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From Otis Gospodnetic <otis_gospodne...@yahoo.com>
Subject Re: FSDirectory patch for file renaming
Date Sun, 23 Feb 2003 06:33:46 GMT
I hate having to make the suggested change for the reasons Matt
mentioned as disadvantages below....but what is one to do?
I'll change the code shortly.

If any other developers are against this change, speak up.

Otis


--- Matt Tucker <matt@jivesoftware.com> wrote:
> Hello all,
> 
> For quite some time, we've been experiencing intermittent indexing
> failures
> that look similar to the following:
> 
> java.io.IOException: couldn't rename segments.new to segments 
>      at
>
org.apache.lucene.store.FSDirectory.renameFile(Ljava.lang.String;Ljava.lang.
> String)V(Unknown Source) 
>      at
>
org.apache.lucene.index.SegmentInfos.write(Lorg.apache.lucene.store.Director
> y)V(Unknown Source)
> 
> This is caused by File.renameTo failing. From previous run-ins with
> that
> method, it's actually fairly flaky, especially under various Windows
> JVMs.
> The fix is pretty easy -- if File.renameTo fails, manually copy the
> file
> from the old to new destination.
> 
> Old code (FSDirectory.renameFile): 
> 
> ------------------------------
>     if (!old.renameTo(nu))
>       throw new IOException("couldn't rename " + from + " to " + to);
> ------------------------------
> 
> New code ("buf" variable is declared at top of file as null):
> 
> ------------------------------
>     // Rename the old file to the new one. Unfortunately, the
> renameTo()
> method doesn't
>     // work reliably under some JVMs. Therefore, if the rename fails,
> we
> manually rename by
>     // copying the old file to the new one.
>     if (!old.renameTo(nu)) {
>       try {
>         java.io.InputStream in = new FileInputStream(old);
>         java.io.OutputStream out = new FileOutputStream(nu);
>         int len;
>         // See if the buf needs to be initialized. Initialization is
> only
> done on-demand
>         // since many VM's will never run into the renameTo bug and
> hence
> shouldn't waste
>         // 1K of mem for no reason.
>         if (buf == null) {
>           buf = new byte[1024];
>         }
>         while ((len = in.read(buf)) >= 0) {
>            out.write(buf, 0, len);
>         }
>         in.close();
>         out.close();
> 
>         // Delete the old file.
>         old.delete();
>       }
>       catch (IOException ioe) {
>         throw new IOException("couldn't rename " + from + " to " +
> to);
>       }
>     }
> ------------------------------
> 
> Advantages to this fix:
> 
>  * Makes indexing more reliable, especially under VM's where the
> renameTo
> method doesn't always work.
>  * Uses no additional memory or resources when File.renameTo works
> normally.
> 
> Disadvantages:
> 
>  * It always sucks to add workarounds to bugs in other libraries, but
> what
> is one to do?
>  * We've run into File.renameTo issues on multiple machines and VM
> versions,
> but it would be good if others could confirm they've had problems as
> well. 
> 
> I'd suggest this fix as a good candidate for Lucene 1.3 unless others
> see
> problems with it.
> 
> Regards,
> Matt
> 
> 
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