- 100即为这个truncate对应的gtid的事务号
    # mysqlbinlog --no-defaults -v -v --base64-output=DECODE-ROWS /data/node233-binlog.000004|grep -i \
    > "truncate table t2" -A3 -B10 
    ### @3='http://blog.csdn.net/robinson_0612' /* VARSTRING(50) meta=50 nullable=1 is_null=0 */
    # at 6939
    #161009 18:04:58 server id 233 end_log_pos 6970 CRC32 0x71c5121c Xid = 1775
    COMMIT/*!*/;
    # at 6970
    #161009 18:08:42 server id 233 end_log_pos 7035 CRC32 0x00ba9437 GTID last_committed=26 sequence_number=27
    SET @@SESSION.GTID_NEXT= '1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:100'/*!*/;
    # at 7035
    #161009 18:08:42 server id 233 end_log_pos 7121 CRC32 0x5a8b9723 Query thread_id=26 exec_time=0 error_code=0
    SET TIMESTAMP=1476007722/*!*/;
    truncate table t2
    /*!*/;
    SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
    DELIMITER ;

### 5、主库binlog被purge的情形(Errno: 1236) ###

-- 首先停止从库，模拟从库被意外宕机
    (root@Slave)[tempdb]>stop slave;
    Query OK, 0 rows affected (0.08 sec)
    
    --在主库上进行相应的操作
    --此时主库上的gtid_purged为空
    (root@Master)[tempdb]>show variables like '%gtid_purged%';
    +---------------+-------+
    | Variable_name | Value |
    +---------------+-------+
    | gtid_purged   |       |
    +---------------+-------+
    
    --查看主库binlog
    (root@Master)[tempdb]>show binary logs;
    +-----------------------+-----------+
    | Log_name | File_size |
    +-----------------------+-----------+
    | node233-binlog.000001 |   1362104 |
    | node233-binlog.000002 |      1331 |
    | node233-binlog.000003 |       217 |
    | node233-binlog.000004 |      7121 |
    +-----------------------+-----------+
    
    (root@Master)[tempdb]>select * from t1;
    +----+---------+------------------------------------+
    | id | ename   | blog                               |
    +----+---------+------------------------------------+
    |  1 | leshami | http://blog.csdn.net/robinson_0612 |
    |  2 | robin   | http://blog.csdn.net/leshami       |
    +----+---------+------------------------------------+
    
    --从主库删除记录
    (root@Master)[tempdb]>delete from t1;
    
    --切换日志
    (root@Master)[tempdb]>flush logs;
    
    --新增记录
    (root@Master)[tempdb]>insert into t1 values(1,
     -> 'xuputi','http://blog.csdn.net/leshami');
    
    (root@Master)[tempdb]>show binary logs;
    +-----------------------+-----------+
    | Log_name | File_size |
    +-----------------------+-----------+
    | node233-binlog.000001 |   1362104 |
    | node233-binlog.000002 |      1331 |
    | node233-binlog.000003 |       217 |
    | node233-binlog.000004 |      7513 |
    | node233-binlog.000005 |       490 |
    +-----------------------+-----------+
    
    --清理binlog
    (root@Master)[tempdb]>purge binary logs to 'node233-binlog.000005';
    Query OK, 0 rows affected (0.01 sec)
    
    (root@Master)[tempdb]>show binary logs;
    +-----------------------+-----------+
    | Log_name | File_size |
    +-----------------------+-----------+
    | node233-binlog.000005 |       490 |
    +-----------------------+-----------+
    
    --此时可以看到相应的gtid_purged值
    (root@Master)[tempdb]>show variables like '%gtid_purged%';
    +---------------+--------------------------------------------+
    | Variable_name | Value                                      |
    +---------------+--------------------------------------------+
    | gtid_purged   | 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-101 |
    +---------------+--------------------------------------------+
    
    --下面启动从库
    (root@Slave)[tempdb]>start slave;
    Query OK, 0 rows affected (0.00 sec)
    
    --从库状态提示有日志被purged
    (root@Slave)[tempdb]>show slave status\G
    *************************** 1. row ***************************
     Slave_IO_State: 
     Master_Host: Master
     Master_User: repl
     Master_Port: 3306
     Connect_Retry: 60
     Master_Log_File: node233-binlog.000004
     Read_Master_Log_Pos: 7121
     Relay_Log_File: node245-relay-bin.000003
     Relay_Log_Pos: 3133
     Relay_Master_Log_File: node233-binlog.000004
     Slave_IO_Running: No
     Slave_SQL_Running: Yes
     ...............
     Last_IO_Errno: 1236
     Last_IO_Error: Got fatal error 1236 from master when reading data from binary log:
     'The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, 
     but the master has purged binary logs containing GTIDs that the slave requires.'
     ..................
     Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-100
     Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-100,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-4
     Auto_Position: 1
    
    -- 从库上gtid_purged参数，此时为75
    (root@Slave)[tempdb]>show variables like '%gtid_purged%';
    +---------------+-------------------------------------------+
    | Variable_name | Value                                     |
    +---------------+-------------------------------------------+
    | gtid_purged   | 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-75 |
    +---------------+-------------------------------------------+                
    
    --停止从库
    (root@Slave)[tempdb]>stop slave;
    Query OK, 0 rows affected (0.01 sec)
    
    --下面尝试使用gtid_purged进行跳过事务，，如下，提示仅仅当GLOBAL.GTID_EXECUTED为空才能被设置
    (root@Slave)[tempdb]>set global gtid_purged = '1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-101';
    ERROR 1840 (HY000): @@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_EXECUTED is empty.
    
