尝试在后台线程中获取缓存的PreparedStatement时发生错误 [英] Error occured while trying to acquire a cached PreparedStatement in a background thread
本文介绍了尝试在后台线程中获取缓存的PreparedStatement时发生错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我们正在使用数据库组件中的m子提供的连接池.当我们施加巨大的负载时，我们将遇到错误.
we are using connection pooling which is provided by mule in Database component. we are getting below error when we applied huge load.
配置的参数为:maxConnection = 100，minConn = 0，autoIncrement = 15 waitMillisec = 10000，并且准备好的语句缓存大小将其保留为默认值(即未配置任何内容). 您能请这个在下面重新爱上吗?
configured parameters as : maxConnection=100, minConn=0, autoIncrement =15 waitMillisec=10000 and prepared statement cache size kept it as default(i.e did not configure anything). Could you please assit on this to reslove below.
{"timestamp":"2016-10-22T09:28:13,611","level":"WARN","thread":"ActiveMQ Session Task-25","loggerName":"com.mchange.v2.c3p0.impl.NewPooledConnection","message":"[c3p0] A PooledConnection that has already signalled a Connection error is still in use!"}
{"timestamp":"2016-10-22T09:28:13,611","level":"WARN","thread":"ActiveMQ Session Task-25","loggerName":"com.mchange.v2.c3p0.impl.NewPooledConnection","message":"[c3p0] Another error has occurred [ java.sql.SQLException: A problem occurred while trying to acquire a cached PreparedStatement in a background thread. ] which will not be reported to listeners!"}
java.sql.SQLException: A problem occurred while trying to acquire a cached PreparedStatement in a background thread.
at com.mchange.v2.c3p0.stmt.GooGooStatementCache.acquireStatement(GooGooStatementCache.java:571) ~[?:?]
at com.mchange.v2.c3p0.stmt.GooGooStatementCache.checkoutStatement(GooGooStatementCache.java:204) ~[?:?]
at com.mchange.v2.c3p0.impl.NewPooledConnection.checkoutStatement(NewPooledConnection.java:321) ~[?:?]
at com.mchange.v2.c3p0.impl.NewProxyConnection.prepareStatement(NewProxyConnection.java:455) ~[?:?]
at org.mule.module.db.internal.domain.connection.DefaultDbConnection.prepareStatement(DefaultDbConnection.java:52) ~[?:?]
at org.mule.module.db.internal.domain.autogeneratedkey.NoAutoGeneratedKeyStrategy.prepareStatement(NoAutoGeneratedKeyStrategy.java:34) ~[?:?]
at org.mule.module.db.internal.domain.statement.QueryStatementFactory.create(QueryStatementFactory.java:59) ~[?:?]
at org.mule.module.db.internal.domain.executor.AbstractSingleQueryExecutor.execute(AbstractSingleQueryExecutor.java:44) ~[?:?]
at org.mule.module.db.internal.processor.UpdateMessageProcessor.doExecuteQuery(UpdateMessageProcessor.java:59) ~[?:?]
at org.mule.module.db.internal.processor.AbstractSingleQueryDbMessageProcessor.executeQuery(AbstractSingleQueryDbMessageProcessor.java:42) ~[?:?]
at org.mule.module.db.internal.processor.AbstractDbMessageProcessor.process(AbstractDbMessageProcessor.java:66) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:88) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:80) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:50) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.access$001(InterceptingChainLifecycleWrapper.java:22) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper$1.process(InterceptingChainLifecycleWrapper.java:66) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:61) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:88) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:80) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:98) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:98) ~[?:?]
at org.mule.construct.DynamicPipelineMessageProcessor.process(DynamicPipelineMessageProcessor.java:55) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:88) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:80) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:98) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:98) ~[?:?]
at org.mule.interceptor.AbstractEnvelopeInterceptor.processBlocking(AbstractEnvelopeInterceptor.java:58) ~[?:?]
