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From "Cliff Resnick (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AVRO-1475) Bad Avro write in mapper causes ArrayIndexOutOfBoundsException in reducer
Date Wed, 05 Mar 2014 19:28:43 GMT
Cliff Resnick created AVRO-1475:
-----------------------------------

             Summary: Bad Avro write in mapper causes ArrayIndexOutOfBoundsException in reducer
                 Key: AVRO-1475
                 URL: https://issues.apache.org/jira/browse/AVRO-1475
             Project: Avro
          Issue Type: Bug
          Components: java
    Affects Versions: 1.7.6
         Environment: hadoop 1.0.3
            Reporter: Cliff Resnick


This may or may not be a retread of AVRO-792 (which was inconclusively resolved) , but it's
consistently occurring in 1.7.6. The role of the map phase in the problem was not addressed
in AVRO-792 so I'm bringing it up here.

My hypothesis is that the AvroSerializer sinks bytes to output as it validates, so when a
write of a schema-invalid Datum is attempted in the mapper, the data written up to that point
makes its way to the reducer, even as an exception is thrown in the mapper. This results in
a reduce failing with a mysterious ArrayIndexOutOfBoundsException as below. To test this I
had the AvroDeserializer catch and log rather than throw an exception, and the cardinalities
of reduce errors match exactly with the mapper errors.

The obvious problem with the current situation is that there is no way for a mapreduce job
to omit bad data without doubly serializing it, first to verify and then to write. A proper
solution would be for the Encoder to transactionally buffer the serialized bytes so that when
the serialization breaks, it's caught in the mapper without blowing the entire mapreduce (since
the error below occurs before any "userland" mapreduce code is called).




Caused by: java.lang.ArrayIndexOutOfBoundsException: 10
	at org.apache.avro.io.parsing.Symbol$Alternative.getSymbol(Symbol.java:365)
	at org.apache.avro.io.ResolvingDecoder.doAction(ResolvingDecoder.java:229)
	at org.apache.avro.io.parsing.Parser.advance(Parser.java:88)
	at org.apache.avro.io.ResolvingDecoder.readIndex(ResolvingDecoder.java:206)
	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:155)
	at org.apache.avro.generic.GenericDatumReader.readField(GenericDatumReader.java:193)
	at org.apache.avro.reflect.ReflectDatumReader.readField(ReflectDatumReader.java:230)
	at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:183)
	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:151)
	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:142)
	at org.apache.avro.hadoop.io.AvroDeserializer.deserialize(AvroDeserializer.java:123)





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