Question

我在Tomcat中使用C3P0作为连接池，我看到非常令人担忧的错误：

2010-09-16 13:25:00,160 [Timer-0] WARN  com.mchange.v2.async.ThreadPoolAsynchronousRunner  - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@43502400 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
2010-09-16 13:25:01,407 [Timer-0] WARN  com.mchange.v2.async.ThreadPoolAsynchronousRunner  - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@43502400 -- APPARENT DEADLOCK!!! Complete Status:
  Managed Threads: 10
  Active Threads: 0
  Active Tasks:
  Pending Tasks:
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@6e4151a7
  Pool thread stack traces:
  Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#6,5,main]
    java.lang.Object.wait(Native Method)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
  Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
    java.lang.Object.wait(Native Method)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
  Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
    java.lang.Object.wait(Native Method)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
  Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
    java.lang.Object.wait(Native Method)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
  Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#5,5,main]
    java.lang.Object.wait(Native Method)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
  Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#4,5,main]
    java.lang.Object.wait(Native Method)

... many more, exact same stack trace

第534行是：

 while (true) {
   Runnable myTask;
   synchronized ( ThreadPoolAsynchronousRunner.this ) {
     while ( !should_stop && pendingTasks.size() == 0 )
       ThreadPoolAsynchronousRunner.this.wait( POLL_FOR_STOP_INTERVAL ); // <- here
     if (should_stop) ...

它看起来非常像所有线程都空闲。他们在等待工作。 0活动线程，只完成1个任务。什么出错的线索？

以下是配置：

ds.setUser(userName);
ds.setPassword(password);
ds.setMaxPoolSize(16);
ds.setMaxConnectionAge(1800);
ds.setAcquireRetryAttempts(4);
ds.setMaxIdleTime(900);
ds.setNumHelperThreads(10);
ds.setCheckoutTimeout(1000);

Answer 1

我刚刚遇到了针对Oracle数据库的类似问题，但在我的情况下，Managed Thread和Active Thread计数是相同的。

    Managed Threads: 3
    Active Threads: 3

对我来说，这实际上是一个身份验证错误，但由于我正在进行登录审核的方式，因此出现APPARENT DEADLOCK错误。

    2013-08-12 11:29:04,910 [Timer-4] WARN  com.mchange.v2.async.ThreadPoolAsynchronousRunner: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@34996454 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
    2013-08-12 11:29:04,914 [Timer-4] WARN  com.mchange.v2.async.ThreadPoolAsynchronousRunner: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@34996454 -- APPARENT DEADLOCK!!! Complete Status: 
            Managed Threads: 3
            Active Threads: 3
            Active Tasks: 
                    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@6730b844 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
                    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@2f91ad49 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
                    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@507ac05 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
            Pending Tasks: 
                    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@3aae7ed7
    Pool thread stack traces:
            Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
                    java.net.SocketInputStream.socketRead0(Native Method)
                    java.net.SocketInputStream.read(SocketInputStream.java:150)
                    java.net.SocketInputStream.read(SocketInputStream.java:121)
                    oracle.net.ns.Packet.receive(Packet.java:300)
                    oracle.net.ns.DataPacket.receive(DataPacket.java:106)
                    oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:315)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:260)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:185)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:102)
                    oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:124)
                    oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:80)
                    oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1137)
                    oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:290)
                    oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:192)
                    oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:380)
                    oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:760)
                    oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:401)
                    oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)
                    oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:236)
                    oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
                    oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)
                    com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
                    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]
                    java.net.SocketInputStream.socketRead0(Native Method)
                    java.net.SocketInputStream.read(SocketInputStream.java:150)
                    java.net.SocketInputStream.read(SocketInputStream.java:121)
                    oracle.net.ns.Packet.receive(Packet.java:300)
                    oracle.net.ns.DataPacket.receive(DataPacket.java:106)
                    oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:315)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:260)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:185)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:102)
                    oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:124)
                    oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:80)
                    oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1137)
                    oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:290)
                    oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:192)
                    oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:380)
                    oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:760)
                    oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:401)
                    oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)
                    oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:236)
                    oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
                    oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)
                    com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
                    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]
                    java.net.SocketInputStream.socketRead0(Native Method)
                    java.net.SocketInputStream.read(SocketInputStream.java:150)
                    java.net.SocketInputStream.read(SocketInputStream.java:121)
                    oracle.net.ns.Packet.receive(Packet.java:300)
                    oracle.net.ns.DataPacket.receive(DataPacket.java:106)
                    oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:315)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:260)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:185)
                    oracle.net.ns.NetInputStream.read(NetInputStream.java:102)
                    oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:124)
                    oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:80)
                    oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1137)
                    oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:290)
                    oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:192)
                    oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:380)
                    oracle.jdbc.driver.T4CTTIoauthenticate.doOAUTH(T4CTTIoauthenticate.java:760)
                    oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:401)
                    oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)
                    oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:236)
                    oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
                    oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)
                    com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
                    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)

Answer 2

这听起来好像你已经从游泳池获得了一个连接而且没有及时归还。

C3P0在获取连接但未在死锁检测超时内返回池时确定“明显的死锁”。

如果您将连接采集移近“操作”并在数据库工作完成后立即将其返回到池中，则此消息将消失。

Answer 3

这将解决您的问题

ds.setMaxStatements(1000);
ds.setMaxStatementsPerConnection(100); (the maximum number of prepared statments your system can execute on a single connection)

结帐：https://forum.hibernate.org/viewtopic.php?t=947246&highlight=apparent+deadlock+c3p0

完成后，请记得关闭你的陈述!!

