MySQL 復制詳解及簡單實例
主從復制技術在MySQL中被廣泛使用，主要用于同步一臺服務器上的數據至多臺從服務器，可以用于實現負載均衡，高可用和故障切換，以及提供備份等等。MySQL支持多種不同的復制技術，諸如單向，半同步異步復制等以及不同級別的復制，諸如數據庫級別，表級，跨庫同步等等。本文簡要描述了一個基本的主從復制并給出示例。
1、復制的基本原理(步驟)
a、在主庫上把數據更改記錄的二進制日志(binary log)
b、從庫上的I/O線程連接到主庫并請求發送其二進制日志文件(主庫上的binlog dump線程將二進制日志內容發送到從庫)
c、從庫上的I/O線程讀取主服務發送的二進制內容并將其拷貝到中繼日志
d、從庫上的SQL線程讀取中繼日志并執行日志中包含的更新
2、為配置文件添加復制項
# 本文的演示基于同一服務器上的多實例環境，其中3406端口用作主庫，而3506用作從庫。
# 關于多實例的部署可參考：
# MySQL多實例配置(一) http://blog.csdn.net/leshami/article/details/40339167
# MySQL多實例配置(二) http://blog.csdn.net/leshami/article/details/40339295
# 3406與3506為都為新裝且含缺省庫等，所以本文演示中未涉及先遷移主庫數據到備庫步驟
a、主庫上的配置文件
# more my3406.cnf
[mysqld]
socket = /tmp/mysql3406.sock
port = 3406
pid-file = /data/inst3406/data3406/my3406.pid
user = mysql
log-error=/data/inst3406/data3406/inst3406.err
datadir=/data/inst3406/data3406
basedir=/app/soft/mysql5
#### for master items ####
server-id=3406
log_bin=/data/inst3406/log/bin/inst3406bin
innodb_flush_log_at_trx_commit=1
sync_binlog=1
b、從庫上的配置文件
# more my3506.cnf
[mysqld]
socket = /tmp/mysql3506.sock # Author : Leshami
port = 3506 # Blog : a target="_blank" rel="external nofollow" >http://blog.csdn.net/leshami
pid-file/a> = /data/inst3506/data3506/my3506.pid
user = mysql
log-error=/data/inst3506/data3506/inst3506.err
datadir=/data/inst3506/data3506
basedir=/app/soft/mysql5
#### for slave items ####
server-id=3506
relay_log=/data/inst3506/log/relay/relay-bin
read_only=1
3、創建復制賬號
#啟動端口為3406的實例并添加賬戶
[mysql@app ~]$ mysqld_safe --defaults-file=/data/inst3406/data3406/my3406.cnf
[mysql@app ~]$ mysql -P3406 #登陸到3406
master@localhost[(none)]> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id | 3406 |
+---------------+-------+
#創建用于復制的賬戶
master@localhost[(none)]> grant replication slave,replication client on *.*
-> to repl@'192.168.1.177' identified by 'repl';
#初始化主庫日志文件，生成環境慎用reset
master@localhost[(none)]> reset master;
Query OK, 0 rows affected (0.01 sec)
#查看主庫的狀態，日志初始化至000001，
master@localhost[(none)]> show master status,Position為120
+--------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+--------------------+----------+--------------+------------------+-------------------+
| inst3406bin.000001 | 120 | | | |
+--------------------+----------+--------------+------------------+-------------------+
4、配置主從同步
#啟動端口為3506的實例
[mysql@app ~]$ mysqld_safe --defaults-file=/data/inst3506/data3506/my3506.cnf
[mysql@app ~]$ msyql -P3506
slave@localhost[(none)]> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id | 3506 |
+---------------+-------+
1 row in set (0.00 sec)
#為從庫添加指向主庫的相關配置信息，該命令會生成及修改備庫上的master.info及relay-log.info文件
slave@localhost[(none)]> CHANGE MASTER TO MASTER_HOST='192.168.1.177',
-> MASTER_USER='repl',
-> MASTER_PASSWORD='repl',
-> MASTER_PORT=3406,
-> MASTER_LOG_FILE='inst3406bin.000001',
-> MASTER_LOG_POS=0;
Query OK, 0 rows affected, 2 warnings (0.04 sec)
#出現了2個warnings，查看一下
slave@localhost[(none)]> show warnings \G
*************************** 1. row ***************************
Level: Note
Code: 1759
Message: Sending passwords in plain text without SSL/TLS is extremely insecure.
