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 status\G;
*************************** . row ***************************
               Slave_IO_State:
                  Master_Host: 192.168.90.190
                  Master_User: rsync
                  Master_Port:
                Connect_Retry:
              Master_Log_File: mysql-bin.
          Read_Master_Log_Pos:
               Relay_Log_File: mysql-relay-bin.
                Relay_Log_Pos:
        Relay_Master_Log_File: mysql-bin.
             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:
                   Last_Error:
                 Skip_Counter:
          Exec_Master_Log_Pos:
              Relay_Log_Space:
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos:
           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:
                Last_IO_Error: Got a packet bigger than 'max_allowed_packet' bytes
               Last_SQL_Errno:
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id:
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 |  |
+--------------------+---------+
 row in set (0.00 sec)

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

mysql> set global max_allowed_packet =  **;
Query OK,  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 |  |
+--------------------+---------+
 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 |  |
+--------------------+-----------+
 row in set (0.00 sec)

第四步：重启slave

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

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

mysql> show slave status\G;
*************************** . row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.90.90
                  Master_User: rsync
                  Master_Port:
                Connect_Retry:
              Master_Log_File: mysql-bin.
          Read_Master_Log_Pos:
               Relay_Log_File: mysql-relay-bin.
                Relay_Log_Pos:
        Relay_Master_Log_File: mysql-bin.
             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:
                   Last_Error:
                 Skip_Counter:
          Exec_Master_Log_Pos:
              Relay_Log_Space:
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos:
           Master_SSL_Allowed: No
           Master_SSL_CA_File:
           Master_SSL_CA_Path:
              Master_SSL_Cert:
            Master_SSL_Cipher:
               Master_SSL_Key:
        Seconds_Behind_Master:
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno:
                Last_IO_Error:
               Last_SQL_Errno:
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id:
 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@--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@--- data3311]# more my.cnf
[mysqld]
basedir=/usr/local/mysql5.
datadir=/home/mysql5./data3311
tmpdir=/home/mysql5./data3311/temp
port =
server_id =
socket=/home/mysql5./data3311/mysql3311.sock
character_set_server='utf8'
max_allowed_packet=100M