Maxime Duchemin created VFS-528:
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Summary: DefaultFileMonitor missing to report some file creation.
Key: VFS-528
URL: https://issues.apache.org/jira/browse/VFS-528
Project: Commons VFS
Issue Type: Bug
Affects Versions: 2.0, 1.0, 1.1, 2.1
Environment: Windows
Reporter: Maxime Duchemin
It's hard to reproduce but sometimes the DefaultFileMonitor does not report
some file creation. It happens when a file is added in a directory that has
just been added in the DefaultFileMonitor.
It is more likely to appear when the DefaultFileMonitor is starting.
To reproduce (might take several tries to fail)
- Start the DefaultFileMonitor
- Quickly create a directory inside the monitored directory.
- Quickly create a file inside this directory.
The issue is caused by a flaw in the code.
When the new directory is detected, the DefaultFileMonitor fires the creation
event as expected (in fireAllCreate method). However does not immediately
register the directory's content for comparison with the next check. It rather
postpones the registration with a call to "queueAddFile(child)" (line 425).
The directory and its content actually registered a bit later at the end of the
main loop on line 335.
The issue is when a file is added between the queueAddFile and the actual
addFile. No events is fired for this file as it does not exists in the
fireAllCreate method. But as it gets registered a bit later, the next check
don't detect any change on the file system and does not trigger en event too.
I see too possible fix for this issue:
1. Don't queue the registration of the file.
2. Make sure that when the actual registration occurs (the call to addFile),
the exact same set of files is used as in the fireAllCreate method.
For my project I used the first solution by overriding the queueAddFile method.
It made me realized that it might be the reason why it is protected. It seems
to work, but I'm not sure if it as other consequences.
The bug has been found on vfs 1.0 and 2.2.
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