myBatis连接MySQL报异常:No operations allowed after connection closed.Connection was i
2017-06-06 11:31
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连接池报错
Mysql服务器默认的“wait_timeout”是8小时,也就是说一个connection空闲超过8个小时,Mysql将自动断开该connection。这就是问题的所在,在C3P0 pools中的connections如果空闲超过8小时,Mysql将其断开,而C3P0并不知道该connection已经失效,如果这时有Client请求connection,C3P0将该失效的Connection提供给Client,将会造成上面的异常。
增加 wait_timeout 的时间。
减少 Connection pools 中 connection 的 lifetime。
测试 Connection pools 中 connection 的有效性。
当然最好的办法是同时综合使用上述3种方法,下面就 DBCP、C3P0 和 simple jdbc dataSource 分别做一说明,假设 wait_timeout 为默认的8小时
文件,在 [mysqld] 后面添加上:
?
其中 n 为服务器关闭交互式连接前等待活动的秒数。可是就部署而言每次修改 my.ini 比较麻烦,而且 n 等于多少才是合适的值呢? 所以并不推荐这个解决办法。)
-------------------------相关-------------------------
1. 即使在创建Mysql时url中加入了autoReconnect=true参数,一但这个连接两次访问数据库的时间超出了服务器端wait_timeout的时间限制,还是会CommunicationsException: The last packet successfully
received from the server was xxx milliseconds ago.
2. 服务器端的参数可以用
show global variables like 'wait_timeout';
set global wait_timeout=10;
来进行设置,但是wait_timeout值不应该设的太高.
3. 较好的策略是对处于idle状态的connection定时发送一个sql,来刷新服务器上的时间戳.这可以使用c3p0r的连接池.http://bzhang.iteye.com/blog/321832
4. 对于tomcat的server.xml中使用的连接池,http://tomcat.apache.org/tomcat-6.0-doc/jndi-datasource-examples-howto.html,http://commons.apache.org/dbcp/configuration.html使用DBCP的连接池可以采用
<Resource name="jdbc/test" auth="Container"
type="javax.sql.DataSource" driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/test?characterEncoding=utf-8"
username="root" password="test" maxActive="500" maxIdle="10"
maxWait="-1" timeBetweenEvictionRunsMillis="10000" minEvictableIdleTimeMillis="10000" />
4.1 设置validationQuery,这样每次borrow(默认为开启)时会通过这个sql校验连接的有效性,但是增加了时间.
4.2 设置timeBetweenEvictionRunsMillis="10000" minEvictableIdleTimeMillis="10000" 依赖evictor thread线程来把超时的连接关闭.
4.3 设置testWhileIdle="true" timeBetweenEvictionRunsMillis="10000" validationQuery="select 1" 使得定时去用query检测处于idle状态的连接,也就刷新了服务器端的时间.
5.每次提交的最大packet大小
show global variables like 'max_allowed_packet';
set global max_allowed_packet=1024*1024;
6. SQLyog 中连接参数的设置
6.1 在SQLyog中的设置 set autocommit=0,这样当前连接的自动提交为false,可以控制事务了.
6.2 begin; 事务开始
6.3 select * from test where 1=1 and id =1 for update;这样就把选到的记录行锁上了,再开一个SQLyog,也执行以上相同的操作,就会一直wait在那里.
6.4 commit; 提交
6.5 rollback; 回滚
6.6 set autocommit=0;后应该加上
set transaction isolation level read committed;
这样其它客户端就能看到commit的数据,
疑问:
如果不设置set transaction isolation level read committed;如果两个客户端都select 相同的数据,一个客户端修改然后提交,另一个客户端不提交当前事务的前提下,去执行select ,取不到另一客户端提交的数据,不知道SQLyog默认的事务级别是什么样的.
7. SQLyog中查看mysql的状态,show global variables like '%lock%'; 是个好方法.对于事务锁(例如for update)报Lock wait timeout exceeded ,只能通过修改my.ini文件innodb_lock_wait_timeout = 100;才能生效.
