We had an issue with block-cache growing beyond configured size & reducing very rarely. Describing the sequence of events
1. Shard receives incoming mutations, adds it to Index & triggers background merge. 2. Merge produces new-set of files. We have write-thru cache enabled & adds new files to block-cache.. 3. Shard goes silent & doesn't receive any mutation for many minutes all together 4. Since we perform commit only upon receiving mutations, the older-files are not evicted from block-cache.. 5. Problem is exacerbated with KeepNLastCommit policy, where even after commit, unused files are not evicted from block-cache.. We are planning to patch up SharedMergeScheduler by refreshing IndexReader when a merge completes & then delete merged files from block-cache. This way, I believe block-cache can be reigned in whenever it exceeds capacity, irrespective of Commit-Policy used Do let know if this is fine... On Thu, Jun 16, 2016 at 4:33 PM, Ravikumar Govindarajan < [email protected]> wrote: > I didn't fully understand the underlying Lucene reader, writer, >> open, close semantics > > > I too don't know the correct behavior. Lucene code is incredibly hairy to > follow... :) > > Have pinged lucene mailing list. Hope someone replies... > > On Tue, Jun 7, 2016 at 4:46 PM, Aaron McCurry <[email protected]> wrote: > >> On Wed, Jun 1, 2016 at 7:34 AM, Ravikumar Govindarajan < >> [email protected]> wrote: >> >> > Just one more observation here... >> > >> > Even if readerPooling is set to true, lucene has 2 readers (One for >> search >> > & one updates/deletes) >> > >> > But the reader for updates/deletes is not opened/closed for every commit >> > call which is the default behavior as of today. It is opened only once >> > (During first update/delete call) >> > >> >> I will take a closer look at the code for this one. Likely when I wrote >> this code I didn't fully understand the underlying Lucene reader, writer, >> open, close semantics. Thank you for pointing this out! >> >> Aaron >> >> >> > >> > On Wed, Jun 1, 2016 at 3:10 PM, Ravikumar Govindarajan < >> > [email protected]> wrote: >> > >> > > In newer versions of the code there are multiple streams involved. >> One >> > for >> > >> each open file handle plus if a sequential read is detected a new >> stream >> > >> is >> > >> created for the instance for better performance >> > > >> > > >> > > Great. We just patched up our Blur version with this code. >> > > >> > > While I was digging at the reader-closed issue, was quite surprised to >> > > observe the following behavior >> > > >> > > - Issue a commit >> > > - Lucene opens a new reader via IndexWriter. (Doesn't re-use our >> > > already opened DirectoryReader) >> > > - Processes all updates/deletes/merges >> > > - Closes the new reader >> > > - Complete commit >> > > >> > > For a big index & lots of commits, opening a new-reader for every >> commit >> > > is prohibitively expensive. >> > > >> > > >> > > Here is the JIRA for it... >> > > https://issues.apache.org/jira/browse/LUCENE-2297 >> > > >> > > All we need to do is just set "readerPooling=true" in >> IndexWriterConfig >> > > class >> > > >> > > Please do explore this option when you find time. >> > > >> > > -- >> > > Ravi >> > > >> > > >> > > >> > > On Tue, May 24, 2016 at 7:48 PM, Aaron McCurry <[email protected]> >> > wrote: >> > > >> > >> On Tue, May 24, 2016 at 6:06 AM, Ravikumar Govindarajan < >> > >> [email protected]> wrote: >> > >> >> > >> > We have solved it temporarily by using a KeepLastTwoCommits del >> > policy. >> > >> We >> > >> > don't get these exceptions now!!! >> > >> > >> > >> >> > >> Great! >> > >> >> > >> >> > >> > >> > >> > Btw, I see that pread calls in FSDataInputStream.java are >> > synchronized. >> > >> Is >> > >> > it possible that merge DFS read calls could potentially block >> search >> > DFS >> > >> > read calls? >> > >> > >> > >> >> > >> Yes. >> > >> >> > >> >> > >> > >> > >> > Would it be a good idea to have 2 DFSInputStreams for every file, >> one >> > >> for >> > >> > merge & another for search? >> > >> > >> > >> >> > >> In newer versions of the code there are multiple streams involved. >> One >> > >> for >> > >> each open file handle plus if a sequential read is detected a new >> stream >> > >> is >> > >> created for the instance for better performance. Checkout the >> > >> HdfsDirectory class. >> > >> >> > >> Aaron >> > >> >> > >> >> > >> > >> > >> > On Tue, May 10, 2016 at 7:43 PM, Ravikumar Govindarajan < >> > >> > [email protected]> wrote: >> > >> > >> > >> > > Sorry, I mis-understood the code. >> > >> > > I see that it has 2 locks IndexRefreshWriteLock & >> > >> IndexRefreshReadLock. >> > >> > > They look to be separate >> > >> > > >> > >> > > On Tue, May 10, 2016 at 7:16 PM, Ravikumar Govindarajan < >> > >> > > [email protected]> wrote: >> > >> > > >> > >> > >> Thanks a lot Aaron. >> > >> > >> >> > >> > >> I guess we took a commit of 0.2.2 that doesn't have the >> > >> > >> IndexRefreshWriteLock (IRWL). It looks like it co-ordinates >> between >> > >> > >> searches & incoming mutation commits. If so, then it will likely >> > >> solve >> > >> > the >> > >> > >> first issue for us (AlreadyClosedException) >> > >> > >> >> > >> > >> >> > >> > >> Can you recollect if that was the reason IRWL was introduced? >> > >> > >> >> > >> > >> On Tue, May 10, 2016 at 6:40 PM, Aaron McCurry < >> [email protected] >> > > >> > >> > >> wrote: >> > >> > >> >> > >> > >>> On Tue, May 10, 2016 at 2:30 AM, Ravikumar Govindarajan < >> > >> > >>> [email protected]> wrote: >> > >> > >>> >> > >> > >>> > Actually there are 2 issues... >> > >> > >>> > >> > >> > >>> > 1. IndexReaderClosedException >> > >> > >>> > 2. HDFS Stream Closed >> > >> > >>> > >> > >> > >>> >> > >> > >>> Likely when the index is closed it closes the underlying >> > >> indexinputs as >> > >> > >>> well causing the HDFS Stream closed exception. >> > >> > >>> >> > >> > >>> >> > >> > >>> > >> > >> > >>> > Merge completion results in File Deletion & ultimately HDFS >> > Stream >> > >> > >>> Closed >> > >> > >>> > during Search.... >> > >> > >>> > >> > >> > >>> > I use IndexFileDeleter with KeepOnlyLastCommitDeletionPolicy. >> > This >> > >> > >>> blindly >> > >> > >>> > deletes the file, without bothering to cross-check >> > >> > >>> IndexReader.RefCount > >> > >> > >>> > 0. >> > >> > >>> > >> > >> > >>> >> > >> > >>> Hmm. You can see here: >> > >> > >>> >> > >> > >>> >> > >> > >>> >> > >> > >> > >> >> > >> https://github.com/apache/incubator-blur/blob/release-0.2.2-incubating/blur-core/src/main/java/org/apache/blur/manager/writer/BlurIndexSimpleWriter.java#L303 >> > >> > >>> >> > >> > >>> That once the new index is available it is swapped into the >> index >> > >> ref >> > >> > >>> object and the old one is sent to the index closer. Once the >> ref >> > to >> > >> > the >> > >> > >>> index are low enough it closes the index. Or at least it >> should. >> > >> > >>> >> > >> > >>> I will continue looking into the problem but I don't have a >> > solution >> > >> > for >> > >> > >>> you