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From "Dave Marion (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-4353) Stabilize tablet assignment during transient failure
Date Thu, 23 Jun 2016 22:45:16 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-4353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15347356#comment-15347356
] 

Dave Marion commented on ACCUMULO-4353:
---------------------------------------

bq. there's always a concern of technical debt (in terms of complexity)

Fair enough.

bq. If this is really about trying to make rolling-restarts better.

Not sure, I think it has to do with quick unplanned restarts, but it would be good to clear
that up. I see a rolling restart being an intentional, planned activity. I think (based on
"failure" in the title) this is for the unintentional, unplanned short duration outage (e.g.
losing connectivity to a rack for a short time) where the administrator wants to bring the
failed tablet servers up as soon as possible. 

> Stabilize tablet assignment during transient failure
> ----------------------------------------------------
>
>                 Key: ACCUMULO-4353
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4353
>             Project: Accumulo
>          Issue Type: Improvement
>            Reporter: Shawn Walker
>            Assignee: Shawn Walker
>            Priority: Minor
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> When a tablet server dies, Accumulo attempts to reassign the tablets it was hosting as
quickly as possible to maintain availability.  If multiple tablet servers die in quick succession,
such as from a rolling restart of the Accumulo cluster or a network partition, this behavior
can cause a storm of reassignment and rebalancing, placing significant load on the master.
> To avert such load, Accumulo should be capable of maintaining a steady tablet assignment
state in the face of transient tablet server loss.  Instead of reassigning tablets as quickly
as possible, Accumulo should be await the return of a temporarily downed tablet server (for
some configurable duration) before assigning its tablets to other tablet servers.



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