MySQL备份工具，支持各种参数选项，使用不同的选项极有可能影响备份处理过程。本文使用我们常规认为合理的备份参数，测试/验证是否存在容易忽视的坑

# 常规备份参数

# mysqldump

shell> mysqldump --single-transaction --master-data=2 -B replcrash >dbname_dump_serverid_`date +%Y%m%d`.sql

# mysqlpump

shell> mysqlpump --single-transaction -B replcrash >dbname_pump_serverid_`date +%Y%m%d`.sql

# mydumper

shell> mydumper -B replcrash -o /data/backup/mydumper

# XtraBackup

# backup

shell> innobackupex [--defaults-file=MY.CNF] BACKUP-ROOT-DIR

# apply-log

shell> innobackupex --apply-log [--defaults-file=MY.CNF] BACKUP-DIR

# copy-back

shell> innobackupex --copy-back [--defaults-file=MY.CNF] BACKUP-DIR

常规备份参数

官方社区版MySQL 5.7.19 基于Row+Position搭建的一主一从异步复制结构：Master->{Slave}

ROLE

HOSTNAME

BASEDIR

DATADIR

IP

PORT

Master

ZST1

/usr/local/mysql

/data/mysql/mysql3306/data

192.168.85.132

3306

Slave

ZST1

/usr/local/mysql

/data/mysql/mysql3308/data

192.168.85.132

3308

每次使用备份文件还原数据库后，重新搭建这个复制结构

备份工具版本：mysqldump、mysqlpump是MySQL 5.7.19中自带的；mydumper version 0.9.3、innobackupex version 2.4.8

一、mysqldump

1.1、DML操作对备份的影响

创建两张测试表

# 创建两张测试表(192.168.85.132,3306)usereplcrash;create tablepy_user_innodb(

uidint not nullauto_increment,

namevarchar(32),

add_timedatetime default current_timestamp,

server_idvarchar(10),primary key(uid),key(name)

)engine=innodb;create tablepy_user_myisam(

uidint not nullauto_increment,

namevarchar(32),

add_timedatetime default current_timestamp,

server_idvarchar(10),primary key(uid),key(name)

)engine=myisam;

View Code

运行下面的脚本持续往测试表中写入数据

#!/user/bin/python

importstringimportrandomimportMySQLdbimporttime

conn= MySQLdb.connect(host='192.168.85.132',

port=3306,

user='mydba',

passwd='mysql5719',

db='replcrash')"""create table py_user(

uid int not null auto_increment,

name varchar(32),

add_time datetime default current_timestamp,

server_id varchar(10),

primary key(uid),

key(name)

);"""

whileTrue:

r_name= ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(random.randint(20,30)))printr_name

cursor=conn.cursor()

cursor.execute("insert into py_user_myisam(name,add_time,server_id) values('%s',now(),@@server_id);" %str(r_name))

cursor.execute("insert into py_user_innodb(name,add_time,server_id) values('%s',now(),@@server_id);" %str(r_name))

conn.commit()

time.sleep(0.001)

Python DML

开启general_log，用来查看mysqldump执行过程

# 开启general_log

mydba@192.168.85.132,3306 [replcrash]> set global general_log_file='/data/mysql/mysql3306/data/mysql-general.log';

mydba@192.168.85.132,3306 [replcrash]> set global general_log=1;

# 清空general_log

[root@ZST1 logs]#cat /dev/null > /data/mysql/mysql3306/data/mysql-general.log

# 备份replcrash数据库

[root@ZST1 backup]# mysqldump-h127.0.0.1 -P3306 -uroot -p --single-transaction --master-data=2 replcrash >/data/backup/replcrash_dump_1323306_`date +%Y%m%d`.sql

View Code

使用备份文件搭建复制

# 还原实例清空GTID信息

mydba@192.168.85.132,3308 [replcrash]>reset master;

# 还原数据

[root@ZST1 backup]# mysql-h127.0.0.1 -P3308 -uroot -p replcrash

# 搭建复制

mydba@192.168.85.132,3308 [replcrash]>change master to

master_host='192.168.85.132',

master_port=3306,

master_user='repl',

master_password='repl',

master_auto_position=1;

# 启动复制，查看复制状态

mydba@192.168.85.132,3308 [replcrash]>start slave;

mydba@192.168.85.132,3308 [replcrash]>show slave status\G*************************** 1. row ***************************Master_Log_File: mysql-bin.000183Read_Master_Log_Pos:1541377Relay_Log_File: relay-bin.000002Relay_Log_Pos:741Relay_Master_Log_File: mysql-bin.000183Slave_IO_Running: Yes

Slave_SQL_Running: No

Exec_Master_Log_Pos:1042768Last_SQL_Errno:1062Last_SQL_Error: Could not execute Write_rows event on table replcrash.py_user_myisam; Duplicate entry'332' for key 'PRIMARY', Error_code: 1062; handler error HA_ERR_FOUND_DUPP_KEY; the event''s master log mysql-bin.000183, end_log_pos 1043062Retrieved_Gtid_Set: 8ab82362-9c37-11e7-a858-000c29c1025c:251874-253268Executed_Gtid_Set: 8ab82362-9c37-11e7-a858-000c29c1025c:1-251874Auto_Position:1

View Code

从上面的结果中可以看到，主键冲突了，在从库查询一下这个表中大于等于冲突key的数据

# 查询从库出错表大于等于冲突key的数据

mydba@192.168.85.132,3308 [replcrash]> select * from replcrash.py_user_myisam where uid>=332;+-----+--------------------------------+---------------------+-----------+

| uid | name | add_time | server_id |

+-----+--------------------------------+---------------------+-----------+

| 332 | X1LME9HO5V7WXNOKBVZE | 2018-01-02 09:05:07 | 1323306 |

| 333 | 2PBFQ7KS4BPIJ27G88EYXWEDSX5 | 2018-01-02 09:05:07 | 1323306 |

| 334 | E85Y2SS9UD0FZG4YGCNTRSWA8L | 2018-01-02 09:05:07 | 1323306 |

| 335 | Y2TQOEVJ58NN7EREL4WRZ | 2018-01-02 09:05:07 | 1323306 |

| 336 | O0MEATAXYIAE2V2IZG96YVQ56WEUHF | 2018-01-02 09:05:07 | 1323306 |

| 337 | A6QKRWEXHRGUA3V2CH61VXUNBVA3H2 | 2018-01-02 09:05:07 | 1323306 |

| 338 | NYCSI1HS61BN6QAVVYTZSC | 2018-01-02 09:05:07 | 1323306 |

| 339 | 7CFC1JQPIQGNC97MDTT8ZIMIZL7D | 2018-01-02 09:05:07 | 1323306 |

| 340 | GA78AR4Z12WQTEAM41JB | 2018-01-02 09:05:07 | 1323306 |

+-----+--------------------------------+---------------------+-----------+

9 rows in set (0.08 sec)

View Code

我们查看mysqldump备份文件获取的binlog pos

[root@ZST1 backup]# morereplcrash_dump_1323306_20180102.sql--GTID state at the beginning of the backup

