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https://issues.apache.org/jira/browse/HADOOP-1986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12540687
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Vivek Ratan commented on HADOOP-1986:
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>> If class names are serialized with class data, then a single serializer
>> instance could be returned for a large number of different classes. If class
>> names are not serialized with class data, then a different serializer
>> instance could be returned for each class, but these could be cached, so
>> that no more than a single instance is created per serialized class.
Agreed.
>> If a factory creates multiple instances of its serializer, and those
>> instances share state, then yes, they are responsible for coordinating their
>> state. That seems reasonable and expected.
This is what I thought can get difficult. It is up to us (Hadoop), as owners of
the factory, to ensure that state is coordinated between instances, and is not
X's responsibility. It may or may not be easy. It seems reasonably easy for
Thrift and Record I/O, though.
> Add support for a general serialization mechanism for Map Reduce
> ----------------------------------------------------------------
>
> Key: HADOOP-1986
> URL: https://issues.apache.org/jira/browse/HADOOP-1986
> Project: Hadoop
> Issue Type: New Feature
> Components: mapred
> Reporter: Tom White
> Assignee: Tom White
> Fix For: 0.16.0
>
> Attachments: SerializableWritable.java, serializer-v1.patch
>
>
> Currently Map Reduce programs have to use WritableComparable-Writable
> key-value pairs. While it's possible to write Writable wrappers for other
> serialization frameworks (such as Thrift), this is not very convenient: it
> would be nicer to be able to use arbitrary types directly, without explicit
> wrapping and unwrapping.
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