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https://issues.apache.org/jira/browse/CONFIGURATION-390?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Oliver Heger updated CONFIGURATION-390:
---------------------------------------
Attachment: commons-configuration-390.patch
I have created a unit test that fails more reliably and a proposed fix.
The idea is that the lock used by the {{reload()}} method is exposed so that
external synchronization can be performed.
{{AbstractHierarchicalFileConfiguration}} now synchronizes at this lock in its
{{getProperty()}} method. This does not fix all problems with this
architecture, e.g. other methods like {{isEmpty()}} or {{containsKey()}} should
be treated in a similar way. But concurrent property reads should now be
possible.
> AbstractHierarchicalFileConfiguration is not thread safe
> --------------------------------------------------------
>
> Key: CONFIGURATION-390
> URL: https://issues.apache.org/jira/browse/CONFIGURATION-390
> Project: Commons Configuration
> Issue Type: Bug
> Components: File reloading
> Affects Versions: 1.6
> Reporter: Emmanuel Bourg
> Fix For: 1.7
>
> Attachments: commons-configuration-390.patch, configtest.tar.gz,
> TestSuite.txt
>
>
> AbstractHierarchicalFileConfiguration doesn't implement the same locking
> mechanism found in AbstractFileConfiguration. The consequence is that getting
> a property while the configuration is being reloaded by another thread can
> return an invalid result.
> This can be demonstrated by changing testDeadlockWithReload() in
> TestCombinedConfiguration to use an XMLConfiguration instead of a
> PropertiesConfiguration.
> Here is a reduced test case:
> {code:java}
> public void testConcurrentGetAndReload() throws Exception
> {
> //final FileConfiguration config = new
> PropertiesConfiguration("test.properties");
> final FileConfiguration config = new XMLConfiguration("test.xml");
> config.setReloadingStrategy(new FileAlwaysReloadingStrategy());
> assertTrue("Property not found", config.getProperty("test.short") !=
> null);
> new Thread()
> {
> public void run()
> {
> for (int i = 0; i < 1000; i++)
> {
> config.reload();
> }
> }
> }.start();
>
> for (int i = 0; i < 1000; i++)
> {
> assertTrue("Property not found", config.getProperty("test.short") !=
> null); // failure here
> }
> }
> {code}
> The test doesn't always fail. It does about 50% of the time.
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