SET @@GLOBAL.GTID_PURGED='8ab82362-9c37-11e7-a858-000c29c1025c:1-251873';-- Position to start replication or point-in-timerecovery from-- CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000183', MASTER_LOG_POS=1042441;

[root@ZST1 backup]#

View Code

这里的pos信息是mysqldump通过SHOW MASTER STATUS获取。查看mysqldump得到的general-log;

[root@ZST1 data]# vim /data/mysql/mysql3306/data/mysql-general.log

...2018-01-02T01:05:07.693104Z 10 Query FLUSH /*!40101 LOCAL*/TABLES2018-01-02T01:05:07.694738Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('7ATZSNFNIBW5DZNMNZYBMV',now(),@@server_id)2018-01-02T01:05:07.701616Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('7ATZSNFNIBW5DZNMNZYBMV',now(),@@server_id)2018-01-02T01:05:07.702139Z 10Query FLUSH TABLES WITH READ LOCK2018-01-02T01:05:07.702344Z 9Query commit2018-01-02T01:05:07.702411Z 10Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ2018-01-02T01:05:07.702597Z 10 Query START TRANSACTION /*!40100 WITH CONSISTENT SNAPSHOT*/

2018-01-02T01:05:07.702721Z 10 Query SHOW VARIABLES LIKE 'gtid\_mode'

2018-01-02T01:05:07.713019Z 10Query SELECT @@GLOBAL.GTID_EXECUTED2018-01-02T01:05:07.713179Z 10Query SHOW MASTER STATUS2018-01-02T01:05:07.725821Z 10Query UNLOCK TABLES2018-01-02T01:05:07.732125Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('X1LME9HO5V7WXNOKBVZE',now(),@@server_id)2018-01-02T01:05:07.733237Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('X1LME9HO5V7WXNOKBVZE',now(),@@server_id)2018-01-02T01:05:07.734240Z 9Query commit2018-01-02T01:05:07.740508Z 10 Query SELECT LOGFILE_GROUP_NAME, FILE_NAME, TOTAL_EXTENTS, INITIAL_SIZE, ENGINE, EXTRA FROM INFORMATION_SCHEMA.FILES WHERE FILE_TYPE = 'UNDO LOG' AND FILE_NAME IS NOT NULL AND LOGFILE_GROUP_NAME IS NOT NULL AND LOGFILE_GROUP_NAME IN (SELECT DISTINCT LOGFILE_GROUP_NAME FROM INFORMATION_SCHEMA.FILES WHERE FILE_TYPE = 'DATAFILE' AND TABLESPACE_NAME IN (SELECT DISTINCT TABLESPACE_NAME FROM INFORMATION_SCHEMA.PARTITIONS WHERE TABLE_SCHEMA IN ('replcrash'))) GROUP BY LOGFILE_GROUP_NAME, FILE_NAME, ENGINE, TOTAL_EXTENTS, INITIAL_SIZE ORDER BY LOGFILE_GROUP_NAME2018-01-02T01:05:07.741895Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('2PBFQ7KS4BPIJ27G88EYXWEDSX5',now(),@@server_id)2018-01-02T01:05:07.742720Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('2PBFQ7KS4BPIJ27G88EYXWEDSX5',now(),@@server_id)2018-01-02T01:05:07.743257Z 9Query commit2018-01-02T01:05:07.749840Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('E85Y2SS9UD0FZG4YGCNTRSWA8L',now(),@@server_id)2018-01-02T01:05:07.750588Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('E85Y2SS9UD0FZG4YGCNTRSWA8L',now(),@@server_id)2018-01-02T01:05:07.750989Z 9Query commit2018-01-02T01:05:07.754180Z 10 Query SELECT DISTINCT TABLESPACE_NAME, FILE_NAME, LOGFILE_GROUP_NAME, EXTENT_SIZE, INITIAL_SIZE, ENGINE FROM INFORMATION_SCHEMA.FILES WHERE FILE_TYPE = 'DATAFILE' AND TABLESPACE_NAME IN (SELECT DISTINCT TABLESPACE_NAME FROM INFORMATION_SCHEMA.PARTITIONS WHERE TABLE_SCHEMA IN ('replcrash')) ORDER BY TABLESPACE_NAME, LOGFILE_GROUP_NAME2018-01-02T01:05:07.756229Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('Y2TQOEVJ58NN7EREL4WRZ',now(),@@server_id)2018-01-02T01:05:07.757030Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('Y2TQOEVJ58NN7EREL4WRZ',now(),@@server_id)2018-01-02T01:05:07.757598Z 9Query commit2018-01-02T01:05:07.763629Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('O0MEATAXYIAE2V2IZG96YVQ56WEUHF',now(),@@server_id)2018-01-02T01:05:07.764626Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('O0MEATAXYIAE2V2IZG96YVQ56WEUHF',now(),@@server_id)2018-01-02T01:05:07.765654Z 9Query commit2018-01-02T01:05:07.766769Z 10 Query SHOW VARIABLES LIKE 'ndbinfo\_version'

2018-01-02T01:05:07.773997Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('A6QKRWEXHRGUA3V2CH61VXUNBVA3H2',now(),@@server_id)2018-01-02T01:05:07.774757Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('A6QKRWEXHRGUA3V2CH61VXUNBVA3H2',now(),@@server_id)2018-01-02T01:05:07.775198Z 9Query commit2018-01-02T01:05:07.779582Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('NYCSI1HS61BN6QAVVYTZSC',now(),@@server_id)2018-01-02T01:05:07.780174Z 10Init DB replcrash2018-01-02T01:05:07.780249Z 10Query SAVEPOINT sp2018-01-02T01:05:07.780913Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('NYCSI1HS61BN6QAVVYTZSC',now(),@@server_id)2018-01-02T01:05:07.781387Z 9Query commit2018-01-02T01:05:07.781776Z 10Query show tables2018-01-02T01:05:07.782078Z 10 Query show table status like 'py\_user'

2018-01-02T01:05:07.782400Z 10 Query SET SQL_QUOTE_SHOW_CREATE=1

2018-01-02T01:05:07.782513Z 10 Query SET SESSION character_set_results = 'binary'

2018-01-02T01:05:07.787051Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('7CFC1JQPIQGNC97MDTT8ZIMIZL7D',now(),@@server_id)2018-01-02T01:05:07.787810Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('7CFC1JQPIQGNC97MDTT8ZIMIZL7D',now(),@@server_id)2018-01-02T01:05:07.788502Z 9Query commit2018-01-02T01:05:07.788774Z 10Query show create table `py_user`2018-01-02T01:05:07.789570Z 10 Query SET SESSION character_set_results = 'utf8'

2018-01-02T01:05:07.789725Z 10Query show fields from `py_user`2018-01-02T01:05:07.790423Z 10Query show fields from `py_user`2018-01-02T01:05:07.791163Z 10 Query SELECT /*!40001 SQL_NO_CACHE*/ *FROM `py_user`2018-01-02T01:05:07.791447Z 10 Query SET SESSION character_set_results = 'binary'