yet. >> > >> > >>> >> > >> > >>> Aaron >> > >> > >>> >> > >> > >>> >> > >> > >>> >> > >> > >>> > >> > >> > >>> > >> > >> > >>> > *Exception(message:Unknown error during rewrite, >> > >> > >>> > stackTraceStr:java.io.IOException: Stream closed* >> > >> > >>> > at >> > >> > >>> >> > >> org.apache.hadoop.hdfs.DFSInputStream.pread(DFSInputStream.java:1385) >> > >> > >>> > at >> > >> > >> org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:1374) >> > >> > >>> > at >> > >> > >>> >> > >> >> org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:89) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.hdfs.HdfsIndexInput.readInternal(HdfsIndexInput.java:62) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.buffer.ReusedBufferedIndexInput.readBytes(ReusedBufferedIndexInput.java:167) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.buffer.ReusedBufferedIndexInput.readBytes(ReusedBufferedIndexInput.java:122) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.hdfs.MmapCacheIndexInput.readAndcache(MmapCacheIndexInput.java:24) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.blockcache_v2.CacheIndexInput.fillNormally(CacheIndexInput.java:354) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.blockcache_v2.CacheIndexInput.fill(CacheIndexInput.java:379) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.blockcache_v2.CacheIndexInput.tryToFill(CacheIndexInput.java:297) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.store.blockcache_v2.CacheIndexInput.readByte(CacheIndexInput.java:151) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.lucene.warmup.TraceableIndexInput.readByte(TraceableIndexInput.java:62) >> > >> > >>> > at >> > org.apache.lucene.store.DataInput.readVInt(DataInput.java:108) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.codecs.BlockTreeTermsReader$FieldReader$SegmentTermsEnum$Frame.loadBlock(BlockTreeTermsReader.java:2366) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.codecs.BlockTreeTermsReader$FieldReader$SegmentTermsEnum.seekCeil(BlockTreeTermsReader.java:1949) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.index.ExitableReader$ExitableTermsEnum.seekCeil(ExitableReader.java:250) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.index.FilteredTermsEnum.next(FilteredTermsEnum.java:225) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.search.TermCollectingRewrite.collectTerms(TermCollectingRewrite.java:78) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.search.ConstantScoreAutoRewrite.rewrite(ConstantScoreAutoRewrite.java:95) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.search.MultiTermQuery$ConstantScoreAutoRewrite.rewrite(MultiTermQuery.java:220) >> > >> > >>> > at >> > >> > >>> >> > >> > >> > org.apache.lucene.search.MultiTermQuery.rewrite(MultiTermQuery.java:288) >> > >> > >>> > at >> > >> > >> org.apache.lucene.search.BooleanQuery.rewrite(BooleanQuery.java:412) >> > >> > >>> > at >> > >> > >> org.apache.lucene.search.BooleanQuery.rewrite(BooleanQuery.java:412) >> > >> > >>> > at >> > >> > >> org.apache.lucene.search.BooleanQuery.rewrite(BooleanQuery.java:412) >> > >> > >>> > at >> > >> > >>> > >> > >> > >>> > On Mon, May 9, 2016 at 4:42 PM, Ravikumar Govindarajan < >> > >> > >>> > [email protected]> wrote: >> > >> > >>> > >> > >> > >>> > > One extra info we gleaned from the logs... >> > >> > >>> > > >> > >> > >>> > > 1. Merge Starts & is about to complete >> > >> > >>> > > 2. Searcher is opened >> > >> > >>> > > 3. Merge Completes >> > >> > >>> > > 4. Ref-count drops to 0 in IndexReader >> > >> > >>> > > 