由於GTID的優勢，我們需要將傳統基於file-pos的復制更改為基於GTID的復制，如何在線變更成為我們關心的一個點，如下為具體的方法：
目前我們有一個傳統復制下的M-S結構：
port 3301 master
port 3302 slave
master上（3301）： [zejin] 3301>select * from t_users; +----+------+ | id | name | +----+------+ | 1 | hao | | 2 | zhou | +----+------+ 2 rows in set (0.00 sec) slave上（3302）： [zejin] 3302>show slave status\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.1.240 Master_User: repl Master_Port: 3301 Connect_Retry: 60 Master_Log_File: binlog57.000002 Read_Master_Log_Pos: 417 Relay_Log_File: zejin240-relay-bin.000004 Relay_Log_Pos: 628 Relay_Master_Log_File: binlog57.000002 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 417 Relay_Log_Space: 884 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: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 3301 Master_UUID: a97983fc-5a29-11e6-9d28-000c29d4dc3f Master_Info_File: /home/mysql/I3302/master.info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: Executed_Gtid_Set: Auto_Position: 0 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version: 1 row in set (0.00 sec) [zejin] 3302>select * from t_users; +----+------+ | id | name | +----+------+ | 1 | hao | | 2 | zhou | +----+------+ 2 rows in set (0.00 sec)
如下為在線變更的具體的操作步驟：
前提：
1.要求所有的mysql版本5.7.6或更高的版本。
2.目前拓撲結構中所有的mysql的gtid_mode的值為off狀態。
3.如下的操作步驟都是有序的，不要跳躍着進行。
補充一下全局系統變量GTID_MODE變量值說明：
OFF 新事務是非GTID, Slave只接受不帶GTID的事務，傳送來GTID的事務會報錯
OFF_PERMISSIVE 新事務是非GTID, Slave即接受不帶GTID的事務也接受帶GTID的事務
ON_PERMISSIVE 新事務是GTID, Slave即接受不帶GTID的事務也接受帶GTID的事務
ON 新事務是GTID, Slave只接受帶GTID的事務
需要注意的是，這幾個值的改變是有順序的，即
off<--->OFF_PERMISSIVE<--->ON_PERMISSIVE<--->ON
不能跳躍執行，會報錯。
step1:在每個mysql實例上，將
ENFORCE_GTID_CONSISTENCY設置為warning，哪台先執行不影響結果。
[zejin] 3302>set @@global.enforce_gtid_consistency=warn; Query OK, 0 rows affected (0.00 sec) [zejin] 3301>set @@global.enforce_gtid_consistency=warn; Query OK, 0 rows affected (0.00 sec)
注意：執行完這條語句后，如果出現GTID不兼容的語句用法，在錯誤日志會記錄相關信息，那么需要調整應該程序避免不兼容的寫法，
直到完全沒有產生不兼容的語句，可以通過應該程序去排查所有的sql，也可以設置后觀察錯誤日志一段時間，
這一步非常重要。
step2：在每個mysql實例上，設置
ENFORCE_GTID_CONSISTENCY為ON,哪台先執行不影響結果
在第一步完成后，就可以將值設置為on。
[zejin] 3301>set @@global.enforce_gtid_consistency=on; Query OK, 0 rows affected (0.03 sec) [zejin] 3302>set @@global.enforce_gtid_consistency=on; Query OK, 0 rows affected (0.00 sec)
step3:在每個mysql實例上，設置GTID_MODE為off_permissiv;
哪台先執行不影響結果
[zejin] 3301>SET @@GLOBAL.GTID_MODE = OFF_PERMISSIVE; Query OK, 0 rows affected (0.00 sec) [zejin] 3302>SET @@GLOBAL.GTID_MODE = OFF_PERMISSIVE; Query OK, 0 rows affected (0.00 sec)
step4:在每個mysql實例上，設置GTID_MODE為on_permissiv;;
哪台先執行不影響結果
[zejin] 3302>SET @@GLOBAL.GTID_MODE = on_permissive; Query OK, 0 rows affected (0.00 sec) [zejin] 3301>SET @@GLOBAL.GTID_MODE = on_permissive; Query OK, 0 rows affected (0.01 sec)
step5:在每個mysql實例上檢查變量
ONGOING_ANONYMOUS_TRANSACTION_COUNT
