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• enable unaligned checkpoints by default
• change the aligned checkpoint timeout from 0ms to 5s 

Compatibility, Deprecation, and Migration Plan

Those settings should make the change completely transparent for most of the users. Especially jobs that are working either without back pressure or with just small back pressure would be unaffected. Only jobs with some noticeable back pressure would switch to using unaligned checkpoints.

This would help for most of the jobs that are experiencing some back pressure. There are some edge cases, like very large parallelism jobs, with relatively small state, where user doesn't care about the checkpointing to completely timely, while the back pressure is not large enough to cause checkpoint timeouts. For those users In such a scenario the change to the unaligned checkpoints will significantly increase state size, without any benefits. However I expect such cases to be far more rare compared less common to the jobs that would benefit from enabling unaligned checkpoints.

Compatibility, Deprecation, and Migration Plan

Those settings should make the change completely transparent for most of the users. Especially jobs that are working either without back pressure or with just small back pressure would be unaffected. Only jobs with some noticeable back pressure would switch to using unaligned checkpoints.

This would help for most of the jobs that are experiencing some back pressure. There are some edge cases, like very large parallelism jobs, with relatively small state, where user doesn't care about the checkpointing to completely timely, while the back pressure is not large enough to cause checkpoint timeouts. For those users change to the unaligned checkpoints will significantly increase state size, without any benefits. However I expect such cases to be far more rare compared to the jobs that would benefit from enabling unaligned checkpointsAnother thing to consider is that we currently do not support job upgrades and Flink minor version upgrades with unaligned checkpoints, so users would have to be guided to using savepoints in those cases.

This change would have to be clearly visible in the release notes.

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