This document discusses the versioning conventions and history of Hadoop releases. It notes that features were occasionally developed on branches off the trunk codeline and that some releases included features from different branches, causing confusion. It also summarizes the status of Hadoop 1.0, which unified many previously separated features, and the versioning of the Cloudera CDH distribution in relation to Apache Hadoop releases.

1. Hadoop Versioning
July 9, 2012
Anty Rao
Big Data Engineering Team
Hanborq Inc.
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2. Development Convention
• Trunk
– The main codeline, new features are developed on
trunk
• Branch
– Occasionally very large features are developed on
their own branchers with the expectation they’ll later
merge into trunk.
• Release
– Candidate releases are branched from trunk
– Stop accepting new features
– Bugs get fixed and after a vote, a release is declared
for that particular branch.
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3. Hadoop 0.20 branch
• Two major features were added to branches
off 0.20.2
– Authentication
• Enabling strong security for core hadoop
– Append
• Enabling users to run apache HBase without risk of data
loss
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5. Confusion about Version
• Release off the 0.20 branches had features
that release off the trunk did not have and
vice versa.
• Apache Hadoop 0.23 is a strict superset of
features over 0.22, but it actually released a
month before 0.22
• The 0.20 branch formerly known as 0.20.205
was renumbered 1.0. This is just a
renumbering, no functional difference.
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6. Status
• There has been 18 month period where there
has been no one apache release that had all
the committed features of Apache Hadoop!
• Recently released Hadoop 1.0, including
following features
– 0.20 Append
– 0.20 security
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8. Cloudera CDH
• CDH1
– 0.18.3 Apache Hadoop Release
• CDH2
– 0.20.1 Apache Hadoop Release
• CDH3
– 0.20.2 Apache Hadoop Release
– 0.20. Append
– 0.20. Security
• CDH4
– 0.23.X Apache Hadoop Release
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10. Reference
• http://www.cloudera.com/blog/2012/01/an-
update-on-apache-hadoop-1-0/
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