Chunked file upload

Introduction

Uploading large files is always a bit problematic as your connection can be interrupted which will fail your entire upload. Nextcloud has a chunking API where you can upload smaller chunks which will be assembled on the server once they are all uploaded.

Usage

The API is only available for registered users of your instance. And uses the path: <server>/remote.php/dav/uploads/<userid>. For this guide we will assume: https://server/remote.php/dav/uploads/roeland

Starting a chunked upload

A chunked upload is handled in 1 folder. This is the location all the chunks are uploaded to.

Start by creating a folder with a unique name. You can list the current available folder but if you take a random UUID chances of collision are tiny.

curl -X MKCOL -u roeland:pass https://server/remote.php/dav/uploads/roeland/myapp-e1663913-4423-4efe-a9cd-26e7beeca3c0

Uploading chunks

Once a folder for the chunks has been created we can start uploading the chunks. We pose no limitations on the order or the sizes of the chunks you try to upload. which means you can even adapt your chunk size to your available bandwidth. For example if you switch from mobile internet to WiFi you might want to increase the chunk size.

We sort the chunks. Before assembling. So it is recommended to name them in a way sorting always works.

XXXXXXXXXXXXXXX-YYYYYYYYYYYYYYY

Where XXXXXXXXXXXXXXX is the start byte of the chunk (with leading zeros) and YYYYYYYYYYYYYYY is the end byte of the chunk with leading zeros.

curl -X PUT -u roeland:pass https://server/remote.php/dav/uploads/roeland/myapp-e1663913-4423-4efe-a9cd-26e7beeca3c0/000000000000000-000000010485759 -d @chunk1 curl -X PUT -u roeland:pass https://server/remote.php/dav/uploads/roeland/myapp-e1663913-4423-4efe-a9cd-26e7beeca3c0/000000010485760-000000015728640 -d @chunk2

This will upload 2 chunks of a file. The first chunk is 10MB in size and the second chunk is 5MB in size.

Assembling the chunks

Assembling the chunk on the server is a matter of initiating a move from the client.

curl -X MOVE -u roeland:pass --header 'Destination:https://server/remote.php/dav/files/roeland/dest/file.zip' https://server/remote.php/dav/uploads/roeland/myapp-e1663913-4423-4efe-a9cd-26e7beeca3c0/.file

The server will now assemble the chunks and move the final file to the folder dest/file.zip.

If a modification time should be set, you can by adding it as header with date as unixtime: curl -X MOVE -u roeland:pass --header 'X-OC-Mtime:1547545326' --header 'Destination:https://server/remote.php/dav/files/roeland/dest/file.zip' https://server/remote.php/dav/uploads/roeland/myapp-e1663913-4423-4efe-a9cd-26e7beeca3c0/.file” Otherwise the current upload date will be used as modification date.

The chunks and the upload folder will be deleted afterwards.

Aborting the upload

If the upload has to be aborted this is a simple matter or deleting the upload folder.

curl -X DELETE -u roeland:pass https://server/remote.php/dav/uploads/roeland/myapp-e1663913-4423-4efe-a9cd-26e7beeca3c0/