如何跟踪和防止在单独进程中运行的c3po出现死锁？

我有一个非常简单的计算，可以生成字母矩阵，可以找到矩阵中的所有单词。单词中的字母是相邻的单元格。

   for (int i = 0; i < 500; i++) {
        System.out.println(i);
        Matrix matrix = new Matrix(4);
        matrix.scanWordsRandomly(9);
        matrix.printMatrix();
        System.out.println(matrix.getSollSize());
        matrix.write_to_db();
    }

这是持久代码。

public void write_to_db() {
    Session session = null;
    try {
        session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();
        Matrixtr onematrixtr = new Matrixtr();
        onematrixtr.setDimension(dimension);
        onematrixtr.setMatrixstr(this.toString());
        onematrixtr.setSolsize(getSollSize());
        session.save(onematrixtr);
        for (Map.Entry<Kelimetr, List<Cell>> sollution : sollutions.entrySet()) {
            Kelimetr kelimetr = sollution.getKey();
            List<Cell> solpath = sollution.getValue();
            Solstr onesol = new Solstr();
            onesol.setKelimetr(kelimetr);
            onesol.setMatrixtr(onematrixtr);
            onesol.setSoltext(solpath.toString().replace("[", "").replace("]", "").replace("true", "").replace("false", ""));
            session.save(onesol);
        }

        session.getTransaction().commit();
        session.close();

    }
    catch (HibernateException he) {
        System.out.println("DB Error : " + he.getMessage());
        session.close();
    } 
    catch (Exception ex) {
        System.out.println("General Error : " + ex.getMessage());
    }
}

这是休眠配置文件。

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/kelimegame_db_dev?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=UTF-8</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password">!.Wlu9RrCA</property>
    <property name="hibernate.show_sql">false</property>
    <property name="hibernate.query.factory_class">org.hibernate.hql.classic.ClassicQueryTranslatorFactory</property>
    <property name="hibernate.format_sql">false</property>
    <!-- Use the C3P0 connection pool provider -->
    <property name="hibernate.c3p0.acquire_increment">50</property>
    <property name="hibernate.c3p0.min_size">10</property>
    <property name="hibernate.c3p0.max_size">100</property>
    <property name="hibernate.c3p0.timeout">300</property>
    <property name="hibernate.c3p0.max_statements">5</property>
    <property name="hibernate.c3p0.idle_test_period">3000</property>
    <mapping resource="kelimegame/entity/Progress.hbm.xml"/>
    <mapping resource="kelimegame/entity/Solstr.hbm.xml"/>
    <mapping resource="kelimegame/entity/Kelimetr.hbm.xml"/>
    <mapping resource="kelimegame/entity/User.hbm.xml"/>
    <mapping resource="kelimegame/entity/Achievement.hbm.xml"/>
    <mapping resource="kelimegame/entity/Matrixtr.hbm.xml"/>
  </session-factory>
</hibernate-configuration>

找到所有可能的解决方案后，我使用休眠来保留矩阵和解决方案。我也在使用 c3pO 库。我没有产生任何线程。所有工作都是以非常简单的迭代方式完成的。但我在单独的进程中运行该罐子。 我从不同的终端执行此操作：

java -jar NewDB.jar

我陷入了僵局，如下所示：

Apr 25, 2013 8:38:05 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@7f0c09f9 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Apr 25, 2013 9:08:23 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@7f0c09f9 -- APPARENT DEADLOCK!!! Complete Status: 
    Managed Threads: 3
    Active Threads: 3
    Active Tasks: 
        com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@2933f261
            on thread: C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#1
        com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@116dd369
            on thread: C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#0
        com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@41529b6f
            on thread: C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#2
    Pending Tasks: 
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@165ab5ea
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@1d5d211d
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@4d2905fa
Pool thread stack traces:
    Thread[C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#1,5,main]
        com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:662)
    Thread[C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#0,5,main]
        com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:662)
    Thread[C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#2,5,main]
        com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:662)


