項目進行壓力測試的時候，運行大概1小時候，后台拋出以下異常：
Nov 9, 2012 1:41:59 AM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@4b9cafa7 -- APPARENT DEADLOCK!!! Complete Status:
Managed Threads: 3
Active Threads: 3
Active Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@19f67d43 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@599c706 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@32d95dc9 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
Pending Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@5c9c5133
com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@1a971ac5
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@365e8926
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@787e39ac
Pool thread stack traces:
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
java.lang.StringCoding.set(StringCoding.java:53)
java.lang.StringCoding.encode(StringCoding.java:270)
java.lang.String.getBytes(String.java:946)
com.mysql.jdbc.ConnectionImpl.configureCharsetProperties(ConnectionImpl.java:1578)
com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1628)
com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3425)
com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2045)
com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)
com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
sun.reflect.GeneratedConstructorAccessor35.newInstance(Unknown Source)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
java.lang.reflect.Constructor.newInstance(Constructor.java:513)
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.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
com.mchange.v2.resourcepool.BasicResourcePool$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.mysql.jdbc.ResultSetImpl.getInstance(ResultSetImpl.java:344)
com.mysql.jdbc.MysqlIO.buildResultSetWithUpdates(MysqlIO.java:2607)
com.mysql.jdbc.MysqlIO.readResultsForQueryOrUpdate(MysqlIO.java:2490)
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.setupServerForTruncationChecks(ConnectionImpl.java:5240)
com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3508)
com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2045)
com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)
com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
sun.reflect.GeneratedConstructorAccessor35.newInstance(Unknown Source)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
java.lang.reflect.Constructor.newInstance(Constructor.java:513)
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.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:562)
目測該問題是c3p0連接池導致的線程死鎖。
這種數據庫連接池線程死鎖的問題發生的原因可能有很多，我將我的配置環境以及解決方法貼出來供大家參考一下：
使用環境，spring + hibernate +c3p0
配置如下：
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close">
<property name="driverClass" value="com.mysql.jdbc.Driver"/>
<property name="jdbcUrl" value="${db.url}?useUnicode=true&characterEncoding=UTF-8"/>
<property name="user" value="${db.usrname}"/>
<property name="password" value="${db.password}"/>
<!--連接池中保留的最小連接數。-->
<property name="minPoolSize" value="5"/>
<!--連接池中保留的最大連接數。Default: 15 -->
<property name="maxPoolSize" value="500"/>
<!--初始化時獲取的連接數，取值應在minPoolSize與maxPoolSize之間。Default: 3 -->
<property name="initialPoolSize" value="10"/>
<!--最大空閑時間,60秒內未使用則連接被丟棄。若為0則永不丟棄。Default: 0 -->
<property name="maxIdleTime" value="60"/>
<!--當連接池中的連接耗盡的時候c3p0一次同時獲取的連接數。Default: 3 -->
<property name="acquireIncrement" value="5"/>
<!--JDBC的標准參數，用以控制數據源內加載的PreparedStatements數量。但由於預緩存的statements
屬於單個connection而不是整個連接池。所以設置這個參數需要考慮到多方面的因素。
如果maxStatements與maxStatementsPerConnection均為0，則緩存被關閉。Default: 0-->
<property name="maxStatements" value="0"/>
<!--每60秒檢查所有連接池中的空閑連接。Default: 0 -->
<property name="idleConnectionTestPeriod" value="60"/>
<!--定義在從數據庫獲取新連接失敗后重復嘗試的次數。Default: 30 -->
<property name="acquireRetryAttempts" value="30"/>
<!--獲取連接失敗將會引起所有等待連接池來獲取連接的線程拋出異常。但是數據源仍有效
保留，並在下次調用getConnection()的時候繼續嘗試獲取連接。如果設為true，那么在嘗試
獲取連接失敗后該數據源將申明已斷開並永久關閉。Default: false-->
<property name="breakAfterAcquireFailure" value="false"/>
<!--因性能消耗大請只在需要的時候使用它。如果設為true那么在每個connection提交的
時候都將校驗其有效性。建議使用idleConnectionTestPeriod或automaticTestTable
等方法來提升連接測試的性能。Default: false -->
<property name="testConnectionOnCheckout" value="false"/>
</bean>
這個配置中有一些屬性可能和死鎖有關：maxStatements 和checkoutTimeout(我沒有使用該屬性)
有人說c3p0本身沒有問題，導致問題是spring的原因，c3p0作為hibernate官方推薦的連接池，在性能和穩定性上都是中規中矩的。根據以前的使用經驗，我判斷也不是c3p0的問題。
我的修改如下：
<!--JDBC的標准參數，用以控制數據源內加載的PreparedStatements數量。但由於預緩存的statements
屬於單個connection而不是整個連接池。所以設置這個參數需要考慮到多方面的因素。
如果maxStatements與maxStatementsPerConnection均為0，則緩存被關閉。Default: 0-->
<property name="maxStatements" value="0"/>
<!--連接池用完時客戶調用getConnection()后等待獲取連接的時間，單位：毫秒。超時后會拋出-->
<!--SQLEXCEPTION，如果設置0，則無限等待。Default:0-->
<property name="checkoutTimeout" value="100"/>
修改后，問題沒有重現。
---------------------
作者：睿子
來源：CSDN
原文：https://blog.csdn.net/ge_zhiqiang/article/details/8637684
版權聲明：本文為博主原創文章，轉載請附上博文鏈接！