Multipart, resumable and signed uploads

This feature has many names, but it basically divides a single upload into multiple stages. It can be used in following situations:

• a really big file must be uploaded to cloud. It cannot fit into server's temporal storage, so you split the file into smaller part and upload them separately. Every part is uploaded to server and next part must wait till the previous moved from server to cloud. This is a multipart upload.
• client has unstable or slow connection. Any upload takes ages and quite often connection is interrupted so user has to spend extra time re-uploading files. To improve user experience, you want to track the upload progress and keep incomplete file on server. If connection is interrupted, user can continue upload from the point he stopped the last time, appending content to existing incomplete file. This is a resumable upload.
• files are kept on cloud and uploads are quite intense on the portal. You don't want to spend server resources on transferring content from client to cloud. Instead you generate a URL that allows user to upload a single file directly into specific location on cloud. User sends data to this URL and only notifies the application, when upload is finished, so that the application can make file visible. This is a signed upload.

Note

This functionality is not stable. Check multipart_*, resumable_* and signed methods of the storage for current examples of implementations.