Java 休眠“明显死锁！！！为未分配的挂起任务创建紧急线程！”
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原文地址: http://stackoverflow.com/questions/29158560/
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StackOverFlow
Hibernate "APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!"
提问by Casey Jordan
I recently got the following messages in our logs followed by a JVM crash (Due to OOME). I am not sure what to make of this and would really appreciate any guidance.
我最近在我们的日志中收到以下消息，然后是 JVM 崩溃（由于 OOME）。我不知道该怎么做，非常感谢任何指导。
2015-03-19 21:15:02,457 [Timer-0] WARN (ThreadPoolAsynchronousRunner.java [run]:608) - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@6824f21c -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
2015-03-19 21:26:29,543 [Timer-0] WARN (ThreadPoolAsynchronousRunner.java [run]:624) - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@6824f21c -- APPARENT DEADLOCK!!! Complete Status:
Managed Threads: 3
Active Threads: 3
Active Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@15da1b6b (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@b35b08a (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@51cfdd17 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
Pending Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@19397937
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@5c7d3838
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7aea62dd
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@55622ff2
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@74004a8
Pool thread stack traces:
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:560)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
java.net.SocketOutputStream.socketWrite0(Native Method)
java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109)
java.net.SocketOutputStream.write(SocketOutputStream.java:153)
java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140)
com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3227)
com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1917)
com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536)
com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1751)
com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3425)
com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2196)
com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)
com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
sun.reflect.GeneratedConstructorAccessor306.newInstance(Unknown Source)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
java.lang.reflect.Constructor.newInstance(Constructor.java:408)
com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)
com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282)
com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
com.mchange.v2.resourcepool.BasicResourcePool.access0(BasicResourcePool.java:32)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:560)
2015-03-19 21:56:59,137 [Timer-0] WARN (ThreadPoolAsynchronousRunner.java [run]:608) - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@6824f21c -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
2015-03-19 21:56:59,143 [eXistThread-18676] ERROR (XQueryServlet.java [process]:566) - Java heap space
java.lang.OutOfMemoryError: Java heap space
at org.exist.storage.btree.BTree$BTreeNode.read(BTree.java:1269)
at org.exist.storage.btree.BTree$BTreeNode.access(BTree.java:1239)
at org.exist.storage.btree.BTree.getBTreeNode(BTree.java:460)
at org.exist.storage.btree.BTree.scanSequential(BTree.java:413)
at org.exist.storage.btree.BTree$BTreeNode.scanNextPage(BTree.java:2039)
at org.exist.storage.btree.BTree$BTreeNode.query(BTree.java:1835)
at org.exist.storage.btree.BTree$BTreeNode.query(BTree.java:1759)
at org.exist.storage.btree.BTree$BTreeNode.query(BTree.java:1759)
at org.exist.storage.btree.BTree$BTreeNode.query(BTree.java:1759)
at org.exist.storage.btree.BTree$BTreeNode.access(BTree.java:1734)
at org.exist.storage.btree.BTree.query(BTree.java:379)
at org.exist.storage.structural.NativeStructuralIndexWorker.scanByType(NativeStructuralIndexWorker.java:259)
at org.exist.dom.VirtualNodeSet.getNodesFromIndex(VirtualNodeSet.java:457)
at org.exist.dom.VirtualNodeSet.realize(VirtualNodeSet.java:585)
at org.exist.dom.VirtualNodeSet.iterator(VirtualNodeSet.java:860)
at org.exist.dom.AbstractNodeSet.iterator(AbstractNodeSet.java:1)
at org.exist.storage.structural.NativeStructuralIndexWorker.findDescendantsByTagName(NativeStructuralIndexWorker.java:162)
at org.exist.xquery.LocationStep.getAttributes(LocationStep.java:645)
at org.exist.xquery.LocationStep.eval(LocationStep.java:434)
at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:71)
at org.exist.xquery.PathExpr.eval(PathExpr.java:264)
at org.exist.xquery.Predicate.selectByNodeSet(Predicate.java:446)
at org.exist.xquery.Predicate.evalPredicate(Predicate.java:326)
at org.exist.xquery.LocationStep.processPredicate(LocationStep.java:251)
at org.exist.xquery.LocationStep.applyPredicate(LocationStep.java:238)
at org.exist.xquery.LocationStep.eval(LocationStep.java:462)
at org.exist.xquery.AbstractExpression.eval(AbstractExpression.java:71)
at org.exist.xquery.PathExpr.eval(PathExpr.java:264)
at org.exist.xquery.LetExpr.eval(LetExpr.java:142)
at org.exist.xquery.LetExpr.eval(LetExpr.java:187)
at org.exist.xquery.LetExpr.eval(LetExpr.java:187)
at org.exist.xquery.BindingExpression.eval(BindingExpression.java:164)
2015-03-19 21:56:59,147 [Timer-0] WARN (ThreadPoolAsynchronousRunner.java [run]:624) - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@6824f21c -- APPARENT DEADLOCK!!! Complete Status:
Managed Threads: 3
Active Threads: 3
Active Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@79180a12 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@243c6d0c (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@50191373 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
Pending Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@3a9d08ca
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@3ecdd11
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@44ff846d
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@5ce5850a
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@eec1d04
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@6b8d4d9d
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@53e9706d
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@23d472cf
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@4dbe4f8c
