Problem

After upgrading to 2.6.42, deleting remote backups on some S3-compatible providers fails because the new batch delete path (DeleteObjects) is used by default.

Example error:

api error InvalidRequest: Missing required header for this request: Content-MD5

This is reproducible on Huawei S3.

Why this regressed in 2.6.42

2.6.42 introduced batch deletion via DeleteObjects. Some S3-compatible providers require Content-MD5 for this API call. Previous versions (2.6.41 and earlier) used one-by-one DeleteObject and did not hit this requirement.

Current workaround

Set:

s3:
  request_content_md5: true

Expected behavior

When batch delete fails specifically due to missing Content-MD5, clickhouse-backup should retry once with Content-MD5 automatically, so existing installations keep working after upgrade.

Acceptance criteria

• RemoveBackupRemote with S3 batch delete succeeds on providers that require Content-MD5.
• No behavior change for AWS S3 and providers that do not require it.
• Existing explicit request_content_md5: true still works.