[s3] $INDEX in s3_key_format can be incorrect with multipart uploads

[PettitWesley]

Am I impacted?

If you have an S3 output: https://docs.fluentbit.io/manual/pipeline/outputs/s3

And have use_put_object false (the default) and have an s3_key_format that uses $INDEX you may be impacted.

Bug Impact

When a multipart UploadPart call fails, the index can be incorrectly decremented, leading it to be wrong (smaller value that expected) for the next file upload. This may cause the same INDEX number to be used repeatedly in a row.

Root Cause: Code Bug

The code should only decrement the $INDEX when the multipart upload is marked for failure.

Currently it decrements here instead:

• master: https://github.com/fluent/fluent-bit/blob/master/plugins/out_s3/s3.c#L1124
• AWS Distro: https://github.com/PettitWesley/fluent-bit/blob/master/plugins/out_s3/s3.c#L1129

[PettitWesley]

Quick fix for AWS distro: https://github.com/PettitWesley/fluent-bit/pull/25/files

The S3 stability refactor that I am working on here also has a full logic fix: https://github.com/PettitWesley/fluent-bit/pull/24/files

[PettitWesley]

https://github.com/fluent/fluent-bit/pull/7393/files
https://github.com/fluent/fluent-bit/pull/7394/files

[PettitWesley]

This will be fixed once I get 2.31.12 out: https://github.com/aws/aws-for-fluent-bit/blob/mainline/CHANGELOG.md

[PettitWesley]

https://github.com/aws/aws-for-fluent-bit/releases/tag/v2.31.12