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@4c5e0203
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@54ac79fd
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@546e2bad
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@6b13cc83
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@57e185f8
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@60357d68
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@45231180
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@3021aa73
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@6bb437ca
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@2021c9e9
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@7d53637c
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@409c2c97
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@adc5929
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@241ca71a
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@42b26866
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@636b1c33
com.mchange.v2.resourcepool.BasicResourcePoolDestroyResourceTask@b160466
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4af34669
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1b53e609
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@2062ebd4
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1b6cfe8a
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4b7c2380
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4f9be748
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@78108924
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@474b002
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@2ebee32f
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@3e0fe017
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@42aa175b
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@637f5bac
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@3a017b77
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7b4f2b78
Pool thread stack traces:
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
java.lang.reflect.Constructor.newInstance(Constructor.java:408)
com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
com.mysql.jdbc.ResultSetImpl.getInstance(ResultSetImpl.java:370)
com.mysql.jdbc.MysqlIO.buildResultSetWithRows(MysqlIO.java:2532)
com.mysql.jdbc.MysqlIO.getResultSet(MysqlIO.java:477)
com.mysql.jdbc.MysqlIO.readResultsForQueryOrUpdate(MysqlIO.java:2510)
com.mysql.jdbc.MysqlIO.readAllResults(MysqlIO.java:1746)
com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2135)
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536)
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2465)
com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1383)
com.mysql.jdbc.DatabaseMetaData.forEach(DatabaseMetaData.java:4826)
com.mysql.jdbc.IterateBlock.doForAll(IterateBlock.java:50)
com.mysql.jdbc.DatabaseMetaData.getTables(DatabaseMetaData.java:4804)
com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnectionNoQuery(DefaultConnectionTester.java:185)
com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnection(DefaultConnectionTester.java:62)
com.mchange.v2.c3p0.AbstractConnectionTester.activeCheckConnection(AbstractConnectionTester.java:67)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:310)
com.mchange.v2.resourcepool.BasicResourcePool$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]
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2596)
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2465)
com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1383)
com.mysql.jdbc.DatabaseMetaData.forEach(DatabaseMetaData.java:4826)
com.mysql.jdbc.IterateBlock.doForAll(IterateBlock.java:50)
com.mysql.jdbc.DatabaseMetaData.getTables(DatabaseMetaData.java:4804)
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.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.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$PoolThread-#0,5,main]
java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1012)
java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006)
com.newrelic.agent.TransactionService.addTransaction(TransactionService.java:142)
com.newrelic.agent.Transaction.getTransaction(Transaction.java:1104)
com.newrelic.agent.Transaction.getTransaction(Transaction.java:1087)
com.newrelic.agent.TracerService$TracerServiceImpl.getTracer(TracerService.java:136)
com.newrelic.agent.TracerService.getTracer(TracerService.java:41)
com.newrelic.agent.instrumentation.InvocationPoint.invoke(InvocationPoint.java:55)
com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java)
com.mysql.jdbc.DatabaseMetaData.forEach(DatabaseMetaData.java:4826)
com.mysql.jdbc.IterateBlock.doForAll(IterateBlock.java:50)
com.mysql.jdbc.DatabaseMetaData.getTables(DatabaseMetaData.java:4804)
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.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:310)
com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run(BasicResourcePool.java:1999)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
We are using hiberanate and c3p0 with the following c3p0 configuration:
我们使用具有以下 c3p0 配置的 hiberanate 和 c3p0：
We are using the following maven artifacts for hibernate and c3p0:
我们将以下 maven 工件用于 hibernate 和 c3p0：
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.3.6.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-c3p0</artifactId>
<version>4.3.6.Final</version>
</dependency>
with the following c3p0 configuration:
使用以下 c3p0 配置：
configuration = new Configuration().setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5InnoDBDialect")
.setProperty("hibernate.connection.provider_class", "org.hibernate.connection.C3P0ConnectionProvider")
.setProperty("hibernate.c3p0.idle_test_period", "1000")
.setProperty("hibernate.c3p0.min_size", "20")
.setProperty("hibernate.c3p0.max_size", "50")
.setProperty("hibernate.c3p0.timeout", "1800")
.setProperty("hibernate.c3p0.max_statements", "50")
The server is under very light load ~5 queries a second. (Java 8)
服务器的负载非常轻，每秒约 5 次查询。(Java 8)
采纳答案by Steve Waldman
So, directly the issue is that the Connection pool was trying to acquire new Connections, but the tasks attempting to acquire those tasks froze for a long period of time, so long that c3p0 decided the tasks must be deadlocked and then discarded and replaced the Thread pool. Later, the Thread pool was hung on idle connection test tasks.
