Mysql数据库的压力

问题描述

使用django+celery时, 运行长时间的任务, 一开始操作一次数据库, 20个小时后再次操作数据库.

过了20多个小时, 再次操作数据库时报错.

raised unexpected: OperationalError(2006, ‘MySQL server has gone away‘)
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 374, in get
    num = len(clone)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 232, in __len__
    self._fetch_all()
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1118, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 53, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py", line 894, in execute_sql
    raise original_exception
OperationalError: (2006, ‘MySQL server has gone away‘)

原因

连接超时

我出现问题就是这个原因. 
进入mysql,执行下面的命令:

mysql> show global variables like ‘%timeout‘;

+----------------------------+----------+
| Variable_name              | Value    |
+----------------------------+----------+
| connect_timeout            | 10       |
| delayed_insert_timeout     | 300      |
| innodb_lock_wait_timeout   | 50       |
| innodb_rollback_on_timeout | OFF      |
| interactive_timeout        | 28800    |
| lock_wait_timeout          | 31536000 |
| net_read_timeout           | 30       |
| net_write_timeout          | 60       |
| slave_net_timeout          | 3600     |
| wait_timeout               | 28800    |
+----------------------------+----------+

wait_timeout 是28800秒，即mysql链接在无操作28800秒后被自动关闭

解决方法

立即生效

执行下面的sql命令

mysql> set global wait_timeout=60*60*30;

• 1

该命令是将wait_timeout设置为30小时. 
用这种方法,修改完立即生效. 如果重启mysql, 又恢复原来的28800秒.

永久生效

该方法修改完之后, 需要重启mysql才能生效. 
编辑mysql配置文件my.cnf,添加或修改为下面这条命令. 
(我的mysql配置文件路径: /etc/mysql/my.cnf )

wait_timeout = 108000

• 1

其他原因

还有一些其他原因, 简单描述一下 
1: mysql服务关闭 
2: 数据包 过大 
解决方法: 修改 max_allowed_packet 的值, 方法同上.