概述
复制通常用来创建主节点的副本，通过添加冗余节点来保证高可用性，当然复制也可以用于其他 用途，例如在从节点上进行数据读、分析等等。在横向扩展的业务中，复制很容易实施，主要表现在在利用主节点进行写操作，多个从节点进行读操作，在mysql5.5中默认为异步复制。
mysql 复制的异步性是指：事物首先在主节点上提交，然后复制给从节点并在从节点上应用，这样意味着在同一个时间点主从上的数据可能不一致，异步复制的好处在于它 比同步复制要快，如果对数据的一致性要求很高，还是采用同步复制较好。
mysql-5.5 开始支持semi-synchronous的复制，也叫半同步复制，目的在于事务环境下保持主从一致
mysql-5.6 开始支持延时复制。
mysql复制的原理现阶段都是一样的，master将操作记录到bin-log中，slave的一个线程去master读取bin-log，并将他们保存到relay-log中，slave的另外一个线程去重放relay-log中的操作来实现和master数据同步。
wKioL1OWgmrSKROTAAEnELMIXRI329.jpg
该过程的第一部分就是master记录二进制日志。在每个事务更新数据完成之前，master在二日志记录这些改变。MySQL将事务串行的写入二进制日志，即使事务中的语句都是交叉执行的。在事件写入二进制日志完成后，master通知存储引擎提交事务。
下一步就是slave将master的binary log拷贝到它自己的中继日志。首先，slave开始一个工作线程——I/O线程。I/O线程在master上打开一个普通的连接，然后开始binlog dump process。Binlog dump process从master的二进制日志中读取事件，如果已经跟上master，它会睡眠并等待master产生新的事件。I/O线程将这些事件写入中 继日志。
SQL slave thread（SQL从线程）处理该过程的最后一步。SQL线程从中继日志读取事件，并重放其中的事件而更新slave的数据，使其与master中的数 据一致。只要该线程与I/O线程保持一致，中继日志通常会位于OS的缓存中，所以中继日志的开销很小。
此外，在master中也有一个工作线程：和其它MySQL的连接一样，slave在master中打开一个连接也会使得master开始一个线程。复制 过程有一个很重要的限制——复制在slave上是串行化的，也就是说master上的并行更新操作不能在slave上并行操作。
异步主从复制配置
准备：
OS：rhel5.8_i386
SoftWare: mysql-5.5.28-linux2.6-i686.tar.gz
1、主从安装mysql
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tar xf mysql-5.5.28-linux2.6-i686.tar.gz -C /usr/local/
# cd /usr/local/
# ln -s mysql-5.5.28-linux2.6-i686/ mysql
# groupadd -r mysql
# useradd -r -g mysql -s /sbin/nologin mysql
# mkdir /mydata/data -p
# chown -R mysql.mysql /mydata/data/
# chown -R root.mysql /usr/local/mysql/*
# cp support-files/my-large.cnf /etc/my.cnf
# cp support-files/mysql.server /etc/init.d/mysqld
[mysqld]
innodb_file_per_table = 1
datadir = /mydata/data #由于是二进制安装的mysql所以必须指定数据库目录位置
# vim /etc/profile.d/mysqld.sh
export PAHT=$PATH:/usr/local/mysql/bin
# . /etc/profile.d/mysqld.sh
2、主服务器配置
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# vim /etc/my.cnf
[mysqld]
log-bin = master-bin
log-bin-index = master-bin.index
server-id = 1
# scripts/mysql_install_db --user=mysql --datadir=/mydata/data/
# service mysqld start
# mysql
mysql> grant replication slave on *.* to repl@'192.168.100.12' identified by 'asdasd';
mysql> flush privileges;
mysql> flush logs;
mysql> show master logs;
+-------------------+-----------+
| Log_name | File_size |
+-------------------+-----------+
| master-bin.000001 | 27326 |
| master-bin.000002 | 1038693 |
| master-bin.000003 | 379 |
| master-bin.000004 | 107 |
+-------------------+-----------+
mysql> purge binary logs to 'master-bin.000004';
3、从服务器配置
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# vim /etc/my.cnf
[mysqld]
relay-log = relay-log
relay-log-index = relay-log.index
read-only = 1
#innodb_file_per_table = 1
#binlog_format=mixed
server-id = 10
# scripts/mysql_install_db --user=mysql --datadir=/mydata/data/
# service mysqld start
mysql> change master to master_host='192.168.100.11',master_user='repl',master_password='asdasd',master_log_file='master-bin.000004',master_log_pos=107;
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 192.168.100.11
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.000004
Read_Master_Log_Pos: 107
Relay_Log_File: relay-log.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: master-bin.000004
Slave_IO_Running: No
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: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 107
Relay_Log_Space: 107
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: NULL
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: 0
1 row in set (0.00 sec)
mysql> start slave;
mysql> show slave status\G
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
..............
