MySQL修改max_allowed_packet

因mysql从库报错Last_IO_Error: Got a packet bigger than 'max_allowed_packet' bytes

mysql> show slave statusG;
*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: 192.168.90.190
                  Master_User: rsync
                  Master_Port: 3311
                Connect_Retry: 60
              Master_Log_File: mysql-bin.001891
          Read_Master_Log_Pos: 897184977
               Relay_Log_File: mysql-relay-bin.003780
                Relay_Log_Pos: 897185056
        Relay_Master_Log_File: mysql-bin.001891
             Slave_IO_Running: No
            Slave_SQL_Running: Yes
              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: 897184910
              Relay_Log_Space: 897185322
              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: 1153
                Last_IO_Error: Got a packet bigger than 'max_allowed_packet' bytes
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
row in set (0.00 sec)

第一步：先登录数据库，查看 max_allowed_packet 这个参数值

连接数据库服务器，登录 mysql， 执行命令 ： show variables like '%max_allowed_packet%'; 默认是1M

mysql> show variables like '%max_allowed_packet%';
+--------------------+---------+
| Variable_name      | Value   |
+--------------------+---------+
| max_allowed_packet | 1048576 |
+--------------------+---------+
1 row in set (0.00 sec)

第二步：set global max_allowed_packet = 100 *1024*1024;

mysql> set global max_allowed_packet = 100 *1024*1024;
Query OK, 0 rows affected (0.00 sec)

#接着查看没有变过来，需要退出重新登陆，查看的是原始值（缓存）
mysql> show variables like '%max_allowed_packet%';
+--------------------+---------+
| Variable_name      | Value   |
+--------------------+---------+
| max_allowed_packet | 1048576 |
+--------------------+---------+
1 row in set (0.00 sec)

第三步：重新登陆确认是否生效：

mysql> show variables like '%max_allowed_packet%';
+--------------------+-----------+
| Variable_name      | Value     |
+--------------------+-----------+
| max_allowed_packet | 104857600 |
+--------------------+-----------+
1 row in set (0.00 sec)

第四步：重启slave

mysql> stop slave;
Query OK, 0 rows affected (0.02 sec)

mysql> start slave;
Query OK, 0 rows affected (0.00 sec)

mysql> show slave statusG;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.90.90
                  Master_User: rsync
                  Master_Port: 3311
                Connect_Retry: 60
              Master_Log_File: mysql-bin.001891
          Read_Master_Log_Pos: 948459439
               Relay_Log_File: mysql-relay-bin.003780
                Relay_Log_Pos: 897185056
        Relay_Master_Log_File: mysql-bin.001891
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              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: 897184910
              Relay_Log_Space: 948459887
              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: 1356
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: 1
1 row in set (0.00 sec)

第五步：修改配置文件  

修改配置文件--Linux在 Linux 中，MySQL 对应的配置文件是 my.cnf , 我们在Linux终端输入如下命令 ：

[root@192-168-90-90 ~]# mysql --help | grep my.cnf
                      order of preference, my.cnf, $MYSQL_TCP_PORT,
/etc/mysql/my.cnf /etc/my.cnf ~/.my.cnf 
#如果在启动时没有指定my.cnf 就优先列表，先找到的配置文件生效

[root@192-168-90-90 data3311]# more my.cnf 
[mysqld]
basedir=/usr/local/mysql5.5
datadir=/home/mysql5.5/data3311
tmpdir=/home/mysql5.5/data3311/temp
port = 3311
server_id = 3311
socket=/home/mysql5.5/data3311/mysql3311.sock
character_set_server='utf8'
max_allowed_packet=100M