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From Greg Preston <gpres...@marinsoftware.com>
Subject Re: Possible memory leak after segment merge? (related to DocValues?)
Date Thu, 26 Dec 2013 22:03:20 GMT
Does anybody with knowledge of solr internals know why I'm seeing
instances of Lucene42DocValuesProducer when I don't have any fields
that are using DocValues?  Or am I misunderstanding what this class is
for?

-Greg


On Mon, Dec 23, 2013 at 12:07 PM, Greg Preston
<gpreston@marinsoftware.com> wrote:
> Hello,
>
> I'm loading up our solr cloud with data (from a solrj client) and
> running into a weird memory issue.  I can reliably reproduce the
> problem.
>
> - Using Solr Cloud 4.4.0 (also replicated with 4.6.0)
> - 24 solr nodes (one shard each), spread across 3 physical hosts, each
> host has 256G of memory
> - index and tlogs on ssd
> - Xmx=7G, G1GC
> - Java 1.7.0_25
> - schema and solrconfig.xml attached
>
> I'm using composite routing to route documents with the same clientId
> to the same shard.  After several hours of indexing, I occasionally
> see an IndexWriter go OOM.  I think that's a symptom.  When that
> happens, indexing continues, and that node's tlog starts to grow.
> When I notice this, I stop indexing, and bounce the problem node.
> That's where it gets interesting.
>
> Upon bouncing, the tlog replays, and then segments merge.  Once the
> merging is complete, the heap is fairly full, and forced full GC only
> helps a little.  But if I then bounce the node again, the heap usage
> goes way down, and stays low until the next segment merge.  I believe
> segment merges are also what causes the original OOM.
>
> More details:
>
> Index on disk for this node is ~13G, tlog is ~2.5G.
> See attached mem1.png.  This is a jconsole view of the heap during the
> following:
>
> (Solr cloud node started at the left edge of this graph)
>
> A) One CPU core pegged at 100%.  Thread dump shows:
> "Lucene Merge Thread #0" daemon prio=10 tid=0x00007f5a3c064800
> nid=0x7a74 runnable [0x00007f5a41c5f000]
>    java.lang.Thread.State: RUNNABLE
>         at org.apache.lucene.util.fst.Builder.add(Builder.java:397)
>         at org.apache.lucene.codecs.BlockTreeTermsWriter$TermsWriter.finishTerm(BlockTreeTermsWriter.java:1000)
>         at org.apache.lucene.codecs.TermsConsumer.merge(TermsConsumer.java:112)
>         at org.apache.lucene.codecs.FieldsConsumer.merge(FieldsConsumer.java:72)
>         at org.apache.lucene.index.SegmentMerger.mergeTerms(SegmentMerger.java:365)
>         at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:98)
>         at org.apache.lucene.index.IndexWriter.mergeMiddle(IndexWriter.java:3772)
>         at org.apache.lucene.index.IndexWriter.merge(IndexWriter.java:3376)
>         at org.apache.lucene.index.ConcurrentMergeScheduler.doMerge(ConcurrentMergeScheduler.java:405)
>         at org.apache.lucene.index.ConcurrentMergeScheduler$MergeThread.run(ConcurrentMergeScheduler.java:482)
>
> B) One CPU core pegged at 100%.  Manually triggered GC.  Lots of
> memory freed.  Thread dump shows:
> "Lucene Merge Thread #0" daemon prio=10 tid=0x00007f5a3c064800
> nid=0x7a74 runnable [0x00007f5a41c5f000]
>    java.lang.Thread.State: RUNNABLE
>         at org.apache.lucene.codecs.DocValuesConsumer$1$1.hasNext(DocValuesConsumer.java:127)
>         at org.apache.lucene.codecs.lucene42.Lucene42DocValuesConsumer.addNumericField(Lucene42DocValuesConsumer.java:144)
>         at org.apache.lucene.codecs.lucene42.Lucene42DocValuesConsumer.addNumericField(Lucene42DocValuesConsumer.java:92)
>         at org.apache.lucene.codecs.DocValuesConsumer.mergeNumericField(DocValuesConsumer.java:112)
>         at org.apache.lucene.index.SegmentMerger.mergeNorms(SegmentMerger.java:221)
>         at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:119)
