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。
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
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
# 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
# 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：
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
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
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
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。
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
# 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
# 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
# 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
# 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
# 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
# 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
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
# 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
# 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
mysql> change master to -> master_host='192.168.100.11', -> 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：
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