所以，直接的问题是连接池试图获取新的连接，但是尝试获取这些任务的任务冻结了很长时间，以至于 c3p0 决定任务必须死锁，然后丢弃并替换线程水池。后来线程池挂在空闲连接测试任务上。
Normally, "hung" tasks tend to look like the second Thread underneath the first "Pool thread stack traces:" label above: performing network IO that fails to complete. Your circumstances are odd in that two of the three threads are not stuck in IO. They have barely begun to do anything, yet they aren't live. Then you experience an OutOfMemoryError, and you get another APPARENT DEADLOCK on idle connection test tasks that also look like they mostly should be live.
通常，“挂起”任务往往看起来像上面第一个“池线程堆栈跟踪：”标签下的第二个线程：执行未能完成的网络 IO。您的情况很奇怪，因为三个线程中的两个没有卡在 IO 中。他们几乎没有开始做任何事情，但他们还没有活着。然后您会遇到 OutOfMemoryError，并且您在空闲连接测试任务上遇到另一个明显死锁，这些任务看起来也应该是实时的。
Maybe your application is very close to some kind of resource limits that are causing things to run very sluggishly? Straightforwardly, you might increase the amount of memory available to this application (or modify it to have a lower memory footprint). You experience an OOME the second time the Thread pool tries to flush and recreate hung Threads, not directly provoked by that, but quite possibly caused by the growing Thread footprint. (In your logs, are there lots of these APPARENT DEADLOCKs previously? If you force a JVM Thread dump, do you see lots of com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThreadinstances around, still hung on old, not completing tasks?
也许您的应用程序非常接近某种导致运行非常缓慢的资源限制？简单地说，您可以增加此应用程序可用的内存量（或修改它以减少内存占用）。线程池第二次尝试刷新和重新创建挂起的线程时，您会遇到 OOME，这不是直接引起的，但很可能是由不断增长的线程占用空间引起的。（在您的日志中，以前是否有很多这些明显的死锁？如果您强制执行 JVM 线程转储，您是否看到com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread周围有很多实例，仍然挂在旧的，未完成任务上？
Some general comments: If your load is no more than 5-ish simultaneous queries, why such a heavy pool? why not min_size5-ish, max 10-ish? Your max_statements setting is way too small for the number of Connections you permit in the pool. I'd omit this entirely until you get things working smoothly. Then, to get a bit better performance, you might set the more-straightforward-to-reason-about maxStatementsPerConnectionparameter if you want.
一些一般性评论：如果您的负载不超过 5 个同时查询，为什么会有这么重的池？为什么不是min_size5-ish，最多 10-ish？您的 max_statements 设置对于您在池中允许的连接数来说太小了。在你让事情顺利进行之前，我会完全忽略这一点。然后，为了获得更好的性能，您可以根据需要设置 more-straightforward-to-reason-aboutmaxStatementsPerConnection参数。
Mostly you need to keep your application's footprint (memory? Threads?) well below the resources alotted to it, either by increasing resources, reducing its footprint, or fixing any issue that might exist that cause its resource footprint to increase into limits. I'd start by making the pool smaller, the available memory larger, and configuring the pool to be much smaller.
大多数情况下，您需要保持应用程序的占用空间（内存？线程？）远低于分配给它的资源，方法是增加资源、减少其占用空间或修复可能存在的导致其资源占用增加到限制的任何问题。我首先使池更小，可用内存更大，并将池配置得更小。
回答by linuxatico
I stumbled into the same exception and the reason was a wrong password of the db user...
我偶然发现了同样的异常，原因是数据库用户的密码错误......
c3p0 you're a funny guy
c3p0 你是个有趣的人
回答by Gep
Authentication issue for me too. I just added the domain part to the database server name and it all worked. Very misleading error.
我的身份验证问题也是如此。我只是将域部分添加到数据库服务器名称中，并且一切正常。非常误导性的错误。
