[HADOOP-15206] BZip2 drops and duplicates records when input split size is small

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.8.3, 3.0.0
• Fix Version/s: 3.1.0, 2.10.0, 2.9.1, 2.8.4, 2.7.6, 3.0.3
• Hadoop Flags: Reviewed
• Assignee: Aki Tanaka
• Reporter: Aki Tanaka
• Created: 01/Feb/18 20:43
• Updated: 05/Apr/18 17:16
• Resolved: 16/Feb/18 21:30

Description

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)

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

> 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)

 

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

 

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)