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https://issues.apache.org/jira/browse/ACCUMULO-533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adam Fuchs resolved ACCUMULO-533.
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Resolution: Fixed
> make system iterators thread-safer
> ----------------------------------
>
> Key: ACCUMULO-533
> URL: https://issues.apache.org/jira/browse/ACCUMULO-533
> Project: Accumulo
> Issue Type: Bug
> Affects Versions: 1.4.0
> Reporter: Adam Fuchs
> Assignee: Adam Fuchs
> Fix For: 1.5.0, 1.4.1
>
>
> It is possible that at some point in the future users will want to write
> multi-threaded iterators. This could possibly introduce thread safety
> problems in the system iterators, especially in the case where multiple
> threads might be calling "next", "getTopKey", etc. at the same time. In order
> to maintain some semblance of sanity, we need to synchronize these methods at
> the top of the system iterator tree. Eventually, we might also want to change
> the iterator API to make it useful to call multiple of these methods
> concurrently, but that will be in another ticket.
> The immediate solution calls for a simple iterator that is similar to the
> WrappingIterator called the SynchronizedIterator, all of whose public methods
> are synchronized on the object's monitor. In single-node performance testing
> we found the read performance cost of this solution to be below the noise
> threshold, approximately less than a 1% cost.
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