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https://issues.apache.org/jira/browse/HBASE-25891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17359302#comment-17359302
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Mallikarjun commented on HBASE-25891:
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[~anoop.hbase] Did you get a chance to look at it?
> Remove dependence storing WAL filenames for backup
> --------------------------------------------------
>
> Key: HBASE-25891
> URL: https://issues.apache.org/jira/browse/HBASE-25891
> Project: HBase
> Issue Type: Improvement
> Components: backup&restore
> Affects Versions: 3.0.0-alpha-1
> Reporter: Mallikarjun
> Assignee: Mallikarjun
> Priority: Major
> Fix For: 3.0.0-alpha-1
>
>
> Context:
> Currently WAL logs are stored in `backup:system` meta table
> {code:java}
> // code placeholder
> wals:preprod-dn-1%2C16020%2C1614844389000.1621996160175 column=meta:backupId,
> timestamp=1622003479895, value=backup_1622003358258
> wals:preprod-dn-1%2C16020%2C1614844389000.1621996160175 column=meta:file,
> timestamp=1622003479895,
> value=hdfs://store/hbase/oldWALs/preprod-dn-1%2C16020%2C1614844389000.1621996160175
> wals:preprod-dn-1%2C16020%2C1614844389000.1621996160175 column=meta:root,
> timestamp=1622003479895, value=s3a://2021-05-25--21-45-00--full/set1
> wals:preprod-dn-1%2C16020%2C1614844389000.1621999760280 column=meta:backupId,
> timestamp=1622003479895, value=backup_1622003358258
> wals:preprod-dn-1%2C16020%2C1614844389000.1621999760280 column=meta:file,
> timestamp=1622003479895,
> value=hdfs://store/hbase/oldWALs/preprod-dn-1%2C16020%2C1614844389000.1621999760280
> wals:preprod-dn-1%2C16020%2C1614844389000.1621999760280 column=meta:root,
> timestamp=1622003479895, value=s3a://2021-05-25--21-45-00--full/set1
> {code}
> Also, Every backup (Incremental and Full) performs a log roll just before
> taking backup and stores what was the timestamp at which log roll was
> performed per regionserver per backup using following format.
>
> {code:java}
> // code placeholder
> rslogts:hdfs://xx.xx.xx.xx:8020/tmp/backup_yaktest\x00preprod-dn-2:16020
> column=meta:rs-log-ts, timestamp=1622887363301,value=\x00\x00\x01y\xDB\x81ar
> rslogts:hdfs://xx.xx.xx.xx:8020/tmp/backup_yaktest\x00preprod-dn-3:16020
> column=meta:rs-log-ts, timestamp=1622887363294, value=\x00\x00\x01y\xDB\x81aP
> rslogts:hdfs://xx.xx.xx.xx:8020/tmp/backup_yaktest\x00preprod-dn-1:16020
> column=meta:rs-log-ts, timestamp=1622887363275,
> value=\x00\x00\x01y\xDB\x81\x85
> {code}
>
>
> There are 2 cases for which WAL log refrences stored in `backup:system` and
> are being used.
> 1. To cleanup WAL's for which backup is already taken using
> `BackupLogCleaner`
> Since log roll timestamp is stored as part of backup per regionserver. We can
> check all previous successfull backup's and then identify which logs are to
> be retained and which ones are to be cleaned up as follows
> * Identify which are the latest successful backups performed per table.
> * Per backup identified above, identify what is the oldest log rolled
> timestamp perfomed per regionserver per table.
> * All those WAL's which are older than oldest log rolled timestamp perfomed
> for any table backed can be removed by `BackupLogCleaner`
>
> 2. During incremental backup, to check system table if there are any
> duplicate WAL's for which backup is taken again.
> * Incremental backup already identifies which all WAL's to be backed up
> using `rslogts:` mentioned above.
> * Additionally it checks `wals:` to ensure no logs are backuped for second
> time. And this is redundant and not seen any extra benefit.
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