While using MP uploads via pre-signed URL on bucket with custom domain pointing to it. Below are the steps code follows

• Initiate the MP upload (CreateMultipartUpload)
• Generate pre-signed urls for the parts for this upload.
• Complete the MP upload.

When using the bucket with custom domain, with config flags bucket_as_host and virtual_host both set to true. The pre-sign URL generation generates the URL of the form

https://<my-bucket-domain>/<key>?....

Correctly but the CreateMultipartUpload has made the underlying HTTP request at the URL

POST https://<my-bucket-domain>/<my-bucket-domain>/<key>?uploads.

This creates the association of the uploadId with the key = <my-bucket-domain>/<key> instead of just <key>. So while using the generated pre-presigned put URL for the parts the upload fails because it fails to validate the key and uploadId mapping.

SDK needs to honor bucket_as_host and virtual_host combination in the CreateMultipartUpload as well.