at org.mule.processor.AbstractRequestResponseMessageProcessor.process(AbstractRequestResponseMessageProcessor.java:47) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:98) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:98) ~[?:?]
at org.mule.processor.AbstractFilteringMessageProcessor.process(AbstractFilteringMessageProcessor.java:41) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:98) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:98) ~[?:?]
at org.mule.processor.AbstractRequestResponseMessageProcessor.processBlocking(AbstractRequestResponseMessageProcessor.java:56) ~[?:?]
at org.mule.processor.AbstractRequestResponseMessageProcessor.process(AbstractRequestResponseMessageProcessor.java:47) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.executeNext(BlockingProcessorExecutor.java:88) ~[?:?]
at org.mule.processor.BlockingProcessorExecutor.execute(BlockingProcessorExecutor.java:59) ~[?:?]
at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:80) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:50) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.access$001(InterceptingChainLifecycleWrapper.java:22) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper$1.process(InterceptingChainLifecycleWrapper.java:66) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:61) ~[?:?]
at org.mule.construct.AbstractPipeline$3.process(AbstractPipeline.java:231) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.chain.SimpleMessageProcessorChain.doProcess(SimpleMessageProcessorChain.java:43) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:50) ~[?:?]
at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:76) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.access$001(InterceptingChainLifecycleWrapper.java:22) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper$1.process(InterceptingChainLifecycleWrapper.java:66) ~[?:?]
at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:24) ~[?:?]
at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:107) ~[?:?]
at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:44) ~[?:?]
at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:61) ~[?:?]
at org.mule.transport.AbstractMessageReceiver.routeEvent(AbstractMessageReceiver.java:511) ~[?:?]
at org.mule.transport.AbstractMessageReceiver.routeMessage(AbstractMessageReceiver.java:226) ~[?:?]
at org.mule.transport.AbstractMessageReceiver.routeMessage(AbstractMessageReceiver.java:208) ~[?:?]
at org.mule.transport.AbstractReceiverWorker$1$1.process(AbstractReceiverWorker.java:145) ~[?:?]
at org.mule.transport.AbstractReceiverWorker$1$1.process(AbstractReceiverWorker.java:113) ~[?:?]
at org.mule.execution.ExecuteCallbackInterceptor.execute(ExecuteCallbackInterceptor.java:16) ~[?:?]
at org.mule.execution.CommitTransactionInterceptor.execute(CommitTransactionInterceptor.java:35) ~[?:?]
at org.mule.execution.CommitTransactionInterceptor.execute(CommitTransactionInterceptor.java:22) ~[?:?]
at org.mule.execution.HandleExceptionInterceptor.execute(HandleExceptionInterceptor.java:30) ~[?:?]
at org.mule.execution.HandleExceptionInterceptor.execute(HandleExceptionInterceptor.java:14) ~[?:?]
at org.mule.execution.BeginAndResolveTransactionInterceptor.execute(BeginAndResolveTransactionInterceptor.java:67) ~[?:?]
at org.mule.execution.ResolvePreviousTransactionInterceptor.execute(ResolvePreviousTransactionInterceptor.java:44) ~[?:?]
at org.mule.execution.SuspendXaTransactionInterceptor.execute(SuspendXaTransactionInterceptor.java:50) ~[?:?]
at org.mule.execution.ValidateTransactionalStateInterceptor.execute(ValidateTransactionalStateInterceptor.java:40) ~[?:?]
at org.mule.execution.IsolateCurrentTransactionInterceptor.execute(IsolateCurrentTransactionInterceptor.java:41) ~[?:?]
at org.mule.execution.ExternalTransactionInterceptor.execute(ExternalTransactionInterceptor.java:48) ~[?:?]
at org.mule.execution.RethrowExceptionInterceptor.execute(RethrowExceptionInterceptor.java:28) ~[?:?]
at org.mule.execution.RethrowExceptionInterceptor.execute(RethrowExceptionInterceptor.java:13) ~[?:?]