至此主从异步复制就完成了
说明：
slave_id 必须是唯一的
slave没有必要开启二进制日志，但在有些情况下必须设置，如mysql级联. slave为其它slave的master,所以要设置bin_log，默认为hostname，但如果hostname改变则会出问题。
有些人可能开启了slave二进制日志，却没有设置log_slave_updates,然后查看slave的数据是否改变，这是错误的配置。所以尽量使用read_only = 1 ，防止改变数据（除了sql_thread进程）。
start slave :启动从服务器IO_Thread和SQL_Thread线程，这里也可以单独对它们进行启动
在主服务器上需设置sync-binlog = 1 ,用于事务安全
重置change master参数：
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mysql> slave stop;
mysql> reset slave;
mysql> change master to master_host='192.168.100.11',master_user='repl',master_password='asdasd',master_log_file='master-bin.000005',master_log_pos=107;
由于slave都会自动连接上master，当我们有时需要手动调整时可以在启动前移动slave数据目录下的master.ino和relay.info文件，或者查看variables中有无“skip-slave-start”变量，有就设置为ON
半同步复制
/usr/local/mysql/lib/plugin/semisync_master.so
/usr/local/mysql/lib/plugin/semisync_slave.so
1、主服务器配置
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mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
mysql> show variables like '%semi%';
+------------------------------------+-------+
| Variable_name | Value |
+------------------------------------+-------+
| rpl_semi_sync_master_enabled | OFF |
| rpl_semi_sync_master_timeout | 10000 |
| rpl_semi_sync_master_trace_level | 32 |
| rpl_semi_sync_master_wait_no_slave | ON |
+------------------------------------+-------+
mysql> set global rpl_semi_sync_master_enabled=1;
mysql> set global rpl_semi_sync_master_timeout=1000;
2、Slave上配置
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mysql> install plugin rpl_semi_sync_slave soname 'semisync_slave.so';
mysql> show variables like '%semi%';
+---------------------------------+-------+
| Variable_name | Value |
+---------------------------------+-------+
| rpl_semi_sync_slave_enabled | OFF |
| rpl_semi_sync_slave_trace_level | 32 |
+---------------------------------+-------+
mysql> set global rpl_semi_sync_slave_enabled=1;
如果需要永久生效，请将上面几个变量分别写入master与slave中mysqld字段中。
MySQL复制过滤
MySQL复制过滤可以在Master,也可以在Slave
由于基于Master的过滤操作为影响到二进制日志的完整性，对于我们以后做及时点还原会有影响，所以我们一般不建议在Maser上做复制过滤。
1、基于数据库
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binlog-do-db //binlog-do-db表示和哪个数据库相关的写入类、修改类指令会被写入
binlog-ignore-db //binlog-ignore-db表示忽略（黑名单）
2、基于表
replicate-do-table=
replicate-ignore-table=
3、对于表，还可以用通配符配置过滤
replicate-wild-do-table=
replicate-wild-ignore-table=
SSL复制
要求主从服务器各自都要有证书和私钥；默认情况下主从服务器的SSL功能是没有启用的，需要先启用。
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mysql> show variables like '%ssl%';
+---------------+----------+
| Variable_name | Value |
+---------------+----------+
| have_openssl | DISABLED |
| have_ssl | DISABLED |
| ssl_ca | |
| ssl_capath | |
| ssl_cert | |
| ssl_cipher | |
| ssl_key | |
+---------------+----------+
1、配置Master为CA证书服务器
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# vim /etc/pki/tls/openssl.cnf
# cd /etc/pki/CA/
# (umask 077; openssl genrsa 1024 >private/cakey.pem)
# openssl req -new -x509 -key private/cakey.pem -out cacert.pem
Country Name (2 letter code) [GB]:CN
State or Province Name (full name) [Berkshire]:GD
Locality Name (eg, city) [Newbury]:ZS
Organization Name (eg, company) [My Company Ltd]:NEO
Organizational Unit Name (eg, section) []:tech
Common Name (eg, your name or your server's hostname) []:station01.neo.com
# mkdir newcerts certs crl
# touch index.txt
# echo 01 >serial
2、为Master上的MySQL准备私钥以及颁发证书
