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https://issues.apache.org/jira/browse/FLINK-27114?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Piotr Nowojski updated FLINK-27114:
-----------------------------------
Fix Version/s: (was: 1.16.0)
(was: 1.15.1)
(was: 1.14.6)
> On JM restart, the information about the initial checkpoints can be lost
> ------------------------------------------------------------------------
>
> Key: FLINK-27114
> URL: https://issues.apache.org/jira/browse/FLINK-27114
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Checkpointing
> Affects Versions: 1.15.0, 1.14.4, 1.16.0
> Reporter: Roman Khachatryan
> Priority: Major
>
> Scenario (1.14):
> # A job starts from an existing checkpoint 1, with incremental checkpoints
> enabled
> # Checkpoint 1 is loaded with discardOnSubsume=false by
> CheckpointCoordinator.restoreSavepoint
> # A new checkpoint 2 completes, it reuses some state from the initial
> checkpoint
> # At some point, checkpoint 1 is subsumed, but the state is not discarded
> (thanks to discardOnSubsume=false, ref counts stay 1)
> # JM crashes
> # JM restarts, loads the checkpoints 2..x from ZK (or other store) -
> discardOnSubsume=true (as deserialized from handles)
> # At some point, checkpoint 2 is subsumed and the initial shared state is
> not used anymore; because checkpoint 2 has discardOnSubsume=true, shared
> state will be erroneously discarded
> In 1.15, there were the following changes:
> # RestoreMode was added; only LEGACY mode is affected (in NO_CLAIM mode,
> checkpoint 2 can't reuse any initial state; and in CLAIM mode, it's fine to
> discard the initial state)
> # SharedStateRegistry was changed from refCounts to highest checkpoint ID
> (FLINK-24611)
> # In step (7), state will not be discarded (FLINK-26985); however, because
> it's impossible to distinguish initial state from the state created by this
> job, the latter will not be discarded as well, leading to left-over state
> artifacts.
> The proposed solution is to store the initial checkpoint ID (in store such as
> ZK or in checkpoints) and adjust steps 6 or 7.
> Storing restore information in checkpoint allows to handle multiple restore
> modes in the "lineage", e.g.:
> Initial run -> restore in NO_CLAIM -> restore in CLAIM
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