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https://issues.apache.org/jira/browse/HDFS-6940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14123873#comment-14123873
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Konstantin Boudnik commented on HDFS-6940:
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bq. Sure, but by creating a plugin interface or something of that ilk we can
precisely define the contract
I have a great idea [~atm] - let's in fact do everything as plugins! For
example 2.4.0 release introduced 3 backward incompatible fixes that broke _at
least_ two huge components in the downsteam. In fact, we are catching stuff
like that in Bigtop all the time. I am sure it could've been avoided if we only
we had a better plugin contracts for everything that depends on the Hadoop bits.
I think everyone should've figured out by now that being in the position of a
base-layer puts a tremendous pressure on the development practices and
architectural decisions. Changes in the Hadoop shouldn't be breaking user space
(similarly to that of Linux kernel). Likewise, changes in a super class should
not be breaking its children if the said super-class' contracts are well
designed and implemented - that's a basic principle of OOP after all. By
artificially limiting choices of the future consumers of a library instead of
implementing accommodative APIs one doesn't build a better system. One'd simply
be forcing downstream developers to hack-in or around those arbitrary
limitations. And such development won't produce a well integrated stack. The
evidences of it are plenty.
> Initial refactoring to allow ConsensusNode implementation
> ---------------------------------------------------------
>
> Key: HDFS-6940
> URL: https://issues.apache.org/jira/browse/HDFS-6940
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Affects Versions: 3.0.0
> Reporter: Konstantin Shvachko
> Assignee: Konstantin Shvachko
> Attachments: HDFS-6940.patch
>
>
> Minor refactoring of FSNamesystem to open private methods that are needed for
> CNode implementation.
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