java - 表观死锁为未分配的挂起任务创建紧急线程

Question

我正在使用带有 mybatis 的 mysql，我在我们的实时服务器上遇到了这个错误

com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@6538f8f2 
-- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!

我不明白为什么会出现这个错误是因为我的 C3P0 设置？我的C3P0设置是这样的

----开始更新-----

下面是我的 spring-servlet.xml 配置

我更新了数据源bean为

<bean id="datasource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close" p:driverClass="com.mysql.jdbc.Driver"
p:jdbcUrl="jdbc:mysql://localhost/jdb" p:user="root" p:password="root" 
p:acquireIncrement="10" 
p:idleConnectionTestPeriod="60"
p:maxPoolSize="100" 
    p:maxStatements="0" 
    p:minPoolSize="10" 
    p:initialPoolSize="10"
    p:statementCacheNumDeferredCloseThreads="1" />
   <!-- Declare a transaction manager -->

<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager"
p:dataSource-ref="datasource" />


<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="datasource" />
</bean>

<!-- scan for mappers and will automatically scan the whole classpath for xmls -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    <property name="basePackage" value="com.mycom.myproject.db.mybatis.dao" />
</bean>  

在我的 Dao 类中，我调用映射器方法，例如

 myDao.updateRecords()

这是我的服务类方法

@Override
public List<UserDetailedBean> selectAllUsersDetail(long groupId, List<Long> ids) {

    List<UserDetailedBean> usersDetailList = null;

    try {
        usersDetailList = userDao.selectAllUsersDetail(groupId, ids);
    } catch (Exception e) {
        e.printStackTrace();
    }

    return usersDetailList;
}

在 Dao 类中，我只注入(inject)映射器。

@Resource
private UserMapper userMapper;

@Override
public List<UserDetailedBean> selectAllUsersDetail(long groupId, List<Long> ids) {
    return userMapper.selectAllUsersDetail(groupId,ids);
}

---结束更新-----

如果需要任何其他信息，请告诉我。

这是完整的堆栈跟踪

[ WARN] 2013-01-08 20:13:39       com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@70497e11 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
[ WARN] 2013-01-08 20:13:39 com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@70497e11 -- APPARENT DEADLOCK!!! Complete Status: 
 Managed Threads: 3
 Active Threads: 3
 Active Tasks: 
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@2e81b8c5 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@4689a55d (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@76c7a0d8 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
 Pending Tasks: 
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@2c1101d4
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@108f1be6
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@2370a188
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@377cf9e5
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@6dfa45d8
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@49ffa050
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@2d760a24
    Pool thread stack traces:
 Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
     java.net.SocketInputStream.socketRead0(Native Method)
     java.net.SocketInputStream.read(SocketInputStream.java:150)
     java.net.SocketInputStream.read(SocketInputStream.java:121)
     com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
     com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
     com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
     com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2549)
     com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3002)
     com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2991)
     com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3532)
     com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2002)
     com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2163)
     com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2618)
     com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
     com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1557)
     com.mysql.jdbc.DatabaseMetaData$9.forEach(DatabaseMetaData.java:4984)
     com.mysql.jdbc.IterateBlock.doForAll(IterateBlock.java:51)
     com.mysql.jdbc.DatabaseMetaData.getTables(DatabaseMetaData.java:4962)
     com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnectionNoQuery(DefaultConnectionTester.java:185)
     com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnection(DefaultConnectionTester.java:62)
     com.mchange.v2.c3p0.AbstractConnectionTester.activeCheckConnection(AbstractConnectionTester.java:67)
     com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
     com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:310)
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run(BasicResourcePool.java:1999)
     com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
 Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
     java.net.SocketInputStream.socketRead0(Native Method)
     java.net.SocketInputStream.read(SocketInputStream.java:150)
     java.net.SocketInputStream.read(SocketInputStream.java:121)
     com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
     com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
     com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
     com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2549)
     com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3002)
     com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2991)
     com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3532)
     com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2002)
     com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2163)
     com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2618)
     com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
     com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1557)
     com.mysql.jdbc.DatabaseMetaData$9.forEach(DatabaseMetaData.java:4984)
     com.mysql.jdbc.IterateBlock.doForAll(IterateBlock.java:51)
     com.mysql.jdbc.DatabaseMetaData.getTables(DatabaseMetaData.java:4962)
     com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnectionNoQuery(DefaultConnectionTester.java:185)
     com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnection(DefaultConnectionTester.java:62)
     com.mchange.v2.c3p0.AbstractConnectionTester.activeCheckConnection(AbstractConnectionTester.java:67)
     com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
     com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:310)
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run(BasicResourcePool.java:1999)
     com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
 Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
     java.net.SocketInputStream.socketRead0(Native Method)
     java.net.SocketInputStream.read(SocketInputStream.java:150)
     java.net.SocketInputStream.read(SocketInputStream.java:121)
     com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
     com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
     com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
     com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2549)
     com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3002)
     com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2991)
     com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3532)
     com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2002)
     com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2163)
     com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2618)
     com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
     com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1557)
     com.mysql.jdbc.DatabaseMetaData$9.forEach(DatabaseMetaData.java:4984)
     com.mysql.jdbc.IterateBlock.doForAll(IterateBlock.java:51)
     com.mysql.jdbc.DatabaseMetaData.getTables(DatabaseMetaData.java:4962)
     com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnectionNoQuery(DefaultConnectionTester.java:185)
     com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnection(DefaultConnectionTester.java:62)
     com.mchange.v2.c3p0.AbstractConnectionTester.activeCheckConnection(AbstractConnectionTester.java:67)
     com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
     com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:310)
     com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run(BasicResourcePool.java:1999)
     com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

