MySQL的GTID复制
从mysql5.6开始引入全局事务标识符(GTID),即每个事务都有一个唯一的标识符。服务器上的每个事务都被分配一个唯一的事务标识符,这是一个64位非零的数值,根据事务提交的顺序分配。GTID的构成是由服务器的Uuid和事务的提交顺序两部分组成的。
复制事务的时候如果启用了全局事务标识符,不管事务被复制了多少次,事务的GTID保持不变。
注意的是:GTID被写入二进制日志,并且只会分配给已经写入二进制日志的事务。也就是说,如果关闭二进制日志,事务就不会分配GTID了。不管master还是slave都是这样。所以,如果想使用slave做故障转移,需要开启二进制日志,如果没有开启二进制日志,slave就不会记下事务的GTID。
首先来配置GTID复制
首先在从上清除当前的基于filename和pos的复制状态
mysql> stop slave;Query OK, 0 rows affected (0.01 sec)mysql> reset slave all;Query OK, 0 rows affected (0.02 sec)mysql> show slave status\GEmpty set (0.00 sec)
主和从均开启GTID,设置GTID复制!因为之前两台服务器时主从复制,因此状态是一致的,因此不用再拷贝数据!
同步数据,设置复制账户都需要做!因为之前已经是主从,复制账户已经存在。
binmodegtidconsistency
log-bin= #在基于filename和pos做主从时,没有开启备用服务器的二进制日志,做gtid复制时,需要开启二进制日志,原因后面会提到!
: 这个是在基于filename和pos做主从时,用于做级联复制,在MySQL5.6中左gtid好像必须要开启这个参数,MySQL5.7不再强制必须!
设置完之后重启服务器:
在从上做如下设置
mysql change master master_host".", master_port,master_user"repl",master_password"",master_auto_position rows affected, warnings (
# master_auto_position使slave在连接master的时候,自动与master协商应该发送什么事务。
mysql> show slave status\G #与之前的复制相比,多了gitd的信息
*************************** 1. row ***************************
...........
Master_UUID: 4687e05d-f37f-11e8-8fc7-fa336351fc00 #master的UUID
Retrieved_Gtid_Set: 4687e05d-f37f-11e8-8fc7-fa336351fc00:1-2
Executed_Gtid_Set: 4687e05d-f37f-11e8-8fc7-fa336351fc00:1-2
Retrieved_Gtid_Set:这是从master获取而来的,存储在中继日志中的一组GTID.
Executed_Gtid_Set: 这是slave上执行,并且已经写入slave的二进制日志的一组GTID。
在从上查看二进制日志
mysql Log_name Pos Event_type Server_id End_log_pos Info test2bin. Format_desc Server ver: ., Binlog ver: test2bin. Previous_gtids test2bin. Gtid .GTID_NEXT test2bin. Query `mytest`; tb2(id auto_increment ) test2bin. Gtid .GTID_NEXT test2bin. Query test2bin. Table_map table_id: (mytest.tb2) test2bin. Write_rows table_id: flags: STMT_END_F test2bin. Xid rows ( sec)#在二进制日志事件中可以看到Executed_Gtid_Set的gitd集合已经在slave上执行
gitd的复制是怎么找到二进制日志的复制点的?
在我们做filename和pos的复制时,手动指定了二进制日志的文件和位置,但是gtid怎么找到二进制日志的复制点的?从上面的二进制日志看到,event有一个Previous_gtids事件,这个事件指定的是前一个二进制日志事件的最后的gtid的数值,把当前从执行到的gtid与Previous_gtids比较,确定二进制日志的文件,然后再对比gtid的大小,确定日志的位置!因为当前是一个新开始的gitd复制,因此Previous_gtids值为0,我们强制轮换主的二进制,查看数据如下!
mysql> flush logs; #强制轮换二进制日志,会进行一次显式刷新磁盘Query OK, 0 rows affected (0.00 sec)mysql> show binlog events in "test3-bin.000006"; #因为之前的执行了两个事务,因此Previous_gtids指向为1-2.+------------------+------+----------------+-----------+-------------+-------------------------------------------------------------------+| Log_name | Pos | Event_type | Server_id | End_log_pos | Info |+------------------+------+----------------+-----------+-------------+-------------------------------------------------------------------+| test3-bin.000006 | 4 | Format_desc | 5 | 123 | Server ver: 5.7.22-log, Binlog ver: 4 || test3-bin.000006 | 123 | Previous_gtids | 5 | 194 | 4687e05d-f37f-11e8-8fc7-fa336351fc00:1-2 || test3-bin.000006 | 194 | Gtid | 5 | 259 | SET @@SESSION.GTID_NEXT= '4687e05d-f37f-11e8-8fc7-fa336351fc00:3' || test3-bin.000006 | 259 | Query | 5 | 333 | BEGIN || test3-bin.000006 | 333 | Table_map | 5 | 381 | table_id: 109 (mytest.tb1) || test3-bin.000006 | 381 | Write_rows | 5 | 421 | table_id: 109 flags: STMT_END_F || test3-bin.000006 | 421 | Xid | 5 | 452 | COMMIT /* xid=40 */ || test3-bin.000006 | 452 | Gtid | 5 | 517 | SET @@SESSION.GTID_NEXT= '4687e05d-f37f-11e8-8fc7-fa336351fc00:4' |
我们知道GTID是由服务器的UUID+事务的执行顺序组成的,服务器的UUID存在于datadir指定目录下面:
mysql> show variables like "datadir";+---------------+--------------+| Variable_name | Value |+---------------+--------------+| datadir | /data/mysql/ |+---------------+--------------+1 row in set (0.00 sec)mysql> system cat /data/mysql/auto.cnf; #服务器的UUID[auto]server-uuid=4687e05d-f37f-11e8-8fc7-fa336351fc00
上面我们搭建了一个简易的GITD复制,那么GTID是怎么复制的,GTID的复制原理是什么?
master更新数据时,会在事务前产生GTID,一同记录到binlog日志中。slave端的i/o线程将变更的binlog,写入到本地的relay log中。sql线程从relay log中获取GTID,然后对比slave端的binlog是否有记录。【对比本地的binlog中是否有记录,因此slave需要开通二进制日志】如果有记录,说明该GTID的事务已经执行,slave会忽略。如果没有记录,slave就会从relay log中执行该GTID的事务,并记录到binlog。
查看当前master和从的二进制日志点和gtid值!
