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https://issues.apache.org/jira/browse/HDDS-9189?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stephen O'Donnell reassigned HDDS-9189:
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Assignee: Stephen O'Donnell
> EC: Investigage how EC read path deals with unhealthy replicas
> --------------------------------------------------------------
>
> Key: HDDS-9189
> URL: https://issues.apache.org/jira/browse/HDDS-9189
> Project: Apache Ozone
> Issue Type: Sub-task
> Reporter: Stephen O'Donnell
> Assignee: Stephen O'Donnell
> Priority: Major
>
> When SCM provides a read pipeline to a client, it simply returns a pipeline
> containing all replicas it knows about. The state of a replica is not
> included in the pipeline, so the client cannot distinguish between healthy
> and unhealthy replicas. However the pipeline nodes are sorted, so that if
> there are multiple replicas for a given replica index, and some of those
> nodes are not IN_SERVICE (eg decommissioning etc), then the IN_SERVICE nodes
> are always sorted first.
> On SCM we should be able to do something similar to put UNHEALTHY replicas to
> the back of the list, so the client will try to read healthy ones first.
> It is also worth checking what the client does when it encounters an
> unhealthy replica - will it fall back to reconstruction read, or if there is
> a spare index will it use it first?
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