Tomcat 使用 c3p0 数据源，超出 maxPoolSize答案

【问题标题】：Tomcat using c3p0 Datasource, maxPoolSize exceededTomcat 使用 c3p0 数据源，超出 maxPoolSize
【发布时间】：2014-09-12 14:54:20
【问题描述】：

我已将 Tomcat 配置为使用 ComboPooledDataSource，方法是在我的 context.xml 中添加以下内容。

<Resource
    name="jdbc/abcdatasource"
    auth="Container"
    type="com.mchange.v2.c3p0.ComboPooledDataSource"
    factory="org.apache.naming.factory.BeanFactory"
    maxPoolSize="20"
    minPoolSize="5"
    maxIdleTime="3000"
    acquireIncrement="1"
    user="abc"
    password="pw_here"
    driverClass="oracle.jdbc.driver.OracleDriver"
    jdbcUrl="jdbc:oracle:thin:@abc.def.ghi.net:1521:BLAH"
/>

我想按照 maxPoolSize 中的定义将 db 连接数限制为 20，但我的打开连接数超过了这个数。例如，昨天，我有 35 个打开的连接。我的日志正在捕获以下内容。

2014-09-11 00:37:47,077  INFO [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2] NewPooledConnection:725 -  - [c3p0] Exceptions occurred while trying to close a PooledConnection's resources normally.
2014-09-11 00:37:47,077  INFO [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2] NewPooledConnection:735 -  - [c3p0] NewPooledConnection close Exception.
java.sql.SQLException: Io exception: Connection timed out
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:255)
        at oracle.jdbc.driver.T4CConnection.logoff(T4CConnection.java:481)
        at oracle.jdbc.driver.PhysicalConnection.close(PhysicalConnection.java:1203)
        at com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:549)
        at com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:234)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.destroyResource(C3P0PooledConnectionPool.java:470)
        at com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask.run(BasicResourcePool.java:964)
        at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
2014-09-11 00:37:47,078  WARN [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2] BasicResourcePool:972 -  - Failed to destroy resource: com.mchange.v2.c3p0.impl.NewPooledConnection@3ca5d95d
java.sql.SQLException: Some resources failed to close properly while closing com.mchange.v2.c3p0.impl.NewPooledConnection@3ca5d95d
        at com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:571)
        at com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:234)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.destroyResource(C3P0PooledConnectionPool.java:470)
        at com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask.run(BasicResourcePool.java:964)
        at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

鉴于此信息，我的打开连接数超过我的 maxPoolSize 的可能原因是什么？

我知道有相关的 stackoverflow 线程，例如 here 和 here,，但不清楚我的情况可能是什么问题。在这些类似的线程中，有多个连接池 - 但当我将 Web 应用程序容器配置为使用 c3p0 ComboPooledDataSource 时，我希望有一个不同的连接池。也许我在那里遗漏了一些东西......

任何帮助将不胜感激！！！！！！

编辑 1：对于一些额外的上下文，这不是一个新的应用程序。它已经运行多年。然而，新的是将 Tomcat 与 c3p0 数据源一起使用。从 WebLogic 转换到 Tomcat 后出现此问题。

编辑 2：当我最初创建这篇文章时，我未能提供可能非常有用的日志信息。在 log4j 中捕获的 DEADLOCK 问题如下所示。自从我注意到这个问题以来，我一直在密切监视连接，并且连接增加似乎与死锁问题有关。如果我不得不猜测，我会说它在死锁之后创建了一个新的连接池。

