[GitHub] [flink] pnowojski commented on a change in pull request #14632: [FLINK-20960][doc] Add warning in 1.12 release notes for potential co…

[GitBox <gi...@apache.org>]

pnowojski commented on a change in pull request #14632:
URL: https://github.com/apache/flink/pull/14632#discussion_r557325687



##########
File path: docs/release-notes/flink-1.12.md
##########
@@ -163,4 +163,10 @@ Beginning from Flink 1.12, jobs will be scheduled in the unit of pipelined regio
 
 The old scheduler can be enabled using the `jobmanager.scheduler.scheduling-strategy: legacy` setting.
 
+### Known Issues
 
+#### Unaligned checkpoint recovery may lead to corrupted data stream [FLINK-20654](https://issues.apache.org/jira/browse/FLINK-20654)
+
+Using UnalignedCheckpoints in Flink 1.12.0 combined with two/multiple inputs tasks or with union inputs for single input tasks can result in corrupted state. 
+
+This can happen if a new checkpoint is triggered before recovery is fully completed. For state to be corrupted a task with two or more input gates must receive a checkpoint barrier exactly at the same time this tasks finishes recovering spilled in-flight data. In such case this new checkpoint can succeed, with corrupted/missing in-flight data, which will result in various deserialisation/corrupted data stream errors when someone attempts to recover from such corrupted checkpoint.

Review comment:
       I would put it on top




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