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https://issues.apache.org/jira/browse/ACCUMULO-2140?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Christopher Tubbs resolved ACCUMULO-2140.
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Resolution: Not A Problem
[~vines], I think you're right.
> Race conditions between client operations and upgrade
> -----------------------------------------------------
>
> Key: ACCUMULO-2140
> URL: https://issues.apache.org/jira/browse/ACCUMULO-2140
> Project: Accumulo
> Issue Type: Bug
> Reporter: Christopher Tubbs
> Assignee: Christopher Tubbs
> Priority: Blocker
> Fix For: 1.6.0
>
>
> While the master is upgrading, it also has a thread that is responding to
> client requests. Since the upgrade renames tables and puts them in
> namespaces, there is a short period of time where table existence checks that
> rely on the new zookeeper schema for tables are failing to provide the
> correct answer.
> Example: when the tracer starts, it tries to create a "trace" table, if it
> doesn't exist. The existence check returns false, so it creates a new trace
> table in the default namespace, even though there exists an old one that has
> not yet been moved into the default namespace during the upgrade. This
> results in two tables with the same name.
> An easy solution would be to fail to respond to client requests until after
> the upgrade is complete. (eg. wait to start up the MasterClientServiceHandler
> thread).
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