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提问者：小点点

Java连接池不限制打开到DB服务器的TCP连接数


我正在使用Hibernate属性来定义连接池大小，以及LocalSessionFactoryBean和DriverManagerDataSource来创建一个org. hibernate.SessionFactory并且我观察到1000的TCP连接被打开到DB服务器，而不是我期望的连接池大小的上限100。

设置连接Hibernate池的代码如下所示。注意最大大小为100，但是我从我的工作站观察到1000个到DB服务器的连接-我在Windows机器上使用TCPView连接到由Vagrat（VirtualBox）管理的CentosOSVM上的MariabDB实例

Properties hibernateProperties = new Properties();
hibernateProperties.put("hibernate.dialect", "org.hibernate.dialect.MySQL5InnoDBDialect");
hibernateProperties.put("hibernate.show_sql", false);
hibernateProperties.put("hibernate.generate_statistics", false);
hibernateProperties.put("hibernate.hbm2ddl.auto", "update");
hibernateProperties.put("hibernate.use_sql_comments", false);

hibernateProperties.put("hibernate.c3p0.min_size", 10);
hibernateProperties.put("hibernate.c3p0.max_size", 100);
hibernateProperties.put("hibernate.c3p0.timeout", 1500);
hibernateProperties.put("hibernate.c3p0.max_statements", 5000);
hibernateProperties.put("hibernate.c3p0.idle_test_period", 60);

LocalSessionFactoryBean localSessionFactoryBean = new   LocalSessionFactoryBean();
localSessionFactoryBean.setDataSource(dataSource);
localSessionFactoryBean.setHibernateProperties(hibernateProperties);
localSessionFactoryBean.setMappingResources("job.persistence.xml");

我希望看到这些连接达到最大值为100，并在以后执行循环时被重用，但我观察到超过1000个连接在关闭之前TIME_WAIT了大约一分钟。以下是TCPView输出的示例：

[System Process]    0   TCP localhost   62794   192.168.98.102  3306    TIME_WAIT                                       
[System Process]    0   TCP localhost   62796   192.168.98.102  3306    TIME_WAIT                                       
[System Process]    0   TCP localhost   62797   192.168.98.102  3306    TIME_WAIT                                       
[System Process]    0   TCP localhost   62795   192.168.98.102  3306    TIME_WAIT                                       
[System Process]    0   TCP localhost   62798   192.168.98.102  3306    TIME_WAIT                                       
[System Process]    0   TCP localhost   62801   192.168.98.102  3306    TIME_WAIT

我显然做错了什么，但不确定是什么。我正在使用Spring来管理提供数据访问逻辑的DAO。DAO被注册为原型Spring范围，而SingletonSessionFactory被注入到DAO中，如下所示：

@Bean(name="jobDao")
@Scope(SpringBeanScope.Prototype)
public JobDao jobDao(SessionFactory jobSessionFactory) { //...}

在DAO中，我调用session sionFactory. getCurrentSession（）来访问DB会话。以下是从通用DAO库中提取的，用于演示这一点：

protected Session currentSession() {
    return sessionFactory.getCurrentSession();
}

@Transactional
@Override
public void Add(TEntity entity) {

    currentSession().save(entity);
}

有人知道为什么连接池限制为100时会打开这么多TCP连接吗？

更新

由于这个问题是在Windows开发机器上，我整理了一个小的.NET控制台应用程序，它使用并行for循环执行一个简单的SQLselect语句，最大线程数为64，每次都创建一个新连接：

public void Test()
{
    ParallelOptions options = new ParallelOptions();
    options.MaxDegreeOfParallelism = 64;

    Parallel.For(0,
                1000,
                options,
                (i, state) =>
                {
                    ExecuteSql();
                });
}

private void ExecuteSql()
{
    SqlDataAdapter adapter = new SqlDataAdapter(sql, new SqlConnection(connectionString));

    DataSet orders = new DataSet();
    adapter.Fill(orders, "Order");

    Console.WriteLine("Thread {0} returned {1} rows", Thread.CurrentThread.ManagedThreadId, orders.Tables[0].Rows.Count);
}

