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From "Brian Dougan (JIRA)" <>
Subject [jira] [Commented] (CRUNCH-266) AvroSpecificDeepCopier needs to use constructor on SpecificDatumReader that takes a class.
Date Mon, 16 Sep 2013 21:45:52 GMT


Brian Dougan commented on CRUNCH-266:

Hmm, I bet that doesn't work.  Right now it relies on the parent folder being crunch, which
I'm guessing yours is not.  It tries to throw out all crunch jars from the classloader to
add them to a child classloader.  

Can we count on the jars to always be crunch-*?  If so we can change to that.
> AvroSpecificDeepCopier needs to use constructor on SpecificDatumReader that takes a class.
> ------------------------------------------------------------------------------------------
>                 Key: CRUNCH-266
>                 URL:
>             Project: Crunch
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 0.7.0
>            Reporter: Brian Dougan
>            Assignee: Josh Wills
>            Priority: Minor
>         Attachments: CRUNCH-266.patch, CRUNCH-266.patch
> As per, when the avro jar is in a parent
classloader of the classloader that contains SpecificData classes, a ClassCastException can
occur if you don't use the SpecificDatumReader constructor that takes a class (and accounts
for the classloader).
> Since standard hadoop commands seem to use parent classloaders, and avro is included
in the hadoop parent classloader, this issue can be seen if you run a command from a jar including
SpecificData classes that attempts to use them from the hadoop command (such as materializing
a PCollection of avro objects.  
> It looks like all that is needed is to update AvroSpecificDatumReader to call a different
> * public SpecificDatumReader(Class<T> c) 
> To add in more confusion, since avro is an included hadoop dependency, and avro itself
had a bug until 1.7.4, this fix will only work if avro in hadoop has been updated to 1.7.4
(or is running on a version that has already done this).  

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