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https://issues.apache.org/jira/browse/KUDU-1703?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Alves closed KUDU-1703.
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Resolution: Duplicate
This is largely a duplicate of KUDU-1127
> Handle snapshot reads that might block indefinitely
> ---------------------------------------------------
>
> Key: KUDU-1703
> URL: https://issues.apache.org/jira/browse/KUDU-1703
> Project: Kudu
> Issue Type: Sub-task
> Affects Versions: 1.1.0
> Reporter: David Alves
> Assignee: David Alves
>
> When we fix safe time advancement, replicas will start to block on snapshot
> scans until a timeout occurs, waiting to have a consistent view of the world
> at that timestamp before serving the scan. This will be a serious problem for
> lagging replicas, which might be several seconds or even minutes behind.
> Moreover in the absence of writes, the same will happen even for non-lagging
> replicas, which will have their safe times updated only when the leader
> heartbeats.
> We need to at least make sure that:
> - Blocked scanner threads are not starving other work.
> - If the replica's safe time is lagging by a lot, the replica refuses to do
> the scan and the client retries it on another replica.
> We might also consider other optimizations (like pinging the leader for
> up-to-date replicas that are just waiting on a heartbeat).
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