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Re: Thoughts on filesystem action driven hot deployment

created by Jason Greene in JBoss AS7 Development - View the full discussion

Todd Trimmer wrote:


I've been experiencing a problem with atomic moves in AS5 under Windows. About twice a day, AS5's JVM refuses to release a file handle to META-INF/application.xml or an EJB descriptor file. I cannot swap out the old exploded archive when this happens. This is perplexing since it's not like AS5 is hung. All my apps are still working fine.


In light of this, I would much rather have to touch/copy/delete a marker file than rely on atomic moves.

Thanks for the feedback. The locking semantics on windows are certainly a major problem with the current approaches. So assuming we fixed the access to descriptors, to not hold locks (the correct behavior), delete-undeploy could still fail if there are web requests coming in. Servicing the request requires reading the file, which holds a lock. Granted there is a short lifespan, but all it takes is one happening at the same time to prevent the move.

Also, while I'm sure the HDScanner is performant, the amount of juggling it has to do seems like a convoluted solution for what shouldn't be such a big problem. But then again, if it were that easy, this thread wouldn't even exist.

Yeah we want to limit this to be as simple and clean as possible. If we make this more "correct" then we can speed up the scanning time. Part of the reason it ends up with low values is to hide the various race problems. Ultimately though we are limited by what the FS gives us.


Another thing AS7 will have is a CLI, which would be more explicit, intuitive, and immediate e.g. "deploy blah.ear, redeploy blah.ear, undeploy blah.ear". This could even have a maven, or ant plugin on it.

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