mysql client occasionally encounters errors

[yejr]

mysql> show create table t1;
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| TABLE | CREATE TABLE                                                                                                                                                                                                                                                        |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t1    | CREATE TABLE `t1` (
        `id` bigint(11) NOT NULL AUTO_INCREMENT,
        `score` tinyint(4) NOT NULL,
        `grade` tinyint(4) NOT NULL,
        PRIMARY KEY (`id`),
        KEY `ig` (`grade`)
) ENGINE = InnoDB AUTO_INCREMENT = 12 DEFAULT CHARSET = utf8
PARTITION BY KEY(`id`)
PARTITIONS 8 |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> alter table t1 add age tinyint not null;
ERROR 2013 (HY000): Lost connection to MySQL server during query
No connection. Trying to reconnect...
ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 0
ERROR:
Can't connect to the server

mysql> alter table t1 add age tinyint not null;
No connection. Trying to reconnect...
Connection id:    3
Current database: d3

Query OK, 0 rows affected (3.63 sec)

[hustfxj]

how much rows has the Table ? And you can check the params as follows:

cat /proc/sys/net/ipv4/tcp_keepalive_time
cat /proc/sys/net/ipv4/tcp_keepalive_intvl
cat /proc/sys/net/ipv4/tcp_keepalive_probes

Maybe the tcp close the idle connection due to the ddl take long time.