2018-01-02T01:05:07.791648Z 10Query use `replcrash`2018-01-02T01:05:07.791778Z 10 Query select@@collation_database2018-01-02T01:05:07.791929Z 10 Query SHOW TRIGGERS LIKE 'py\_user'

2018-01-02T01:05:07.792383Z 10 Query SET SESSION character_set_results = 'utf8'

2018-01-02T01:05:07.792492Z 10Query ROLLBACK TO SAVEPOINT sp2018-01-02T01:05:07.792651Z 10 Query show table status like 'py\_user\_innodb'

2018-01-02T01:05:07.792874Z 10 Query SET SQL_QUOTE_SHOW_CREATE=1

2018-01-02T01:05:07.792948Z 10 Query SET SESSION character_set_results = 'binary'

2018-01-02T01:05:07.793024Z 10Query show create table `py_user_innodb`2018-01-02T01:05:07.793131Z 10 Query SET SESSION character_set_results = 'utf8'

2018-01-02T01:05:07.793220Z 10Query show fields from `py_user_innodb`2018-01-02T01:05:07.793607Z 10Query show fields from `py_user_innodb`2018-01-02T01:05:07.793985Z 10 Query SELECT /*!40001 SQL_NO_CACHE*/ *FROM `py_user_innodb`2018-01-02T01:05:07.794435Z 9 Query insert into py_user_myisam(name,add_time,server_id) values('GA78AR4Z12WQTEAM41JB',now(),@@server_id)2018-01-02T01:05:07.795204Z 9 Query insert into py_user_innodb(name,add_time,server_id) values('GA78AR4Z12WQTEAM41JB',now(),@@server_id)2018-01-02T01:05:07.795688Z 9Query commit2018-01-02T01:05:07.798108Z 10 Query SET SESSION character_set_results = 'binary'

2018-01-02T01:05:07.798205Z 10Query use `replcrash`2018-01-02T01:05:07.798303Z 10 Query select@@collation_database2018-01-02T01:05:07.798408Z 10 Query SHOW TRIGGERS LIKE 'py\_user\_innodb'

2018-01-02T01:05:07.798884Z 10 Query SET SESSION character_set_results = 'utf8'

2018-01-02T01:05:07.798965Z 10Query ROLLBACK TO SAVEPOINT sp2018-01-02T01:05:07.799049Z 10 Query show table status like 'py\_user\_myisam'

2018-01-02T01:05:07.799271Z 10 Query SET SQL_QUOTE_SHOW_CREATE=1

2018-01-02T01:05:07.799344Z 10 Query SET SESSION character_set_results = 'binary'

2018-01-02T01:05:07.799420Z 10Query show create table `py_user_myisam`2018-01-02T01:05:07.799554Z 10 Query SET SESSION character_set_results = 'utf8'

2018-01-02T01:05:07.799661Z 10Query show fields from `py_user_myisam`2018-01-02T01:05:07.800098Z 10Query show fields from `py_user_myisam`2018-01-02T01:05:07.800418Z 10 Query SELECT /*!40001 SQL_NO_CACHE*/ * FROM `py_user_myisam`

View Code

mysqldump备份过程(--single-transaction --master-data)：

会话先执行FTWRL(实例只读)，然后设置RR隔离级别->START TRANSACTION WITH CONSISTENT SNAPSHOT;->SHOW MASTER STATUS;->UNLOCK TABLES;->SELECT /*!40001 SQL_NO_CACHE */ * FROM `tbname`;

在UNLOCK TABLES解锁后其他事务就可以进行写入操作。general-log中我们可看到 UNLOCK TABLES 到 SELECT /*!40001 SQL_NO_CACHE */ * FROM `py_user_myisam` 之间往py_user_myisam、py_user_innodb各写入9条数据

SELECT /*!40001 SQL_NO_CACHE */ * FROM `py_user_innodb`;读取的是START TRANSACTION WITH CONSISTENT SNAPSHOT建立时的数据

SELECT /*!40001 SQL_NO_CACHE */ * FROM `py_user_myisam`;读取的是最新的数据

再来查看上述过程期间binary log记录

[root@ZST1 logs]# mysqlbinlog -vv --base64-output=decode-rows mysql-bin.000183 |more...

COMMIT/*!*/;

# at1042059#180102 9:05:07 server id 1323306 end_log_pos 1042124 CRC32 0x221cda50 GTID last_committed=2917 sequence_number=2918 rbr_only=yes/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;

SET @@SESSION.GTID_NEXT= '8ab82362-9c37-11e7-a858-000c29c1025c:251873'/*!*/;

# at1042124#180102 9:05:07 server id 1323306 end_log_pos 1042209 CRC32 0x5df266e4 Query thread_id=9 exec_time=0 error_code=0SET TIMESTAMP=1514855107/*!*/;

BEGIN/*!*/;

# at1042209#180102 9:05:07 server id 1323306 end_log_pos 1042279 CRC32 0xc1d41c5f Table_map: `replcrash`.`py_user_myisam` mapped to number 254# at1042279#180102 9:05:07 server id 1323306 end_log_pos 1042355 CRC32 0x27badc02 Write_rows: table id 254flags: STMT_END_F

### INSERT INTO `replcrash`.`py_user_myisam`

### SET

### @1=331 /*INT meta=0 nullable=0 is_null=0*/### @2='7ATZSNFNIBW5DZNMNZYBMV' /*VARSTRING(96) meta=96 nullable=1 is_null=0*/### @3='2018-01-02 09:05:07' /*DATETIME(0) meta=0 nullable=1 is_null=0*/### @4='1323306' /*VARSTRING(30) meta=30 nullable=1 is_null=0*/# at1042355#180102 9:05:07 server id 1323306 end_log_pos 1042441 CRC32 0x67285443 Query thread_id=9 exec_time=0 error_code=0SET TIMESTAMP=1514855107/*!*/;

COMMIT/*!*/;

# at1042441

==================== mysqldump备份文件获取的binlog pos ====================

==================== 备份文件还原后，从库GTID_PURGED位置 ====================#180102 9:05:07 server id 1323306 end_log_pos 1042506 CRC32 0xf77ede80 GTID last_committed=2918 sequence_number=2919 rbr_only=yes/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;

SET @@SESSION.GTID_NEXT= '8ab82362-9c37-11e7-a858-000c29c1025c:251874'/*!*/;

# at1042506#180102 9:05:07 server id 1323306 end_log_pos 1042591 CRC32 0x506a2875 Query thread_id=9 exec_time=0 error_code=0SET TIMESTAMP=1514855107/*!*/;

BEGIN/*!*/;

# at1042591#180102 9:05:07 server id 1323306 end_log_pos 1042661 CRC32 0x90b154e8 Table_map: `replcrash`.`py_user_innodb` mapped to number 255# at1042661#180102 9:05:07 server id 1323306 end_log_pos 1042737 CRC32 0x1d693238 Write_rows: table id 255flags: STMT_END_F

