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  1. Machine Learning
  2. MLEARN-17

Concurrency issues in NN ranker

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Neutral
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 1.2.1
    • Labels:
    • Release notes required:
      Yes
    • Sprint:
      Maintenance 15, Maintenance 16
    • Story Points:
      5
    • Magnolia Release:
      6.2.3

      Description

      It appears that NN result ranker suffers from an intermittent concurrency issue. The problem seems to be related to the simultaneous unsynched r/w access to the NeuralNetworkResultRanker#resultTexts (see the stacktrace below).

      After some code review it can be cocnluded that in situation when there are two different browser sessions authenticated with the same account (e.g. superuser), it is going to be the case that NeuralNetworkResultRanker instance will be shared between them (since the corresponding ranker factory caches the instances by user).

      Even though it was hard to detect the issue during manual testing and simulations, it does appear in e.g. load tests and even sometimes during development.

      All the API that let's to interact with NN result ranker needs to be synchronised.

      
      2019-06-10 13:21:48,899 ERROR gnolia.admincentral.findbar.search.ResultCollector: An error occurred during the search process, therefore an empty collection will be returned.
      java.util.concurrent.CompletionException: java.util.ConcurrentModificationException
              at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273) ~[?:1.8.0_144]
              at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280) ~[?:1.8.0_144]
              at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1592) ~[?:1.8.0_144]
              at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_144]
              at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_144]
              at java.lang.Thread.run(Thread.java:748) ~[?:1.8.0_144]
      Caused by: java.util.ConcurrentModificationException
              at org.apache.commons.collections4.map.AbstractLinkedMap$LinkIterator.nextEntry(AbstractLinkedMap.java:552) ~[commons-collections4-4.1.jar:4.1]
              at org.apache.commons.collections4.map.AbstractLinkedMap$KeySetIterator.next(AbstractLinkedMap.java:450) ~[commons-collections4-4.1.jar:4.1]
              at java.util.AbstractCollection.toArray(AbstractCollection.java:141) ~[?:1.8.0_144]
              at java.util.ArrayList.<init>(ArrayList.java:177) ~[?:1.8.0_144]
              at info.magnolia.periscope.rank.ml.IndexedBuffer.asList(IndexedBuffer.java:97) ~[magnolia-periscope-result-ranker-1.1-SNAPSHOT.jar:?]
              at info.magnolia.periscope.rank.ml.NeuralNetworkResultRanker.outputArrayToResults(NeuralNetworkResultRanker.java:192) ~[magnolia-periscope-result-ranker-1.1-SNAPSHOT.jar:?]
              at info.magnolia.periscope.rank.ml.NeuralNetworkResultRanker.rank(NeuralNetworkResultRanker.java:142) ~[magnolia-periscope-result-ranker-1.1-SNAPSHOT.jar:?]
              at info.magnolia.periscope.Periscope.fetchSupplierAwareSearchResults(Periscope.java:135) ~[magnolia-periscope-core-1.1-SNAPSHOT.jar:?]
              at info.magnolia.periscope.Periscope.lambda$search$0(Periscope.java:113) ~[magnolia-periscope-core-1.1-SNAPSHOT.jar:?]
              at info.magnolia.periscope.search.SearchRunner.lambda$execute$0(SearchRunner.java:85) ~[magnolia-periscope-core-1.1-SNAPSHOT.jar:?]
              at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1590) ~[?:1.8.0_144]
              ... 3 more
      

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              Assignee:
              chuong.doan Chuong Doan Huy
              Reporter:
              apchelintcev Aleksandr Pchelintcev
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                Updated:
                Resolved:

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