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https://issues.apache.org/jira/browse/HBASE-29448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18051773#comment-18051773
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Dieter De Paepe commented on HBASE-29448:
-----------------------------------------
It looks like this ticket hasn't been backported to branch-3 and branch-2 yet.
There's also no PR yet for branch-3.
What is needed to make this happen?
> Modern backup failures can cause backup system to lock up
> ---------------------------------------------------------
>
> Key: HBASE-29448
> URL: https://issues.apache.org/jira/browse/HBASE-29448
> Project: HBase
> Issue Type: Bug
> Components: backup&restore
> Reporter: Hernan Romer
> Assignee: Hernan Romer
> Priority: Major
> Labels: pull-request-available
>
> Prior to any backup operation, a snapshot of the backup:system table will be
> taken. If the backup operation fails, we attempt to restore the backup system
> table from the snapshot. This is done as a way to revert to a previously
> successful state.
>
> In order to restore, we run different
> [procedures|https://github.com/apache/hbase/blob/8ddf925daac7af48a5b624c6192bd2cdc45f7955/hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/impl/BackupSystemTable.java#L1400]
> in sequence. The problem is that these procedures aren't guaranteed to run
> back to back without interference; there are no atomicity guarantees that
> prevent other {{backup:system}} operations from being interleaved here. This
> can cause the backup system to get into a stuck state, Where it is unable to
> proceed until it receives manual intervention.
>
> For example, we may fail a backup for whatever reason, and go to restore from
> the snapshot. However, an EnableTableProcedure might sneak through and run
> between the DisableTableProcedure and the restore snapshot. A concrete
> example is the BackupHFileCleaner running and enabling the {{backup:system}}
> table when it creates a
> [BackupSystemTable|https://github.com/apache/hbase/blob/8ddf925daac7af48a5b624c6192bd2cdc45f7955/hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/BackupHFileCleaner.java#L69]
> object
>
> {code:java}
> 2025-07-06T11:39:23,061 [hfile_cleaner-dir-scan-pool-285] INFO
> org.apache.hadoop.hbase.client.HBaseAdmin: Started enable of
> backup:system{code}
>
> Now, subsequent backups cannot run, b/c they cannot snapshot the table due to
> an existing snapshot that wasn't correctly cleaned up
>
> {code:java}
> 2025-07-06 11:41:48.004 [pool-115-thread-1] ERROR
> o.a.h.h.b.impl.TableBackupClient - Unexpected Exception :
> org.apache.hadoop.hbase.snapshot.SnapshotExistsException: Snapshot
> 'snapshot_backup_system' already stored on the filesystem. at
> org.apache.hadoop.hbase.master.snapshot.SnapshotManager.sanityCheckBeforeSnapshot(SnapshotManager.java:804)
> at
> org.apache.hadoop.hbase.master.snapshot.SnapshotManager.access$000(SnapshotManager.java:127)
> at
> org.apache.hadoop.hbase.master.snapshot.SnapshotManager$1.run(SnapshotManager.java:725)
> at
> org.apache.hadoop.hbase.master.procedure.MasterProcedureUtil.submitProcedure(MasterProcedureUtil.java:132)
> at
> org.apache.hadoop.hbase.master.snapshot.SnapshotManager.submitSnapshotProcedure(SnapshotManager.java:722)
> at
> org.apache.hadoop.hbase.master.snapshot.SnapshotManager.takeSnapshot(SnapshotManager.java:713)
> at
> org.apache.hadoop.hbase.master.MasterRpcServices.snapshot(MasterRpcServices.java:1723)
> at
> org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos$MasterService$2.callBlockingMethod(MasterProtos.java)
> at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:443) at
> org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:124) at
> org.apache.hadoop.hbase.ipc.RpcHandler.run(RpcHandler.java:105) at
> org.apache.hadoop.hbase.ipc.RpcHandler.run(RpcHandler.java:85)
> {code}
> I can think of two possible solutions:
> # Create a specific procedure that restores the {{backup:system}} table from
> a snapshot that takes a table-level lock against the backup system table.
> This would ensure the restore process runs without interference
> # Implement a different checkpointing system, that doesn't require
> snapshotting the backup system table
> I'm err'ing towards the first option, as it would be easier to implement, and
> wouldn't require a massive re-work
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