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From "Francesco Bellomi" <>
Subject Re: Locking problems with NFS
Date Tue, 20 Apr 2004 18:45:04 GMT
Doug, thanks for your suggestions!

I will implement your solution and make it public.
We already use a 1.4 JVM, so we have no problems with that.

The only problem is that, as lucene 1.4rc2, FSDirectory is 'final'; I would
go for the subclassing solution if you can make it not final; otherwise, if
someone has good arguments for the single 'fat' FSDirectory solution, just
let me know it.
In fact, a third architectural approach would be to define an API for
"pluggable" lock implementations: IMHO that would be more robust to changes
in the Directory interface and implementations.

Thanks again!

Doug Cutting <> wrote:
> Francesco Bellomi wrote:
>> we are experiencing some difficulties in using Lucene with a NFS
>> filesystem. Basically, locking seems not to work properly, since it
>> appears that
>> attempted concurring writing on the index (from different VMs) are
>> not
>> blocked, and this often causes the index to be corrupted.
>> Does anybody have a solution for this problem? Does anyone have some
>> suggestions about the implementation of some alternative approach for
>> locking, in order to make Lucene compatible with NFS?
> I just found the following article, which might point the way:
> FSDirectory.lock currently implements what this article calls
> "dotlocking".  One can implement fcntl() locking using nio, but this
> requires a 1.4 JVM, which Lucene does not (yet).
> A couple of alternatives:
> 1. One could implement a 1.4-only subclass of FSDirectory in the
> Sandbox
> that implements dotlocking plus fcntl() locking.
> 2. We could add this directly into FSDirectory so that it will only
> compile in 1.4+ JDKs, but that it will run in earlier JDKs by only
> performing fcntl() locking when in a 1.4+ JVM.  Some folks would
> complain.
> Thoughts?
> Doug
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Francesco Bellomi
"Use truth to show illusion,
and illusion to show truth."

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