---更新----

当我将 p:statementCacheNumDeferredCloseThreads="1"添加到 datasouce bean 时，我收到以下错误

     Error creating bean with name 'sqlSessionFactory' defined in ServletContext resource [/WEB-INF/spring-servlet.xml]: 
     Cannot resolve reference to bean 'datasource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'datasource' defined in ServletContext resource [/WEB-INF/spring-servlet.xml]: 
   Error setting property values; nested exception is org.springframework.beans.NotWritablePropertyException: Invalid property 'statementCacheNumDeferredCloseThreads' of bean class [com.mchange.v2.c3p0.ComboPooledDataSource]: 
   Bean property 'statementCacheNumDeferredCloseThreads' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?

Answer 1

来自 http://www.mchange.com/projects/c3p0/#other_ds_configuration

numHelperThreads 和 ma​​xAdministrativeTaskTime 有助于配置 DataSource 线程池的行为。默认情况下，每个 DataSource 只有三个关联的帮助线程。如果性能似乎在重负载下拖累，或者如果您通过 JMX 或直接检查 PooledDataSource 观察到“待处理任务”的数量通常大于零，请尝试增加 numHelperThreads。 ma​​xAdministrativeTaskTime 对于遇到无限期挂起的任务和“APPARENT DEADLOCK”消息的用户可能很有用。 (更多信息请参见附录 A。)

ma​​xAdministrativeTaskTime 默认值:0 在 c3p0 的线程池将尝试中断一个明显挂起的任务之前的几秒钟。很少有用。 c3p0 的许多功能不是由客户端线程执行的，而是由内部线程池异步执行的。 c3p0 的异步性直接增强了客户端性能，并通过确保在非锁持有线程中执行慢速 jdbc 操作来最小化持有关键锁的时间长度。但是，如果其中一些任务“挂起”，即它们在很长一段时间内既没有成功也没有失败并出现异常，c3p0 的线程池可能会耗尽并且管理任务会被备份。如果任务只是很慢，解决问题的最佳方法是通过 numHelperThreads 增加线程数。但是如果任务有时会无限期挂起，您可以使用此参数在任务超过设定的时间限制时强制调用任务线程的 interrupt() 方法。 [c3p0 最终将通过发出“明显的死锁”信号(您将在日志中将其视为警告)、替换线程池任务线程和中断()原始线程来从挂起的任务中恢复。但是让池进入表观死锁然后恢复意味着在某些时期内，c3p0 的性能会受到损害。因此，如果您看到这些消息，增加 numHelperThreads 并设置 maxAdministrativeTaskTime 可能会有所帮助。 maxAdministrativeTaskTime 应该足够大，以使任何从数据库获取连接、测试连接或两次破坏连接的合理尝试都可以预期在设定的时间内成功或失败。零(默认)意味着任务从不中断，这是大多数情况下最好和最安全的策略。如果任务很慢，请分配更多线程。如果任务永远挂起，请尝试找出原因，同时设置 maxAdministrativeTaskTime 可能会有所帮助。

The default is 3 for numHelperThreads , increase this to 8-10 

setting maxAdministrativeTaskTime will help