Differential download falls back to full download on GitHub Releases due to multi-range request (501 Not Implemented)

[rekcahdev]

Description

GitHub Releases (Varnish CDN) advertises accept-ranges: bytes but returns 501 Not Implemented for multi-range requests. electron-updater sends all changed blocks as a single multi-range request → GitHub rejects it → falls back to full download.

In my case, only 7 ranges / 3.3 MB (3%) needed downloading out of a 106 MB installer. The blockmap diff worked perfectly, but the download fell back to the full file.

Log:

File has 162 changed blocks
Full: 108,358.93 KB, To download: 3,327.3 KB (3%)
Cannot download differentially, fallback to full download: HttpError: 501
Headers: { "accept-ranges": "bytes", "server": "Varnish" }
Request

Before falling back to full download on 501, retry using sequential single-range requests (one per block). This would work fine on GitHub Releases and benefit the majority of Electron developers using it as free hosting.

Alternatively expose a singleRangeMode: true option in setFeedURL config for explicit opt-in.

[erickzhao]

Hey, electron-updater is part of electron-builder's infrastructure, which is separate from this repo.