c3p0数据库连接池死锁问题

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项目进行压力测试的时候，运行大概1小时候，后台抛出以下异常：

Java代码  

1. Nov 9, 2012 1:41:59 AM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run  
2. WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@4b9cafa7 -- APPARENT DEADLOCK!!! Complete Status:   
3.         Managed Threads: 3  
4.         Active Threads: 3  
5.         Active Tasks:   
6.                 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@19f67d43 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)  
7.                 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@599c706 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)  
8.                 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@32d95dc9 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)  
9.         Pending Tasks:   
10.                 com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@5c9c5133  
11.                 com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@1a971ac5  
12.                 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@365e8926  
13.                 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@787e39ac  
14. Pool thread stack traces:  
15.         Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]  
16.                 java.lang.StringCoding.set(StringCoding.java:53)  
17.                 java.lang.StringCoding.encode(StringCoding.java:270)  
18.                 java.lang.String.getBytes(String.java:946)  
19.                 com.mysql.jdbc.ConnectionImpl.configureCharsetProperties(ConnectionImpl.java:1578)  
20.                 com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1628)  
21.                 com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3425)  
22.                 com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2045)  
23.                 com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)  
24.                 com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)  
25.                 sun.reflect.GeneratedConstructorAccessor35.newInstance(Unknown Source)  
26.                 sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)  
27.                 java.lang.reflect.Constructor.newInstance(Constructor.java:513)  
28.                 com.mysql.jdbc.Util.handleNewInstance(Util.java:406)  
29.                 com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)  
30.                 com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282)  
31.                 com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)  
32.                 com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)  
33.                 com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)  
34.                 com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)  
35.                 com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)  
36.                 com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)  
37.                 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)  
38.                 com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)  
39.         Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]  
40.                 com.mysql.jdbc.ResultSetImpl.getInstance(ResultSetImpl.java:344)  
41.                 com.mysql.jdbc.MysqlIO.buildResultSetWithUpdates(MysqlIO.java:2607)  
42.                 com.mysql.jdbc.MysqlIO.readResultsForQueryOrUpdate(MysqlIO.java:2490)  
43.                 com.mysql.jdbc.MysqlIO.readAllResults(MysqlIO.java:1746)  
44.                 com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2135)  
45.                 com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536)  
46.                 com.mysql.jdbc.ConnectionImpl.setupServerForTruncationChecks(ConnectionImpl.java:5240)  
47.                 com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3508)  
48.                 com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2045)  
49.                 com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)  
50.                 com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)  
51.                 sun.reflect.GeneratedConstructorAccessor35.newInstance(Unknown Source)  
52.                 sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)  
53.                 java.lang.reflect.Constructor.newInstance(Constructor.java:513)  
54.                 com.mysql.jdbc.Util.handleNewInstance(Util.java:406)  
55.                 com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)  
56.                 com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282)  
57.                 com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)  
58.                 com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)  
59.                 com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)  
60.                 com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)  
61.                 com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)  
62.                 com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)  
63.                 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)  
64.                 com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)  
65.         Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]  
66.                 com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:562)  

 目测该问题是c3p0连接池导致的线程死锁。

这种数据库连接池线程死锁的问题发生的原因可能有很多，我将我的配置环境以及解决方法贴出来供大家参考一下：

使用环境，spring + hibernate +c3p0

配置如下：<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"

Java代码  

1.     destroy-method="close">  
2.   <property name="driverClass" value="com.mysql.jdbc.Driver"/>  
3.   <property name="jdbcUrl" value="${db.url}?useUnicode=true&amp;characterEncoding=UTF-8"/>  
4.           <property name="user" value="${db.usrname}"/>  
5.           <property name="password" value="${db.password}"/>  
6.   <!--连接池中保留的最小连接数。-->  
7.   <property name="minPoolSize" value="5"/>  
8.   <!--连接池中保留的最大连接数。Default: 15 -->  
9.   <property name="maxPoolSize" value="500"/>  
10.   <!--初始化时获取的连接数，取值应在minPoolSize与maxPoolSize之间。Default: 3 -->  
11.   <property name="initialPoolSize" value="10"/>  
12.   <!--最大空闲时间,60秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0 -->  
13.   <property name="maxIdleTime" value="60"/>  
14.   <!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。Default: 3 -->  
15.   <property name="acquireIncrement" value="5"/>  
16.   <!--JDBC的标准参数，用以控制数据源内加载的PreparedStatements数量。但由于预缓存的statements  
17.  属于单个connection而不是整个连接池。所以设置这个参数需要考虑到多方面的因素。  
18.  如果maxStatements与maxStatementsPerConnection均为0，则缓存被关闭。Default: 0-->  
19.   <property name="maxStatements" value="0"/>  
20.   <!--每60秒检查所有连接池中的空闲连接。Default: 0 -->  
21.   <property name="idleConnectionTestPeriod" value="60"/>  
22.   <!--定义在从数据库获取新连接失败后重复尝试的次数。Default: 30 -->  
23.   <property name="acquireRetryAttempts" value="30"/>  
24.   <!--获取连接失败将会引起所有等待连接池来获取连接的线程抛出异常。但是数据源仍有效  
25.  保留，并在下次调用getConnection()的时候继续尝试获取连接。如果设为true，那么在尝试  
26.  获取连接失败后该数据源将申明已断开并永久关闭。Default: false-->  
27.   <property name="breakAfterAcquireFailure" value="false"/>  
28.   <!--因性能消耗大请只在需要的时候使用它。如果设为true那么在每个connection提交的  
29. 时候都将校验其有效性。建议使用idleConnectionTestPeriod或automaticTestTable  
30. 等方法来提升连接测试的性能。Default: false -->  
31.   <property name="testConnectionOnCheckout" value="false"/>  
32.     </bean>  

 这个配置中有一些属性可能和死锁有关：maxStatements 和checkoutTimeout(我没有使用该属性)

有人说c3p0本身没有问题，导致问题是spring的原因，c3p0作为hibernate官方推荐的连接池，在性能和稳定性上都是中规中矩的。根据以前的使用经验，我判断也不是c3p0的问题。

Java代码  

1. <!--JDBC的标准参数，用以控制数据源内加载的PreparedStatements数量。但由于预缓存的statements  
2.        属于单个connection而不是整个连接池。所以设置这个参数需要考虑到多方面的因素。  
3.        如果maxStatements与maxStatementsPerConnection均为0，则缓存被关闭。Default: 0-->  
4.  <property name="maxStatements" value="0"/>  
5. <!--连接池用完时客户调用getConnection()后等待获取连接的时间，单位：毫秒。超时后会抛出-->  
6.  <!--SQLEXCEPTION，如果设置0，则无限等待。Default:0-->  
7.  <property name="checkoutTimeout" value="100"/>  

  修改后，问题没有重现。

来自：http://www.cnblogs.com/zhishan/archive/2012/11/09/2761980.html

c3p0数据库连接池死锁问题

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原文地址：http://www.cnblogs.com/love540376/p/5832212.html