如何跟踪数据库连接泄漏

Question

我们有一个应用程序似乎有连接泄漏(SQL Server说已经达到最大池大小)。我一个人在我的开发机器上(很明显)，仅仅通过导航应用程序，我就触发了这个错误。SQL Server活动监视器显示大量使用我的数据库的进程。

我想找出哪些文件打开了连接，但没有使用它。我在考虑使用像grep这样的东西来计算每个文件的".Open()“和".Close()”的数量，并获得这两个数字不相等的文件。这现实吗？

附加问题:在SQL Server活动监视器中找到的进程是否与连接相对应？如果没有，我如何找出我的数据库上有多少个连接是打开的？

该应用程序是带有SQL Server2005的asp.net (vb) 3.5。我们目前还没有使用LINQ或任何类似的东西。

谢谢

Answer 1

当从SQL Server端查看代码时，您可以运行以下查询来查看上一次在休眠连接上运行哪些查询。(未执行任何操作的打开连接)

SELECT ec.session_id, last_read, last_write, text, client_net_address, program_name, host_process_id, login_name
FROM sys.dm_exec_connections  ec
JOIN sys.dm_exec_sessions es
  ON ec.session_id = es.session_id
CROSS APPLY sys.dm_exec_sql_text(ec.most_recent_sql_handle) AS dest
where es.status = 'sleeping'

在应用程序端，您可以使用sos.dll进行调试，如以下文章所述：

• How to troubleshoot leaked SqlConnection Objects Part 1
• How to troubleshoot leaked SqlConnection Objects Part 2

如果你需要更多关于如何使用windbg的信息，这些文章是一个很好的介绍：

• Getting Started with WinDBG Part 1
• Getting Started with WinDBG Part 2

Answer 2

解决连接泄漏的最好方法是在测试期间进行。

您可以使用自动实用程序，以便每次测试都验证是否存在连接泄漏。

@BeforeClass
public static void initConnectionLeakUtility() {
    if ( enableConnectionLeakDetection ) {
        connectionLeakUtil = new ConnectionLeakUtil();
    }
}
 
@AfterClass
public static void assertNoLeaks() {
    if ( enableConnectionLeakDetection ) {
        connectionLeakUtil.assertNoLeaks();
    }
}

ConnectionLeakUtil如下所示：

public class ConnectionLeakUtil {
 
    private JdbcProperties jdbcProperties = JdbcProperties.INSTANCE;
 
    private List idleConnectionCounters = 
        Arrays.asList(
            H2IdleConnectionCounter.INSTANCE,
            OracleIdleConnectionCounter.INSTANCE,
            PostgreSQLIdleConnectionCounter.INSTANCE,
            MySQLIdleConnectionCounter.INSTANCE
    );
 
    private IdleConnectionCounter connectionCounter;
 
    private int connectionLeakCount;
 
    public ConnectionLeakUtil() {
        for ( IdleConnectionCounter connectionCounter : 
            idleConnectionCounters ) {
            if ( connectionCounter.appliesTo( 
                Dialect.getDialect().getClass() ) ) {
                this.connectionCounter = connectionCounter;
                break;
            }
        }
        if ( connectionCounter != null ) {
            connectionLeakCount = countConnectionLeaks();
        }
    }
 
    public void assertNoLeaks() {
        if ( connectionCounter != null ) {
            int currentConnectionLeakCount = countConnectionLeaks();
            int diff = currentConnectionLeakCount - connectionLeakCount;
            if ( diff > 0 ) {
                throw new ConnectionLeakException( 
                    String.format(
                        "%d connection(s) have been leaked! Previous leak count: %d, Current leak count: %d",
                        diff,
                        connectionLeakCount,
                        currentConnectionLeakCount
                    ) 
                );
            }
        }
    }
 
    private int countConnectionLeaks() {
        try ( Connection connection = newConnection() ) {
            return connectionCounter.count( connection );
        }
        catch ( SQLException e ) {
            throw new IllegalStateException( e );
        }
    }
 
    private Connection newConnection() {
        try {
            return DriverManager.getConnection(
                jdbcProperties.getUrl(),
                jdbcProperties.getUser(),
                jdbcProperties.getPassword()
            );
        }
        catch ( SQLException e ) {
            throw new IllegalStateException( e );
        }
    }
}

可以在这篇博客文章中找到IdleConnectionCounter实现，MySQL版本如下：

public class MySQLIdleConnectionCounter implements IdleConnectionCounter {
 
    public static final IdleConnectionCounter INSTANCE = 
        new MySQLIdleConnectionCounter();
 
    @Override
    public boolean appliesTo(Class<? extends Dialect> dialect) {
        return MySQL5Dialect.class.isAssignableFrom( dialect );
    }
 
    @Override
    public int count(Connection connection) {
        try ( Statement statement = connection.createStatement() ) {
            try ( ResultSet resultSet = statement.executeQuery(
                    "SHOW PROCESSLIST" ) ) {
                int count = 0;
                while ( resultSet.next() ) {
                    String state = resultSet.getString( "command" );
                    if ( "sleep".equalsIgnoreCase( state ) ) {
                        count++;
                    }
                }
                return count;
            }
        }
        catch ( SQLException e ) {
            throw new IllegalStateException( e );
        }
    }
}

现在，当你运行你的测试时，当一个连接被泄露时，你会得到一个失败：

:hibernate-core:test
 
org.hibernate.jpa.test.EntityManagerFactoryClosedTest > classMethod FAILED
    org.hibernate.testing.jdbc.leak.ConnectionLeakException