Michael Berman created ACCUMULO-2542:
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Summary: Add mechanism to cancel scans
Key: ACCUMULO-2542
URL: https://issues.apache.org/jira/browse/ACCUMULO-2542
Project: Accumulo
Issue Type: Improvement
Components: tserver
Reporter: Michael Berman
ScannerBase.close() closes all connections to a given scan, but if there's an
iterator spinning on the scan, it will keep running at least until a record
makes it all the way out of the iterator stack. If you have a bug in an
iterator, or a filter that doesn't match anything, or a combiner that matches
everything, then that could mean scanning an entire table. It would be nice if
there were some mechanism to interrupt that process.
We probably couldn't do anything about a really buggy externally provided
iterator that just spins without calling next() downstream (short of calling
Thread.close(), which is probably a bad idea), but accumulo iterators could
periodically check for cancellation and bail gracefully (maybe each time we're
about to load a new block?). It would be nice to provide a mechanism for
external iterators to check their cancellation status so they can have an
opportunity to be well behaved if they're doing anything that might take a
while, but that seems less important.
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