MySQL 複製簡要描述及樣本

MySQL 複製簡要描述及樣本

主從複製技術在MySQL中被廣泛使用，主要用於同步一台伺服器上的資料至多台從伺服器，可以用於實現負載平衡，高可用和故障切換，以及提供備份等等。MySQL支援多種不同的複製技術，諸如單向，半同步非同步複製等以及不同層級的複製，諸如資料庫層級，表級，跨庫同步等等。本文簡要描述了一個基本的主從複製並給出樣本。

1、複製的基本原理(步驟)

a、在主庫上把資料更改記錄的二進位日誌(binary log)

b、從庫上的I/O線程串連到主庫並請求發送其二進位記錄檔(主庫上的binlog dump線程將二進位日誌內容發送到從庫)

c、從庫上的I/O線程讀取主服務發送的二進位內容並將其拷貝到中繼日誌

d、從庫上的SQL線程讀取中繼日誌並執行日誌中包含的更新

2、為設定檔添加複製項

# 本文的示範基於同一伺服器上的多執行個體環境，其中3406連接埠用作主庫，而3506用作從庫。
# 關於多執行個體的部署可參考：
# MySQL多執行個體配置 
# 3406與3506為都為新裝且含預設庫等，所以本文示範中未涉及先遷移主庫資料到備庫步驟
a、主庫上的設定檔
# 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、從庫上的設定檔
# more my3506.cnf
[mysqld]
socket = /tmp/mysql3506.sock      # Author : Leshami
port = 3506                      # Blog  : <A href="www.bkjia.com" target=_blank>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、建立複製帳號

#啟動連接埠為3406的執行個體並添加賬戶
[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  |
+---------------+-------+

#建立用於複製的賬戶
master@localhost[(none)]> grant replication slave,replication client on *.*
    -> to repl@'192.168.1.177' identified by 'repl';

#初始化主庫記錄檔，產生環境慎用reset
master@localhost[(none)]> reset master;
Query OK, 0 rows affected (0.01 sec)

#查看主庫的狀態，日誌初始化至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

#啟動連接埠為3506的執行個體
[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資訊，該命令會產生及修改備庫上的master.info及relay-log.info檔案
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資訊
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線程處於運行狀態
            Slave_SQL_Running: Yes        #SQL線程處於運行狀態
                      ..............
          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 #重要的提示資訊

#可以看到從庫上的2個線程，一個是用於I/O線程，用於串連到主程式庫要求主庫發送binlog，一個是用於執行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線程用於發送binlog記錄檔到從庫，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
 
#主庫建立資料庫及表
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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