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From Paul Smith <psm...@aconex.com>
Subject CompoundFileReader question/'leaking' file descriptors ?
Date Mon, 13 Feb 2006 06:43:15 GMT

I've been hunting an insidious problem whereby during heavy  
incremental indexing operations in production on redhat el3 machine I  
notice that the java process has a lot of open files which appear to  
be deleted.

Now, before anyone jumps in, yes I know the # open file limit needs  
to be incremented, i've done that (it's at a hideous 16000 at the  
moment..).  Things I've verified include Writers/readers/searchers  
get closed when they should (finally blocks etc).

Using the 'lsof' command to track the open files, we see tonnes of  
these entries:

[root@index1 logs]# lsof -p `ps -efww | grep '[m]el.xml' | awk  
'{print $2}'` | grep deleted | head
java    23749 root  120r   REG       8,3     17507  61079633 /aconex/ 
index/current/project/39/56/0000025639/corr/000001/_dga.cfs (deleted)
java    23749 root  121r   REG       8,3     21775  61079684 /aconex/ 
index/current/project/39/56/0000025639/corr/000001/_dlc.cfs (deleted)
java    23749 root  123r   REG       8,3     17507  61079728 /aconex/ 
index/current/project/39/56/0000025639/corr/000001/_dq4.cfs (deleted)
......

What is REALLY weird is that they eventually do get released.  And  
scarily enough, it seems to track with when the garbage collector  
does a major collection (we managed to figure this out using Yourkit  
profiler and hitting the force GC), and lo, they disappear...  We  
have many indexes (2000, one for each project-entity), and not an  
UberIndex, and hence having indexes leak file handles is much more  
noticeable.

We're using Lucene 1.4.3, and after hunting around in the source code  
just to see what I might be missing, I came across this, and I'd just  
like some comments.

CompoundFileReader has an inner-class CSInputStream which is used to  
read the stream (and we're using the Compound format, so this is  
relevant here).

However it overrides InputStream.close(), but does not call  
super.close().  After tracing around where this is all used I believe  
that this method REALLY SHOULD be calling super.close() (or not  
overriding) it,because CompoundFileReader will be given an  
InputStream to wrap, eventually coming down to FSInputStream which  
apparently then calss Descriptor.close().

Scarily enough this ends up calling RandomAccessFile.close, which  
goes into native library calls and, assumably, close the file.

The guard here is that the finalizer method in FSInputStream does  
call close() so that would well explain the releasing of file handles  
at garbage collection intervals.

Why would CompoundFileReader not need to call .close()?

Am I going mad here and just seeing ghosts? Comments appreciated.

Paul Smith


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