Resume S3 MultipartUpload across PHP process boundaries via persisted UploadId

[TobyTheHutt]

Tip

Help move this idea forward

• Use the 👍 reaction to show support for this feature.
• Avoid commenting unless you have relevant information to add; unnecessary comments create noise for subscribers.
• Subscribe to receive notifications about status changes and new comments.

---

Is your feature request related to a problem? Please describe.

\OC\Files\ObjectStore\S3ObjectTrait::writeMultiPart holds the Aws\Multipart\UploadState (containing the UploadId) as a local variable. The state is not persisted. When the PHP process terminates abnormally, the UploadId is lost.

The in-progress multipart upload remains on the S3 destination. Nextcloud has no reference to it. Subsequent MOVE/COPY/PUT attempts on the same source restart from part 0 and orphan the previous parts.

Describe the solution you'd like

Persist the UploadId, source-storage id, source internal path, and destination internal path at CreateMultipartUpload time. Store in oc_filecache_extended or an equivalent table.

On the next MOVE/COPY/PUT against the same source, writeMultiPart MUST look up the persisted UploadId. When present, reconstruct the UploadState via \Aws\S3\MultipartUploadingTrait::getStateFromService($client, $bucket, $key, $uploadId) and pass it to MultipartUploader via the state config option.

Delete the persisted record on CompleteMultipartUpload or AbortMultipartUpload.

Describe alternatives you've considered

• Retry from part 0 on the next attempt. Wastes upload bandwidth equal to the completed part count.
• Client-side chunked-upload resume (PR #27034). WebDAV Chunk-v2, client-driven, unrelated to server-side MultipartUploader.
• Same-request retry with reduced concurrency (PR #53580). Bounded to a single PHP process, does not survive process death.
• Orphan reap via scheduled ListMultipartUploads + AbortMultipartUpload. Cleanup pattern only, forfeits progress.

Additional context

• MultipartUploadingTrait::getStateFromService reconstructs UploadState from bucket, key, uploadId via ListParts pagination. Documented at https://docs.aws.amazon.com/aws-sdk-php/v3/api/class-Aws.S3.MultipartUploadingTrait.html.
• Related open issues: #48823, #51860, #39088, #29841.