### INSERT INTO `replcrash`.`py_user_innodb`

### SET

### @1=331 /*INT meta=0 nullable=0 is_null=0*/### @2='7ATZSNFNIBW5DZNMNZYBMV' /*VARSTRING(96) meta=96 nullable=1 is_null=0*/### @3='2018-01-02 09:05:07' /*DATETIME(0) meta=0 nullable=1 is_null=0*/### @4='1323306' /*VARSTRING(30) meta=30 nullable=1 is_null=0*/# at1042737#180102 9:05:07 server id 1323306 end_log_pos 1042768 CRC32 0x87864022 Xid = 4420COMMIT/*!*/;

# at1042768

==================== 启动复制后，py_user_innodb写入uid=331记录，成功 ====================#180102 9:05:07 server id 1323306 end_log_pos 1042833 CRC32 0xe492578a GTID last_committed=2919 sequence_number=2920 rbr_only=yes/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;

SET @@SESSION.GTID_NEXT= '8ab82362-9c37-11e7-a858-000c29c1025c:251875'/*!*/;

# at1042833#180102 9:05:07 server id 1323306 end_log_pos 1042918 CRC32 0xf08c4165 Query thread_id=9 exec_time=0 error_code=0SET TIMESTAMP=1514855107/*!*/;

BEGIN/*!*/;

# at1042918#180102 9:05:07 server id 1323306 end_log_pos 1042988 CRC32 0xf16731d6 Table_map: `replcrash`.`py_user_myisam` mapped to number 257# at1042988#180102 9:05:07 server id 1323306 end_log_pos 1043062 CRC32 0x128aec5e Write_rows: table id 257flags: STMT_END_F

### INSERT INTO `replcrash`.`py_user_myisam`

### SET

### @1=332 /*INT meta=0 nullable=0 is_null=0*/### @2='X1LME9HO5V7WXNOKBVZE' /*VARSTRING(96) meta=96 nullable=1 is_null=0*/### @3='2018-01-02 09:05:07' /*DATETIME(0) meta=0 nullable=1 is_null=0*/### @4='1323306' /*VARSTRING(30) meta=30 nullable=1 is_null=0*/# at1043062#180102 9:05:07 server id 1323306 end_log_pos 1043148 CRC32 0x5cc8cc30 Query thread_id=9 exec_time=0 error_code=0SET TIMESTAMP=1514855107/*!*/;

COMMIT/*!*/;

# at1043148

==================== 启动复制后，py_user_myisam写入uid=332记录，失败 ====================

==================== 从库py_user_myisam表已存在332记录，sql_thread停止 ====================#180102 9:05:07 server id 1323306 end_log_pos 1043213 CRC32 0xceb1ce4d GTID last_committed=2920 sequence_number=2921 rbr_only=yes/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;

SET @@SESSION.GTID_NEXT= '8ab82362-9c37-11e7-a858-000c29c1025c:251876'/*!*/;

# at1043213#180102 9:05:07 server id 1323306 end_log_pos 1043298 CRC32 0x38591b71 Query thread_id=9 exec_time=0 error_code=0SET TIMESTAMP=1514855107/*!*/;

BEGIN/*!*/;

# at1043298#180102 9:05:07 server id 1323306 end_log_pos 1043368 CRC32 0xf80c2ae9 Table_map: `replcrash`.`py_user_innodb` mapped to number 258# at1043368#180102 9:05:07 server id 1323306 end_log_pos 1043442 CRC32 0x0bf4ae26 Write_rows: table id 258flags: STMT_END_F

### INSERT INTO `replcrash`.`py_user_innodb`

### SET

### @1=332 /*INT meta=0 nullable=0 is_null=0*/### @2='X1LME9HO5V7WXNOKBVZE' /*VARSTRING(96) meta=96 nullable=1 is_null=0*/### @3='2018-01-02 09:05:07' /*DATETIME(0) meta=0 nullable=1 is_null=0*/### @4='1323306' /*VARSTRING(30) meta=30 nullable=1 is_null=0*/# at1043442#180102 9:05:07 server id 1323306 end_log_pos 1043473 CRC32 0x1b75f9e0 Xid = 4431COMMIT/*!*/;

# at1043473...

View Code

二进志日志显示，按照py_user_myisam->py_user_innodb->py_user_myisam这样的顺序往表中写入数据。

使用备份文件搭建的从库，py_user_myisam表已包含UNLOCK TABLES之后的9条数据，但在备份文件中的@@GLOBAL.GTID_PURGED却是UNLOCK TABLES时刻的位置。因此在启动复制后，第一条操作py_user_innodb表成功，第二条操作py_user_myisam表失败，从库报主键冲突错误

那么应该如何修复这个错误呢?

# 删除从库py_user_myisam表大于等于冲突key的记录

mydba@192.168.85.132,3308 [replcrash]> delete from py_user_myisam where uid>=332;

# 重新启动sql_thread

mydba@192.168.85.132,3308 [replcrash]> start slave sql_thread;

View Code

总得来说就是只有innodb才会提供一致性备份！！！

1.2、DDL操作对备份的影响

建议先阅读后续章节，理解各备份过程后再返回阅读DDL操作对备份的影响

运行下面的脚本持续DDL操作

#!/user/bin/python

importstringimportrandomimportMySQLdbimporttime

conn= MySQLdb.connect(host='192.168.85.132',

port=3306,

user='mydba',

passwd='mysql5719',

db='replcrash')"""create table py_user(

uid int not null auto_increment,

name varchar(32),

add_time datetime default current_timestamp,

server_id varchar(10),

primary key(uid),

key(name)

);"""counter= 1

while counter<=100:

addcol= 'col' +str(counter)printaddcol

cursor=conn.cursor()#DDL

cursor.execute("alter table py_user_innodb add %s int;" %addcol)

cursor.execute("alter table py_user_innodb drop column %s;" %addcol)

conn.commit()

counter+= 1time.sleep(0.0001)

Python DDL

逻辑备份数据库

# 清空general_log

[root@ZST1 logs]#cat /dev/null > /data/mysql/mysql3306/data/mysql-general.log

# mysqldump

[root@ZST1 backup]# mysqldump-h127.0.0.1 -P3306 -uroot -p --single-transaction --master-data=2 replcrash >/data/backup/replcrash_dump_1323306_`date +%Y%m%d`.sql

Enter password:

Warning: A partial dump from a server that has GTIDs will by default include the GTIDs of all transactions, even those that changed suppressed parts of the database. If you don not want to restore GTIDs, pass--set-gtid-purged=OFF. To make a complete dump, pass --all-databases --triggers --routines --events.

mysqldump: Error1412: Table definition has changed, please retry transaction when dumping table `py_user_innodb` at row: 0# mysqlpump

[root@ZST1 backup]# mysqlpump-h127.0.0.1 -P3306 -uroot -p --single-transaction --add-drop-table --exclude-databases=mysql,sakila,backupdb -A >/data/backup/replcrash_pump_1323306_`date +%Y%m%d`.sql

Enter password:

mysqlpump: [ERROR] (1412) Table definition has changed, please retry transaction

Dump process encountered error and will not continue.

