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https://issues.apache.org/jira/browse/HBASE-25861?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17353650#comment-17353650
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Baiqiang Zhao commented on HBASE-25861:
---------------------------------------
This issue does not need to be changed except UT. If we use Hadoop3.3, this
issue may not be necessary(Not test). But with previous versions of Hadoop 3.3,
we have to apply this patch.
> Correct the usage of Configuration#addDeprecation
> -------------------------------------------------
>
> Key: HBASE-25861
> URL: https://issues.apache.org/jira/browse/HBASE-25861
> Project: HBase
> Issue Type: Bug
> Affects Versions: 3.0.0-alpha-1, 2.5.0
> Reporter: Baiqiang Zhao
> Assignee: Baiqiang Zhao
> Priority: Major
> Fix For: 3.0.0-alpha-1, 2.5.0
>
>
> When I was solving HBASE-25745
> ([PR3139|https://github.com/apache/hbase/pull/3139]), I found that our use of
> Configuration#addDeprecation API was wrong.
>
> At present, we will call Configuration#addDeprecation in the static block for
> the deprecated configuration. But after testing, it is found that this does
> not complete backward compatibility. When user upgrades HBase and does not
> change the deprecated configuration to the new configuration, he will find
> that the deprecated configuration does not effect, which may not be
> consistent with expectations. The specific test results can be seen in the PR
> above, and we can found the calling order of Configuration#addDeprecation is
> very important.
>
> Configuration#addDeprecation is a Hadoop API, looking through the Hadoop
> source code, we will find that before creating the Configuration object, the
> addDeprecatedKeys() method will be called first:
> [https://github.com/apache/hadoop/blob/b93e448f9aa66689f1ce5059f6cdce8add130457/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/HdfsConfiguration.java#L34]
> .
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