Apr 25, 2013 9:41:29 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@7f0c09f9 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Apr 25, 2013 9:55:18 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@7f0c09f9 -- APPARENT DEADLOCK!!! Complete Status: 
    Managed Threads: 3
    Active Threads: 3
    Active Tasks: 
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@5a337b7d
            on thread: C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#0
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@69f079ce
            on thread: C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#1
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@2accf9b8
            on thread: C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#2
    Pending Tasks: 
        com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@771eb4fb
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@fc07d6
        com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@2266731b
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@740f0341
        com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@59edbee
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@78e924
        com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@2123aba
        com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@7acd8a65
Pool thread stack traces:
    Thread[C3P0PooledConnectionPoolManager[identityToken->z8kfsx8uibeyqevbbapc|4045cf35]-HelperThread-#0,5,main]
        java.text.NumberFormat.getInstance(NumberFormat.java:769)
        java.text.NumberFormat.getInstance(NumberFormat.java:393)
        java.text.MessageFormat.subformat(MessageFormat.java:1262)
        java.text.MessageFormat.format(MessageFormat.java:860)
        java.text.Format.format(Format.java:157)
        java.text.MessageFormat.format(MessageFormat.java:836)
        com.mysql.jdbc.Messages.getString(Messages.java:106)
        com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2552)
        com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3002)
        com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2991)
        com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3532)
        com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:943)
        com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:4113)
        com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1308)
        com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2336)
        com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2176)
        com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2158)
        com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
        com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
        sun.reflect.GeneratedConstructorAccessor7.newInstance(Unknown Source)
        sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        java.lang.reflect.Constructor.newInstance(Constructor.java:525)
        com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
        com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
        com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
        com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
        com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:183)
        com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:172)
        com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:188)Killed
caglar@ubuntu:~/NetBeansProjects/NewDB/dist$ 

我的问题如下：

1. 因为我正在运行程序，所以 c3po 中会发生这种死锁吗？ 单独的进程？
2. 我应该在其中使用一个进程和多个线程吗 过程？
3. 我如何追踪这个僵局并了解其原因？有没有办法跟踪导致死锁的多个 JVM？

这是一个有趣的问题。

您已经发布了两个不同的明显僵局。第一个是由 c3p0 尝试 close() 连接引起的，这些 close() 操作既没有成功，也没有及时失败并出现异常。第二个明显的死锁显示了连接获取的问题：c3p0 正在尝试获取新的连接，并且这些尝试既没有成功也没有及时失败并出现异常。事实上，非常不同的操作被冻结表明，这可能是一个更普遍的问题，因为您的数据库管理系统在您正在做的事情或类似的压力下锁定。对数据库运行多个进程应该没有问题，但您需要认识到限制。

关于您的配置有一些有趣的事情：

1) hibernate.c3p0.max_statements=5 是一个非常糟糕的主意，几乎在任何池上，特别是在这么大的池上。您最多有 100 个连接，并且只允许在所有连接之间缓存总共 5 个语句。这可能会给池和 DBMS 带来压力，因为您将不断地翻阅PreparedStatements，并且语句缓存会对此进行大量记录。你的意思可能是 5 个缓存语句每个连接，但这不是您配置的。您已为池设置了全局最大值。也许尝试 hibernate.c3p0.maxStatementsPerConnection=5 代替？或者将 max_statements 设置为零以关闭语句缓存，至少在解决死锁之前如此。看http://www.mchange.com/projects/c3p0/#configuring_statement_pooling http://www.mchange.com/projects/c3p0/#configuring_statement_pooling

2）如果您在多个进程而不是多个线程中运行计算，您真的需要每个进程容纳 50 - 100 个连接吗？事情很可能会冻结，因为您的多个进程中的每个进程都获取大量资源密集型连接，因此过多的未完成连接给数据库管理系统带来了压力。在任何进程中，您不需要比在该进程中同时运行的客户端线程更多的连接。我将 hibernate.c3p0.acquire_increment 和可能的 hibernate.c3p0.max_size 设置为小得多的值。

3) 如果您确实需要所有这些连接同时运行，您可以通过将配置参数 numHelperThreads 增加到大于默认值 3 的某个值来减少池死锁的可能性。您可能希望 numHelperThreads 大约是该数字的两倍您的机器上可用的核心数。但考虑到您正在运行多个进程，您可能会发现 CPU 已饱和，从而导致系统冻结。所以要注意这一点。

基本上，尝试更新您的配置，以便尽可能高效地使用资源（文件句柄、网络连接、CPU），这样您就不会不必要地对池/语句缓存/dbms 造成不必要的压力。

如果这些建议不能解决问题，请发布您的池的填充配置。 c3p0 在池初始化时在 INFO 级别转储其配置。

祝你好运！