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https://issues.apache.org/jira/browse/HDDS-11036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18102678#comment-18102678
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Chia-Chuan Ho commented on HDDS-11036:
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Thanks for the clarification.
I understand that Recon now detects sequence number mismatches on restart and
reinitializes the affected Recon OM tasks using the delta DB events already
applied to the Recon OM DB.
> Ozone Recon Data Recovery Tool
> ------------------------------
>
> Key: HDDS-11036
> URL: https://issues.apache.org/jira/browse/HDDS-11036
> Project: Apache Ozone
> Issue Type: Improvement
> Components: Ozone Recon
> Reporter: Devesh Kumar Singh
> Priority: Major
>
> Recon do periodic sync with OM to keep OM namespace metadata like keys,
> volumes, buckets up-to date and use it for various other tasks and derive
> data out of it using various tasks (ContainerKeyMapperTask, NSSummaryTask,
> OMDBInsightTask etc).
> If due to unexpected errors at OM or Recon , Recon may lag or OM namespace
> metadata may not be in sync either due to
> # RocksDB lock issues.
> # Recon has fetched OM DB snapshot since last sequence number, but before
> processing those incremental events (PUT, DELETE, UPDATE), if some unexpected
> error caused any processed or derived data failed to save in recon DB, Recon
> will not fetch that incremental data again and will not process those events
> again.
> In such cases, Recon should have a recovery tool to fetch the OM DB snapshot
> from last fetched sequence number and then explicitly process and run tasks
> on fetched events for Recon.
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