接收到警報通知，db3這台群組複製成員故障down機了，等修復好，啟動伺服器，然後再啟動mysql實例，進去查看狀態，變成了RECOVERING，如下所示；
mysql> SELECT * FROM performance_schema.replication_group_members; +---------------------------+--------------------------------------+----------------------+-------------+--------------+ | CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE | +---------------------------+--------------------------------------+----------------------+-------------+--------------+ | group_replication_applier | 3381d155-d7d1-11e6-94f7-b8ca3af6e36c | hch_test_dbm2_121_71 | 3317 | ONLINE | | group_replication_applier | 664b9ce9-d7de-11e6-9e8c-18a99b763071 | hch_test_web_1_24 | 3317 | ONLINE | | group_replication_applier | 84dba8ff-d7d2-11e6-aa9a-18a99b76310d | bpe_service | 3317 | RECOVERING | +---------------------------+--------------------------------------+----------------------+-------------+--------------+ 3 rows in set (0.00 sec) mysql>
這種狀態有點類似mongodb的sendary的RECOVERING狀態，對於剛出現的MySQL Group Replication新技術，遇到這種情況，這種情況怎麼辦？
在mongodb的這種模式下，一般是secondary從primary庫上不停複製數據，所以我們遵循這種思路，去看下db2的數據目錄，看到有很多relay-bin的recovery日誌在應用執行，如下所示relay日誌包記錄
-rw-r----- 1 mysql mysql 383 1月 17 16:08 bpe_service-relay-bin-group_replication_applier.000019 -rw-r----- 1 mysql mysql 502 1月 17 16:11 bpe_service-relay-bin-group_replication_applier.000020 -rw-r----- 1 mysql mysql 502 1月 17 16:23 bpe_service-relay-bin-group_replication_applier.000021 -rw-r----- 1 mysql mysql 421 1月 17 16:23 bpe_service-relay-bin-group_replication_applier.000022 -rw-r----- 1 mysql mysql 228 1月 17 16:23 bpe_service-relay-bin-group_replication_applier.index -rw-r----- 1 mysql mysql 312 1月 17 16:24 bpe_service-relay-bin-group_replication_recovery.000007 -rw-r----- 1 mysql mysql 1.1G 1月 17 16:24 bpe_service-relay-bin-group_replication_recovery.000008 -rw-r----- 1 mysql mysql 391 1月 17 16:24 bpe_service-relay-bin-group_replication_recovery.000009 -rw-r----- 1 mysql mysql 312 1月 17 16:24 bpe_service-relay-bin-group_replication_recovery.000010 -rw-r----- 1 mysql mysql 1.1G 1月 17 16:24 bpe_service-relay-bin-group_replication_recovery.000011 -rw-r----- 1 mysql mysql 391 1月 17 16:24 bpe_service-relay-bin-group_replication_recovery.000012 -rw-r----- 1 mysql mysql 312 1月 17 16:24 bpe_service-relay-bin-group_replication_recovery.000013 -rw-r----- 1 mysql mysql 1.1G 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000014 -rw-r----- 1 mysql mysql 391 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000015 -rw-r----- 1 mysql mysql 312 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000016 -rw-r----- 1 mysql mysql 1.1G 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000017 -rw-r----- 1 mysql mysql 391 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000018 -rw-r----- 1 mysql mysql 312 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000019 -rw-r----- 1 mysql mysql 1.1G 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000020 -rw-r----- 1 mysql mysql 391 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000021 -rw-r----- 1 mysql mysql 312 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000022 -rw-r----- 1 mysql mysql 1.1G 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000023 -rw-r----- 1 mysql mysql 391 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000024 -rw-r----- 1 mysql mysql 312 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.000025 -rw-r----- 1 mysql mysql 181M 1月 17 16:26 bpe_service-relay-bin-group_replication_recovery.000026 -rw-r----- 1 mysql mysql 1.2K 1月 17 16:25 bpe_service-relay-bin-group_replication_recovery.index drwxr-x--- 2 mysql mysql 4.0K 1月 17 14:11 business_db
