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Posted to common-issues@hadoop.apache.org by "Jason Lowe (JIRA)" <ji...@apache.org> on 2018/02/14 23:07:00 UTC
[jira] [Assigned] (HADOOP-15206) BZip2 drops and duplicates records
when input split size is small
[ https://issues.apache.org/jira/browse/HADOOP-15206?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jason Lowe reassigned HADOOP-15206:
-----------------------------------
Assignee: Aki Tanaka
> 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
> Assignee: Aki Tanaka
> Priority: Major
> Attachments: HADOOP-15206-test.patch, HADOOP-15206.001.patch, HADOOP-15206.002.patch, HADOOP-15206.003.patch, HADOOP-15206.004.patch, HADOOP-15206.005.patch, HADOOP-15206.006.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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