2014-09-11 11:36:45,320  WARN [Timer-0] ThreadPoolAsynchronousRunner:608 -  - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@1c203f2b -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
2014-09-11 11:36:45,323  WARN [Timer-0] ThreadPoolAsynchronousRunner:624 -  - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@1c203f2b -- APPARENT DEADLOCK!!! Complete Status:
        Managed Threads: 3
        Active Threads: 3
        Active Tasks:
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@4a50503d (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@5ec3fae8 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@148dc5f3 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
        Pending Tasks:
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@67bedf0f
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@242686ff
                com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@5d68e1e3
                com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@10c62dfe
                com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@42f5874c
                com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@585b0ec
                com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@c2258c9
Pool thread stack traces:
        Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
                java.net.SocketInputStream.socketRead0(Native Method)
                java.net.SocketInputStream.read(SocketInputStream.java:129)
                oracle.net.ns.Packet.receive(Unknown Source)
                oracle.net.ns.DataPacket.receive(Unknown Source)
                oracle.net.ns.NetInputStream.getNextPacket(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1104)
                oracle.jdbc.driver.T4CMAREngine.unmarshalSB1(T4CMAREngine.java:1075)
                oracle.jdbc.driver.T4C7Ocommoncall.receive(T4C7Ocommoncall.java:106)
                oracle.jdbc.driver.T4CConnection.logoff(T4CConnection.java:465)
                oracle.jdbc.driver.PhysicalConnection.close(PhysicalConnection.java:1203)
                com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:549)
                com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:234)
                com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.destroyResource(C3P0PooledConnectionPool.java:470)
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask.run(BasicResourcePool.java:964)
                com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
        Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
                java.net.SocketInputStream.socketRead0(Native Method)
                java.net.SocketInputStream.read(SocketInputStream.java:129)
                oracle.net.ns.Packet.receive(Unknown Source)
                oracle.net.ns.DataPacket.receive(Unknown Source)
                oracle.net.ns.NetInputStream.getNextPacket(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1104)
                oracle.jdbc.driver.T4CMAREngine.unmarshalSB1(T4CMAREngine.java:1075)
                oracle.jdbc.driver.T4C7Ocommoncall.receive(T4C7Ocommoncall.java:106)
                oracle.jdbc.driver.T4CConnection.logoff(T4CConnection.java:465)
                oracle.jdbc.driver.PhysicalConnection.close(PhysicalConnection.java:1203)
                com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:549)
                com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:234)
                com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.destroyResource(C3P0PooledConnectionPool.java:470)
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask.run(BasicResourcePool.java:964)
                com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
        Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
                java.net.SocketInputStream.socketRead0(Native Method)
                java.net.SocketInputStream.read(SocketInputStream.java:129)
                oracle.net.ns.Packet.receive(Unknown Source)
                oracle.net.ns.DataPacket.receive(Unknown Source)
                oracle.net.ns.NetInputStream.getNextPacket(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.net.ns.NetInputStream.read(Unknown Source)
                oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1104)
                oracle.jdbc.driver.T4CMAREngine.unmarshalSB1(T4CMAREngine.java:1075)
                oracle.jdbc.driver.T4C7Ocommoncall.receive(T4C7Ocommoncall.java:106)
                oracle.jdbc.driver.T4CConnection.logoff(T4CConnection.java:465)
                oracle.jdbc.driver.PhysicalConnection.close(PhysicalConnection.java:1203)
                com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:549)
                com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:234)
                com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.destroyResource(C3P0PooledConnectionPool.java:470)
                com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask.run(BasicResourcePool.java:964)
                com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

正在使用的c3p0版本是0.9.1.2

【问题讨论】：

几个问题：您如何测量打开的连接（在数据库中或仅在 Java 代码中打印连接对象）？你是如何从代码中获取连接的？ getConnection() 还是 getConnection(username,password)？从您的异常跟踪中，看起来连接没有关闭。你能从数据库的角度找出原因吗？
首先，从我正在运行 tomcat 的服务器上，我使用命令 # netstat -an | 测量打开的连接。 grep 1521。我们的 DBA 还仅从数据库的角度检查了打开的连接，这与我所看到的一致。
关于获取连接的方法，我可以深入研究，但我的印象是即使使用getConnection(username,password)方法，也不会创建更多不是一个连接池，因为我在 context.xml 中配置了一个用户名和密码。
如果我们使用不同的用户名会这样。但我在想close() 通话期间的错误。你能调试你的方法来捕捉超时的根本原因吗？

标签： java tomcat datasource connection-pooling c3p0

【解决方案1】：

为了它的价值，我更新了 Tomcat 的 server.xml 并设置了 autoDeploy=false，从那以后我没有遇到任何问题。

我的 c3p0 连接池设置在 Tomcat 的 context.xml 中，并且在运行时对此文件的任何修改都将导致应用程序被重新部署并创建一个额外的连接池。将 autoDeploy 设置为 false 可以防止这种 Tomcat 行为产生不必要的 c3p0 连接池副作用。

【讨论】：