然後在mysql窗口，可以看到幾個線程，其中有一個就是Reading event from the relay log線程，就是表示正在應用relay日誌：
mysql> show full processlist; +----+-------------+-----------+------+---------+------+--------------------------------------------------------+-----------------------+ | Id | User | Host | db | Command | Time | State | Info | +----+-------------+-----------+------+---------+------+--------------------------------------------------------+-----------------------+ | 28 | system user | | NULL | Connect | 701 | Suspending | NULL | | 31 | system user | | NULL | Connect | 701 | Slave has read all relay log; waiting for more updates | NULL | | 35 | system user | | NULL | Connect | 699 | Waiting for master to send event | NULL | | 36 | system user | | NULL | Connect | 4519 | Reading event from the relay log | NULL | | 38 | root | localhost | NULL | Query | 0 | starting | show full processlist | +----+-------------+-----------+------+---------+------+--------------------------------------------------------+-----------------------+ 5 rows in set (0.00 sec) mysql>
再過一會兒，資料同步完成之後，bpe_service就會從RECOVERING變成ONLINE狀態。這個更加證實了，數據已經同步完成。
mysql> SELECT * FROM performance_schema.replication_group_members; +---------------------------+--------------------------------------+----------------------+-------------+--------------+ | CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE | +---------------------------+--------------------------------------+----------------------+-------------+--------------+ | group_replication_applier | 3381d155-d7d1-11e6-94f7-b8ca3af6e36c | hch_test_dbm2_121_71 | 3317 | ONLINE | | group_replication_applier | 664b9ce9-d7de-11e6-9e8c-18a99b763071 | hch_test_web_1_24 | 3317 | ONLINE | | group_replication_applier | 84dba8ff-d7d2-11e6-aa9a-18a99b76310d | bpe_service | 3317 | ONLINE | +---------------------------+--------------------------------------+----------------------+-------------+--------------+ 3 rows in set (0.00 sec) mysql>
去查看後台error log日誌顯示，剛開始啟動，在做CHANGE MASTER TO FOR CHANNEL 'group_replication_applier' executed'的時候，沒有取到值，然後看後面同步完後，就會執行加入群組複製成員的命令
“CHANGE MASTER TO FOR CHANNEL 'group_replication_recovery' executed'. Previous state master_host='hch_test_web_1_24', master_port= 3317, master_log_file='', master_log_pos= 4, master_bind=''. New state master_host='<NULL>', master_port= 0, master_log_file='', master_log_pos= 4, master_bind=''”，
在執行結束後，最後告訴我們「'This server was declared online within the replication group'」已經加入了群組成員，而且變成了即時的ONLINE狀態：
2017-01-17T08:23:15.710146Z 4 [Note] Plugin group_replication reported: 'auto_increment_increment is reset to 1' 2017-01-17T08:23:15.710200Z 4 [Note] Plugin group_replication reported: 'auto_increment_offset is reset to 1' 2017-01-17T08:23:15.710401Z 20 [Note] Error reading relay log event for channel 'group_replication_applier': slave SQL thread was killed 2017-01-17T08:23:15.711212Z 17 [Note] Plugin group_replication reported: 'The group replication applier thread was killed' 2017-01-17T08:23:42.141239Z 4 [Note] Plugin group_replication reported: 'Group communication SSL configuration: group_replication_ssl_mode: "DISABLED"' 2017-01-17T08:23:42.141451Z 4 [Note] Plugin group_replication reported: '[GCS] Added automatically IP ranges 127.0.0.1/8,192.168.121.111/23 to the whitelist' 2017-01-17T08:23:42.141990Z 4 [Note] Plugin group_replication