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From "Luke Shannon" <lshan...@hypermedia.com>
Subject Re: Lucene : avoiding locking (incremental indexing)
Date Mon, 15 Nov 2004 23:11:17 GMT
I like the sound of the Queue approach.  I also don't like that I have to
focefully unlock the index.

I'm not the most experience programmer and am on a tight deadline. The
approach I ended up with was the best I could do with the experience I've
got and the time I had.

My indexer works so far and doesn't have to forcefully release the lock on
the Index too often (the case is most likely to occur when someone removes a
content file(s) and the reader needs to delete from the existing index for
the first time). We will see what happens as more people use the system with
large content directories.

As I learn more I plan to expand the functionality of my class.

Luke S

----- Original Message ----- 
From: <jeichels@optonline.net>
To: "Lucene Users List" <lucene-user@jakarta.apache.org>
Sent: Monday, November 15, 2004 5:50 PM
Subject: Re: Lucene : avoiding locking (incremental indexing)


> It really seems like I am not the only person having this issue.
>
> So far I am seeing 2 solutions and honestly I don't love either totally.
I am thinking that without changes to Lucene itself, the best "general" way
to implement this might be to have a queue of changes and have Lucene work
off this queue in a single thread using a time-settable batch method.   This
is similar to what you are using below, but I don't like that you forcibly
unlock Lucene if it shows itself locked.   Using the Queue approach, only
that one thread could be accessing Lucene for writes/deletes anyway so there
should be no "unknown" locking.
>
> I can imagine this being a very good addition to Lucene - creating a high
level interface to Lucene that manages incremental updates in such a manner.
If anybody has such a general piece of code, please post it!!!   I would use
it tonight rather then create my own.
>
> I am not sure if there is anything that can be done to Lucene itself to
help with this need people seem to be having.  I realize the likely reasons
why Lucene might need to only have one Index writer and the additional load
that might be caused by locking off pieces of the database rather then the
whole database.  I think I need to look in the developer archives.
>
> JohnE
>
>
>
> ----- Original Message -----
> From: Luke Shannon <lshannon@hypermedia.com>
> Date: Monday, November 15, 2004 5:14 pm
> Subject: Re: Lucene : avoiding locking (incremental indexing)
>
> > Hi Luke;
> >
> > I have a similar system (except people don't need to see results
> > immediatly). The approach I took is a little different.
> >
> > I made my Indexer a thread with the indexing operations occuring
> > the in run
> > method. When the IndexWriter is to be created or the IndexReader
> > needs to
> > execute a delete I called the following method:
> >
> > private void manageIndexLock() {
> >  try {
> >   //check if the index is locked and deal with it if it is
> >   if (index.exists() && IndexReader.isLocked(indexFileLocation)) {
> >    System.out.println("INDEXING INFO: There is more than one
> > process trying
> > to write to the index folder. Will wait for index to become
> > available.");    //perform this loop until the lock if released or
> > 3 mins
> >    // has expired
> >    int indexChecks = 0;
> >    while (IndexReader.isLocked(indexFileLocation)
> >      && indexChecks < 6) {
> >     //increment the number of times we check the index
> >     // files
> >     indexChecks++;
> >     try {
> >      //sleep for 30 seconds
> >      Thread.sleep(30000L);
> >     } catch (InterruptedException e2) {
> >      System.out.println("INDEX ERROR: There was a problem waiting
> > for the
> > lock to release. "
> >          + e2.getMessage());
> >     }
> >    }//closes the while loop for checking on the index
> >    // directory
> >    //if we are still locked we need to do something about it
> >    if (IndexReader.isLocked(indexFileLocation)) {
> >     System.out.println("INDEXING INFO: Index Locked After 3
> > minute of
> > waiting. Forcefully releasing lock.");
> >     IndexReader.unlock(FSDirectory.getDirectory(index, false));
> >     System.out.println("INDEXING INFO: Index lock released");
> >    }//close the if that actually releases the lock
> >   }//close the if ensure the file exists
> >  }//closes the try for all the above operations
> >  catch (IOException e1) {
> >   System.out.println("INDEX ERROR: There was a problem waiting
> > for the lock
> > to release. "
> >       + e1.getMessage());
> >  }
> > }//close the manageIndexLock method
> >
> > Do you think this is a bad approach?
> >
> > Luke
> >
> > ----- Original Message ----- 
> > From: "Luke Francl" <luke.francl@stellent.com>
> > To: "Lucene Users List" <lucene-user@jakarta.apache.org>
> > Sent: Monday, November 15, 2004 5:01 PM
> > Subject: Re: Lucene : avoiding locking (incremental indexing)
> >
> >
> > > This is how I implemented incremental indexing. If anyone sees
> > anything> wrong, please let me know.
> > >
> > > Our motivation is similar to John Eichel's. We have a digital asset
> > > management system and when users update, delete or create a new
> > asset,> they need to see their results immediately.
> > >
> > > The most important thing to know about incremental indexing that
> > > multiple threads cannot share the same IndexWriter, and only one
> > > IndexWriter can be open on an index at a time.
> > >
> > > Therefore, what I did was control access to the IndexWriter
> > through a
> > > singleton wrapper class that synchronizes access to the
> > IndexWriter and
> > > IndexReader (for deletes). After finishing writing to the index, you
> > > must close the IndexWriter to flush the changes to the index.
> > >
> > > If you do this you will be fine.
> > >
> > > However, opening and closing the index takes time so we had to
> > look for
> > > some ways to speed up the indexing.
> > >
> > > The most obvious thing is that you should do as much work as
> > possible> outside of the synchronized block. For example, in my
> > application, the
> > > creation of Lucene Document objects is not synchronized. Only
> > the part
> > > of the code that is between your IndexWriter.open() and
> > > IndexWriter.close() needs to be synchronized.
> > >
> > > The other easy thing I did to improve performance was batch
> > changes in a
> > > transaction together for indexing. If a user changes 50 assets, that
> > > will all be indexed using one Lucene IndexWriter.
> > >
> > > So far, we haven't had to explore further performance
> > enhancements, but
> > > if we do the next thing I will do is create a thread that
> > gathers assets
> > > that need to be indexed and performs a batch job every five
> > minutes or
> > > so.
> > >
> > > Hope this is helpful,
> > > Luke
> > >
> > >
> > > -----------------------------------------------------------------
> > ----
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> > > For additional commands, e-mail: lucene-user-help@jakarta.apache.org
> > >
> > >
> >
> >
> >
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> > --
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> >
> >
>
>
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