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我最近切换到 Spring Framework 而不是手动处理 JDBC，这主要是一个很好的过渡。但是，一个程序开始遇到奇怪的问题：如果数据库很慢，则调用getJdbcTemplate().update( ... )它时有时永远不会返回。

经过一番研究，我从 Apache DBCP 切换到C3PO，但问题仍然存在。

这是我正在使用的代码：

public class MyDao extends SimpleJdbcDaoSupport {
    private static Logger logger = Logger.getLogger(MyDao.class);

    public MyDao(Config config) {
        super();

        ComboPooledDataSource cpds = new ComboPooledDataSource();
        try {
            cpds.setDriverClass("com.mysql.jdbc.Driver");
        } catch (PropertyVetoException e) {
            throw new RuntimeException(e);
        }
        cpds.setUser("username");
        cpds.setPassword("password");
        cpds.setJdbcUrl("jdbc:mysql://localhost/schema" + 
                        "?useUnicode=true&characterEncoding=UTF-8");
        cpds.setMaxStatements( 180 );
        cpds.setPreferredTestQuery("SELECT 1");
        cpds.setTestConnectionOnCheckout(true);

        this.setDataSource(cpds);
    }

    public void addToWorkQueue(String item) {
        long[] ids = Utils.getItemIds(item);

        try {
            logger.debug("About to insert to work table");
            getJdbcTemplate().update(
                    "INSERT IGNORE INTO work " +
                    "SELECT * FROM queue WHERE id_1 = ? AND id_2 = ?",
                    new Object[] { ids[0], ids[1] }
            );
        } finally {
            logger.debug("Updated work table");
        }
    }
}

这是它在日志文件中的样子：

2009-07-29 17:37:13.570 com.mycomp.MyDao About to insert into work table
2009-07-29 17:37:13.570 com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@170984c] on CHECKOUT.
2009-07-29 17:37:13.571 com.mchange.v2.c3p0.stmt.GooGooStatementCache checkinAll(): com.mchange.v2.c3p0.stmt.GlobalMaxOnlyStatementCache stats -- total size: 1; checked out: 0; num connections: 1; num keys: 1
2009-07-29 17:37:13.571 com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@170984c] on CHECKOUT has SUCCEEDED.
2009-07-29 17:37:13.571 com.mchange.v2.resourcepool.BasicResourcePool trace com.mchange.v2.resourcepool.BasicResourcePool@d402dd [managed: 3, unused: 2, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@170984c)
2009-07-29 17:37:13.571 com.mchange.v2.c3p0.stmt.GooGooStatementCache com.mchange.v2.c3p0.stmt.GlobalMaxOnlyStatementCache ----> CACHE HIT
2009-07-29 17:37:13.571 com.mchange.v2.c3p0.stmt.GooGooStatementCache checkoutStatement: com.mchange.v2.c3p0.stmt.GlobalMaxOnlyStatementCache stats -- total size: 1; checked out: 1; num connections: 1; num keys: 1

这是代码挂起的地方。通常它只是这样进行：

2009-07-29 17:37:13.762 com.mchange.v2.c3p0.stmt.GooGooStatementCache checkinStatement(): com.mchange.v2.c3p0.stmt.GlobalMaxOnlyStatementCache stats -- total size: 1; checked out: 0; num connections: 1; num keys: 1
2009-07-29 17:37:13.763 com.mchange.v2.c3p0.stmt.GooGooStatementCache checkinAll(): com.mchange.v2.c3p0.stmt.GlobalMaxOnlyStatementCache stats -- total size: 1; checked out: 0; num connections: 1; num keys: 1
2009-07-29 17:37:13.763 com.mchange.v2.resourcepool.BasicResourcePool trace com.mchange.v2.resourcepool.BasicResourcePool@d402dd [managed: 3, unused: 2, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@170984c)
2009-07-29 17:37:13.763 com.mycomp.MyDao Updated work table

我不知道为什么我没有从 Spring Framework 本身收到任何日志消息。我在我的主代码中添加了这些行：

Logger springLogger = Logger.getLogger("org.springframework");
springLogger.setLevel(Level.TRACE);
springLogger.debug("testing spring logger");

测试消息显示，但没有其他内容。很抱歉分道扬镳。

在挂起之前我确实注意到减速。上次成功运行查询需要一分半钟才能完成，而不是通常的 200 毫秒。下一次，我让它运行 25 分钟，然后终止进程。

我知道我正在处理的数据库（InnoDB）有一些问题，但这似乎是在超时之后，Spring Framework 只是“放弃”并挂起。

任何意见，将不胜感激。

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1 回答 1

3

最终，通过修复底层数据库问题避免了该问题。

我使用 InnoDB 表作为工作队列，这意味着我向其中添加和删除了很多项目。该表在给定时间从未有太多行，但显然 InnoDB 无法处理此类工作，或者正如我的 DBA 朋友所说，“从表中删除行对性能没有任何作用”。

After switching to a much crazier db strategy, which involved creating and dropping tables all the time, the performance was much improved and the hangs went away.

So I guess what I'm saying is, skaffman's comment was probably right. This didn't have anything to do with Spring.

于 2009-10-29T21:33:22.400 回答