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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17434) New Synchronization Scheme for Compaction Pipeline
Date Fri, 06 Jan 2017 20:26:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15805653#comment-15805653
] 

Ted Yu commented on HBASE-17434:
--------------------------------

One difference between Eshcar's patch and mine is that her patch makes the copy in the pipeline
methods (such as pushHead()) while mine makes the copy in primitive methods (such as add,
removeAll())
I think mine is friendlier to developers in that as long as we are certain (through unit tests,
etc) the building blocks are correct, developers can add methods which modify pipeline without
having to remember adding the clone statement.

The building block methods can be extracted to a generic base class which can be reused by
other classes which need to use copy-on-write semantics.

> New Synchronization Scheme for Compaction Pipeline
> --------------------------------------------------
>
>                 Key: HBASE-17434
>                 URL: https://issues.apache.org/jira/browse/HBASE-17434
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Eshcar Hillel
>         Attachments: HBASE-17434-V01.patch
>
>
> A new copyOnWrite synchronization scheme is introduced for the compaction pipeline.
> The new scheme is better since it removes the lock from getSegments() which is invoked
in every get and scan operation, and it reduces the number of LinkedList objects that are
created at runtime, thus can reduce GC (not by much, but still...).
> In addition, it fixes the method getTailSize() in compaction pipeline. This method creates
a MemstoreSize object which comprises the data size and the overhead size of the segment and
needs to be atomic.



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