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From Harsh J <ha...@cloudera.com>
Subject Re: org.apache.avro.file.DataFileWriter$AppendWriteException: java.lang.ClassCastException: org.apache.avro.generic.GenericData$Record cannot be cast to java.util.Map
Date Sun, 09 Feb 2014 04:46:25 GMT
Hello Anil,

Your eventSchema is a record that carries a single Map type field named "Event".
Your sessionSchema is a record that carries a Map type field "Common"
and an array of _Maps_ called "Event".

What your writer is assuming instead is that the sessionSchema carries
an array of _eventSchema_ records. Therefore, in expecting a map data
type when writing the array, it gets a record data type and throws
"Record cannot be cast to java.util.Map"

Does this help you understand the error?

If you want to instead write an array of eventSchema records (as you
are apparently doing in your code), you should alter your
sessionSchema to inline the eventSchema record schema as the array's
contained data type, such as the below:

{"namespace": "ci.avro",
    "type": "record",
    "name": "Session",
    "fields": [
    {"name":"Common", "type": {"type": "map", "values":"string"}},
    {"name":"events",
        "type": {
            "type": "array",
            "items":{
                "type": "record",
                "namespace": "ci.avro",
                "name": "AvroEvent",
                "fields": [
                {"name":"Event",
                    "type": {
                        "type": "map", "values":"string"
                    }
                }
                ]
            }
        }
    }
    ]
}

On Fri, Feb 7, 2014 at 6:11 PM, AnilKumar B <akumarb2010@gmail.com> wrote:
> Hi,
>
> In my Mapreduce job, I am using AvroKeyValueOutputFormat as one of my
> MultipleOutputs. So I declared my multiple outputs as below.
>
>  MultipleOutputs.addNamedOutput(stage2Job,
>         SessionConstants.COMPLETED_SESSIONS,
>         AvroKeyValueOutputFormat.class, AvroKey.class, AvroValue.class);
>
> And In reducer, I am constructing and emitting GenericData.Record for the
> below schema:
>
> sessionSchema:
> {"namespace": "ci.avro",
>  "type": "record",
>  "name": "Session",
>  "fields": [
>    {"name":"Common", "type": {
>            "type": "map", "values":"string"}},
>    {"name":"events",
>     "type": {
>         "type": "array",
>     "items":{
>     "name":"Event",
>     "type":"map",
>     "values":"string"}
>     }
>     }
>  ]
> }
>
> eventSchema:
> {"namespace": "ci.avro",
>  "type": "record",
>  "name": "AvroEvent",
>  "fields": [
>     {"name":"Event",
>       "type": {
>            "type": "map", "values":"string"
>               }
>     }
>  ]
> }
>
> //record generation
>
>  GenericData.Record record = new GenericData.Record(sessionSchema);
>     GenericData.Record eRecord = new GenericData.Record(eventSchema);
>     GenericData.Array<GenericData.Record> eventRecords =
>         new GenericData.Array<GenericData.Record>(vc.getEvents().size(),
>             sessionSchema.getField("events").schema());
>     record.put("Common", vc.getCommon().getM_parameterMap());
>     for (Event ev : vc.getEvents()) {
>       eRecord = new GenericData.Record(eventSchema);
>       eRecord.put("Event", ev.getM_parameterMap());
>       eventRecords.add(eRecord);
>     }
>     record.put("events", eventRecords);
>
>     sessionRecord.datum(record);
>
>
> // record emmitted as below
> context.getConfiguration().set(CONF_OUTPUT_KEY_SCHEMA,
>           Schema.create(Schema.Type.STRING).toString());
>       context.getConfiguration().set(CONF_OUTPUT_VALUE_SCHEMA,
>           sessionSchema.toString());
>       multipleOutputs.write(SessionConstants.COMPLETED_SESSIONS,
>           new AvroKey<String>(key.toString()), sessionRecord,
>           SessionConstants.COMPLETED_SESSIONS);
>
> But I am getting below exception. I am also declaring
> "avro.schema.output.value" as sessionSchema.toString().  What could be the
> issue?
>
> Exception:
> org.apache.avro.file.DataFileWriter$AppendWriteException:
> java.lang.ClassCastException: org.apache.avro.generic.GenericData$Record
> cannot be cast to java.util.Map
>         at
> org.apache.avro.file.DataFileWriter.append(DataFileWriter.java:296)
>         at
> org.apache.avro.mapreduce.AvroKeyValueRecordWriter.write(AvroKeyValueRecordWriter.java:127)
>         at
> org.apache.hadoop.mapreduce.lib.output.MultipleOutputs$RecordWriterWithCounter.write(MultipleOutputs.java:304)
>         at
> org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.write(MultipleOutputs.java:370)
>         at
> com.paypal.ci.CISuperSessionStage2AvroReducer.reduce(CISuperSessionStage2AvroReducer.java:156)
>         at
> com.paypal.ci.CISuperSessionStage2AvroReducer.reduce(CISuperSessionStage2AvroReducer.java:24)
>         at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:177)
>         at
> org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:649)
>         at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:418)
>         at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at javax.security.auth.Subject.doAs(Subject.java:396)
>         at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1232)
>         at org.apache.hadoop.mapred.Child.main(Child.java:249)
> Caused by: java.lang.ClassCastException:
> org.apache.avro.generic.GenericData$Record cannot be cast to java.util.Map
>         at
> org.apache.avro.generic.GenericDatumWriter.getMapSize(GenericDatumWriter.java:194)
>         at
> org.apache.avro.generic.GenericDatumWriter.writeMap(GenericDatumWriter.java:173)
>         at
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:69)
>         at
> org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:143)
>         at
> org.apache.avro.generic.GenericDatumWriter.writeArray(GenericDatumWriter.java:138)
>         at
> org.apache.avro.reflect.ReflectDatumWriter.writeArray(ReflectDatumWriter.java:64)
>         at
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:68)
>         at
> org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:143)
>         at
> org.apache.avro.generic.GenericDatumWriter.writeField(GenericDatumWriter.java:114)
>         at
> org.apache.avro.reflect.ReflectDatumWriter.writeField(ReflectDatumWriter.java:175)
>         at
> org.apache.avro.generic.GenericDatumWriter.writeRecord(GenericDatumWriter.java:104)
>         at
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:66)
>         at
> org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:143)
>         at
> org.apache.avro.generic.GenericDatumWriter.writeField(GenericDatumWriter.java:114)
>         at
> org.apache.avro.reflect.ReflectDatumWriter.writeField(ReflectDatumWriter.java:175)
>         at
> org.apache.avro.generic.GenericDatumWriter.writeRecord(GenericDatumWriter.java:104)
>         at
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:66)
>         at
> org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:143)
>         at
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:58)
>         at
> org.apache.avro.file.DataFileWriter.append(DataFileWriter.java:290)
>
>
>
> Thanks & Regards,
> B Anil Kumar.



-- 
Harsh J

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