>         at org.apache.lucene.index.IndexWriter.mergeMiddle(IndexWriter.java:3772)
>         at org.apache.lucene.index.IndexWriter.merge(IndexWriter.java:3376)
>         at org.apache.lucene.index.ConcurrentMergeScheduler.doMerge(ConcurrentMergeScheduler.java:405)
>         at org.apache.lucene.index.ConcurrentMergeScheduler$MergeThread.run(ConcurrentMergeScheduler.java:482)
>
> C) One CPU core pegged at 100%.  Manually triggered GC.  No memory
> freed.  Thread dump shows:
> "Lucene Merge Thread #0" daemon prio=10 tid=0x00007f5a3c064800
> nid=0x7a74 runnable [0x00007f5a41c5f000]
>    java.lang.Thread.State: RUNNABLE
>         at org.apache.lucene.codecs.DocValuesConsumer$1$1.hasNext(DocValuesConsumer.java:127)
>         at org.apache.lucene.codecs.lucene42.Lucene42DocValuesConsumer.addNumericField(Lucene42DocValuesConsumer.java:108)
>         at org.apache.lucene.codecs.lucene42.Lucene42DocValuesConsumer.addNumericField(Lucene42DocValuesConsumer.java:92)
>         at org.apache.lucene.codecs.DocValuesConsumer.mergeNumericField(DocValuesConsumer.java:112)
>         at org.apache.lucene.index.SegmentMerger.mergeNorms(SegmentMerger.java:221)
>         at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:119)
>         at org.apache.lucene.index.IndexWriter.mergeMiddle(IndexWriter.java:3772)
>         at org.apache.lucene.index.IndexWriter.merge(IndexWriter.java:3376)
>         at org.apache.lucene.index.ConcurrentMergeScheduler.doMerge(ConcurrentMergeScheduler.java:405)
>         at org.apache.lucene.index.ConcurrentMergeScheduler$MergeThread.run(ConcurrentMergeScheduler.java:482)
>
> D) One CPU core pegged at 100%.  Thread dump shows:
> "Lucene Merge Thread #0" daemon prio=10 tid=0x00007f5a3c064800
> nid=0x7a74 runnable [0x00007f5a41c5f000]
>    java.lang.Thread.State: RUNNABLE
>         at org.apache.lucene.codecs.compressing.CompressingTermVectorsReader.get(CompressingTermVectorsReader.java:322)
>         at org.apache.lucene.index.SegmentReader.getTermVectors(SegmentReader.java:169)
>         at org.apache.lucene.codecs.compressing.CompressingTermVectorsWriter.merge(CompressingTermVectorsWriter.java:789)
>         at org.apache.lucene.index.SegmentMerger.mergeVectors(SegmentMerger.java:312)
>         at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:130)
>         at org.apache.lucene.index.IndexWriter.mergeMiddle(IndexWriter.java:3772)
>         at org.apache.lucene.index.IndexWriter.merge(IndexWriter.java:3376)
>         at org.apache.lucene.index.ConcurrentMergeScheduler.doMerge(ConcurrentMergeScheduler.java:405)
>         at org.apache.lucene.index.ConcurrentMergeScheduler$MergeThread.run(ConcurrentMergeScheduler.java:482)
>
> E) CPU usage drops to nominal levels.  Thread dump shows no Lucene Merge Thread.
>
> F) Manually triggered full GC.  Some memory freed, but much remains.
>
> G) Restarted solr.  Very little memory used.
>
>
> Throughout all of this, there was no indexing or querying happening.
> In ordered to try to determine what's using up the memory, I took a
> heap dump at point (F) and analyzed it in Eclipse MAT (see attached
> screenshot).  This shows 311 instances of Lucene42DocValuesProducer$3,
> each holding a large byte[].  By attaching a remote debugger and
> re-running, it looks like there is one of these byte[] for each field
> in the schema (we have several of the "dim_*" dynamic fields).  And as
> far as I know, I'm not using DocValues at all.
>
>
> Any hints as to what might be going on here would be greatly
> appreciated.  It takes me about 10 minutes to reproduce this, so I'm
> willing to try things.  I don't know enough about the internals of
> solr's memory usage to proceed much further on my own.
>
> Thank you.
>
> -Greg

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