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From "Ralph Goers (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CONFIGURATION-390) AbstractHierarchicalFileConfiguration is not thread safe
Date Sun, 27 Sep 2009 06:28:16 GMT

    [ https://issues.apache.org/jira/browse/CONFIGURATION-390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12759991#action_12759991
] 

Ralph Goers commented on CONFIGURATION-390:
-------------------------------------------

I was able to get my test to pass by synchronizing the public methods.  This gets even more
interesting because of SubnodeConfiguration objects.

I'm beginning to think that AbstractHierarchicalFileConfiguration, CombinedConfiguration and
SubnodeConfiguration all need to extend a new class named HierarchicalReloadableConfiguration.
This class would provide the reload lock object (or set it to the lock provided by the parent)
and then lock all the appropriate methods. Subclasses wouldn't then have to provide overrides
for all the methods and would be able to lock with the appropriate lock when they do override
methods.

> 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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