Dump progress:0/3 tables, 250/2431rows

[root@ZST1 backup]#

# mydumper

[root@ZST1 mydumper]# mydumper-h 127.0.0.1 -P 3306 -u root -p mysql5719 --trx-consistency-only -v 3 -t 2 -o /data/backup/mydumper

..** Message: Thread 2 dumping data for`replcrash`.`py_user_innodb`** Message: Thread 1 dumping data for`replcrash`.`py_user_myisam`** (mydumper:5179): CRITICAL **: Could not read data from replcrash.py_user_innodb: Table definition has changed, please retry transaction**Message: Empty table replcrash.py_user_innodb

...

View Code

mydumper需要使用-v 3 显示详细信息，本身是不会报错的！！！如果想更容易再现错误，最好是备份的数据表较大、较多，适当降低并行线程数(-t)，开启--trx-consistency-only，让其尽早解锁

生成的备份文件中，py_user_innodb表只有结构，没有数据

根据备份逻辑，在UNLOCK TABLES解除FTWRL到SELECT /*!40001 SQL_NO_CACHE */ * FROM `tbname`之间如果有DDL操作，就会造成上述错误

使用了with consistent snapshot子句开启一致性快照事务之后，如果一旦表结构定义发生改变，事务将无法对该表执行查询

使用WITH CONSISTENT SNAPSHOT子句，会话1显式开启一个事务之后先不执行查询，会话B使用DDL语句添加一个字段

会话1

会话2

修改隔离级别为RR

mydba@192.168.85.132,3306 [replcrash]> set tx_isolation='repeatable-read';

Query OK, 0 rows affected (0.00 sec)

修改隔离级别为RR

mydba@192.168.85.132,3306 [replcrash]> set tx_isolation='repeatable-read';

Query OK, 0 rows affected (0.00 sec)

显式开启一个事务，先不执行查询

mydba@192.168.85.132,3306 [replcrash]> start transaction with consistent snapshot;

Query OK, 0 rows affected (0.00 sec)

执行DDL语句添加字段，执行成功

mydba@192.168.85.132,3306 [replcrash]> alter table py_user_innodb add col1 int;

Query OK, 0 rows affected (0.13 sec)

Records: 0 Duplicates: 0 Warnings: 0

执行查询，报表定义已经改变的错误

mydba@192.168.85.132,3306 [replcrash]> select * from py_user_innodb;

ERROR 1412 (HY000): Table definition has changed, please retry transaction

物理备份数据库

[root@ZST1 backup]# innobackupex --defaults-file=/data/mysql/mysql3306/my.cnf -S /tmp/mysql3306.sock -uroot -pmysql5719 /data/backup/full/

180104 15:29:31 [01] Copying ./sakila/payment.ibd to /data/backup/full/2018-01-04_15-29-21/sakila/payment.ibd180104 15:29:32 [01] ...doneInnoDB: Last flushed lsn:19337348200 load_index lsn 19337354022InnoDB: An optimized (without redo logging) DDLoperation has been performed. All modified pages may not have been flushed to the disk yet.

PXB will not be able take a consistent backup. Retry the backup operation180104 15:29:32 [01] Copying ./replcrash/py_user.ibd to /data/backup/full/2018-01-04_15-29-21/replcrash/py_user.ibd180104 15:29:32 [01] ...done

180104 15:29:32 [01] Copying ./replcrash/py_user_innodb.ibd to /data/backup/full/2018-01-04_15-29-21/replcrash/py_user_innodb.ibd180104 15:29:32 [01] ...done

View Code

只要在备份期间(实际是备份InnoDB表期间，因为备份non-InnoDB表期间会加FTWRL只读锁，阻塞DDL、DML操作)执行DDL操作，innobackupex就会报错退出。原因就是DDL操作不会记录到redo log，PXB will not be able take a consistent backup.

因此备份期间要避免执行不记录事务日志的操作(ALTER TABLE, CREATE TABLE, DROP TABLE, RENAME TABLE, TRUNCATE TABLE)

二、mysqlpump

2.1、备份过程

借助前面已开启general_log，来查看mysqlpump执行过程

MySQL 5.7.11起解决了--single-transaction和--default-parallelism的互斥问题

# 清空general_log

[root@ZST1 logs]#cat /dev/null > /data/mysql/mysql3306/data/mysql-general.log

# 备份replcrash数据库，一致性备份(源码限制只有备份整个实例时才能返回GTID信息，因此这里使用-A，然后使用--exclude-databases排除不需要备份的db)

[root@ZST1 backup]# mysqlpump-h127.0.0.1 -P3306 -uroot -p --single-transaction --add-drop-table --exclude-databases=mysql,sakila,backupdb -A >/data/backup/replcrash_pump_1323306_`date +%Y%m%d`.sql

默认mysqlpump使用一个队列两个线程

[root@ZST1 data]# vim/data/mysql/mysql3306/data/mysql-general.log

...4Time Id Command Argument5 2018-01-03T01:24:06.623704Z 14 Connect root@localhost on using TCP/IP6 2018-01-03T01:24:06.631266Z 14Query FLUSH TABLES WITH READ LOCK7 2018-01-03T01:24:06.667093Z 14Query SHOW WARNINGS8 2018-01-03T01:24:06.667310Z 14Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ9 2018-01-03T01:24:06.667520Z 14Query SHOW WARNINGS10 2018-01-03T01:24:06.667647Z 14Query START TRANSACTION WITH CONSISTENT SNAPSHOT11 2018-01-03T01:24:06.667792Z 14Query SHOW WARNINGS12 2018-01-03T01:24:06.679491Z 15 Connect root@localhost on using TCP/IP13 2018-01-03T01:24:06.683019Z 15Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ14 2018-01-03T01:24:06.684865Z 15Query SHOW WARNINGS15 2018-01-03T01:24:06.685015Z 15Query START TRANSACTION WITH CONSISTENT SNAPSHOT16 2018-01-03T01:24:06.685114Z 15Query SHOW WARNINGS17 2018-01-03T01:24:06.686057Z 16 Connect root@localhost on using TCP/IP18 2018-01-03T01:24:06.688856Z 16Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ19 2018-01-03T01:24:06.716231Z 16Query SHOW WARNINGS20 2018-01-03T01:24:06.716447Z 16Query START TRANSACTION WITH CONSISTENT SNAPSHOT21 2018-01-03T01:24:06.716558Z 16Query SHOW WARNINGS22 2018-01-03T01:24:06.716701Z 14Query UNLOCK TABLES23 2018-01-03T01:24:06.716857Z 14Query SHOW WARNINGS

...各种SHOW...1176 2018-01-03T01:24:07.344380Z 16Query SHOW CREATE DATABASE IF NOT EXISTS `replcrash`1177 2018-01-03T01:24:07.344468Z 16Query SHOW WARNINGS1178 2018-01-03T01:24:07.344565Z 16Query SHOW TABLE STATUS FROM `replcrash`1179 2018-01-03T01:24:07.380209Z 16Query SHOW WARNINGS1180 2018-01-03T01:24:07.380416Z 16Query SHOW COLUMNS IN `py_user` FROM `replcrash`1181 2018-01-03T01:24:07.381223Z 16Query SHOW WARNINGS1182 2018-01-03T01:24:07.381408Z 16Query SHOW CREATE TABLE `replcrash`.`py_user`1183 2018-01-03T01:24:07.381614Z 16Query SHOW WARNINGS1184 2018-01-03T01:24:07.381950Z 16 Query SHOW TRIGGERS FROM `replcrash` LIKE 'py_user'

