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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-3348) Interrupt the ScanTask's thread when the Session is cancelled.
Date Wed, 19 Nov 2014 22:24:33 GMT
Josh Elser created ACCUMULO-3348:
------------------------------------

             Summary: Interrupt the ScanTask's thread when the Session is cancelled.
                 Key: ACCUMULO-3348
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3348
             Project: Accumulo
          Issue Type: Improvement
          Components: tserver
            Reporter: Josh Elser
            Priority: Minor


As far as I can tell, we have no means in the TabletServer which actively {{interrupt()}}
a Thread which is running a Scan.

As long as all of the Iterators in the ScanTask are actively making progress (fetching data
from memory or disk), they'll see the interruptFlag which is set via {{InterruptibleIterator}}.
This does not suffice if an Iterator is performing some long-running task or blocked on some
external call which might hang/fail/pause/block/etc.

In general, we've worked around this issue by recommending to "not do that": Iterators shouldn't
access external resources or perform long-running computations (or do anything that won't
return reliably). It would be better if we could make a stronger guarantee server-side about
cleaning up ScanTasks and their iterator stack.



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