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https://issues.apache.org/jira/browse/HADOOP-15206?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16353510#comment-16353510
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Aki Tanaka commented on HADOOP-15206:
-------------------------------------
[~jlowe]
Thank you for your insights. I have created a patch based on your comment.
As far as I tested, all the unit tests passed and I confirmed that the issue I
was seeing was solved.
I greatly appreciate any and someone take a look. Alternative proposals are
also very welcome.
Regarding the duplicated record scenario, the record was read twice when
BZip2Codec starts reading at position 0 (BZip2 header) and position 4 (first
BZip2 marker).
test.bz2:0+1 -> read 100 records
test.bz2:3+4 -> read 99 records
2018-02-05 20:49:51,598 ERROR [Thread-3] mapred.TestTextInputFormat2
(TestTextInputFormat2.java:verifyPartitions(324)) -
splits[0]=file:/Users/tanakah/work/count-mismatch2/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/target/test-dir/TestTextInputFormat/test.bz2:0+1
count=100
2018-02-05 20:49:51,605 ERROR [Thread-3] mapred.TestTextInputFormat2
(TestTextInputFormat2.java:verifyPartitions(326)) -
splits[1]=file:/Users/tanakah/work/count-mismatch2/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/target/test-dir/TestTextInputFormat/test.bz2:1+1
count=0
2018-02-05 20:49:51,608 ERROR [Thread-3] mapred.TestTextInputFormat2
(TestTextInputFormat2.java:verifyPartitions(326)) -
splits[2]=file:/Users/tanakah/work/count-mismatch2/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/target/test-dir/TestTextInputFormat/test.bz2:2+1
count=0
2018-02-05 20:49:51,614 ERROR [Thread-3] mapred.TestTextInputFormat2
(TestTextInputFormat2.java:verifyPartitions(313)) - read 1
2018-02-05 20:49:51,617 WARN [Thread-3] mapred.TestTextInputFormat2
(TestTextInputFormat2.java:verifyPartitions(315)) - conflict with 1 in split 3
at position 7
> BZip2 drops and duplicates records when input split size is small
> -----------------------------------------------------------------
>
> Key: HADOOP-15206
> URL: https://issues.apache.org/jira/browse/HADOOP-15206
> Project: Hadoop Common
> Issue Type: Bug
> Affects Versions: 2.8.3, 3.0.0
> Reporter: Aki Tanaka
> Priority: Major
> Attachments: HADOOP-15206-test.patch, HADOOP-15206.001.patch
>
>
> BZip2 can drop and duplicate record when input split file is small. I
> confirmed that this issue happens when the input split size is between 1byte
> and 4bytes.
> I am seeing the following 2 problem behaviors.
>
> 1. Drop record:
> BZip2 skips the first record in the input file when the input split size is
> small
>
> Set the split size to 3 and tested to load 100 records (0, 1, 2..99)
> {code:java}
> 2018-02-01 10:52:33,502 INFO [Thread-17] mapred.TestTextInputFormat
> (TestTextInputFormat.java:verifyPartitions(317)) -
> splits[1]=file:/work/count-mismatch2/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/target/test-dir/TestTextInputFormat/test.bz2:3+3
> count=99{code}
> > The input format read only 99 records but not 100 records
>
> 2. Duplicate Record:
> 2 input splits has same BZip2 records when the input split size is small
>
> Set the split size to 1 and tested to load 100 records (0, 1, 2..99)
>
> {code:java}
> 2018-02-01 11:18:49,309 INFO [Thread-17] mapred.TestTextInputFormat
> (TestTextInputFormat.java:verifyPartitions(318)) - splits[3]=file
> /work/count-mismatch2/hadoop/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/target/test-dir/TestTextInputFormat/test.bz2:3+1
> count=99
> 2018-02-01 11:18:49,310 WARN [Thread-17] mapred.TestTextInputFormat
> (TestTextInputFormat.java:verifyPartitions(308)) - conflict with 1 in split 4
> at position 8
> {code}
>
> I experienced this error when I execute Spark (SparkSQL) job under the
> following conditions:
> * The file size of the input files are small (around 1KB)
> * Hadoop cluster has many slave nodes (able to launch many executor tasks)
>
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