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# mkdir /usr/local/mysql/ssl
# cd /usr/local/mysql/ssl/
#(umask 077; openssl genrsa 1024 > mysql.key)
# openssl req -new -key mysql.key -out mysql.csr -days 3650
Country Name (2 letter code) [GB]:CN
State or Province Name (full name) [Berkshire]:GD
Locality Name (eg, city) [Newbury]:ZS
Organization Name (eg, company) [My Company Ltd]:NEO
Organizational Unit Name (eg, section) []:tech
Common Name (eg, your name or your server's hostname) []:station01.neo.com
Email Address []:
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
# openssl ca -in mysql.csr -out mysql.crt
Using configuration from /etc/pki/tls/openssl.cnf
Check that the request matches the signature
Signature ok
Certificate Details:
Serial Number: 1 (0x1)
Validity
Not Before: May 28 02:26:17 2014 GMT
Not After : May 28 02:26:17 2015 GMT
Subject:
countryName = CN
stateOrProvinceName = GD
organizationName = NEO
organizationalUnitName = tech
commonName = station01.neo.com
X509v3 extensions:
X509v3 Basic Constraints:
CA:FALSE
Netscape Comment:
OpenSSL Generated Certificate
X509v3 Subject Key Identifier:
A4:B7:A6:98:9F:60:08:BE:86:87:65:5F:B6:13:BC:4A:5B:D4:44:3A
X509v3 Authority Key Identifier:
keyid:4F:D8:57:42:D9:39:17:7D:39:44:91:01:A4:01:DE:32:92:D6:F9:DF
Certificate is to be certified until May 28 02:26:17 2015 GMT (365 days)
Sign the certificate? [y/n]:y
1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated
# chown mysql.mysql *
3、Slave上申请证书
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# mkdir /usr/local/mysql/ssl
# (umask 077; openssl genrsa 1024 >mysql.key)
# openssl req -new -key mysql.key -out mysql.csr -days 3650
Country Name (2 letter code) [GB]:CN
State or Province Name (full name) [Berkshire]:GD
Locality Name (eg, city) [Newbury]:ZS
Organization Name (eg, company) [My Company Ltd]:NEO
Organizational Unit Name (eg, section) []:tech
Common Name (eg, your name or your server's hostname) []:station02.neo.com
Email Address []:
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
# scp mysql.csr 192.168.100.11:/root/
4、Master上为Slave签发证书
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# openssl ca -in mysql.csr -out mysql.crt
Using configuration from /etc/pki/tls/openssl.cnf
Check that the request matches the signature
Signature ok
Certificate Details:
Serial Number: 2 (0x2)
Validity
Not Before: May 28 02:36:24 2014 GMT
Not After : May 28 02:36:24 2015 GMT
Subject:
countryName = CN
stateOrProvinceName = GD
organizationName = NEO
organizationalUnitName = tech
commonName = station02.neo.com
X509v3 extensions:
X509v3 Basic Constraints:
CA:FALSE
Netscape Comment:
OpenSSL Generated Certificate
X509v3 Subject Key Identifier:
81:9F:5B:E7:06:D0:64:B7:E6:81:3F:98:95:71:D4:DF:C6:B8:CE:3D
X509v3 Authority Key Identifier:
keyid:4F:D8:57:42:D9:39:17:7D:39:44:91:01:A4:01:DE:32:92:D6:F9:DF
Certificate is to be certified until May 28 02:36:24 2015 GMT (365 days)
Sign the certificate? [y/n]:yes
1 out of 1 certificate requests certified, commit? [y/n]yes
Write out database with 1 new entries
Data Base Updated
# scp mysql.crt 192.168.100.12:/usr/local/mysql/ssl/
# scp /etc/pki/CA/cacert.pem 192.168.100.12:/usr/local/mysql/ssl/
5、Master上编缉/etc/my.cnf启用ssl，并设置主从
