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https://issues.apache.org/jira/browse/DBCP-369?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Phil Steitz updated DBCP-369:
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Fix Version/s: 1.4.1
> Exception when using SharedPoolDataSource concurrently
> ------------------------------------------------------
>
> Key: DBCP-369
> URL: https://issues.apache.org/jira/browse/DBCP-369
> Project: Commons Dbcp
> Issue Type: Bug
> Affects Versions: 1.4
> Environment: Java Hotspot Server VM 1.6.0_07, Linux
> Reporter: Michael Pradel
> Fix For: 1.4.1
>
>
> Hi,
> I get a ConcurrentModificationException when using instances of
> SharedPoolDataSource concurrently. The problem occurs when one thread calls
> setDataSourceName() while another thread calls close(), either on the same
> instance of SharedPoolDataSource or on different instances. I'll attach a
> short example program that leads to an exception for almost every run on my
> machine.
> The cause of the exception seems to be in InstanceKeyObjectFactory.
> registerNewInstance() is synchronized, but removeInstance() isn't. This
> allows concurrent accesses to the non-thread-safe 'instanceMap'.
> Is this a bug? Or are SharedPoolDataSource and InstanceKeyObjectFactory not
> supposed to be thread-safe?
> Thanks!
> import java.util.ArrayList;
> import org.apache.commons.dbcp.datasources.SharedPoolDataSource;
> public class SharedPoolDataSourceTest {
> public static void main(String[] args) {
> new SharedPoolDataSourceTest().run();
> }
>
> private void run() {
> final ArrayList<SharedPoolDataSource> dataSources = new
> ArrayList<SharedPoolDataSource>();
> for (int j = 0; j < 10000; j++) {
> SharedPoolDataSource dataSource = new
> SharedPoolDataSource();
> dataSources.add(dataSource);
> }
>
> Thread t1 = new Thread(new Runnable() {
> public void run() {
> for (SharedPoolDataSource dataSource :
> dataSources) {
> dataSource.setDataSourceName("a");
> }
> }
> });
> Thread t2 = new Thread(new Runnable() {
> public void run() {
> for (SharedPoolDataSource dataSource :
> dataSources) {
> try { dataSource.close(); } catch
> (Exception e) {}
> }
>
> }
> });
> t1.start();
> t2.start();
> try {
> t1.join();
> t2.join();
> } catch (InterruptedException ie) {}
> }
> }
> Exception in thread "Thread-0" java.util.ConcurrentModificationException
> at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
> at java.util.HashMap$KeyIterator.next(HashMap.java:828)
> at
> org.apache.commons.dbcp.datasources.InstanceKeyObjectFactory.registerNewInstance(InstanceKeyObjectFactory.java:51)
> at
> org.apache.commons.dbcp.datasources.InstanceKeyDataSource.setDataSourceName(InstanceKeyDataSource.java:246)
> at
> potentialBugs.SharedPoolDataSourceTest$1.run(SharedPoolDataSourceTest.java:23)
> at java.lang.Thread.run(Thread.java:619)
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