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From dlmarion <...@git.apache.org>
Subject [GitHub] accumulo issue #113: ACCUMULO-4341: Preload classes
Date Mon, 13 Jun 2016 23:37:49 GMT
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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