[Bug] Failure to Handle 'Range' Response Header in Chunked Uploads to GCS

[skidder]

Hello Mux Team! 👋

I've encountered an issue with upchunk's handling of resumable chunked uploads to Google Cloud Storage (GCS). Specifically, the library does not appear to process the Range header in HTTP 308 responses correctly, potentially leading to incomplete uploads despite successful transmission of all data chunks.

Current Behavior:

• When uploading chunks (other than the last one) to GCS, the expected server response for a successful upload is 308 Resume Incomplete. This response includes a Range header, as specified in the GCS documentation.
• The upchunk library currently does not evaluate the Range header in these 308 responses. Consequently, it might continue transmitting the full range of bytes without recognizing that the upload has not been completed successfully on the server's end.
• There is also a lack of verification to ensure the final chunk results in the object being marked as complete (typically indicated by an HTTP 200 or 201 response, and specifically not an HTTP 308). This omission could lead clients to mistakenly believe the upload was successful when it wasn't.

Expected Behavior:

• The library should use the upper value in the Range header of each 308 response to accurately determine the starting point for each successive chunk. Alternatively, chunks that were not fully received could be sent again in their entirety.
• After transmitting the final chunk, the library should verify the server's response to confirm that the upload is indeed complete and successful.

Suggested Fix:

• Implement logic to parse and use the Range header in 308 responses to adjust the starting byte position for subsequent chunks, or use the existing retry logic to resend any chunks that were not fully received.
• Add a check after the final chunk is sent to verify the response status (HTTP 200 or 201) to confirm the successful completion of the upload.

I believe that fixing these issues should improve the reliability of chunked uploads to GCS, or any other service that makes use of the response Range header. I'm happy to submit a PR or collab on a solution!

Thanks!

[cjpillsbury]

👋 Hey @skidder! Taking a peep at the PR ASAP, but broadly this ask makes sense to me.

[cjpillsbury]

@skidder you should be good to go! https://www.npmjs.com/package/@mux/upchunk/v/3.3.1 We can re-open/create a new issue if there are any problems.