TCPView结果如下，这是我期望在连接池解决方案中看到的，即重用TCP连接

DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61316   dev-database01  ms-sql-s    ESTABLISHED 1   88  776 2,684,495       43,800      16      
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61317   dev-database01  ms-sql-s    ESTABLISHED 1   88  507 1,998,709       6,326       1       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61318   dev-database01  ms-sql-s    ESTABLISHED 2   176 862 3,081,722       49,640      19      
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61319   dev-database01  ms-sql-s    ESTABLISHED 2   176 952 3,128,657       14,600      9       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61320   dev-database01  ms-sql-s    ESTABLISHED 2   176 1,149   3,569,440       25,747      8       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61321   dev-database01  ms-sql-s    ESTABLISHED 2   176 1,166   3,788,974                       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61322   dev-database01  ms-sql-s    ESTABLISHED 2   176 884 3,197,392       8,713       2       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61323   dev-database01  ms-sql-s    ESTABLISHED 2   176 535 1,816,150                       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61324   dev-database01  ms-sql-s    ESTABLISHED 2   176 631 2,197,973                       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61327   dev-database01  ms-sql-s    ESTABLISHED 2   176 1,037   3,344,226       18,980      5       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61328   dev-database01  ms-sql-s    ESTABLISHED 3   264 1,271   4,057,097       30,660      13      
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61331   dev-database01  ms-sql-s    ESTABLISHED 2   176 780 2,639,988       8,760       2       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61333   dev-database01  ms-sql-s    ESTABLISHED 2   176 1,041   3,352,777       31,248      12      
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61334   dev-database01  ms-sql-s    ESTABLISHED 6   995 729 2,387,668                       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61335   dev-database01  ms-sql-s    ESTABLISHED 6   995 601 1,917,537       23,937      6       
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61336   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61339   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61340   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61342   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61343   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61344   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61345   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61346   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61356   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61357   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61358   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61359   dev-database01  ms-sql-s    ESTABLISHED                                                         
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61362   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61363   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61364   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61365   dev-database01  ms-sql-s    ESTABLISHED                                     
DatabaseTcpPortTester.vshost.exe    5036    TCP localhost   61369   dev-database01  ms-sql-s    ESTABLISHED                                     
[System Process]    0   TCP localhost   61395   dev-database01  epmap   TIME_WAIT

共3个答案

匿名用户

在netstat输出中，所有这些都处于TIME_WAIT状态，指示TCP套接字在实际关闭之前的状态。这并不意味着DB连接是活动的，只是TCP正在关闭套接字。

其中有多少处于ESTABLISHED状态？这将告诉您在该时间点打开的DB连接的确切数量。

您可以参考以下链接了解不同的TCP套接字状态。https://en.wikipedia.org/wiki/Transmission_Control_Protocol

匿名用户

Hibernate配置是正确的，您应该使用C3P0。您会看到比最大池大小更多的连接的唯一方法是为每个请求创建SessionFactory。

从您的配置中，我看到DAO是作为原型创建的，这很不寻常，因为它们应该是单例。确保LocalSessionFactoryBean不使用原型范围。

匿名用户

问题是c3p0在使用DriverManagerDataSource并通过在LocalSessionFactoryBean上设置c3p0属性来管理池时从未被初始化

所以我切换到ComboPooledDataSource并使用此处可用的setter方法设置c3p0属性，而不是在LocalSessionFactoryBean上，因此您实际上最终得到以下内容：

@Bean(name="dataSource")
public DataSource dataSource() throws PropertyVetoException {

    Properties hibernateProperties = new Properties();
    hibernateProperties.put("hibernate.dialect", "org.hibernate.dialect.MySQL5InnoDBDialect");
    hibernateProperties.put("hibernate.show_sql", false);
    hibernateProperties.put("hibernate.generate_statistics", false);
    hibernateProperties.put("hibernate.hbm2ddl.auto", "update");
    hibernateProperties.put("hibernate.use_sql_comments", false);

    //note the "hibernate.c3p0...." properties are no longer in use

    ComboPooledDataSource dataSource = new ComboPooledDataSource();

    dataSource.setDriverClass(jobDatabaseProperties.getJobDatabaseDriverClassName());
    dataSource.setJdbcUrl(jobDatabaseProperties.getJobDatabaseUrl());
    dataSource.setUser(jobDatabaseProperties.getJobDatabaseUsername());
    dataSource.setPassword(jobDatabaseProperties.getJobDatabasePassword());

    dataSource.setAcquireIncrement(1);
    dataSource.setMinPoolSize(5);
    dataSource.setMaxPoolSize(100);
    dataSource.setMaxIdleTime(20);

    return new dataSource;
}

我现在可以看到c3p0正在日志中初始化，并且池控制的连接数符合预期。

http://syntx.io/configuring-c3p0-connection-pooling-with-spring-and-hibernate/上“让Spring管理游泳池”部分的帽子提示

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