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https://issues.apache.org/jira/browse/ACCUMULO-4643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16044884#comment-16044884
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Keith Turner commented on ACCUMULO-4643:
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I created a [test suite|https://github.com/keith-turner/yield-test] and ran the
following test.
Test 1 : 128 tserver threads, 127 non-yielding long running scans, 1 thread
doing 50 batch scans of 5 random ranges. Below are the times in ms for the
batch scans. There were 5,000,000 key/values. Each long runnning scan was
reading all. The total time for all long running scans was : 104 seconds
{noformat}
min: 30.0
max: 2395.0
mean: 882.3599999999999
standard deviation: 653.56063254159
{noformat}
Test 2 : 128 tserver threads, 127 yielding long running scans, 1 thread doing
50 batch scans of 5 random ranges. The long running scans yielded every
10,000. Below are the times in ms for the batch scans. Total time for all
long running scans was : 215 seconds
{noformat}
min: 428.0
max: 827.0
mean: 626.2800000000002
standard deviation: 104.54157263100298
{noformat}
Test 3 : 16 tserver threads, 20 long running scans, 1 thread doing 50 batch
scans of 5 random ranges. Below are the times in ms for the batch scans.
There were 31,750,000 key/values. Each long runnning scan was reading all.
The total time for all long running scans was : 174 seconds
{noformat}
min: 120.0
max: 548.0
mean: 210.54000000000002
standard deviation: 70.64345948031524
{noformat}
> Allow iterators to interrupt themselves
> ---------------------------------------
>
> Key: ACCUMULO-4643
> URL: https://issues.apache.org/jira/browse/ACCUMULO-4643
> Project: Accumulo
> Issue Type: Improvement
> Components: tserver
> Affects Versions: 1.8.1, 2.0.0
> Reporter: Ivan Bella
> Assignee: Ivan Bella
> Labels: features
> Fix For: 2.0.0
>
> Time Spent: 16h 50m
> Remaining Estimate: 0h
>
> The idea here is to allow an iterator stack to send back a special key or
> throw a special exception which will allow the tablet server to tear down the
> scan to be rebuilt later. This is to handle the case where an iterator is
> doing a lot of work without returning results to avoid starving out other
> scans.
> There are two thoughts on how to do this:
> 1) A special "interrupt" key is returned from the getTopKey call that is
> detected in the Tablet.nextBatch call, is not added to the results, but is
> used to add an unfinished range and results in the remaining ranges to be
> deemed unfinished.
> 2) An special exception is thrown from the next or seek call that included
> the key of the current position, and the same actions are taken as in 1).
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