8. linux下修改用户密码 mysqladmin -u root password "new_pass"
myBatis连接MySQL报异常:No operations allowed after connection closed.Connection was implicitly closed
异常信息
?原因分析
查看了Mysql的文档,以及Connector/J的文档以及在线说明发现,出现这种异常的原因是:Mysql服务器默认的“wait_timeout”是8小时,也就是说一个connection空闲超过8个小时,Mysql将自动断开该connection。这就是问题的所在,在C3P0 pools中的connections如果空闲超过8小时,Mysql将其断开,而C3P0并不知道该connection已经失效,如果这时有Client请求connection,C3P0将该失效的Connection提供给Client,将会造成上面的异常。
解决方案
解决的方法有3种:增加 wait_timeout 的时间。
减少 Connection pools 中 connection 的 lifetime。
测试 Connection pools 中 connection 的有效性。
当然最好的办法是同时综合使用上述3种方法,下面就 DBCP、C3P0 和 simple jdbc dataSource 分别做一说明,假设 wait_timeout 为默认的8小时
DBCP 增加以下配置信息:
validationQuery = "select 1" testWhileIdle = "true" //some positive integer timeBetweenEvictionRunsMillis = 3600000 //set to something smaller than 'wait_timeout' minEvictableIdleTimeMillis = 18000000 //if you don't mind a hit for every getConnection(), set to "true" testOnBorrow = "true"
C3P0 增加以下配置信息:
//获取connnection时测试是否有效 testConnectionOnCheckin = true //自动测试的table名称 automaticTestTable=C3P0TestTable //set to something much less than wait_timeout, prevents connections from going stale idleConnectionTestPeriod = 18000 //set to something slightly less than wait_timeout, preventing 'stale' connections from being handed out maxIdleTime = 25000 //if you can take the performance 'hit', set to "true" testConnectionOnCheckout = true
simple jdbc dataSource 增加以下配置信息:
Pool.PingQuery = select 1 Pool.PingEnabled = true Pool.PingConnectionsOlderThan = 0 //对于空闲的连接一个小时检查一次 Pool.PingConnectionsNotUsedFor = 3600000
其他方案(不推荐)
对于 MySQL5 之前的版本,如 Mysql4.x,只需要修改连接池配置中的 URL,添加一个参数:autoReconnect=true(如jdbc:mysql://hostaddress:3306/schemaname?autoReconnect=true),如果是 MySQL5 及以后的版本,则需要修改 my.cnf(或者my.ini)文件,在 [mysqld] 后面添加上:
?
-------------------------相关-------------------------
1. 即使在创建Mysql时url中加入了autoReconnect=true参数,一但这个连接两次访问数据库的时间超出了服务器端wait_timeout的时间限制,还是会CommunicationsException: The last packet successfully
received from the server was xxx milliseconds ago.
2. 服务器端的参数可以用
show global variables like 'wait_timeout';
set global wait_timeout=10;
来进行设置,但是wait_timeout值不应该设的太高.
3. 较好的策略是对处于idle状态的connection定时发送一个sql,来刷新服务器上的时间戳.这可以使用c3p0r的连接池.http://bzhang.iteye.com/blog/321832
4. 对于tomcat的server.xml中使用的连接池,http://tomcat.apache.org/tomcat-6.0-doc/jndi-datasource-examples-howto.html,http://commons.apache.org/dbcp/configuration.html使用DBCP的连接池可以采用
<Resource name="jdbc/test" auth="Container"
type="javax.sql.DataSource" driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/test?characterEncoding=utf-8"
username="root" password="test" maxActive="500" maxIdle="10"
maxWait="-1" timeBetweenEvictionRunsMillis="10000" minEvictableIdleTimeMillis="10000" />
4.1 设置validationQuery,这样每次borrow(默认为开启)时会通过这个sql校验连接的有效性,但是增加了时间.
4.2 设置timeBetweenEvictionRunsMillis="10000" minEvictableIdleTimeMillis="10000" 依赖evictor thread线程来把超时的连接关闭.
4.3 设置testWhileIdle="true" timeBetweenEvictionRunsMillis="10000" validationQuery="select 1" 使得定时去用query检测处于idle状态的连接,也就刷新了服务器端的时间.
5.每次提交的最大packet大小
show global variables like 'max_allowed_packet';
set global max_allowed_packet=1024*1024;
6. SQLyog 中连接参数的设置
6.1 在SQLyog中的设置 set autocommit=0,这样当前连接的自动提交为false,可以控制事务了.
6.2 begin; 事务开始
6.3 select * from test where 1=1 and id =1 for update;这样就把选到的记录行锁上了,再开一个SQLyog,也执行以上相同的操作,就会一直wait在那里.
6.4 commit; 提交
6.5 rollback; 回滚
6.6 set autocommit=0;后应该加上
set transaction isolation level read committed;
这样其它客户端就能看到commit的数据,
疑问:
如果不设置set transaction isolation level read committed;如果两个客户端都select 相同的数据,一个客户端修改然后提交,另一个客户端不提交当前事务的前提下,去执行select ,取不到另一客户端提交的数据,不知道SQLyog默认的事务级别是什么样的.
7. SQLyog中查看mysql的状态,show global variables like '%lock%'; 是个好方法.对于事务锁(例如for update)报Lock wait timeout exceeded ,只能通过修改my.ini文件innodb_lock_wait_timeout = 100;才能生效.
8. linux下修改用户密码 mysqladmin -u root password "new_pass"
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