Bug #38782 RandomBalanceStrategy throws IndexOutOfBoundsException
Submitted: 13 Aug 2008 21:25 Modified: 16 Oct 2008 14:00
Reporter: Todd Farmer (OCA) Email Updates:
Status: Closed Impact on me:
Category:Connector / J Severity:S3 (Non-critical)
Version:5.1.6 OS:Any
Assigned to: Todd Farmer CPU Architecture:Any

[13 Aug 2008 21:25] Todd Farmer
When using the random load balancing strategy and starting with two servers which are both unavailable, I get an IndexOutOfBoundsException when removing a server from the whiteList in the following code:

						Integer whiteListIndex = (Integer) whiteListMap

						// exclude this host from being picked again
						if (whiteListIndex != null) {


It appears that this is happening because the whiteList entries are being culled (affecting the index locations), but the whiteListMap is not updated. 

Stack trace:

java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
	at java.util.ArrayList.RangeCheck(ArrayList.java:546)
	at java.util.ArrayList.remove(ArrayList.java:389)
	at com.mysql.jdbc.RandomBalanceStrategy.pickConnection(RandomBalanceStrategy.java:85)
	at com.mysql.jdbc.LoadBalancingConnectionProxy.pickNewConnection(LoadBalancingConnectionProxy.java:357)
	at com.mysql.jdbc.LoadBalancingConnectionProxy.<init>(LoadBalancingConnectionProxy.java:183)
	at com.mysql.jdbc.NonRegisteringDriver.connectLoadBalanced(NonRegisteringDriver.java:327)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:268)
	at java.sql.DriverManager.getConnection(DriverManager.java:525)
	at java.sql.DriverManager.getConnection(DriverManager.java:171)

How to repeat:
	public static void main(String[] args) {
		Map m = new HashMap();
		Long l = (Long) m.get("test");
        try {
			Class.forName ("com.mysql.jdbc.Driver");
			Connection conn = DriverManager.getConnection ( "jdbc:mysql:loadbalance://localhost:3310,localhost:3311/test", "root", null);

		} catch (Exception e) {
			// TODO Auto-generated catch block


Suggested fix:
Maintain whiteListMap when hosts are deleted from whiteList.
[16 Oct 2008 14:00] Tony Bedford
An entry was added to the 5.1.7 changelog:

When using the random load balancing strategy and starting with two servers that were both unavailable, an IndexOutOfBoundsException was generated when removing a server from the whiteList.