at org.mule.execution.TransactionalErrorHandlingExecutionTemplate.execute(TransactionalErrorHandlingExecutionTemplate.java:110) ~[?:?]
at org.mule.execution.TransactionalErrorHandlingExecutionTemplate.execute(TransactionalErrorHandlingExecutionTemplate.java:30) ~[?:?]
at org.mule.transport.AbstractReceiverWorker$1.process(AbstractReceiverWorker.java:112) ~[?:?]
at org.mule.transport.AbstractReceiverWorker$1.process(AbstractReceiverWorker.java:96) ~[?:?]
at org.mule.execution.ExecuteCallbackInterceptor.execute(ExecuteCallbackInterceptor.java:16) ~[?:?]
at org.mule.execution.BeginAndResolveTransactionInterceptor.execute(BeginAndResolveTransactionInterceptor.java:67) ~[?:?]
at org.mule.execution.ResolvePreviousTransactionInterceptor.execute(ResolvePreviousTransactionInterceptor.java:44) ~[?:?]
at org.mule.execution.SuspendXaTransactionInterceptor.execute(SuspendXaTransactionInterceptor.java:50) ~[?:?]
at org.mule.execution.ValidateTransactionalStateInterceptor.execute(ValidateTransactionalStateInterceptor.java:40) ~[?:?]
at org.mule.execution.IsolateCurrentTransactionInterceptor.execute(IsolateCurrentTransactionInterceptor.java:41) ~[?:?]
at org.mule.execution.ExternalTransactionInterceptor.execute(ExternalTransactionInterceptor.java:48) ~[?:?]
at org.mule.execution.TransactionalExecutionTemplate.execute(TransactionalExecutionTemplate.java:65) ~[?:?]
at org.mule.transport.AbstractReceiverWorker.processMessages(AbstractReceiverWorker.java:179) ~[?:?]
at org.mule.transport.jms.MultiConsumerJmsMessageReceiver$SubReceiver.onMessage(MultiConsumerJmsMessageReceiver.java:439) ~[?:?]
at org.apache.activemq.ActiveMQMessageConsumer.dispatch(ActiveMQMessageConsumer.java:1394) ~[?:?]
at org.apache.activemq.ActiveMQSessionExecutor.dispatch(ActiveMQSessionExecutor.java:131) ~[?:?]
at org.apache.activemq.ActiveMQSessionExecutor.iterate(ActiveMQSessionExecutor.java:202) ~[?:?]
at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:133) ~[?:?]
at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:48) ~[?:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [?:1.8.0_73]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [?:1.8.0_73]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_73]
Caused by: com.microsoft.sqlserver.jdbc.SQLServerException: The connection is closed.
at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:170) ~[?:?]
at com.microsoft.sqlserver.jdbc.SQLServerConnection.checkClosed(SQLServerConnection.java:304) ~[?:?]
at com.microsoft.sqlserver.jdbc.SQLServerConnection.prepareStatement(SQLServerConnection.java:1863) ~[?:?]
at com.microsoft.sqlserver.jdbc.SQLServerConnection.prepareStatement(SQLServerConnection.java:1566) ~[?:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_73]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_73]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_73]
at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_73]
at com.mchange.v2.c3p0.stmt.GooGooStatementCache$1StmtAcquireTask.run(GooGooStatementCache.java:546) ~[?:?]
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696) ~[?:?]
推荐答案
确定.
如果使用的是Statement缓存，则在没有足够的Connection可用缓存语句的情况下，c3p0异步获取用于缓存的Statements.在繁重的负载下，如果没有仔细配置，由于服务器拥塞或c3p0线程池拥塞，此异步获取可能会花费很长时间.试图获取对帐单的客户将无限期等待，直到成功获取对帐单或发生异常.
If you are using Statement caching, c3p0 asynchronously acquires Statements for the cache if there is not an appropriate cached Statement already available for the Connection. Under heavy load and without careful configuration, this asynchronous acquire could take a long time due to congestion at the server or congestion of c3p0's thread pool. Clients trying to acquire a Statement wait indefinitely until the Statement is successfully acquired or an Exception has occurred.
