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https://issues.apache.org/jira/browse/HADOOP-2997?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12578250#action_12578250
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Tom White commented on HADOOP-2997:
-----------------------------------
Tracked down the problem - the change in HADOOP-2399 creates instances of keys
and values to be reused, however this is not possible for Java serialization
since the types don't necessarily have no-arg constructors:
java.lang.RuntimeException: java.lang.NoSuchMethodException:
java.lang.Long.<init>()
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:80)
at
org.apache.hadoop.mapred.ReduceTask$ValuesIterator.<init>(ReduceTask.java:213)
at
org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.<init>(ReduceTask.java:306)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:388)
at
org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2073)
Caused by: java.lang.NoSuchMethodException: java.lang.Long.<init>()
at java.lang.Class.getConstructor0(Class.java:2678)
at java.lang.Class.getDeclaredConstructor(Class.java:1953)
at
org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:74)
... 4 more
The fix is to get the deserializer to create the key and value types, if
needed. I'm testing a patch.
> Add test for non-writable serializer
> ------------------------------------
>
> Key: HADOOP-2997
> URL: https://issues.apache.org/jira/browse/HADOOP-2997
> Project: Hadoop Core
> Issue Type: Test
> Components: mapred
> Reporter: Tom White
> Assignee: Tom White
> Fix For: 0.17.0
>
> Attachments: hadoop-2997-v2.patch, hadoop-2997.patch
>
>
> It would be useful to have a unit test that tests MapReduce works using a
> non-writable serializer.
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