5. IndexReader closed while Searcher is still open >> > >> > >>> > > >> > >> > >>> > > This seems to be the main pattern for causing the Exception >> > >> > >>> > > >> > >> > >>> > > -- >> > >> > >>> > > Ravi >> > >> > >>> > > >> > >> > >>> > > On Mon, May 9, 2016 at 3:08 PM, Ravikumar Govindarajan < >> > >> > >>> > > [email protected]> wrote: >> > >> > >>> > > >> > >> > >>> > >> Thanks Aaron... >> > >> > >>> > >> >> > >> > >>> > >> Just a quick question. Lucene itself has ref-counting to >> > close >> > >> > it's >> > >> > >>> > >> readers no? Or Blur has it's own logic to handle it? >> > >> > >>> > >> >> > >> > >>> > >> -- >> > >> > >>> > >> Ravi >> > >> > >>> > >> >> > >> > >>> > >> On Fri, May 6, 2016 at 7:56 PM, Aaron McCurry < >> > >> [email protected] >> > >> > > >> > >> > >>> > wrote: >> > >> > >>> > >> >> > >> > >>> > >>> Likely yes. If have a few minutes this weekend I can >> look >> > >> > through >> > >> > >>> that >> > >> > >>> > >>> version and see if I can point you in the right >> direction. >> > >> > >>> > >>> >> > >> > >>> > >>> On Fri, May 6, 2016 at 8:46 AM, Ravikumar Govindarajan < >> > >> > >>> > >>> [email protected]> wrote: >> > >> > >>> > >>> >> > >> > >>> > >>> > Sometimes during an ongoing search we receive an >> > >> > >>> > >>> > IndexReaderClosedException... >> > >> > >>> > >>> > >> > >> > >>> > >>> > We are on an older version of Blur (0.2.2). Has this >> been >> > >> fixed >> > >> > >>> in >> > >> > >>> > >>> newer >> > >> > >>> > >>> > versions or we have been using it wrongly? >> > >> > >>> > >>> > >> > >> > >>> > >>> > >> > >> *stackTraceStr:org.apache.lucene.store.AlreadyClosedException: >> > >> > >>> this >> > >> > >>> > >>> > IndexReader cannot be used anymore as one of its child >> > >> readers >> > >> > >>> was >> > >> > >>> > >>> closed* >> > >> > >>> > >>> > at >> > >> > >>> > >> > >> org.apache.lucene.index.IndexReader.ensureOpen(IndexReader.java:257) >> > >> > >>> > >>> > at >> > >> > >>> > >>> > >> > >> > >>> > >>> > >> > >> > >>> > >>> >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.index.FilterAtomicReader.fields(FilterAtomicReader.java:380) >> > >> > >>> > >>> > at >> > >> > >>> > >>> > >> > >> > >>> > >>> > >> > >> > >>> > >>> >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.blur.index.ExitableReader$ExitableFilterAtomicReader.fields(ExitableReader.java:81) >> > >> > >>> > >>> > at >> > >> > >>> > >>> > >> > >> > >>> > >>> > >> > >> > >>> > >>> >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.search.TermCollectingRewrite.collectTerms(TermCollectingRewrite.java:52) >> > >> > >>> > >>> > at >> > >> > >>> > >>> > >> > >> > >>> > >>> > >> > >> > >>> > >>> >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.search.ConstantScoreAutoRewrite.rewrite(ConstantScoreAutoRewrite.java:95) >> > >> > >>> > >>> > at >> > >> > >>> > >>> > >> > >> > >>> > >>> > >> > >> > >>> > >>> >> > >> > >>> > >> > >> > >>> >> > >> > >> > >> >> > >> org.apache.lucene.search.MultiTermQuery$ConstantScoreAutoRewrite.rewrite(MultiTermQuery.java:220) >> > >> > >>> > >>> > at >> > >> > >>> > >>> >> > >> > >>> > >> > >> > >>> >> > >> > >> > org.apache.lucene.search.MultiTermQuery.rewrite(MultiTermQuery.java:288) >> > >> > >>> > >>> > at >> > >> > >>> > >> > >> org.apache.lucene.search.BooleanQuery.rewrite(BooleanQuery.java:412) >> > >> > >>> > >>> > >> > >> > >>> > >>> >> > >> > >>> > >> >> > >> > >>> > >> >> > >> > >>> > > >> > >> > >>> > >> > >> > >>> >> > >> > >> >> > >> > >> >> > >> > > >> > >> > >> > >> >> > > >> > > >> > >> > >