从根本原因Exception(向下到堆栈跟踪的底部)中，很明显，虽然发生了可能很长的Statement获取，但是要从中获取Statement的Connection已关闭(或终止) .这就是您需要调试才能真正理解的内容.可能的原因包括:
From the root cause Exception (way down towards the bottom of your stack trace), it's clear that, while the potentially long Statement acquisition was occurring, the Connection from which the Statement was to be acquired was close()ed or died. That's what you need to debug to really understand this. Possible causes include:
- 在这些情况下，负载/网络问题/神秘的小妖精有时会破坏连接，使它们无效并关闭()ed
- DBMS或某些管理监视程序会关闭(或长时间挂起)这些连接，因为打开的连接太多或打开的时间太长. (也许这是死锁检测器的工作.)
- 您的应用程序(不建议使用)在多个线程中使用连接，其中一个调用close()，而另一个仍在对语句的wait()中.然后，该池(出于多种原因)尝试使用close()方法检查签入的Connection，从而导致此错误.
如果是(3)的情况，您应该停止这样做，但是我认为这是最不可能的情况.如果是(1)或(2)，减轻该问题的主要方法是确保Statement的获取速度快，这样在我们等待一个Statement时就不会发生坏事.
If (3) is the case you should stop doing that, but I think that's the least likely scenario. If (1) or (2), the main way you can mitigate the issue is to make sure that Statement acquisition is fast, so that bad things are unlikely happen while we're wait()ing for a Statement.
我首先要看的是c3p0的线程池，该线程池处于您要使应用程序承受的负载条件下.它跟得上吗? (您可以通过JMX或通过调用PooledDataSource方法(例如
The first thing I'd look at is c3p0's Thread pool under the load conditions you are subjecting your application to. Is it keeping up? (You can check this via JMX, or via calls to PooledDataSource methods like getThreadPoolNumTasksPending() Or, the very easiest thing to do would be simply to scale up c3p0 config param numHelperThreads, so it's less likely that tasks like Statement acquisition are backlogged.
另一个可能真正有用的配置更改将是确保您允许足够数量的高速缓存的语句来防止搅动(不断关闭()并重新获取语句高速缓存中的连接).一个非常常见的配置错误是将全局 maxStatements 配置参数设置为太低的值.实现此权利的简单方法是使用 maxStatementsPerConnection ，而不是全局限制，并将其设置为您的应用程序经常使用的PreparedStatements的数量.
Another configuration change that could really help would be to ensure that you are allowing a sufficient number of cached Statements to prevent churning (constantly close()ing and reacquiring Connections in the Statement cache). A very frequent configuration mistake is to set the global maxStatements config param to a too low value. The easy way to get this right is to use maxStatementsPerConnection, rather than a global limit, and set this to approximately the number of PreparedStatements frequently used by your application.
要真正了解正在发生的事情，您需要查看正在积压什么类型的任务.使用 PooledDataSource.sampleThreadPoolStatus()，再次直接在代码中或通过JMX.
To really understand what's going on, you'll want to see what sort of tasks are getting backlogged. Use PooledDataSource.sampleThreadPoolStatus(), again directly in code or via JMX.
更新:在原始帖子中，您声明准备好的语句缓存大小将其保留为默认值".这可能是一个默认的m子，但是c3p0的默认值是根本不使用语句缓存，即maxStatements=0和maxStatementsPerConnection=0.您的配置可能与您想像的不一样.禁用语句缓存可能是解决此问题的一种非常简单的方法.
Update: In the original post, you state "prepared statement cache size kept it as default". That may be a mule default, but c3p0's default is not to use Statement caching at all, maxStatements=0 and maxStatementsPerConnection=0. Your configuration may not be what you think it is. Disabling Statement caching might be a very easy way to remedy this issue.
这篇关于尝试在后台线程中获取缓存的PreparedStatement时发生错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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