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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 18:30:52 GMT


Brian Dougan commented on CRUNCH-266:

It looks like crunch is already depending on avro 1.7.4, so should be good on that front.

Technically, SpecificDatumWriter has the same issue (though doesn't currently manifest in
any way since SpecificData and GenericData serialize the same), but it might be a good idea
to update both to use the constructors that take classes (in case avro decides to fix it for
some reason too).

So, I think it might actually be a two line change, one for the reader and writer creation

I'll work on a patch (and try to throw in some unit tests to show the issue if I can figure
out a way to get some classloaders configured correctly)
> 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
> 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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