marco polo created ACCUMULO-3510:
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Summary: Create mechanism to support priority based scheduling of
read ahead tasks.
Key: ACCUMULO-3510
URL: https://issues.apache.org/jira/browse/ACCUMULO-3510
Project: Accumulo
Issue Type: Improvement
Components: tserver
Affects Versions: 1.6.0
Reporter: marco polo
Priority: Minor
Fix For: 1.6.3
I have many cases where ScanSessions will consume resources that I otherwise
want shorter running scans to utilize. In some cases, a scan may continue for
hours, while a short running scan may come in and execute quickly. As a result,
I want to be able to adjust the priority of these scan sessions.
I have a patch which is forthcoming, that breaks Session out of TabletServer
and replaces the queue in the readAheadThreadPool with a priority pool. The
comparator I have created as a proof of concept, which can be adjustable,
reduces the priority of the oldest scan. Using an aging technique, we guarantee
execute of these older running scans based upon the previous run time. As a
result, we give preference to newer scans. If they execute quickly, older scans
will have an inherent rise in priority. If they also take a while, their
priority will be reduced and incoming scans will yet again be given a greater
priority with the intent (and/or hope ) their execution will be faster.
Priority should be configurable based on the desired Session Comparator.
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