Answer 4

我对答案https://stackoverflow.com/a/18192588/1019307的评论获得了足够的赞成票，表明它应该是答案。

我收到此错误是因为我无法通过防火墙到达数据库服务器。检查是否是您的问题。

Answer 5

@eebbesen，我遇到了与您相同的错误。我正在运行Tomcat 9.0.6版。我的Maven项目中有休眠核心版本5.2.10，休眠c3p0版本3.6.3。我的不是身份验证错误，而是由于我之前更改了计算机名称。这对tomcat并没有立即产生影响，但是在机器重启后，当我尝试通过eclipse（Oxygen 2）再次启动tomcat时，由于您提出的问题，我无法再开始eclipse。

我搜索了这个，发现了这个链接，提示我该问题：

https://community.oracle.com/thread/339825

它说：

首先查看OracleServiceXE和OracleXETNSListener服务是否运行。将网址中的127.0.0.1替换为您的IP或名称机。它必须与tnsnames.ora文件中声明的主机匹配。

稍后，它提到在哪里可以找到该tnsnames.ora文件，对我来说，它在这里：

C:\oraclexe\app\oracle\product\11.2.0\server\network\ADMIN

看着这个tnsnames.ora文件，我看到了：

XE =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = MyMachineName-7)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = XE)
    )
  )

但是我最近将机器重命名为MyMachineName-5。我将7更改为5并保存了文件。我检查了此目录中的“ listener.ora”文件，它具有相同的问题：

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
      (ADDRESS = (PROTOCOL = TCP)(HOST = MyMachineName-7)(PORT = 1521))
    )
  )

我将7更改为5，然后保存了文件。

然后，我打开任务管理器，单击“服务”选项卡，然后查看“ Oracle”服务。我在以下位置重新启动：OracleXETNSListener，OracleXEClrAgent，OracleServiceXE。我再次在eclipse中重新启动了tomcat，这一次出现了问题。

附录：

我也在Google上搜索过：

https://community.oracle.com/thread/2267906

这使我尝试：

1）关闭Windows Defender中的防火墙（已关闭mcaffee防火墙）

2）启动sqlplus以确保我可以使用在休眠文件hibernate.cfg.xml中使用的凭据登录。

C：\ oraclexe \ app \ oracle \ product \ 11.2.0 \ server \ bin \ sqlplus.exe

3）启动了Oracle Database 11g的桌面快捷方式

即使我修复了机器名称问题，这对我还是失败了，我仍然需要研究一些问题。

4）我尝试使用dbVisualizer与Oracle建立连接。只有在我解决了.ora文件机器名称问题后，此方法才起作用：双击连接，然后单击“ ping服务器”按钮。

Answer 6

我通过正确关闭Statement和Resultset实例（以某种方式未公开）解决了相同的问题（无法检测到）：

String SQL = "SELECT 1";
try {
    con = DriverManager.getConnection(host, userName, userPassword);
    stmt = con.prepareStatement(SQL, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
    try {
        rs = stmt.executeQuery(SQL);
        try {
            rs.next();
            // ...
        } finally {
            rs.close();
        }
    } finally {
        stmt.close();
    }
} catch (SQLException ex) {
    Logger.getLogger(MyClass.class.getName()).log(Level.SEVERE, null, ex);
}

Answer 7

我遇到了同样的问题，但原因有点难以发现，因为它是由同时尝试获取连接的同时资源造成的。

正如您可以阅读的那样，如果池尚未初始化，则通过调用设置函数来提供它以启动它。

public Connection getConnection() throws SQLException {
    if (mCPDS == null) {
        setupPool();
    }

    return mCPDS.getConnection();
}

问题是许多资源试图在程序开始时获取连接，因此不止一个实例化池会在一段时间后导致问题。

解决方案只是声明方法是同步的，以便在调用方法时保留其他资源，并且它仍在实例化池中。

public synchronized Connection getConnection() throws SQLException {
    if (mCPDS == null) {
        setupPool();
    }

    return mCPDS.getConnection();
}

这可能是因为不使用单例而导致的设计错误，但修复了缺少某些性能的问题。

Answer 8

我突然遇到了同样的问题：注意到死锁仅在以调试模式启动我的应用程序时才存在（我正在使用IntelliJ），并且在正常运行情况下很好时，我开始进行挖掘

我终于弄清楚一个断点阻塞了连接：我不知道为什么Intellij不“监听”该应用程序正在通过那个断点，而是被挂在某个断点的位置，这导致了僵局

在删除了项目中的所有断点之后，一切又重新开始了。

希望这对某人有帮助

Answer 9

我们遇到了这个问题并通过将其添加到C3P0配置解决了它：

<property name="statementCacheNumDeferredCloseThreads" value="1"/>

根据：this from the C3P0 doc

Answer 10

在部署应用程序时，glassfish4服务器上遇到了类似的问题。原来这是一个数据库配置问题。只需确保数据库连接配置正确，验证配置中提供的主机名是否允许连接到数据库。尝试使用配置的用户名和主机名/域手动连接到数据库。如果需要，请允许db用户从所需域进行连接。使用正确的数据库配置重建应用程序，然后进行部署。

当线程全部为空时，C3P0明显死锁？

10 个答案: