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https://issues.apache.org/jira/browse/HDFS-4025?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hanisha Koneru updated HDFS-4025:
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Attachment: HDFS-4025.009.patch
Patch v09 has some changes.
* Checkstyle corrections
* Minor optimizations
* LastSyncedTxId has been dropped. It's possible that a checkpoint is done
during sync interval and some segments are purged. To ensure correct
lastSyncedTxId, we would need the checkpointing information from the NameNode.
We can skip this doing this for now and always sync from the first transaction
id. This improvement can be added later on.
Thank you [~jingzhao] for guiding me through with this.
> QJM: Sychronize past log segments to JNs that missed them
> ---------------------------------------------------------
>
> Key: HDFS-4025
> URL: https://issues.apache.org/jira/browse/HDFS-4025
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha
> Affects Versions: QuorumJournalManager (HDFS-3077)
> Reporter: Todd Lipcon
> Assignee: Hanisha Koneru
> Fix For: QuorumJournalManager (HDFS-3077)
>
> Attachments: HDFS-4025.000.patch, HDFS-4025.001.patch,
> HDFS-4025.002.patch, HDFS-4025.003.patch, HDFS-4025.004.patch,
> HDFS-4025.005.patch, HDFS-4025.006.patch, HDFS-4025.007.patch,
> HDFS-4025.008.patch, HDFS-4025.009.patch
>
>
> Currently, if a JournalManager crashes and misses some segment of logs, and
> then comes back, it will be re-added as a valid part of the quorum on the
> next log roll. However, it will not have a complete history of log segments
> (i.e any individual JN may have gaps in its transaction history). This
> mirrors the behavior of the NameNode when there are multiple local
> directories specified.
> However, it would be better if a background thread noticed these gaps and
> "filled them in" by grabbing the segments from other JournalNodes. This
> increases the resilience of the system when JournalNodes get reformatted or
> otherwise lose their local disk.
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