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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2729) Index corruption after 'read past EOF' under heavy update load and snapshot export
Date Wed, 10 Nov 2010 11:39:14 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2729?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12930579#action_12930579
] 

Michael McCandless commented on LUCENE-2729:
--------------------------------------------

bq. Will do, but we also got the error while zoie was opening a new IndexWriter:

You're right... the next attempt to open an IndexWriter, or and IndexReader that's trying
to commit pending deletes, will hit the exc due to the zero-length segments file.

So in fact this already helps us further bracket when the truncation happened, because IW
115 was able to successfully open on the assetIndex, but then the attempt to write deletions
hits the exc, as well as the next attempt to open a writer on the index.

So sometime after IW 115 is opened and before the deletions are applied, something truncates
these index files.

bq. My guess is that the 'read past EOF' is not really specific to applying deletes, but just
happens when the SegementInfos is loaded on a 0kb file.

That's right.  What's really odd is that these 0-length files are very old, ie, indexing has
long ago moved on to newer segments.  I suspect they are in fact the files protected by the
snapshot for backups... so I think it's important we instrument Zoie's backup process next.

{quote}
We ran a test with your patch to throw a RuntimeException when an output already exists.
We did get a 'read past EOF', but the additional RuntimeException is never thrown.
{quote}
Hmmmm.  So it sounds like it's not Lucene's SimpleFSDir.createOutput that's truncating these
files.

> Index corruption after 'read past EOF' under heavy update load and snapshot export
> ----------------------------------------------------------------------------------
>
>                 Key: LUCENE-2729
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2729
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Index
>    Affects Versions: 3.0.1, 3.0.2
>         Environment: Happens on both OS X 10.6 and Windows 2008 Server. Integrated with
zoie (using a zoie snapshot from 2010-08-06: zoie-2.0.0-snapshot-20100806.jar).
>            Reporter: Nico Krijnen
>         Attachments: 2010-11-02 IndexWriter infoStream log.zip, LUCENE-2729-test1.patch
>
>
> We have a system running lucene and zoie. We use lucene as a content store for a CMS/DAM
system. We use the hot-backup feature of zoie to make scheduled backups of the index. This
works fine for small indexes and when there are not a lot of changes to the index when the
backup is made.
> On large indexes (about 5 GB to 19 GB), when a backup is made while the index is being
changed a lot (lots of document additions and/or deletions), we almost always get a 'read
past EOF' at some point, followed by lots of 'Lock obtain timed out'.
> At that point we get lots of 0 kb files in the index, data gets lots, and the index is
unusable.
> When we stop our server, remove the 0kb files and restart our server, the index is operational
again, but data has been lost.
> I'm not sure if this is a zoie or a lucene issue, so i'm posting it to both. Hopefully
someone has some ideas where to look to fix this.
> Some more details...
> Stack trace of the read past EOF and following Lock obtain timed out:
> {code}
> 78307 [proj.zoie.impl.indexing.internal.RealtimeIndexDataLoader@31ca5085] ERROR proj.zoie.impl.indexing.internal.BaseSearchIndex
- read past EOF
> java.io.IOException: read past EOF
>     at org.apache.lucene.store.BufferedIndexInput.refill(BufferedIndexInput.java:154)
>     at org.apache.lucene.store.BufferedIndexInput.readByte(BufferedIndexInput.java:39)
>     at org.apache.lucene.store.ChecksumIndexInput.readByte(ChecksumIndexInput.java:37)
>     at org.apache.lucene.store.IndexInput.readInt(IndexInput.java:69)
>     at org.apache.lucene.index.SegmentInfos.read(SegmentInfos.java:245)
>     at org.apache.lucene.index.IndexFileDeleter.<init>(IndexFileDeleter.java:166)
>     at org.apache.lucene.index.DirectoryReader.doCommit(DirectoryReader.java:725)
>     at org.apache.lucene.index.IndexReader.commit(IndexReader.java:987)
>     at org.apache.lucene.index.IndexReader.commit(IndexReader.java:973)
>     at org.apache.lucene.index.IndexReader.decRef(IndexReader.java:162)
>     at org.apache.lucene.index.IndexReader.close(IndexReader.java:1003)
>     at proj.zoie.impl.indexing.internal.BaseSearchIndex.deleteDocs(BaseSearchIndex.java:203)
>     at proj.zoie.impl.indexing.internal.BaseSearchIndex.loadFromIndex(BaseSearchIndex.java:223)
>     at proj.zoie.impl.indexing.internal.LuceneIndexDataLoader.loadFromIndex(LuceneIndexDataLoader.java:153)
>     at proj.zoie.impl.indexing.internal.DiskLuceneIndexDataLoader.loadFromIndex(DiskLuceneIndexDataLoader.java:134)
>     at proj.zoie.impl.indexing.internal.RealtimeIndexDataLoader.processBatch(RealtimeIndexDataLoader.java:171)
>     at proj.zoie.impl.indexing.internal.BatchedIndexDataLoader$LoaderThread.run(BatchedIndexDataLoader.java:373)
> 579336 [proj.zoie.impl.indexing.internal.RealtimeIndexDataLoader@31ca5085] ERROR proj.zoie.impl.indexing.internal.LuceneIndexDataLoader
- 
>     Problem copying segments: Lock obtain timed out: org.apache.lucene.store.SingleInstanceLock@5ad0b895:
write.lock
> org.apache.lucene.store.LockObtainFailedException: Lock obtain timed out: org.apache.lucene.store.SingleInstanceLock@5ad0b895:
write.lock
>     at org.apache.lucene.store.Lock.obtain(Lock.java:84)
>     at org.apache.lucene.index.IndexWriter.init(IndexWriter.java:1060)
>     at org.apache.lucene.index.IndexWriter.<init>(IndexWriter.java:957)
>     at proj.zoie.impl.indexing.internal.DiskSearchIndex.openIndexWriter(DiskSearchIndex.java:176)
>     at proj.zoie.impl.indexing.internal.BaseSearchIndex.loadFromIndex(BaseSearchIndex.java:228)
>     at proj.zoie.impl.indexing.internal.LuceneIndexDataLoader.loadFromIndex(LuceneIndexDataLoader.java:153)
>     at proj.zoie.impl.indexing.internal.DiskLuceneIndexDataLoader.loadFromIndex(DiskLuceneIndexDataLoader.java:134)
>     at proj.zoie.impl.indexing.internal.RealtimeIndexDataLoader.processBatch(RealtimeIndexDataLoader.java:171)
>     at proj.zoie.impl.indexing.internal.BatchedIndexDataLoader$LoaderThread.run(BatchedIndexDataLoader.java:373)
> {code}
> We get exactly the same behavour on both OS X and on Windows. On both zoie is using a
SimpleFSDirectory.
> We also use a SingleInstanceLockFactory (since our process is the only one working with
the index), but we get the same behaviour with a NativeFSLock.
> The snapshot backup is being made by calling:
> *proj.zoie.impl.indexing.ZoieSystem.exportSnapshot(WritableByteChannel)*
> Same issue in zoie JIRA:
> http://snaprojects.jira.com/browse/ZOIE-51

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