[jira] Commented: (CONFIGURATION-390) AbstractHierarchicalFileConfiguration is not thread safe

["Ralph Goers (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CONFIGURATION-390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12762067#action_12762067 ] 

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

More changes on the branch. I've been able to fix the problem without having to resort to locking all the method calls. When a combined configuration is constructed a copy of each participating configuration is used and locking is now done in appropriate places. This allows the reload to take place without affecting other threads as they will continue using a different tree until a subsequent getRootNode() call is made.

> 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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