Tim Smith created LUCENE-4398:
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Summary: "Memory Leak" in TermsHashPerField memory tracking
Key: LUCENE-4398
URL: https://issues.apache.org/jira/browse/LUCENE-4398
Project: Lucene - Core
Issue Type: Bug
Affects Versions: 3.4
Reporter: Tim Smith
I am witnessing an apparent leak in the memory tracking used to determine when
a flush is necessary.
Over time, this will result in every single document being flushed into its own
segment as the memUsage will remain above the configured buffer size, causing a
flush to be triggered after every add/update.
Best I can figure, this is being caused by TermsHashPerField's tracking of
memory usage for postingsHash and/or postingsArray combined with multi-threaded
feeding.
I suspect that the TermsHashPerField's postingsHash is growing in one thread,
then, when a segment is flushed, a single, different thread will merge all
TermsHashPerFields in FreqProxTermsWriter and then call shrinkHash(). I suspect
this call of shrinkHash() is seeing an old postingsHash array, and subsequently
not releasing all the memory that was allocated.
If this is the case, I am also concerned that FreqProxTermsWriter will not
write the correct terms into the index, although I have not confirmed that any
indexing problem occurs as of yet.
NOTE: i am witnessing this growth in a test by subtracting the amount or memory
allocated (but in a "free" state) by
perDocAllocator/byteBlockAllocator/charBlocks/intBlocks from
DocumentsWriter.memUsage.get() in IndexWriter.doAfterFlush()
I will see this stay at a stable point for a while, then on some flushes, i
will see this grow by a couple of bytes, and all subsequent flushes will never
go back down the the previous state
I will continue to investigate and post any additional findings
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