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Posted to dev@accumulo.apache.org by dlmarion <gi...@git.apache.org> on 2016/06/13 21:34:20 UTC

[GitHub] accumulo pull request #113: ACCUMULO-4341: Preload classes

GitHub user dlmarion opened a pull request:

    https://github.com/apache/accumulo/pull/113

    ACCUMULO-4341: Preload classes

    

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/dlmarion/accumulo ACCUMULO-4341

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/accumulo/pull/113.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #113
    
----
commit e94467be06a1ea766c3e67b163951d3eae665848
Author: Dave Marion <dl...@apache.org>
Date:   2016-06-13T21:26:41Z

    ACCUMULO-4341: Preload classes that will be loaded in the background by the HDFS client

----


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[GitHub] accumulo issue #113: ACCUMULO-4341: Preload classes

Posted by madrob <gi...@git.apache.org>.

Github user madrob commented on the issue:

    https://github.com/apache/accumulo/pull/113
  
    Can we add a test for this? I'm imagining a sequence like 1) Start HDFS, 2) Add a Jar (that includes a KeywordExecutable class?), 3) Run an Accumulo command?
    
    I still don't understand what is causing the actual failure here, nor how to reproduce it compactly outside of my 'I tried it and it didn't work' last week.


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[GitHub] accumulo issue #113: ACCUMULO-4341: Preload classes

Posted by dlmarion <gi...@git.apache.org>.

Github user dlmarion commented on the issue:

    https://github.com/apache/accumulo/pull/113
  
    Will apply this manually.


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[GitHub] accumulo issue #113: ACCUMULO-4341: Preload classes

Posted by dlmarion <gi...@git.apache.org>.

Github user dlmarion commented on the issue:

    https://github.com/apache/accumulo/pull/113
  
    @madrob Here is what is basically what's happening:
    
    The ServiceLoader thread looks in the classpath for services files for classes implementing the KeywordExecutable interface. When it finds them, it tries to load the class, using Class.forName. Since the classloader is the VFSClassLoader and the files are in HDFS, it uses the DFS client code to retrieve the associated object. The DFS client, in another thread, is performing RPC calls to retrieve the object. During the processing of a response (1st call stack in the JIRA), it attempts to load some classes, using Class.forName. Class.forName acquires a lock on the ClassLoader, which is the root of the problem. The solution here is to attempt to preload the classes that the DFS Client is going to load.
    
    I will clean up the code, address the findbugs issues, and try to backport to 1.7.2 tomorrow.


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[GitHub] accumulo pull request #113: ACCUMULO-4341: Preload classes

Posted by dlmarion <gi...@git.apache.org>.

Github user dlmarion closed the pull request at:

    https://github.com/apache/accumulo/pull/113


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[GitHub] accumulo issue #113: ACCUMULO-4341: Preload classes

Posted by madrob <gi...@git.apache.org>.

Github user madrob commented on the issue:

    https://github.com/apache/accumulo/pull/113
  
    Also looks like there is a findbugs failure.
    
        [INFO] --- findbugs-maven-plugin:3.0.3:check (run-findbugs) @ accumulo-start ---
        [INFO] BugInstance size is 1
        [INFO] Error size is 0
        [INFO] Total bugs: 1
        [INFO] Incorrect lazy initialization and update of static field org.apache.accumulo.start.Main.classLoader in org.apache.accumulo.start.Main.getClassLoader() [org.apache.accumulo.start.Main] At Main.java:[lines 75-78] LI_LAZY_INIT_UPDATE_STATIC


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