*************************** 2. row ***************************
Level: Note
Code: 1760
Message: Storing MySQL user name or password information in the master.info repository is not secure and is therefore not recommended.
Please see the MySQL Manual for more about this issue and possible alternatives.
2 rows in set (0.00 sec)
#此時查看從庫的狀態信息
slave@localhost[(none)]> show slave status \G
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 192.168.1.177
Master_User: repl
Master_Port: 3406
Connect_Retry: 60
Master_Log_File: inst3406bin.000001
Read_Master_Log_Pos: 4
Relay_Log_File: relay-bin.000001
Relay_Log_Pos: 4
Relay_Master_Log_File: inst3406bin.000001
Slave_IO_Running: No #IO線程沒有運行
Slave_SQL_Running: No #SQL線程沒有運行
......................
Master_Info_File: /data/inst3506/data3506/master.info
slave@localhost[(none)]> start slave; #啟動slave
Query OK, 0 rows affected (0.01 sec)
#含義如下
START SLAVE with no thread_type options starts both of the slave threads. The I/O thread reads
events from the master server and stores them in the relay log. The SQL thread reads events from the
relay log and executes them.
#再次查看slave的狀態
robin@localhost[(none)]> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.1.177
Master_User: repl
Master_Port: 3406
Connect_Retry: 60
Master_Log_File: inst3406bin.000001
Read_Master_Log_Pos: 120
Relay_Log_File: relay-bin.000002
Relay_Log_Pos: 285
Relay_Master_Log_File: inst3406bin.000001
Slave_IO_Running: Yes #IO線程處于運行狀態
Slave_SQL_Running: Yes #SQL線程處于運行狀態
..............
Exec_Master_Log_Pos: 120
Relay_Log_Space: 452
............
Master_Server_Id: 3406
Master_UUID: 32f53a0a-63ef-11e4-93d9-8c89a5d108ae
Master_Info_File: /data/inst3506/data3506/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it #重要的提示信息
#可以看到從庫上的2個線程，一個是用于I/O線程，用于連接到主庫請求主庫發送binlog，一個是用于執行SQL的SQL線程。
slave@localhost[(none)]> show processlist\G
*************************** 1. row ***************************
Id: 4
User: system user
Host:
db: NULL
Command: Connect
Time: 510993
State: Waiting for master to send event
Info: NULL
*************************** 2. row ***************************
Id: 5
User: system user
Host:
db: NULL
Command: Connect
Time: 333943
State: Slave has read all relay log; waiting for the slave I/O thread to update it
Info: NULL
5、驗證同步情況
#下面在主庫上執行一些操作以檢查從庫的同步情況
master@localhost[(none)]> show variables like 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id | 3406 |
+---------------+-------+
1 row in set (0.00 sec)
#主庫上Binlog Dump線程用于發送binlog日志文件到從庫，如下查詢
master@localhost[(none)]> show processlist\G
*************************** 1. row ***************************
Id: 12
User: repl
Host: 192.168.1.177:57440
db: NULL
Command: Binlog Dump
Time: 511342
State: Master has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
#主庫創建數據庫及表
master@localhost[(none)]> create database tempdb;
Query OK, 1 row affected (0.01 sec)
master@localhost[(none)]> use tempdb
Database changed
master@localhost[tempdb]> create table tb_engines as select * from information_schema.engines;
Query OK, 9 rows affected (0.02 sec)
Records: 9 Duplicates: 0 Warnings: 0
#下面是在從庫上檢查的結果
slave@localhost[(none)]> select count(*) from tempdb.tb_engines;
+----------+
| count(*) |
+----------+
| 9 |
+----------+
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