PreparedStatement won't ever timeout even if explicitly set

问题

I am trying to simulate an scenario where my service loses connection to a database and cannot do an INSERT by blocking the connection with iptables, but I can't make the executeQuery() method to timeout.

What I did is setting a timeout for the PreparedStatement like this statement.setQueryTimeout(5). Here is the code.

HikariConfig config = new HikariConfig();

config.setJdbcUrl("jdbc:mysql://db-url/db");
config.setUsername("user");
config.setPassword("passwd");

config.setMaximumPoolSize(10);
config.setAutoCommit(false);
config.setConnectionTimeout(5000);
config.setDriverClassName("com.mysql.jdbc.Driver");
config.addDataSourceProperty("cachePrepStmts", "true");
config.addDataSourceProperty("prepStmtCacheSize", "250");
config.addDataSourceProperty("prepStmtCacheSqlLimit", "2048");
config.addDataSourceProperty("autoReconnect", "true");

final HikariDataSource pool = new HikariDataSource(config);

final String query = "INSERT INTO xtable VALUES (?, ?, ?, ?, ?)";

try ( Connection connection = pool.getConnection() )
{
    try ( PreparedStatement statement = connection.prepareStatement(query) )
    {
        // this is what I expect to work
        statement.setQueryTimeout(5);

        for ( Info info : infos )
        {
            statement.setString(1, info.getValue1());
            statement.setString(2, info.getValue2());
            statement.setString(3, info.getValue3());
            statement.setString(4, info.getValue4());
            statement.setString(5, info.getValue5());

            try
            {
                System.out.println("Waiting");
                Thread.sleep(5000);
                // I use this sleep to ban the database url with iptables
                // to simulate a disconnection
                System.out.println("Waited");
            }
            catch ( InterruptedException e )
            {
                e.printStackTrace();
            }

            System.out.println("Before executeQuery");
            statement.executeQuery();
            // I assumed that this would timeout after 5 seconds
            // But it never reaches the next System.out.print
            System.out.println("After executeQuery");
        }
    }

    System.out.println("Before commit");
    connection.commit();
    System.out.println("After commit");
}
catch ( SQLException e )
{
    log.error("Couldn't execute query", e);
}

The output would be:

Waiting
Waited
Before executeQuery

and then it hangs forever... What can I do to make it throw an Exception?

回答1:

Call Connection.setNetworkTimeout() in a try-finally.

private final static Executor immediateExecutor = Runnable::run;

try ( Connection connection = pool.getConnection() ) {
   int timeout = connection.getNetworkTimeout();
   connection.setNetworkTimeout(immediateExecutor, TimeUnit.SECONDS.toMillis(5));
   ...
   try (PreparedStatement...) {
      ...
   }
   finally {
      connection.setNetworkTimeout(timeout);
   }
}
finally {
   ...
}

You are suffering from unacknowledged TCP traffic, which can hang a connection if a network timeout is not set.

回答2:

You always could:

try{
     preparedstatement = connection.prepareStatement(query);
     preparedstatement.setQueryTimeout(seconds);
}

Instead of what you did. Maybe that would work better. Same thing goes for the:

Connection connection = pool.getConnection()

来源：https://stackoverflow.com/questions/48703594/preparedstatement-wont-ever-timeout-even-if-explicitly-set

标签

java

mysql

jdbc

prepared-statement