Ceph S3 compatibility > 80%

[ServerSideHannes]

Summary

Improve compatibility with Ceph's S3 (RGW) implementation to pass >80% of S3 compatibility tests when using Ceph as the upstream storage backend.

Problem

Ceph's S3 gateway (RGW) has subtle differences from AWS S3 and MinIO in error responses, header handling, multipart behavior, and XML formatting. s3proxy is currently tested against MinIO. Using Ceph as the upstream may cause unexpected failures.

Proposal

• Set up Ceph RGW in the e2e test suite
• Run the existing integration tests against Ceph and identify failures
• Fix compatibility issues (error code mapping, header differences, XML parsing)
• Add Ceph-specific e2e tests for known edge cases
• Track compatibility percentage and target >80%

Known Ceph S3 differences to investigate

• Multipart upload part numbering and ETag format
• Error response XML structure
• Content-MD5 handling
• Presigned URL parameter ordering
• Bucket versioning behavior