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From Jay Yu ...@AI.SRI.COM>
Subject Re: thread safe shared IndexSearcher
Date Wed, 19 Sep 2007 22:54:45 GMT
Mark,

After reading the implementation of LuceneIndexAccessor.getSearcher(),
I realized that the method is synchronized and wait for writingDirector 
to be released. That means if we getSearcher for each query in each 
thread, there might be a contention and performance hit. In fact, even 
the method of release(searcher) is costly. On the other hand, if 
multiple threads share share one searcher then it'd defeat the
purpose of using LuceneIndexAccessor.
Do I miss sth here? What's your suggested use case for 
LuceneIndexAccessor?

Thanks!

Jay
Mark Miller wrote:
> Ill respond a point at a time:
> 
> 1.
> 
> ****************************** Hi Maik,
> 
> So what happens in this case:
> 
> IndexAccessProvider accessProvider = new IndexAccessProvider(directory,
> 
> analyzer);
> 
> LuceneIndexAccessor accessor = new LuceneIndexAccessor(accessProvider);
> 
> accessor.open();
> 
> IndexWriter writer = accessor.getWriter();
> 
> // reference to the same instance?
> 
> IndexWriter writer2 = accessor.getWriter();
> 
> writer.addDocument(....);
> 
> writer2.addDocument(....);
> 
> 
> 
> // I didn't release the writer yet
> 
> // will this block?
> 
> IndexReader reader = accessor.getReader();
> 
> reader.delete(....);
> 
> ************
> 
> This is not really an issue. First, if you are going to delete with a Reader
> you need to call getWritingReader and not getReader. When you do that, the
> getWritingReader call will block until writer and writer2 are released. If
> you are just adding a couple docs before releasing the writers, this is no
> problem because the block will be very short. If you are loading tons of
> docs and you want to be able to delete with a Reader in a timely manner, you
> should release the writers every now and then (release and re-get the Writer
> every 100 docs or something). An interactive index should not hog the
> Writer, while something that is just loading a lot could hog the Writer.
> This is no different than normal…you cannot delete with a Reader while
> adding with a Writer with Lucene. This code just enforces those semantics.
> The best solution is to just use a Writer to delete – I never get a
> ReadingWriter.
> 
> 2. http://issues.apache.org/bugzilla/show_bug.cgi?id=34995#c3
> 
> This is no big deal either. I just added another getWriter call that takes a
> create Boolean.
> 
> 3. I don't think there is a latest release. This has never gotten much
> official attention and is not in the sandbox. I worked straight from the
> originally submitted code.
> 
> 4. I will look into getting together some code that I can share. The
> multisearcher changes that are need are a couple of one liners really, so at
> a minimum I will give you the changes needed.
> 
> 
> 
> -       Mark
> 
> 
> 
> On 9/19/07, Jay Yu <yu@ai.sri.com> wrote:
> 
> Mark,
> 
> 
> 
> thanks for sharing your insight and experience about LuceneIndexAccessor!
> 
> I remember seeing some people reporting some issues about it, such as:
> 
> http://www.archivum.info/java-dev@lucene.apache.org/2005-05/msg00114.html
> 
> http://issues.apache.org/bugzilla/show_bug.cgi?id=34995#c3
> 
> 
> 
> Have those issues been resolved?
> 
> 
> 
> Where did you get the latest release? It is not in the official Lucene
> 
> sandbox/contrib.
> 
> 
> 
> Finally, are you willing to share your extended version to include your
> 
> tweak relating to the MultiSearcher?
> 
> 
> 
> Thanks a lot!
> 
> 
> 
> Jay
> 
> 
> 
> Mark Miller wrote:
> 
>> I use option 3 extensivley and find it very effective. There is a tweak or
> 
>> two required to get it to work right with MultiSearchers, but other than
> 
>> that, the code is great. I have built a lot on top of it. I'm on the list
> 
>> all the time and would be happy to answer any questions you have in
> regards
> 
>> to LuceneIndexAccessor. Frankly, I think its overlooked far too much.
> 
> 
>> - Mark
> 
> 
> 
>> On 9/19/07, Jay Yu <yu@ai.sri.com> wrote:
> 
> 
>>> In a multithread app like web app, a shared IndexSearcher could throw a
> 
>>> AlreadyClosedException when another thread is trying to update the
> 
>>> underlying IndexReader by closing the shared searcher after the index is
> 
>>> updated. Searching over the past discussions on this mailing list, I
> 
>>> found several approaches to solve the problem.
> 
>>> 1. use solr
> 
>>> 2. use DelayCloseIndexSearcher
> 
>>> 3. use LuceneIndexAccessor
> 
> 
> 
>>> the first one is not feasible for us; some people seemed to have
> 
>>> problems with No. 2 and I do not find a lot of discussions around No.3.
> 
> 
>>> I wonder if anyone has good experience on No 2 and 3?
> 
>>> Or do I miss other better solutions?
> 
> 
>>> Thanks for any suggestion/comment!
> 
> 
>>> Jay
> 
> 
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> 
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> 
> 
> 
> 
> 
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