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# vim /etc/my.cnf
[mysqld]
log-bin=mysql-bin
sync_binlog = 1 ##二进制日志
server-id = 1 ##此id必须全局唯一
innodb_flush_log_at_trx_commit=1 ##每秒将事务日志立刻刷写到磁盘
ssl ##启用ssl默认是不开启的,mysql中show variables like '%ssl%'查看
ssl_ca =/usr/local/mysql/ssl/cacert.pem ##ca文件的位置
ssl_cert= /usr/local/mysql/ssl/mysql.crt ##证书文件的位置
ssl_key = /usr/local/mysql/ssl/mysql.key ##私钥文件的位置
6、启动mysql，并查看ssl信息
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# service mysqld start
# mysql
mysql> show variables like '%ssl%';
+---------------+---------------------------------+
| Variable_name | Value |
+---------------+---------------------------------+
| have_openssl | YES |
| have_ssl | YES |
| ssl_ca | /usr/local/mysql/ssl/cacert.pem |
| ssl_capath | |
| ssl_cert | /usr/local/mysql/ssl/mysql.crt |
| ssl_cipher | |
| ssl_key | /usr/local/mysql/ssl/mysql.key |
+---------------+---------------------------------+
7、为同步建立一最小权限账户，并要求ssl
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mysql> create user 'backup_ssl'@'192.168.100.12' identified by 'redhat';
mysql> revoke all privileges,grant option from 'backup_ssl'@'192.168.100.12';
mysql> grant replication slave,replication client on *.* to 'backup_ssl'@'192.168.100.12' require ssl;
mysql> flush privileges;
mysql> flush logs;
8、Slave上编缉/etc/my.cnf，启用ssl，并设置主从
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# vim /etc/my.cnf
[mysqld]
server-id = 2 ##此id必须全局唯一
##log-bin = mysql-bin ##注释掉，从服务器不需要二进制日志
relay-log = mysql-relay ##中继日志
relay-log-index = mysql-ralay.index ##中继目录
read-only = 1 ##从服务器只读
ssl ##启用ssl默认是不开启的,mysql中show variables like '%ssl%'查看
ssl_ca =/usr/local/mysql/ssl/cacert.pem ##ca文件的位置
ssl_cert= /usr/local/mysql/ssl/mysql.crt ##证书文件的位置
ssl_key = /usr/local/mysql/ssl/mysql.key ##私钥文件的位置
9、启用mysqld并查看ssl相关信息
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# servie mysqld start
mysql> show variables like '%ssl%';
+---------------+---------------------------------+
| Variable_name | Value |
+---------------+---------------------------------+
| have_openssl | YES |
| have_ssl | YES |
| ssl_ca | /usr/local/mysql/ssl/cacert.pem |
| ssl_capath | |
| ssl_cert | /usr/local/mysql/ssl/mysql.crt |
| ssl_cipher | |
| ssl_key | /usr/local/mysql/ssl/mysql.key |
+---------------+---------------------------------+
10、启动slave同步进程，连接主服务器
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mysql> change master to
-> master_host='172.16.1.18',
-> master_user='backup_ssl',
-> master_password='redhat',
-> master_log_file='mysql-bin.000004',
-> master_ssl=1,
-> master_ssl_ca='/usr/local/mysql/ssl/cacert.pem',
-> master_ssl_cert='/usr/local/mysql/ssl/mysql.crt',
-> master_ssl_key='/usr/local/mysql/ssl/mysql.key';
mysql> start slave
mysql> show slave status\G; ##查看slave状态
11、关注以下参数：
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Slave_IO_Running: Yes ##IOthread是否运行，如果为No代表slave运行不正常
Slave_SQL_Running: Yes ##SQLthread是否运行，如果为No代表slave运行不正常
Master_SSL_CA_File: /usr/local/mysql/ssl/cacert.pem ##是否启用了ssl
Master_SSL_Cert: /usr/local/mysql/ssl/mysql.crt
Master_SSL_Key: /usr/local/mysql/ssl/mysql.key
Master_Log_File: mysql-bin.00005 ##最后接收的主服务器的二进制
Exec_Master_Log_Pos: 338 ##最后执行的位置，查看master中是不是该位置
Last_IO_Errno: 0 ##最后一次IOthread有没有报错
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