You are viewing a plain text version of this content. The canonical link for it is here.
Posted to issues@flink.apache.org by "Roman Khachatryan (Jira)" <ji...@apache.org> on 2022/04/07 11:40:00 UTC
[jira] [Updated] (FLINK-27114) On JM restart, the information about the initial checkpoints can be lost
[ https://issues.apache.org/jira/browse/FLINK-27114?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Roman Khachatryan updated FLINK-27114:
--------------------------------------
Description:
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
# In step (7), state will not be discarded; 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.
was:
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 NO_CLAIM and LEGACY modes are affected
# SharedStateRegistry was changed from refCounts to highest checkpoint ID
# In step (7), state will not be discarded; 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.
> 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
> Fix For: 1.16.0, 1.14.5, 1.15.1
>
>
> 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
> # In step (7), state will not be discarded; 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.
--
This message was sent by Atlassian Jira
(v8.20.1#820001)