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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4189) Improve hints replay
Date Wed, 25 Apr 2012 20:50:19 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13262066#comment-13262066
] 

Jonathan Ellis commented on CASSANDRA-4189:
-------------------------------------------

bq. It might be worth shading the hints based on Hour at which the hints are stored. This
can reduce the complexity of the scanning for hints.

Not sure this is a problem now that we drop the tombstones after each handoff.  Since there
is only one handoff per target at a time, we don't need to worry about having to skip tombstones
in a meaningful volume.

bq. What i am suggesting is to throttle but in a multi threaded way

+1
                
> Improve hints replay
> --------------------
>
>                 Key: CASSANDRA-4189
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4189
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.2
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.2
>
>
> Problem: Hints are stored in one row.
> when there are a lot of hints stored and we store Tombstones for the ones which has been
replayed.
> It might be worth shading the hints based on Hour at which the hints are stored. This
can reduce the complexity of the scanning for hints.
> Problem: Hints replay is too slow and single threaded.
> There are use-case where the hints needs to be replayed ASAP to make the cluster more
consistent.
> In Multi region cluster, the throttle is already done due to the latency which is in
the order of 100's of millisecond.
> It might be worth trying to replay the hints in parallel and throttle on the number of
bytes read from the disk or use the existing setting of throttle based on sleep interval on
all the threads.

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