reported: '[GCS] Translated 'db2' to 192.168.121.111' 2017-01-17T08:23:42.142174Z 4 [Note] Plugin group_replication reported: '[GCS] SSL was not enabled' 2017-01-17T08:23:42.142220Z 4 [Note] Plugin group_replication reported: 'Initialized group communication with configuration: group_replication_group_name: "e4668cea-d7ca-11e6-86b5-18a99b76310d"; group_replication_local_address: "db2:24902"; group_replication_group_seeds: "db1:24901,db2:24902,db3:24903"; group_replication_bootstrap_group: false; group_replication_poll_spin_loops: 0; group_replication_compression_threshold: 1000000; group_replication_ip_whitelist: "AUTOMATIC"' 2017-01-17T08:23:42.142936Z 28 [Note] 'CHANGE MASTER TO FOR CHANNEL 'group_replication_applier' executed'. Previous state master_host='<NULL>', master_port= 0, master_log_file='', master_log_pos= 4, master_bind=''. New state master_host='<NULL>', master_port= 0, master_log_file='', master_log_pos= 4, master_bind=''. -- #（1）尝试启动默认的组复制，结果信息不对称，启动失败，然后开始初始化Group Replication 2017-01-17T08:23:42.166956Z 31 [Note] Slave SQL thread for channel 'group_replication_applier' initialized, starting replication in log 'FIRST' at position 0, relay log './bpe_service-relay-bin-group_replication_applier.000019' position: 4 2017-01-17T08:23:42.166960Z 4 [Note] Plugin group_replication reported: 'Group Replication applier module successfully initialized!' 2017-01-17T08:23:42.167064Z 4 [Note] Plugin group_replication reported: 'auto_increment_increment is set to 7' 2017-01-17T08:23:42.167079Z 4 [Note] Plugin group_replication reported: 'auto_increment_offset is set to 12002' 2017-01-17T08:23:42.167219Z 0 [Note] Plugin group_replication reported: 'state 4257 action xa_init' 2017-01-17T08:23:42.167292Z 0 [Note] Plugin group_replication reported: 'Successfully bound to 0.0.0.0:24902 (socket=49).' 2017-01-17T08:23:42.167341Z 0 [Note] Plugin group_replication reported: 'Successfully set listen backlog to 32 (socket=49)!' 2017-01-17T08:23:42.167357Z 0 [Note] Plugin group_replication reported: 'Successfully unblocked socket (socket=49)!' 2017-01-17T08:23:42.167400Z 0 [Note] Plugin group_replication reported: 'connecting to db2 24902' 2017-01-17T08:23:42.167585Z 0 [Note] Plugin group_replication reported: 'Ready to accept incoming connections on 0.0.0.0:24902 (socket=49)!' 2017-01-17T08:23:42.174427Z 0 [Note] Plugin group_replication reported: 'client connected to db2 24902 fd 50' 2017-01-17T08:23:42.174807Z 0 [Note] Plugin group_replication reported: 'connecting to db2 24902' 2017-01-17T08:23:42.175008Z 0 [Note] Plugin group_replication reported: 'client connected to db2 24902 fd 63' 2017-01-17T08:23:42.175234Z 0 [Note] Plugin group_replication reported: 'connecting to db2 24902' 2017-01-17T08:23:42.175411Z 0 [Note] Plugin group_replication reported: 'client connected to db2 24902 fd 65' 2017-01-17T08:23:42.175614Z 0 [Note] Plugin group_replication reported: 'connecting to db2 24902' 2017-01-17T08:23:42.175799Z 0 [Note] Plugin group_replication reported: 'client connected to db2 24902 fd 67' 2017-01-17T08:23:42.176006Z 0 [Note] Plugin group_replication reported: 'connecting to db2 24902' 2017-01-17T08:23:42.176176Z 0 [Note] Plugin group_replication reported: 'client connected to db2 24902 fd 69' 2017-01-17T08:23:42.176377Z 0 [Note] Plugin group_replication reported: 'connecting to db2 24902' 2017-01-17T08:23:42.176563Z 0 [Note] Plugin group_replication reported: 'client connected to db2 24902 fd 71' 