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Steve Rowe commented on LUCENE-7410: ------------------------------------ My Jenkins found a reproducing seed for a {{TestReaderClosed.testReaderChaining()}} failure, and {{git bisect}} running the repro line says: {noformat} df6f83072303b4891a296b700a50c743284d3c30 is the first bad commit commit df6f83072303b4891a296b700a50c743284d3c30 Author: Adrien Grand <jpou...@gmail.com> Date: Tue Feb 28 14:21:30 2017 +0100 LUCENE-7410: Make cache keys and close listeners less trappy. {noformat} {noformat} [junit4] 2> NOTE: reproduce with: ant test -Dtestcase=TestReaderClosed -Dtests.method=testReaderChaining -Dtests.seed=C4374342D2D99B8F -Dtests.slow=true -Dtests.locale=hi -Dtests.timezone=America/Dominica -Dtests.asserts=true -Dtests.file.encoding=US-ASCII [junit4] FAILURE 0.04s J1 | TestReaderClosed.testReaderChaining <<< [junit4] > Throwable #1: java.lang.AssertionError: Query failed, but not due to an AlreadyClosedException [junit4] > at __randomizedtesting.SeedInfo.seed([C4374342D2D99B8F:530116CD6543D942]:0) [junit4] > at org.apache.lucene.index.TestReaderClosed.testReaderChaining(TestReaderClosed.java:96) [junit4] > at java.lang.Thread.run(Thread.java:745) [junit4] 2> NOTE: test params are: codec=Asserting(Lucene70): {field=PostingsFormat(name=LuceneVarGapFixedInterval)}, docValues:{}, maxPointsInLeafNode=1885, maxMBSortInHeap=6.663525927605304, sim=RandomSimilarity(queryNorm=true): {}, locale=hi, timezone=America/Dominica [junit4] 2> NOTE: Linux 4.1.0-custom2-amd64 amd64/Oracle Corporation 1.8.0_77 (64-bit)/cpus=16,threads=1,free=82013152,total=289931264 {noformat} > Make cache keys and closed listeners less trappy > ------------------------------------------------ > > Key: LUCENE-7410 > URL: https://issues.apache.org/jira/browse/LUCENE-7410 > Project: Lucene - Core > Issue Type: Bug > Reporter: Adrien Grand > Fix For: master (7.0) > > Attachments: LUCENE-7410.patch, LUCENE-7410.patch, LUCENE-7410.patch > > > IndexReader currently exposes getCoreCacheKey(), > getCombinedCoreAndDeletesKey(), addCoreClosedListener() and > addReaderClosedListener(). They are typically used to manage resources whose > lifetime needs to mimic the lifetime of segments/indexes, typically caches. > I think this is trappy for various reasons: > h3. Memory leaks > When maintaining a cache, entries are added to the cache based on the cache > key and then evicted using the cache key that is given back by the close > listener, so it is very important that both keys are the same. > But if a filter reader happens to delegate get*Key() and not > add*ClosedListener() or vice-versa then there is potential for a memory leak > since the closed listener will be called on a different key and entries will > never be evicted from the cache. > h3. Lifetime expectations > The expectation of using the core cache key is that it will not change in > case of deletions, but this is only true on SegmentReader and LeafReader > impls that delegate to it. Other implementations such as composite readers or > parallel leaf readers use the same key for "core" and "combined core and > deletes". > h3. Throw-away wrappers cause cache trashing > An application might want to either expose more (with a ParrallelReader or > MultiReader) or less information (by filtering fields/docs that can be seen) > depending on the user who is logged in. In that case the application would > typically maintain a DirectoryReader and then wrap it per request depending > on the logged user and throw away the wrapper once the request is completed. > The problem is that these wrappers have their own cache keys and the > application may build something costly and put it in a cache to throw it away > a couple milliseconds later. I would rather like for such readers to have a > way to opt out from caching on order to avoid this performance trap. > h3. Type safety > The keys that are exposed are plain java.lang.Object instances, which > requires caches to look like a {{Map<Object, ?>}} which makes it very easy to > either try to get, put or remove on the wrong object since any object would > be accepted. -- This message was sent by Atlassian JIRA (v6.3.15#6346) --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org