Hi, AVRO gurus:
I am facing a strange case in the AVRO right now, and hope someone here can at
least give me some hints or a direction debugging it.
Our production cluster is CENTOS 6.5 (2.6.32-358.14.1.el6.x86_64), running IBM
BigInsight V3.0.0.2. In Apache term, it is Hadoop 2.2.0 with MRV1(no yarn), and
comes with AVRO 1.7.4, running with IBM J9 VM (build 2.7, JRE 1.7.0 Linux
amd64-64 Compressed References 20140515_199835 (JIT enabled, AOT enabled). Not
sure if the JDK matters, but it is NOT Oracle JVM.
We have a ETL implemented in a chain of MR jobs. In one MR job, it is going to
merge 2 sets of AVRO data. Dataset1 is in HDFS location A, and Dataset2 is in
HDFS location B, and both contains the AVRO records binding to the same AVRO
schema. The record contains an unique id field, and a timestamp field. The MR
job is to merge the records based on the ID, and use the later timestamp record
to replace previous timestamp record, and omit the final AVRO record out. Very
straightforward.
Now we faced a problem that one reducer keeps failing with the following
stacktrace on JobTracker:
java.lang.IndexOutOfBoundsException
at java.io.ByteArrayInputStream.read(ByteArrayInputStream.java:191)
at java.io.DataInputStream.read(DataInputStream.java:160)
at
org.apache.avro.io.DirectBinaryDecoder.doReadBytes(DirectBinaryDecoder.java:184)
at org.apache.avro.io.BinaryDecoder.readString(BinaryDecoder.java:263)
at
org.apache.avro.io.ValidatingDecoder.readString(ValidatingDecoder.java:107)
at
org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:348)
at
org.apache.avro.reflect.ReflectDatumReader.readString(ReflectDatumReader.java:143)
at
org.apache.avro.reflect.ReflectDatumReader.readString(ReflectDatumReader.java:125)
at
org.apache.avro.reflect.ReflectDatumReader.readString(ReflectDatumReader.java:121)
at
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:154)
at
org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:177)
at
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:148)
at
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:139)
at
org.apache.avro.hadoop.io.AvroDeserializer.deserialize(AvroDeserializer.java:108)
at
org.apache.avro.hadoop.io.AvroDeserializer.deserialize(AvroDeserializer.java:48)
at
org.apache.hadoop.mapreduce.task.ReduceContextImpl.nextKeyValue(ReduceContextImpl.java:142)
at
org.apache.hadoop.mapreduce.task.ReduceContextImpl.nextKey(ReduceContextImpl.java:117)
at
org.apache.hadoop.mapreduce.lib.reduce.WrappedReducer$Context.nextKey(WrappedReducer.java:297)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:165)
at
org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:652)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:420)
at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at
java.security.AccessController.doPrivileged(AccessController.java:366)
at javax.security.auth.Subject.doAs(Subject.java:572)
at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1502)
at org.apache.hadoop.mapred.Child.main(Child.java:249)
Here is the my Mapper and Reducer methods:Mapper:public void
map(AvroKey<SpecificRecord> key, NullWritable value, Context context) throws
IOException, InterruptedException Reducer:protected void
reduce(CustomPartitionKeyClass key, Iterable<AvroValue<SpecificRecord>> values,
Context context) throws IOException, InterruptedException
What bother me are the following facts:1) All the mappers finish without
error2) Most of the reducers finish without error, but one reducer keeps
failing with the above error.3) It looks like caused by the data? But keep in
mind that all the avro records passed the mapper side, but failed in one
reducer. 4) From the stacktrace, it looks like our reducer code was NOT invoked
yet, but failed before that. So my guess is that all the AVRO records pass
through the mapper side, but AVRO complains the intermediate result generated
by the one mapper? In my understanding, that will be a Sequence file generated
by Hadoop, and value part will be the AVRO bytes. Is the above error meaning
that AVRO cannot deserialize the value part from the sequence file?5) Our ETL
run fine for more than one year, but suddenly got this error starting from one
day, and kept getting this problem after that. 6) If it helps, here is the
schema for the avro record:{
"namespace" : "company name",
"type" : "record",
"name" : "Lists",
"fields" : [
{"name" : "account_id", "type" : "long"},
{"name" : "list_id", "type" : "string"},
{"name" : "sequence_id", "type" : ["int", "null"]} ,
{"name" : "name", "type" : ["string", "null"]},
{"name" : "state", "type" : ["string", "null"]},
{"name" : "description", "type" : ["string", "null"]},
{"name" : "dynamic_filtered_list", "type" : ["int", "null"]},
{"name" : "filter_criteria", "type" : ["string", "null"]},
{"name" : "created_at", "type" : ["long", "null"]},
{"name" : "updated_at", "type" : ["long", "null"]},
{"name" : "deleted_at", "type" : ["long", "null"]},
{"name" : "favorite", "type" : ["int", "null"]},
{"name" : "delta", "type" : ["boolean", "null"]},
{
"name" : "list_memberships", "type" : {
"type" : "array", "items" : {
"name" : "ListMembership", "type" : "record",
"fields" : [
{"name" : "channel_id", "type" : "string"},
{"name" : "created_at", "type" : ["long", "null"]},
{"name" : "created_source", "type" : ["string",
"null"]},
{"name" : "deleted_at", "type" : ["long", "null"]},
{"name" : "sequence_id", "type" : ["long", "null"]}
]
}
}
}
]
}
What I am looking for is that someone can help me understand what could cause
this problem in the reducer side? From all the facts, it points to the data. As
whole thing works for more than one year, but suddenly cannot merge the new
coming data. But what kind of data cause the above error, or how should I debug
this issue? The data generated as AVRO records just look fine and read in the
mapper side without any issue, but some data cause this failure in the reducer
side.
Thanks for your help.
Yong
