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Posted to notifications@accumulo.apache.org by "Keith Turner (JIRA)" <ji...@apache.org> on 2013/03/05 22:24:13 UTC
[jira] [Commented] (ACCUMULO-1152) Add more sanity checks to limit
the damage of multiple assignment
[ https://issues.apache.org/jira/browse/ACCUMULO-1152?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13593929#comment-13593929 ]
Keith Turner commented on ACCUMULO-1152:
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Just had a realization, before a walog can be used it must be written to the metadata table. So its likely the metadata table check will prevent a tserver from getting new logs. But this check is just based on cache.
If a tserver does see a metadata table write fail because it does not hold its lock, it should probably do something.
> Add more sanity checks to limit the damage of multiple assignment
> -----------------------------------------------------------------
>
> Key: ACCUMULO-1152
> URL: https://issues.apache.org/jira/browse/ACCUMULO-1152
> Project: Accumulo
> Issue Type: Improvement
> Reporter: Keith Turner
> Fix For: 1.6.0
>
>
> When an issue like ACCUMULO-954 comes along and causes a tablet to be hosted on multiple tablet servers, its nice to have sanity checks that limit the damage this can cause.
> Accumulo already has a sanity check on writes to the metadata table that ensures the tablet server making the write still holds a lock. This has reliably triggered in cases of multiple assignment bugs. It would be nice to have more checks like this. Below are some places I think checks would be useful, are there more?
> * Tserver attempts to positively check it holds its lock before getting a new walog.
> * Clients take some action to clear lockless tservers from their metadata table cache. This would help prevent writing data to a zombie tserver that may lose data, or reading stale data from a zombie tserver.
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