Position Binlog_Do_DB Binlog_Ignore_DB Executed_Gtid_Set test3bin. 4687e05df37f11e88fc7fa336351fc00: row ( Position Binlog_Do_DB Binlog_Ignore_DB Executed_Gtid_Set test2bin. 4687e05df37f11e88fc7fa336351fc00: row ( sec)#可以看到日志名称不一样,日志的pos不一样,但是gtid却是一样的
测试在从上插入一条数据:
mysql tb1 row affected ( Duplicates: Warnings: test3bin. Gtid .GTID_NEXT test3bin. Query test3bin. Table_map table_id: (mytest.tb1) test3bin. Write_rows table_id: flags: STMT_END_F test3bin. Xid mysql> show variables like "binlog_format"; #日志格式是row+---------------+-------+| Variable_name | Value |+---------------+-------+| binlog_format | |+---------------+-------+1 row in set (0.00 sec)
在从上查看二进制日志
#前面执行了flush logs命令!mysql show binlog events "test2bin. Log_name Pos Event_type Server_id End_log_pos Info test2bin. Format_desc Server ver: ., Binlog ver: test2bin. Previous_gtids 4687e05df37f11e88fc7fa336351fc00: test2bin. Gtid .GTID_NEXT test2bin. Query test2bin. Table_map table_id: (mytest.tb1) test2bin. Write_rows table_id: flags: STMT_END_F test2bin. Xid rows ( sec)
使用GTID做故障转移
#主从上都有一张这样的表,数据是一样的mysql> desc tb2;+-------+---------+------+-----+---------+----------------+| Field | Type | Null | Key | Default | Extra |+-------+---------+------+-----+---------+----------------+| id | int(11) | NO | PRI | NULL | auto_increment |+-------+---------+------+-----+---------+----------------+1 row in set (0.00 sec)#现在在从从上插入一条数据mysql> insert into tb2 select 4;Query OK, 1 row affected (0.01 sec)Records: 1 Duplicates: 0 Warnings: 0#在主上也插入一条数据mysql> insert into tb2 select 4;Query OK, 1 row affected (0.01 sec)Records: 1 Duplicates: 0 Warnings: 0
mysql> show slave status\G*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 10.0.102.214 Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: test3-bin.000007 Read_Master_Log_Pos: 452 Relay_Log_File: test2-relay-bin.000007 Relay_Log_Pos: 407 Relay_Master_Log_File: test3-bin.000007 Slave_IO_Running: Yes Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 1062 Last_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 1 failed executing transaction '4687e05d-f37f-11e8-8fc7-fa336351fc00:8' at master log test3-bin.000007, end_log_pos 421. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any. Skip_Counter: 0 Exec_Master_Log_Pos: 194 Relay_Log_Space: 959 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: NULLMaster_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 1062 Last_SQL_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 1 failed executing transaction '4687e05d-f37f-11e8-8fc7-fa336351fc00:8' at master log test3-bin.000007, end_log_pos 421. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any. Replicate_Ignore_Server_Ids: Master_Server_Id: 5 Master_UUID: 4687e05d-f37f-11e8-8fc7-fa336351fc00 Master_Info_File: /data/mysql/master.info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: 181203 10:01:08 Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: 4687e05d-f37f-11e8-8fc7-fa336351fc00:1-8 Executed_Gtid_Set: 4687e05d-f37f-11e8-8fc7-fa336351fc00:1-7,e2bd1bae-f5cb-11e8-9c8c-fa1dae125200:1 Auto_Position: 1 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version: 1 row in set (0.00 sec)mysql>
show slave status查看复制状态
#错误说明Last_SQL_Error: Coordinator stopped because there were error(s) the worker(s). The most recent failure being: Worker failed executing at master test3bin., end_log_pos . See error performance_schema.replication_applier_status_by_worker more details about this failure others, f37f11e88fc7fa336351fc00:f37f11e88fc7fa336351fc00:f5cb11e89c8cfa1dae125200:
我们知道是重复了数值,因此忽略掉这一条gitd的执行事务即可!
mysql> select @@gtid_next; #查看下一个要执行的事务,默认是自动选择+-------------+| @@gtid_next |+-------------+| AUTOMATIC |+-------------+1 row in set (0.00 sec)mysql> set gtid_next="4687e05d-f37f-11e8-8fc7-fa336351fc00:8"; #我们把gtid_next设置为要忽略的哪一个事务的gtidQuery OK, 0 rows affected (0.00 sec)mysql> begin; #执行一个空的事务Query OK, 0 rows affected (0.00 sec)mysql> commit;Query OK, 0 rows affected (0.01 sec)mysql> set gtid_next="AUTOMATIC"; #把gtid_next设置为原来的AUTOMATICQuery OK, 0 rows affected (0.00 sec)mysql> start slave sql_thread; #开启sql线程Query OK, 0 rows affected (0.02 sec)mysql> show slave status\G #查看复制已经恢复正常
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