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https://issues.apache.org/jira/browse/CRUNCH-266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13768581#comment-13768581
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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 respectively.
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: https://issues.apache.org/jira/browse/CRUNCH-266
> Project: Crunch
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.7.0
> Reporter: Brian Dougan
> Assignee: Josh Wills
> Priority: Minor
>
> As per https://issues.apache.org/jira/browse/AVRO-1240, 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 constructor.
> * 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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