I think we need to modify the way we write checkpoints to S3 for high-scale jobs (those with many total tasks). The issue is that we are writing all the checkpoint data under a common key prefix. This is the worst case scenario for S3 performance since the key is used as a partition key.
In the worst case checkpoints fail with a 500 status code coming back from S3 and an internal error type of TooBusyException.
One possible solution would be to add a hook in the Flink filesystem code that allows me to "rewrite" paths. For example say I have the checkpoint directory set to:
I would hook that and rewrite that path to:
s3://bucket/[HASH]/flink/checkpoints, where HASH is the hash of the original path
This would distribute the checkpoint write load around the S3 cluster evenly.
For reference: https://aws.amazon.com/premiumsupport/knowledge-center/s3-bucket-performance-improve/
Any other people hit this issue? Any other ideas for solutions? This is a pretty serious problem for people trying to checkpoint to S3.