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From "Weiwei Yang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12443) Ozone: Improve SCM block deletion throttling algorithm
Date Tue, 24 Oct 2017 11:57:02 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16216760#comment-16216760
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Weiwei Yang commented on HDFS-12443:
------------------------------------

Thanks for taking over [~linyiqun]. Some more background, currently the code uses _push_ mode,
which means SCM collects TXs and caches them for DNs. Instead of _pull_ (DN fetches TXs from
SCM while doing HB processing). This was because we want to make HB lightweight as much as
possible (I/O-less). But this approach makes it a bit difficult to prepare a reasonable size
of TXs for DNs, please take a look at this issue and let me know if you have any idea to resolve
it. Thanks!

> Ozone: Improve SCM block deletion throttling algorithm 
> -------------------------------------------------------
>
>                 Key: HDFS-12443
>                 URL: https://issues.apache.org/jira/browse/HDFS-12443
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ozone, scm
>            Reporter: Weiwei Yang
>            Assignee: Yiqun Lin
>              Labels: OzonePostMerge
>
> Currently SCM scans delLog to send deletion transactions to datanode periodically, the
throttling algorithm is simple, it scans at most {{BLOCK_DELETE_TX_PER_REQUEST_LIMIT}} (by
default 50) at a time. This is non-optimal, worst case it might cache 50 TXs for 50 different
DNs so each DN will only get 1 TX to proceed in an interval, this will make the deletion slow.
An improvement to this is to make this throttling by datanode, e.g 50 TXs per datanode per
interval.



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