    --如下查看，已经存在被执行的gtid，即gtid_executed肯定是不为空，且这些gtid记录在从库的binary log中
    (root@Slave)[tempdb]>show global variables like '%gtid_executed%'\G
    *************************** 1. row ***************************
    Variable_name: gtid_executed
     Value: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-100,
     78336cdc-8cfb-11e6-ba9f-000c29328504:1-4
    *************************** 2. row ***************************
    Variable_name: gtid_executed_compression_period
     Value: 1000
    
    --下面我们在从库上reset master，即清空从库binlog
    (root@Slave)[tempdb]>reset master;
    Query OK, 0 rows affected (0.05 sec)
    
    --再次查看gtid_executed已经为空值
    (root@Slave)[tempdb]>show global variables like '%gtid_executed%'\G
    *************************** 1. row ***************************
    Variable_name: gtid_executed
     Value: 
    *************************** 2. row ***************************
    Variable_name: gtid_executed_compression_period
     Value: 1000
    
    --此时再次设置gtid_purged的值
    (root@Slave)[tempdb]>set global gtid_purged = '1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-101';
    Query OK, 0 rows affected (0.01 sec)
    
    --启动从库
    (root@Slave)[tempdb]>start slave;
    Query OK, 0 rows affected (0.03 sec)
    
    --提示有重复记录，如下所示
    --是由于我们在从库停止期间delete这个事务没有被从库的relay log接受到
    --其次主从的binlog又被purged，而且从库启动后，执行了gtid_purged，因此主库上新增的记录在从库上提示主键重复
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
     Slave_IO_State: Waiting for master to send event
     Master_Host: Master
     Master_User: repl
     Master_Port: 3306
     Connect_Retry: 60
     Master_Log_File: node233-binlog.000005
     Read_Master_Log_Pos: 490
     Relay_Log_File: node245-relay-bin.000004
     Relay_Log_Pos: 417
     Relay_Master_Log_File: node233-binlog.000005
     Slave_IO_Running: Yes
     Slave_SQL_Running: No
     ................
     Last_SQL_Error: Could not execute Write_rows event on table tempdb.t1; 
     Duplicate entry '1' for key 'PRIMARY', Error_code: 1062;
     handler error HA_ERR_FOUND_DUPP_KEY; the event's master log node233-binlog.000005, end_log_pos 459
     Retrieved_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:76-100:102
     Executed_Gtid_Set: 1b64c25d-8d2b-11e6-9ac0-000c29b82d0d:1-101
     Auto_Position: 1
    
    --在从库上删除id为1的记录
    (root@Slave)[tempdb]>delete from t1 where id=1;
    Query OK, 1 row affected (0.05 sec)
    
    --启动从库的sql_thread线程
    (root@Slave)[tempdb]>start slave sql_thread;
    Query OK, 0 rows affected (0.02 sec)
    
    --再次查看正常
    (root@Slave)[tempdb]>show slave status \G
    *************************** 1. row ***************************
     Slave_IO_State: Waiting for master to send event
     Master_Host: Master
     Master_User: repl
     Master_Port: 3306
     Connect_Retry: 60
     Master_Log_File: node233-binlog.000005
     Read_Master_Log_Pos: 490
     Relay_Log_File: node245-relay-bin.000004
     Relay_Log_Pos: 713
     Relay_Master_Log_File: node233-binlog.000005
     Slave_IO_Running: Yes
     Slave_SQL_Running: Yes
    
    --上面的这个示例，主要是演示我们使用gtid_purged方式来达到跳过事务的目的
    --事实上，主从的数据已经不一致了，应根据实际的需要考虑是否进行相应的修复

## 五、小结 ##

1、GTID是全局事务ID，简化了主从架构的部署使得从库不再需要关心log\_file和log\_pos  
2、由于事务ID的唯一性，使得将其他从库的GTID应用到其它从库成为可能，即提供了便利的failover  
3、GTID是连续的，非空洞性的，因此，对于冲突的情形，需要注入空的事务来实现  
4、可以通过配置延迟从来避免主库上意外的删除对象导致的人为错误

[MySQL GTID]: http://blog.csdn.net/leshami/article/details/50630691
[mysqldump_gtid]: http://blog.csdn.net/leshami/article/details/52755472