1185 2018-01-03T01:24:07.382575Z 16Query SHOW WARNINGS1186 2018-01-03T01:24:07.382764Z 16Query SHOW COLUMNS IN `py_user_innodb` FROM `replcrash`1187 2018-01-03T01:24:07.383125Z 14 Query SET SQL_QUOTE_SHOW_CREATE= 1

1188 2018-01-03T01:24:07.383334Z 14Query SHOW WARNINGS1189 2018-01-03T01:24:07.383617Z 14 Query SET TIME_ZONE='+00:00'

1190 2018-01-03T01:24:07.384037Z 14Query SHOW WARNINGS1191 2018-01-03T01:24:07.385106Z 15 Query SELECT `COLUMN_NAME`, `EXTRA` FROM `INFORMATION_SCHEMA`.`COLUMNS`WHERE TABLE_SCHEMA ='replcrash' AND TABLE_NAME ='py_user'

1192 2018-01-03T01:24:07.386099Z 15Query SHOW WARNINGS1193 2018-01-03T01:24:07.386347Z 15Query SELECT SQL_NO_CACHE `uid`,`name`,`add_time`,`server_id` FROM `replcrash`.`py_user`1194 2018-01-03T01:24:07.387102Z 15Query SHOW WARNINGS1195 2018-01-03T01:24:07.387644Z 16Query SHOW WARNINGS1196 2018-01-03T01:24:07.387997Z 16Query SHOW CREATE TABLE `replcrash`.`py_user_innodb`1197 2018-01-03T01:24:07.388216Z 16Query SHOW WARNINGS1198 2018-01-03T01:24:07.388487Z 16 Query SHOW TRIGGERS FROM `replcrash` LIKE 'py_user_innodb'

1199 2018-01-03T01:24:07.389053Z 14 Query SELECT `COLUMN_NAME`, `EXTRA` FROM `INFORMATION_SCHEMA`.`COLUMNS`WHERE TABLE_SCHEMA ='replcrash' AND TABLE_NAME ='py_user_innodb'

1200 2018-01-03T01:24:07.390054Z 14Query SHOW WARNINGS1201 2018-01-03T01:24:07.390293Z 14Query SELECT SQL_NO_CACHE `uid`,`name`,`add_time`,`server_id` FROM `replcrash`.`py_user_innodb`1202 2018-01-03T01:24:07.391566Z 16Query SHOW WARNINGS1203 2018-01-03T01:24:07.391776Z 16Query SHOW COLUMNS IN `py_user_myisam` FROM `replcrash`1204 2018-01-03T01:24:07.392559Z 16Query SHOW WARNINGS1205 2018-01-03T01:24:07.392747Z 16Query SHOW CREATE TABLE `replcrash`.`py_user_myisam`1206 2018-01-03T01:24:07.393065Z 16Query SHOW WARNINGS1207 2018-01-03T01:24:07.393336Z 16 Query SHOW TRIGGERS FROM `replcrash` LIKE 'py_user_myisam'

1208 2018-01-03T01:24:07.394146Z 16Query SHOW WARNINGS1209 2018-01-03T01:24:07.394371Z 16 Query SHOW FUNCTION STATUS WHERE db = 'replcrash'

1210 2018-01-03T01:24:07.396083Z 15 Query SELECT `COLUMN_NAME`, `EXTRA` FROM `INFORMATION_SCHEMA`.`COLUMNS`WHERE TABLE_SCHEMA ='replcrash' AND TABLE_NAME ='py_user_myisam'

1211 2018-01-03T01:24:07.399053Z 15Query SHOW WARNINGS1212 2018-01-03T01:24:07.399425Z 15Query SELECT SQL_NO_CACHE `uid`,`name`,`add_time`,`server_id` FROM `replcrash`.`py_user_myisam`1213 2018-01-03T01:24:07.405719Z 16Query SHOW WARNINGS1214 2018-01-03T01:24:07.405915Z 16 Query SHOW PROCEDURE STATUS WHERE db = 'replcrash'

1215 2018-01-03T01:24:07.412340Z 14Query SHOW WARNINGS1216 2018-01-03T01:24:07.414496Z 15Query SHOW WARNINGS1217 2018-01-03T01:24:07.416755Z 16Query SHOW WARNINGS1218 2018-01-03T01:24:07.417261Z 16Query SHOW EVENTS FROM `replcrash`1219 2018-01-03T01:24:07.417884Z 16 Query SHOW WARNINGS

View Code

即使备份一个db，general_log中也会出现很多其他库的内容(⊙_⊙)

mysqlpump备份过程(--single-transaction)：

对于建立的第一个连接，执行FLUSH TABLES WITH READ LOCK，加上只读锁；对于其他连接(包含第一个连接)，设置RR隔离级别，并开启一致性快照读START TRANSACTION WITH CONSISTENT SNAPSHOT；当所有连接(--default-parallelism设置多少个线程)都建立好后，再执行解锁UNLOCK TABLES；最后通过SELECT colname  FROM `tbname`备份数据

general_log中没有看到SHOW MASTER STATUS，猜测它类似于mydumper，也是在主线程FLUSH TABLES WITH READ LOCK后，就去获取GTID信息。

因此mysqlpump也会遇到在mysqldump中的坑

mysqlpump并行备份的部分参数需要在单线程模式才能应用，实际使用中建议先测试，对比输出结果分辨各参数的作用

2.2、--single-transaction

• --single-transaction

This option sets the transaction isolation mode to REPEATABLE READ and sends a START TRANSACTION SQL statement to the server before dumping data. It is useful only with transactional tables such as InnoDB, because then it dumps the consistent state of the database at the time when START TRANSACTION was issued without blocking any applications.

When using this option, you should keep in mind that only InnoDB tables are dumped in a consistent state. For example, any MyISAM or MEMORY tables dumped while using this option may still change state.

While a --single-transaction dump is in process, to ensure a valid dump file (correct table contents and binary log coordinates), no other connection should use the following statements: ALTER TABLE, CREATE TABLE, DROP TABLE, RENAME TABLE, TRUNCATE TABLE. A consistent read is not isolated from those statements, so use of them on a table to be dumped can cause the SELECT that is performed by mysqldump/mysqlpump to retrieve the table contents to obtain incorrect contents or fail.

• START TRANSACTION

The WITH CONSISTENT SNAPSHOT modifier starts a consistent read for storage engines that are capable of it. This applies only to InnoDB. The effect is the same as issuing a START TRANSACTION followed by a SELECT from any InnoDB table.

