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From "Christopher Tubbs (JIRA)" <>
Subject [jira] [Created] (ACCUMULO-2140) Race conditions between client operations and upgrade
Date Mon, 06 Jan 2014 22:59:50 GMT
Christopher Tubbs created ACCUMULO-2140:

             Summary: Race conditions between client operations and upgrade
                 Key: ACCUMULO-2140
             Project: Accumulo
          Issue Type: Bug
            Reporter: 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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