[zejin] 3301>SHOW STATUS LIKE 'ONGOING_ANONYMOUS_TRANSACTION_COUNT'; +-------------------------------------+-------+ | Variable_name | Value | +-------------------------------------+-------+ | Ongoing_anonymous_transaction_count | 0 | +-------------------------------------+-------+ 1 row in set (0.02 sec) [zejin] 3302>SHOW STATUS LIKE 'ONGOING_ANONYMOUS_TRANSACTION_COUNT'; +-------------------------------------+-------+ | Variable_name | Value | +-------------------------------------+-------+ | Ongoing_anonymous_transaction_count | 0 | +-------------------------------------+-------+ 1 row in set (0.02 sec)
需要等到此變量為0
step6:確保所有的匿名事務（非GTID事務）已經被完全復制到所有的server上。
檢查方法：
在master上： [zejin] 3301>show master status; +-----------------+----------+--------------+------------------+-------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set | +-----------------+----------+--------------+------------------+-------------------+ | binlog57.000005 | 154 | | | | +-----------------+----------+--------------+------------------+-------------------+ 1 row in set (0.00 sec) 在slave上， [zejin] 3302>show slave status\G *************************** 1. row *************************** …… Relay_Master_Log_File: binlog57.000005 Exec_Master_Log_Pos: 154 ……
檢查這兩項Relay_Master_Log_File的值大於binlog57.000005，
或者等於Relay_Master_Log_File等於binlog57.000005並且Exec_Master_Log_Pos的值大於等於154即可
或者slave直接用函數：
[zejin] 3302>SELECT MASTER_POS_WAIT('binlog57.000005', 154); +-----------------------------------------+ | MASTER_POS_WAIT('binlog57.000005', 154) | +-----------------------------------------+ | 0 | +-----------------------------------------+ 1 row in set (0.00 sec)
返回結果大於等於0就說明匿名事務已經全部復制完成
step7:
確認整個拓撲結構中已經沒有匿名事務的存在，如之前產生的所有匿名事務已經全部被執行完畢，甚至二進制日志中也不要有匿名事務，可以通過flush logs，並讓mysql來自動清理舊的二進制日志文件。
step8:在每個mysql實例上，設置GTID_MODE為on，
[zejin] 3301>SET @@GLOBAL.GTID_MODE = ON; Query OK, 0 rows affected (0.04 sec) [zejin] 3302>SET @@GLOBAL.GTID_MODE = ON; Query OK, 0 rows affected (0.04 sec)
step9:
在每個mysql實例的配置文件my.cnf上，增加
gtid-mode=ON
驗證：
[zejin] 3301>insert into t_users values(3,'chen'); Query OK, 1 row affected (0.02 sec) [zejin] 3301>update t_users set name='li' where id=1; Query OK, 1 row affected (0.03 sec) Rows matched: 1 Changed: 1 Warnings: 0 [zejin] 3301>select * from t_users; +----+------+ | id | name | +----+------+ | 1 | li | | 2 | zhou | | 3 | chen | +----+------+ 3 rows in set (0.00 sec) [zejin] 3302>show slave status\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.1.240 Master_User: repl Master_Port: 3301 Connect_Retry: 60 Master_Log_File: binlog57.000006 Read_Master_Log_Pos: 462 Relay_Log_File: zejin240-relay-bin.000012 Relay_Log_Pos: 673 Relay_Master_Log_File: binlog57.000006 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 462 Relay_Log_Space: 969 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: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 3301 Master_UUID: a97983fc-5a29-11e6-9d28-000c29d4dc3f Master_Info_File: /home/mysql/I3302/master.info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: a97983fc-5a29-11e6-9d28-000c29d4dc3f:1-2 Executed_Gtid_Set: a97983fc-5a29-11e6-9d28-000c29d4dc3f:1-2 Auto_Position: 0 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version: 1 row in set (0.00 sec)
至此完成從傳統復制到GTID復制的在線轉換。