[jira] [Created] (HDDS-7919) EC: ECPipelineProvider.createForRead should filter out dead replicas and sort replicas

["Stephen O'Donnell (Jira)" <ji...@apache.org>]

Stephen O'Donnell created HDDS-7919:
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             Summary: EC: ECPipelineProvider.createForRead should filter out dead replicas and sort replicas
                 Key: HDDS-7919
                 URL: https://issues.apache.org/jira/browse/HDDS-7919
             Project: Apache Ozone
          Issue Type: Sub-task
          Components: SCM
            Reporter: Stephen O'Donnell


ECPipelineProvider.createForRead() is used to get a pipeline to read an EC block group.

When there are nodes in maintenance, it is possible for there to be replica details in SCM for dead maintenance nodes, and they should not be returned to the client as they cannot be read.

Additionally, it is possible for there to be multiple copies for a given replica index. Eg an IN_SERVICE replica and a DECOMMISSIONED or DECOMMISSIONING. As things stand, there is no order applied to the replicas, but the client reading code will tend to use the first replica it loads from the pipeline.

Therefore we should exclude dead replicas, and then ensure that where there are multiple copies for a given replica index, HEALTHY (rather than STALE) are sorted first, and then sort by the SERVICE_STATE, putting IN_SERVICE before MAINTENANCE etc.



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