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From Konstantin Priblouda <>
Subject Re: Lock handling and Lucene 1.9 / 2.0
Date Mon, 13 Sep 2004 09:39:29 GMT
I'm also quite unhappy with FSDirectory and locking

Worst thing is that it creates locks on file system,
and those files are not temporary. If JVM crashes for
whatever reason - they are still there
( this is extremely inconveninet while debugging... ) 

Another reasin is that it's in  no way friendly for
IoC environment. It can not be created via

I had to write wrapper which delegates to FSDirectory,
but this is not an elegant solution... 

It's not as unfriendly as hibernate ( for IoC via pico
) , but still unfriendly...

> Therefore we dug in a bit more......
> Long answer - theres a heap of horrible, horrible
> code in the FSDirectory that tries to be clever and
> I think its not quite working correctly. 
> Two types of lock - write.lock and commit.lock. The
> write.lock is used exclusively for synchronising the
> indexing of documents and has *no* impact on
> searching whatsoever.
> Commit.lock is another little story. Commit.lock is
> used for two things - stopping indexing processes
> from overwriting segments that another one is
> currently using, and stopping IndexReaders from
> overwriting each other when they delete entries
> (dcon't even start asking my why a bloody
> IndexReader can delete documents).
> *However*, theres another naughty little usage that
> isn't listed in any of the documentation, and here
> it is....
> Doug Cutting wrote FSDirectory in such a way that it
> caches a directory. Hence, if FSDirectory is called
> more than once with the same directory, the
> FSDirectory class uses a static Hashtable to return
> the current values. However, if FSDirectory is
> called with a *different* directory, it engages a
> commit.lock while it updates the values. It *also*
> makes that Hashtable (sychronised). 

----[ Konstantin Pribluda ( ko5tik ) ]----------------
Zu Verstärkung meines Teams suche ich ab Sofort einen
Softwareentwickler[In] für die Festanstellung. 
Arbeitsort: Mainz 
Skills:  Programmieren, Kenntnisse in OpenSource-Bereich
----[ ]------------------------

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