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From "Gerrit Jansen van Vuuren (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3653) Lucene Search not scalling
Date Sat, 17 Dec 2011 19:43:30 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3653?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171652#comment-13171652
] 

Gerrit Jansen van Vuuren commented on LUCENE-3653:
--------------------------------------------------

Just to explain App.java:

I've created this app to show the problem.
Basically I create 500 threads.
 Each thread do:
        Create a Single Query.
        Does 10000 search requests against the lucene index.
        Calculate max,min,average
 Wait for threads to complete.
 Print out max,min,average


The images attached are taken from profiling while running this class.


                
> Lucene Search not scalling
> --------------------------
>
>                 Key: LUCENE-3653
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3653
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Gerrit Jansen van Vuuren
>         Attachments: App.java, profile_1_a.png, profile_1_b.png, profile_1_c.png, profile_1_d.png,
profile_2_a.png, profile_2_b.png, profile_2_c.png
>
>
> I've noticed that when doing thousands of searches in a single thread the average time
is quite low i.e. a few milliseconds. When adding more concurrent searches doing exactly the
same search the average time increases drastically. 
> I've profiled the search classes and found that the whole of lucene blocks on 
> org.apache.lucene.index.SegmentCoreReaders.getTermsReader
> org.apache.lucene.util.VirtualMethod
>   public synchronized int getImplementationDistance 
> org.apache.lucene.util.AttributeSourcew.getAttributeInterfaces
> These cause search times to increase from a few milliseconds to up to 2 seconds when
doing 500 concurrent searches on the same in memory index. Note: That the index is not being
updates at all, so not refresh methods are called at any stage.
> Some questions:
>   Why do we need synchronization here?
>   There must be a non-lockable solution for these, they basically cause lucene to be
ok for single thread applications but disastrous for any concurrent implementation.
> I'll do some experiments by removing the synchronization from the methods of these classes.

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