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From "David Medinets (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1454) Need good way to perform a rolling restart of all tablet servers
Date Thu, 23 May 2013 00:31:20 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13664737#comment-13664737
] 

David Medinets commented on ACCUMULO-1454:
------------------------------------------

This ticket make me laugh because my team at Toyrus.com developed rolling restart functionality
back in 1999. We tracked the number of sessions assigned to each server using a load balancer.
When a given server needed to be restarted, the load balancer changed the server's state to
something like 'restarting' and did not send any sessions to it. The server would periodically
check it's own status. If it saw 'rebooting' and it had zero sessions then it restarted itself.

Is there some time delay before tablets are reassigned? Can the tserver restart within that
window of time?
                
> Need good way to perform a rolling restart of all tablet servers
> ----------------------------------------------------------------
>
>                 Key: ACCUMULO-1454
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1454
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: tserver
>    Affects Versions: 1.5.0, 1.4.3
>            Reporter: Mike Drob
>
> When needing to change a tserver parameter (e.g. java heap space) across the entire cluster,
there is not a graceful way to perform a rolling restart.
> The naive approach of just killing tservers one at a time causes a lot of churn on the
cluster as tablets move around and zookeeper tries to maintain current state.
> Potential solutions might be via a fancy fate operation, with coordination by the master.
Ideally, the master would know which servers are 'safe' to restart and could minimize overall
impact during the operation.

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