[jira] [Commented] (FLINK-28843) Failed to restore from changelog checkpoint in claim mode

["Yun Tang (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-28843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17576147#comment-17576147 ] 

Yun Tang commented on FLINK-28843:
----------------------------------

Thanks for reporting this bug!

The root cause is that the native savepoint could contain the relative file state handles (all files under {{chk-x}} folder would be {{{}RelativeFileStateHandle{}}}), and the snapshot on changelog state-backend might not trigger the materialization part, which leads to the newly created {{chk-y}} folder does not contain previous snapshots. Thus, once restoring from {{{}chk-y{}}}, relocatable {{chk-x/file-1}} would be transferred to {{{}chk-y/file-1{}}}, resulting in the file not found exception.

Since we already give docs that native savepoint is relocatable (refer to [https://nightlies.apache.org/flink/flink-docs-release-1.15/docs/ops/state/checkpoints_vs_savepoints/#capabilities-and-limitations] ), we might have to let changelog state-backend trigger materialization on the 1st checkpoint if restored snapshot containing relative file state handles. cc [~roman]  [~ym] [~Yanfei Lei] 

> Failed to restore from changelog checkpoint in claim mode
> ---------------------------------------------------------
>
>                 Key: FLINK-28843
>                 URL: https://issues.apache.org/jira/browse/FLINK-28843
>             Project: Flink
>          Issue Type: Bug
>          Components: Runtime / State Backends
>    Affects Versions: 1.15.0, 1.15.1
>            Reporter: Lihe Ma
>            Priority: Critical
>
> # When native checkpoint is enabled and incremental checkpointing is enabled in rocksdb statebackend，if state data is greater than state.storage.fs.memory-threshold，it will be stored in a data file (FileStateHandle，RelativeFileStateHandle, etc) rather than stored with ByteStreamStateHandle in checkpoint metadata, like base-path1/chk-1/file1.
>  # Then restore the job from base-path1/chk-1 in claim mode，using changelog statebackend，and the checkpoint path is set to base-path2, then new checkpoint will be saved in base-path2/chk-2, previous checkpoint file (base-path1/chk-1/file1) is needed.
>  # Then restore the job from base-path2/chk-2 in changelog statebackend, flink will try to read base-path2/chk-2/file1, rather than the actual file location base-path1/chk-1/file1, which leads to FileNotFoundException and job failed.
>  
> How to reproduce?
>  # Set state.storage.fs.memory-threshold to a small value, like '20b'.
>  # {{run org.apache.flink.test.checkpointing.ChangelogPeriodicMaterializationSwitchStateBackendITCase#testSwitchFromDisablingToEnablingInClaimMode}}



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