Bug #2354 JDBC and "Too many connections"

• Submitted: 12 Jan 2004 8:24
• Modified: 12 Jan 2004 8:55
• Reporter: Michel Onoff
• Status: Closed
• Category: Connector / J
• Severity: S2 (Serious)
• Version: 3.0.9 and 3.1.0
• OS: Windows (Windows 2K)
• CPU Architecture: Any

[12 Jan 2004 8:24] Michel Onoff

Description:
When reaching too many connections to the server (100 in the default configuration), the JDBC driver throws a SQLException ex with:

java.sql.SQLException: Server configuration denies access to data source
0 as ex.getErrorCode()
08001 as ex.getSQLState()

There seems to be no way to detect that too many connections have been reached through JDBC.

How to repeat:
Simply write the simplest Java program that opens connections in an endless loop, stores them in an ArrayList to avoid garbage collection, and catches the SQLException by printing the relevant information.

[12 Jan 2004 8:45] Michel Onoff

A sample program that produces the misleading SQLException is:

package test;

import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class ConnectionCounter {

  public static void main(String[] args) {
    int connectionCount = 0;
    List conns = new ArrayList();
    try {
      Class.forName("com.mysql.jdbc.Driver").newInstance();
      System.out.println("now");
      while (true) {
        conns.add(
          DriverManager.getConnection(
            "jdbc:mysql://localhost/test",
            "root",
            ""));
        ++connectionCount;
      }
    }
    catch (SQLException e) {
      e.printStackTrace();
      System.out.println(e.getErrorCode());
      System.out.println(e.getSQLState());
      System.out.println(connectionCount);
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }

}

[12 Jan 2004 8:55] Mark Matthews

Thank you for your bug report. This issue has been committed to our
source repository of that product and will be incorporated into the
next release.

If necessary, you can access the source repository and build the latest
available version, including the bugfix, yourself. More information 
about accessing the source trees is available at
    http://www.mysql.com/doc/en/Installing_source_tree.html

Additional info:

Please try a nightly build of either 3.0.x or 3.1.x from http://downloads.mysql.com/snapshots.php

The latest versions of the driver read the error message from the server in this case, and it can be retrieved via SQLException.getMessage().