Blob content type for chunked upload (in batch) should be validated

[vsoch]

Let's say that I generate an upload session for a blob. Each PATCH request is required to include a content type:

Content-Type: application/octet-stream
Content-Range: <range>
Content-Length: <length>

It's logical that on the first PATCH, I might not know the content type of the blob and can update it. But what happens if the content type changes on subsequent pushes? This should probably return some kind of error response, because (afaik) a blob can't have multiple content types for different chunks.

[jonjohnsonjr]

AFAIK, the content type for blob uploads isn't semantically meaningful to the registry, since it's always just application/octet-stream.

I think it would be nice for the registry to know this, though...

[vsoch]

It might also be useful to have (at least a suggestion) for a chunk size or number.

[vbatts]

how do we propose to fix this?
It seems like behaviour that could be clarified in the docs, and without breaking existing behaviour, correct?

[vsoch]

I think so - I was thinking that it would make sense to add a line to the spec that the content type of each subsequent PATCH is required to be the same as the first, and if it doesn't matches, maybe a particular response code is returned. I don't see any cases where it would be a good thing / realistic for a content type to change mid upload. Another idea would be that it's required for the first, but then just not checked for subsequent (and then errors could happen if the type changes, but this would be a user error).