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https://issues.apache.org/jira/browse/SLING-13271?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joerg Hoh reassigned SLING-13271:
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Assignee: Joerg Hoh
> Concurrent addJob calls corrupt the unsynchronized roundRobinMap in
> TopologyCapabilities
> ----------------------------------------------------------------------------------------
>
> Key: SLING-13271
> URL: https://issues.apache.org/jira/browse/SLING-13271
> Project: Sling
> Issue Type: Improvement
> Components: Event
> Affects Versions: Event Impl 4.4.0
> Reporter: Joerg Hoh
> Assignee: Joerg Hoh
> Priority: Major
>
> {{TopologyCapabilities.roundRobinMap}} is a plain {{HashMap}} that is
> read-modify-written ({{{}get{}}} then {{{}put{}}}) without any
> synchronization. The single shared {{TopologyCapabilities}} instance is
> reached from the public {{JobManager.addJob(...)}} API (via
> {{{}detectTarget(...){}}}), which is called by arbitrary client threads with
> no lock in between, so multiple threads can mutate the same {{HashMap}}
> concurrently.
> h3. Impact
> * *Lost updates:* concurrent job submissions for the same topic can read the
> same round-robin index and be dispatched to the same instance, defeating even
> job distribution across the cluster.
> * *Map corruption:* unsynchronized concurrent {{HashMap.put}} can corrupt
> the map's internal table during resize, causing wrong/stale lookups or a
> spinning lookup. Because this map backs target selection for all topics, the
> impact is not limited to the racing topic.
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