[cuno]

Actually we've found it's often much worse than that. Code written against AWS S3 using the AWS SDK often doesn't work on a great many "S3-compatible" vendors (including on-prem versions). Although there's documentation on S3, it's vague in many ways, and the AWS SDKs rely on actual AWS behaviour. We've had to deal with a lot of commercial and cloud vendors that subtly break things. This includes giant public cloud companies. In one case a giant vendor only failed at high loads, making it appear to "work" until it didn't, because its backoff response was not what the AWS SDK expected. It's been a headache that we've had to deal for cunoFS, as well as making it work with GCP and Azure. At the big HPC conference Supercomputing 2023, when we mentioned supporting "S3 compatible" systems, we would often be told stories about applications not working with their supposedly "S3 compatible" one (from a mix of vendors).

[yencabulator]

Back in 2011 when I was working on making Ceph's RadosGW more S3-compatible, it was pretty common that AWS S3 behavior differed from their documentation too. I wrote a test suite to run against AWS and Ceph, just to figure out the differences. That lives on at https://github.com/ceph/s3-tests

[orf]

What differences in behaviour from the AWS docs did you find, out of interest?

[yencabulator]

What I can dig up today is that back in 2011, they documented that bucket names cannot look like IPv4 addresses and the character set was a-z0-9.-, but they failed to prevent 192.168.5.123 or _foo.

I recall there were more edge cases around HTTP headers, but they don't seem to have been recorded as test cases -- it's been too long for me to remember details, I may have simply ran out of time / real world interop got good enough to prioritize something else.

2011 state, search for fails_on_aws: https://github.com/tv42/s3-tests/blob/master/s3tests/functio...

Current state, I can't speak to the exact semantics of the annotations today, they could simply be annotating non-AWS features: https://github.com/ceph/s3-tests/blob/master/s3tests/functio...