我们的Java Web应用程序当前遇到随机（以前从未经历过）的块问题，这是由所创建线程的突然激增以及随后Tomcat可以创建的最大线程数的耗尽（默认值= 200）引起的。
最后一次高峰看到在10分钟内创建了120个新线程，将计数从80增加到200，并阻止了应用程序。通常线程数为70-80。
进行线程转储时，所有那些线程都处于WAITING状态，并且似乎所有线程都在等待从c3p0到DBMS的新连接。
这是示例堆栈：
"http-nio-8443-exec-77 Waiting Thread ID: 10016","1"
"java.lang.Object.wait(long)","2"
"com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(long) BasicResourcePool.java:1414","2"
"com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(long) BasicResourcePool.java:606","2"
"com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(long) BasicResourcePool.java:526","2"
"com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse() C3P0PooledConnectionPool.java:755","2"
"com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection() C3P0PooledConnectionPool.java:682","2"
"com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection() AbstractPoolBackedDataSource.java:140","2"
"org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource.getConnection() AbstractRoutingDataSource.java:164","2"
"org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection() DatasourceConnectionProviderImpl.java:139","2"
"org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection() AbstractSessionImpl.java:380","2"
"org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection() LogicalConnectionImpl.java:228","2"
"org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection() LogicalConnectionImpl.java:171","2"
"org.hibernate.internal.SessionImpl.connection() SessionImpl.java:450","2"
"org.springframework.orm.hibernate4.HibernateTransactionManager.doBegin(Object, TransactionDefinition) HibernateTransactionManager.java:450","2"
"org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(TransactionDefinition) AbstractPlatformTransactionManager.java:373","2"
"org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(PlatformTransactionManager, TransactionAttribute, String) TransactionAspectSupport.java:463","2"
"org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(Method, Class, TransactionAspectSupport$InvocationCallback) TransactionAspectSupport.java:276","2"
"org.springframework.transaction.interceptor.TransactionInterceptor.invoke(MethodInvocation) TransactionInterceptor.java:96","2"
"org.springframework.aop.framework.ReflectiveMethodInvocation.proceed() ReflectiveMethodInvocation.java:179","2"
"org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(MethodInvocation) ExposeInvocationInterceptor.java:92","2"
"org.springframework.aop.framework.ReflectiveMethodInvocation.proceed() ReflectiveMethodInvocation.java:179","2"
"org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(Object, Method, Object[], MethodProxy) CglibAopProxy.java:653","2"
这是此DataSource的c3p0配置：
<property name="maxIdleTime" value="600" />
<property name="maxPoolSize" value="300" />
<property name="maxStatements" value="200" />
<property name="maxStatementsPerConnection" value="10" />
<property name="minPoolSize" value="15" />
<property name="idleConnectionTestPeriod" value="100" />
<property name="acquireIncrement" value="3" />
<property name="numHelperThreads" value="20" />
我目前正在尝试添加一个timout参数来帮助我调试这些情况
<property name="checkoutTimeout" value="30" />
[我读到我应该使用debugUnreturnedConnectionStackTraces和unreturnedConnectionTimeout来调试这些问题，但是我目前不太了解它们，并且害怕在生产中使用它们。
还有其他种类的配置可以尝试帮助我调试问题吗？其他一些超时配置？
Stack：
我试图将有问题的参数checkoutTimeout放到有问题的数据库中：
<property name="checkoutTimeout" value="30" />
此属性将强制所有等待从c3p0检出Connection的线程在30秒后放弃，以防池耗尽，并抛出SqlException。
在将此属性投入生产后也不太一样，我们开始记录这种错误：
Caused by: org.hibernate.exception.GenericJDBCException: Could not open connection
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:235)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:171)
at org.hibernate.internal.SessionImpl.connection(SessionImpl.java:450)
at org.springframework.orm.hibernate4.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:450)
... 119 more
Caused by: java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:118)
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:77)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:687)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:140)
at org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource.getConnection(AbstractRoutingDataSource.java:164)
at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:139)
at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:380)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:228)
... 122 more
Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@14e83e8f -- timeout at awaitAvailable()
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1416)
at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:606)
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:526)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse(C3P0PooledConnectionPool.java:755)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:682)
... 127 more
所以我想这是一个证据，证明输出池已用尽（maxPoolSize为300）。正确吗？
您可以要求您的Sql Server DBA提供有关特定时期绑定到应用程序的渗透次数，执行SQL所花费的时间等一些统计信息。>>