[AXIOM-249] UUIDGenerator generates same ID multiple times when invoked from multiple threads

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Environment: Ubuntu 6.06, JDK 1.5
• Assignee: Eran Chinthaka
• Reporter: Chathura Ekanayake
• Created: 05/May/07 05:00
• Updated: 27/Mar/11 11:46
• Resolved: 07/May/07 03:56

Description

org.apache.axiom.om.util.UUIDGenerator generates same UUID more than once, when the UUIDGenerator.getUUID() is invoked from multiple threads concurrently. I have tested this with 100 threads, each invoking the getUUID() 1000 times. UUIDGenerator generates about 1500 to 3000 same IDs for 100000 invocations.

I am listing the code I have used to test this below:

package uuidtest;

import org.apache.axiom.om.util.UUIDGenerator;

import java.util.*;

public class UUIDGenTest {

private static final int THREADS = 100;
private static final int ITERATIONS = 1000;

Map generatedIds = Collections.synchronizedMap(new HashMap());
int errorCount = 0;
Object lock = new Object();

public static void main(String[] args)

{ new UUIDGenTest().test(); }

public void test() {

Thread[] threads = new Thread[THREADS];
for (int i = 0; i < THREADS; i++)

{ threads[i] = new Thread(new Generate()); threads[i].start(); }

for (int i = 0; i < THREADS; i++) {
try

{ threads[i].join(); }

catch (InterruptedException e)

{ e.printStackTrace(); }

}
System.out.println("=======================================================");
System.out.println(" Error count : " + errorCount + " for " + THREADS * ITERATIONS);
System.out.println("=======================================================");
}

class Generate implements Runnable {
public void run() {
for (int i=0; i<ITERATIONS; i++) {
String id = UUIDGenerator.getUUID();
if (generatedIds.containsKey(id)) {
System.out.println("ERROR - Same UUID has been generated before. UUID: " + id);
synchronized(lock)

{ errorCount++; }

}
generatedIds.put(id, Thread.currentThread().getName());
}
}
}
}

If you compile and run this with AXIOM jars in the classpath, you could observe an error count about 1500 to 3000.

Issue Links

• relates to: WSS-221 UUIDGenerator generates duplicate identifiers when used in a multi-threaded environment