2017-01-17T08:23:42.176876Z 0 [Note] Plugin group_replication reported: 'connecting to db1 24901' 2017-01-17T08:23:42.177312Z 0 [Note] Plugin group_replication reported: 'client connected to db1 24901 fd 73' 2017-01-17T08:23:43.463474Z 0 [Note] Plugin group_replication reported: 'state 4257 action xa_snapshot' 2017-01-17T08:23:43.463969Z 0 [Note] Plugin group_replication reported: 'new state x_recover' 2017-01-17T08:23:43.464000Z 0 [Note] Plugin group_replication reported: 'state 4277 action xa_complete' 2017-01-17T08:23:43.464275Z 0 [Note] Plugin group_replication reported: 'new state x_run' 2017-01-17T08:23:44.619112Z 0 [Note] Plugin group_replication reported: 'Starting group replication recovery with view_id 14844510167669342:17' --#（2） 开始进行组内数据recovery 2017-01-17T08:23:44.619451Z 34 [Note] Plugin group_replication reported: 'Establishing group recovery connection with a possible donor. Attempt 1/10' 2017-01-17T08:23:44.624181Z 34 [Note] 'CHANGE MASTER TO FOR CHANNEL 'group_replication_recovery' executed'. Previous state master_host='<NULL>', master_port= 0, master_log_file='', master_log_pos= 4, master_bind=''. New state master_host='hch_test_web_1_24', master_port= 3317, master_log_file='', master_log_pos= 4, master_bind=''. 2017-01-17T08:23:44.628853Z 34 [Note] Plugin group_replication reported: 'Establishing connection to a group replication recovery donor 664b9ce9-d7de-11e6-9e8c-18a99b763071 at hch_test_web_1_24 port: 3317.' 2017-01-17T08:23:44.629156Z 35 [Warning] Storing MySQL user name or password information in the master info repository is not secure and is therefore not recommended. Please consider using the USER and PASSWORD connection options for START SLAVE; see the 'START SLAVE Syntax' in the MySQL Manual for more information. 2017-01-17T08:23:44.635870Z 36 [Note] Slave SQL thread for channel 'group_replication_recovery' initialized, starting replication in log 'FIRST' at position 0, relay log './bpe_service-relay-bin-group_replication_recovery.000001' position: 4 2017-01-17T08:23:44.681897Z 35 [Note] Slave I/O thread for channel 'group_replication_recovery': connected to master 'repl@hch_test_web_1_24:3317',replication started in log 'FIRST' at position 4 2017-01-17T08:43:34.219952Z 34 [Note] Plugin group_replication reported: 'Terminating existing group replication donor connection and purging the corresponding logs.' 2017-01-17T08:43:34.220609Z 36 [Note] Slave SQL thread for channel 'group_replication_recovery' exiting, replication stopped in log 'binlog.000042' at position 185511578 2017-01-17T08:43:34.226869Z 35 [Note] Slave I/O thread killed while reading event for channel 'group_replication_recovery' 2017-01-17T08:43:34.226886Z 35 [Note] Slave I/O thread exiting for channel 'group_replication_recovery', read up to log 'binlog.000042', position 185511578 2017-01-17T08:43:34.269973Z 34 [Note] 'CHANGE MASTER TO FOR CHANNEL 'group_replication_recovery' executed'. Previous state master_host='hch_test_web_1_24', master_port= 3317, master_log_file='', master_log_pos= 4, master_bind=''. New state master_host='<NULL>', master_port= 0, master_log_file='', master_log_pos= 4, master_bind=''. -- # （3）已经数据恢复完成，加入组，成为组成员 2017-01-17T08:43:34.290920Z 0 [Note] Plugin group_replication reported: 'This server was declared online within the replication group'
小結：mysql group replication的使用來說，有些理念比如mongodb的分片以及primary-secondary的思路理念可以參考下，這樣理解起來就會比較容易一些。
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