The WITH CONSISTENT SNAPSHOT modifier does not change the current transaction isolation level, so it provides a consistent snapshot only if the current isolation level is one that permits a consistent read. The only isolation level that permits a consistent read is REPEATABLE READ.

该参数将事务隔离级别设置成Repeatable Read，并在dump之前发送start transaction语句给服务端。这只对事务表(比如innodb)很有用，因为在发出start transaction时，保证了在不阻塞任何应用下的一致性状态。对myisam和memory等非事务表，还是会改变状态的，当使用此参数的时候要确保没有其他连接在使用ALTER TABLE、CREATE TABLE、DROP TABLE、RENAME TABLE、TRUNCATE TABLE等语句，否则会出现不正确的内容或者失败。在mysql5.7.11之前，--default-parallelism大于1的时候和此参数互斥，必须使用--default-parallelism=0。5.7.11之后解决了--single-transaction和--default-parallelism的互斥问题

三、mydumper

3.1、备份过程

mydumper备份过程

1、连接目标数据库

2、通过show processlist来判断是否有长查询，根据参数long-query-guard和kill-long-queries决定退出或杀掉长查询

3、主线程flush tables with read lock；start transaction with consistent snapshot

4、主线程读取当前时间点的二进制日志文件名和日志写入的位置并记录在metadata文件中，以供即时点恢复使用

5、创建dump线程，缺省为4个

6、确定候选表，根据类别分别插入non_innodb_table、innodb_tables以及table_schemas链表

7、将候选表通过g_async_queue_push加入任务队列(队列最后元素是thread shutdown)，由dump线程从队列中读取表信息并执行数据导出

8、备份完non_innodb_table后立即unlock tables解锁，以减少锁定时间

9、等待dump InnoDB tables完成

从备份逻辑中可以看出，mydumper需要在备份完非事务表之后才解锁，这就保证了事务表和非事务表的一致性备份。默认情况下，DML操作不会影响mydumper备份的一致性

3.2、--trx-consistency-only

这个参数退化为仅保证事务表的一致性备份，在备份非事务表前如果有数据写入就会导致数据与metadata不一致，有点类似前面的mysqldump、mysqlpump的味道

运行前面的PythonDML脚本，一直往py_user_myisam、py_user_innodb表中写入数据，测试--trx-consistency-only选项的效果

# 清空general_log

[root@ZST1 logs]#cat /dev/null > /data/mysql/mysql3306/data/mysql-general.log

# 备份replcrash库(仅事务表一致性备份)

[root@ZST1 mydumper]# mydumper-h 127.0.0.1 -P 3306 -u root -p mysql5719 --trx-consistency-only -v 3 -B replcrash -o /data/backup/mydumper** (mydumper:2808): WARNING **: Using trx_consistency_only, binlog coordinates will not be accurate ifyou are writing to non transactional tables.**Message: Connected to a MySQL server** Message: Started dump at: 2018-01-04 09:34:53

**Message: Written master status** Message: Thread 1 connected using MySQL connection ID 50

** Message: Thread 2 connected using MySQL connection ID 51

** Message: Thread 3 connected using MySQL connection ID 52

** Message: Thread 4 connected using MySQL connection ID 53

**Message: Transactions started, unlocking tables** Message: Thread 1 dumping data for`replcrash`.`py_user`** Message: Thread 2 dumping data for`replcrash`.`py_user_innodb`** Message: Thread 2 dumping data for`replcrash`.`py_user_myisam`** Message: Thread 1 dumping schema for`replcrash`.`py_user`** Message: Thread 3 dumping schema for`replcrash`.`py_user_innodb`** Message: Thread 1 dumping schema for`replcrash`.`py_user_myisam`** Message: Thread 3shutting down** Message: Thread 1shutting down** Message: Thread 2shutting down** Message: Thread 4shutting down** Message: Finished dump at: 2018-01-04 09:34:53# 查看metadata

[root@ZST1 mydumper]#catmetadata

Started dump at:2018-01-04 09:34:53SHOW MASTER STATUS:

Log: mysql-bin.000185Pos:2452139GTID:8ab82362-9c37-11e7-a858-000c29c1025c:1-272303Finished dump at:2018-01-04 09:34:53[root@ZST1 mydumper]#

# 还原replcrash库

[root@ZST1 mydumper]# myloader-h 127.0.0.1 -P 3308 -u root -p mysql5719 -o -B replcrash -d /data/backup/mydumper

myloader不会产生binlog，也不会应用metadata中的GTID

# 设置GTID_PURGED

mydba@192.168.85.132,3308 [replcrash]>reset master;

mydba@192.168.85.132,3308 [replcrash]> SET @@GLOBAL.GTID_PURGED='8ab82362-9c37-11e7-a858-000c29c1025c:1-272303';

# 搭建复制

mydba@192.168.85.132,3308 [replcrash]>change master to

master_host='192.168.85.132',

master_port=3306,

master_user='repl',

master_password='repl',

master_auto_position=1;

# 启动复制，查看复制状态

mydba@192.168.85.132,3308 [replcrash]>start slave;

mydba@192.168.85.132,3308 [replcrash]>show slave status\G*************************** 1. row ***************************Master_Log_File: mysql-bin.000185Read_Master_Log_Pos:2758886Relay_Log_File: relay-bin.000002Relay_Log_Pos:414Relay_Master_Log_File: mysql-bin.000185Slave_IO_Running: Yes

Slave_SQL_Running: No

Exec_Master_Log_Pos:2452139Last_SQL_Errno:1062Last_SQL_Error: Could not execute Write_rows event on table replcrash.py_user_myisam; Duplicate entry'783' for key 'PRIMARY', Error_code: 1062; handler error HA_ERR_FOUND_DUPP_KEY; the event''s master log mysql-bin.000185, end_log_pos 2452443Retrieved_Gtid_Set: 8ab82362-9c37-11e7-a858-000c29c1025c:272304-273161Executed_Gtid_Set: 8ab82362-9c37-11e7-a858-000c29c1025c:1-272303Auto_Position:1# 大于等于冲突key的数据

mydba@192.168.85.132,3308 [replcrash]> select * from replcrash.py_user_myisam where uid>=783;+-----+--------------------------------+---------------------+-----------+

| uid | name | add_time | server_id |

+-----+--------------------------------+---------------------+-----------+

| 783 | MLGU22VB26RHNNYAY6IPPUJX9A74EM | 2018-01-04 09:34:53 | 1323306 |

+-----+--------------------------------+---------------------+-----------+

1 row in set (0.06sec)

# mydumper产生的general-log

[root@ZST1 data]# vim/data/mysql/mysql3306/data/mysql-general.log

...2018-01-04T01:34:53.769877Z 49 Query SET SESSION net_write_timeout = 2147483

2018-01-04T01:34:53.770302Z 49Query SHOW PROCESSLIST2018-01-04T01:34:53.770886Z 49Query FLUSH TABLES WITH READ LOCK2018-01-04T01:34:53.771236Z 49 Query START TRANSACTION /*!40108 WITH CONSISTENT SNAPSHOT*/

