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From Volodymyr Bychkoviak <>
Subject Re: Compound / non-compound index files and SIGKILL
Date Tue, 06 Jun 2006 12:12:02 GMT
In my application I was queuing IDs of appropriate record in Database 
not whole document. Document was created right before adding it to 
index. All this work was done in separated thread, so other threads 
responded very quickly.

It depends on your application and at what speed your new data comes.

If application is killed or crashes then you'll lost all documents that 
was buffered in memory  (IndexWriter.minMergeDocs property).

Actually I don't know how JVM's shutdown hooks reacts to different kill 
signals. My though is that application should not be killed. :)
Also if you need to enshure that your data is indexed properly then on 
startup you can do special check what data was already added to database 
but wasn't added to index and enqueue it into queue... But it also 

Rob Staveley (Tom) wrote:
> This is a good idea. I had been worried about the additional heap
> requirement maintaining a queue, without being able to serialize/deserialize
> Documents (i.e. a build up of Lucene Documents in RAM). I have been
> marshalling addDocument() calls using a synchronized object; the same
> threads have been taking responsibility for creating Documents
> (unsynchronized) and adding them to the index writer (synchronized). I guess
> I could have a one Document queue feeding a single addDocument thread, which
> would effectively be the same approach, but which would make it easier to
> ensure that only the create Document thread is killed when I get a SIGTERM
> and the addDocument thread is left to run its course (assuming it hasn't
> hanged!).
> Having said that, I'm not sure what I could do in a shutdown hook, which
> wouldn't already have been done by a SIGTERM to get the hanged thread to
> terminate. The reason for SIGKILL was that the daemon wouldn't be killed by
> SIGTERM. I guess I'd feel more confident about using SIGKILL, if I knew that
> the uninterruptible hanged thread was creating a Document, which I could
> interrupt without corrupting the index, rather than adding the document to
> the index, which is liable to result in orphaned files and/or a corrupted
> index, if killed.
> -----Original Message-----
> From: Volodymyr Bychkoviak [] 
> Sent: 06 June 2006 10:54
> To:
> Subject: Re: Compound / non-compound index files and SIGKILL
> If your content handlers should respond quickly then you should move
> indexing process to separate thread and maintain items in queue.
> Rob Staveley (Tom) wrote:
>> This is a real eye-opener, Volodymyr. Many thanks. I guess that means 
>> that my orphan-producing hangs must be addDocument() calls, and not in 
>> the content handlers, as I'd previously assumed. I'll put some debug 
>> before and after my addDocument() calls to confirm (and point my 
>> writer's infoStream to System.out).
>> -----Original Message-----
>> From: Volodymyr Bychkoviak []
>> Sent: 05 June 2006 18:33
>> To:
>> Subject: Re: Compound / non-compound index files and SIGKILL
>> Hi.
>> My five cents :)
>> It might be helpful to know how lucene is working with compound files. 
>> When segment is flushed to disk it is written uncompound and after 
>> that is merged into single .cfs file. If you don't change default 
>> setting for using compound files (which is on) this is only place (I 
>> guess) for these files to appear.
>> If you're working with large indexes, than merging segments can take a 
>> while (Maybe here is your problem? :) ) (merging happens on
>> addDocument() call).  If you will kill indexing process during such 
>> merge you'll get many orphaned files...
>> You can just run optimize on this index. You'll get three files: 
>> segments, deletable, <segment>.cfs; you can look name of segment in 
>> 'segments' file. Everything else is 'garbage' - you can delete it.
>> Rob Staveley (Tom) wrote:
>>> I've been indexing live data into a compound index from an MTA. I'm 
>>> resolving a bunch of problems unrelated to Lucene (disparate hangs in 
>>> my content handlers). When I get a hang, I typically need to kill my 
>>> daemon, alas more often than not using kill -9 (SIGKILL).
>>> However, these SIGKILLs are leaving large temporary(?) files, which I
>> guess
>>> are non-compound index files transiently extracted from the working 
>>> .cfs
>>> files:
>>> -rw-r--r--    1  373138432 Jun  2 13:42 _18hup.fdt
>>> -rw-r--r--    1      5054464 Jun  2 13:42 _18hup.fdx
>>> -rw-r--r--    1              426 Jun  2 13:42 _18hup.fnm
>>> -rw-r--r--    1  457253888 Jun  2 09:22 _15djq.fdt
>>> -rw-r--r--    1      6205440 Jun  2 09:22 _15djq.fdx
>>> -rw-r--r--    1              426 Jun  2 09:21 _15djq.fnm
>>> They are left intact after restarting my daemon. Presumably they are 
>>> not treated as being part of the compound index. I see no 
>>> corresponding .cfs file for them.
>>> As a consequence of these - I suspect - I am getting a very large 
>>> overall disk requirement for my index, presumably because of 
>>> replicated field
>> data.
>>> My guess is that the field data in the orphaned .fdt files needs to 
>>> be regenerated.
>>> In another index directory from a previous test run (again with 
>>> SIGKILLs),
>> I
>>> have 98 GB of index files, with only 12 BG devoted to compound files 
>>> for
>> the
>>> field index (.cfs). The rest of the disk space is used by orphaned 
>>> uncompounded index files; I see 51 GB devoted to uncompounded field 
>>> data (.fdt), 13 BG devoted to term positions (.prx) and 13 BG devoted 
>>> to term frequencies (.frq).
>>> Here's my question:
>>> How can I attempt to merge these orphaned into the compound index, 
>>> using IndexWriter.addIndexes(), or would I be foolish attempting this?
> --
> regards,
> Volodymyr Bychkoviak

Volodymyr Bychkoviak

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