2018-01-04T01:34:53.771430Z 49 Query /*!40101 SET NAMES binary*/

2018-01-04T01:34:53.772084Z 49Query SHOW MASTER STATUS2018-01-04T01:34:53.772331Z 49Query SHOW SLAVE STATUS2018-01-04T01:34:53.773386Z 48 Query insert into py_user_myisam(name,add_time,server_id) values('MLGU22VB26RHNNYAY6IPPUJX9A74EM',now(),@@server_id)2018-01-04T01:34:53.773981Z 50 Connect root@localhost on using TCP/IP2018-01-04T01:34:53.788273Z 50 Query SET SESSION wait_timeout = 2147483

2018-01-04T01:34:53.788874Z 50Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ2018-01-04T01:34:53.788972Z 50 Query START TRANSACTION /*!40108 WITH CONSISTENT SNAPSHOT*/

2018-01-04T01:34:53.789092Z 50 Query /*!40103 SET TIME_ZONE='+00:00'*/

2018-01-04T01:34:53.789201Z 50 Query /*!40101 SET NAMES binary*/

2018-01-04T01:34:53.790091Z 51 Connect root@localhost on using TCP/IP2018-01-04T01:34:53.790315Z 51 Query SET SESSION wait_timeout = 2147483

2018-01-04T01:34:53.791912Z 51Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ2018-01-04T01:34:53.792095Z 51 Query START TRANSACTION /*!40108 WITH CONSISTENT SNAPSHOT*/

2018-01-04T01:34:53.792307Z 51 Query /*!40103 SET TIME_ZONE='+00:00'*/

2018-01-04T01:34:53.792418Z 51 Query /*!40101 SET NAMES binary*/

2018-01-04T01:34:53.793381Z 52 Connect root@localhost on using TCP/IP2018-01-04T01:34:53.794631Z 52 Query SET SESSION wait_timeout = 2147483

2018-01-04T01:34:53.796301Z 52Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ2018-01-04T01:34:53.796404Z 52 Query START TRANSACTION /*!40108 WITH CONSISTENT SNAPSHOT*/

2018-01-04T01:34:53.796538Z 52 Query /*!40103 SET TIME_ZONE='+00:00'*/

2018-01-04T01:34:53.796641Z 52 Query /*!40101 SET NAMES binary*/

2018-01-04T01:34:53.797414Z 53 Connect root@localhost on using TCP/IP2018-01-04T01:34:53.798420Z 53 Query SET SESSION wait_timeout = 2147483

2018-01-04T01:34:53.799316Z 53Query SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ2018-01-04T01:34:53.799425Z 53 Query START TRANSACTION /*!40108 WITH CONSISTENT SNAPSHOT*/

2018-01-04T01:34:53.800345Z 53 Query /*!40103 SET TIME_ZONE='+00:00'*/

2018-01-04T01:34:53.800449Z 53 Query /*!40101 SET NAMES binary*/

2018-01-04T01:34:53.800661Z 49 Query UNLOCK TABLES /*trx-only*/

2018-01-04T01:34:53.801868Z 49Init DB replcrash2018-01-04T01:34:53.802332Z 49Query SHOW TABLE STATUS2018-01-04T01:34:53.804759Z 50 Query SELECT /*!40001 SQL_NO_CACHE*/ *FROM `replcrash`.`py_user`2018-01-04T01:34:53.805137Z 51 Query SELECT /*!40001 SQL_NO_CACHE*/ *FROM `replcrash`.`py_user_innodb`2018-01-04T01:34:53.807164Z 51 Query SELECT /*!40001 SQL_NO_CACHE*/ *FROM `replcrash`.`py_user_myisam`2018-01-04T01:34:53.808786Z 48 Query insert into py_user_innodb(name,add_time,server_id) values('MLGU22VB26RHNNYAY6IPPUJX9A74EM',now(),@@server_id)2018-01-04T01:34:53.809449Z 49Query SHOW CREATE DATABASE `replcrash`2018-01-04T01:34:53.810326Z 52Query SHOW CREATE TABLE `replcrash`.`py_user_innodb`2018-01-04T01:34:53.810638Z 50Query SHOW CREATE TABLE `replcrash`.`py_user`2018-01-04T01:34:53.811307Z 52Quit2018-01-04T01:34:53.811506Z 50Query SHOW CREATE TABLE `replcrash`.`py_user_myisam`2018-01-04T01:34:53.812272Z 50Quit2018-01-04T01:34:53.812512Z 48 Query commit

View Code

48是python持续写入的线程、49是主线程、50~53是dump线程

所有连接建立后，主线程立即解锁UNLOCK TABLES /* trx-only */。主线程SHOW MASTER STATUS的后面紧接着python写入insert into py_user_myisam，实际这个写入操作是在主线程UNLOCK TABLES之后，dump线程备份py_user_myisam数据之前。这就导致备份的数据与metadata不一致，因此不推荐使用--trx-consistency-only选项

3.3、逻辑备份差异

mysqldump：只支持单线程工作，这就使得它无法迅速的备份数据

mysqlpump：并行的最小粒度是单个数据库对象，对于每张表的导出只能是单个线程的

mydumper：支持对单表多个线程备份，参数-r

多线程操作提升空间受限于磁盘的IO能力，在使用前做好磁盘IO的评估

四、XtraBackup

4.1、备份过程

innobackupex全备过程

1、start xtrabackup_log

2、copy .ibd、ibdata1

3、FLUSH TABLES WITH READ LOCK

4、copy .frm、.MYD、.MYI、misc files

5、SHOW MASTER STATUS

6、UNLOCK TABLES

7、stop and copy xtrabackup_log

备份开始时首先会开启一个后台检测进程，从当前checkpoint位置开始拷贝redo log，同时持续检测redo log，一旦发现redo中有新的日志写入，立刻将日志记入后台日志文件xtrabackup_log中。之后拷贝innodb的数据文件和系统表空间文件ibdata1，待拷贝结束后，执行flush tables with read lock操作，拷贝.frm，MYI，MYD，等文件，并且在这一时刻获得binlog的位置，最后会发出unlock tables，把表设置为可读可写状态，最终停止xtrabackup_log。

InnoDB表copy [.ibd、ibdata]+[redo log]借助InnoDB Crash Recovery机制保证一致性；non-InnoDB表使用FTWRL加只读锁后backup non-InnoDB tables and files。DML操作不会影响innobackupex备份的一致性

4.2、总结

mysqldump

mysqlpump

mydumper

innobackupex

FTWRL被阻塞

存在互斥锁，会被阻塞

存在互斥锁，会被阻塞

存在互斥锁，会被阻塞

存在互斥锁，会被阻塞

报错，表定义变更

报错，表定义变更

不报错，-v 3查看

报错，DDL操作没写redo log

DML操作影响数据一致性

non_InnoDB表不一致

non_InnoDB表不一致

默认一致，--trx-consistency-only会导致不一致

一致

其他

没有指定my.cnf导致备份一个错误的实例

对生产库的DDL操作、大事务、或者长时间锁表的操作，一定要避开备份时间(･ω･)

五、参考文档