Make URLs immutable

[simonw]

Absolutely everything should have a far-future expires header

Part of the URL will be the truncated sha1 hash of the database file itself, calculated at build time

[simonw]

This means I need a good solution for these compile time options while running in development mode

[simonw]

How about when the service starts up it checks for a compile.json file and, if it is missing, creates it using the same code we run at compile time normally

[simonw]

Many of the applications I want to implement with this would benefit from having permanent real URLs.

So let’s have both. The sha1 urls will serve far future cache headers (and an etag derived from their path). The non sha1 URLs will serve 302 uncached redirects to the sha1 locations.

We will have a setting that lets people opt out of this behavior.

[simonw]

URL design:

 /database/table.json - redirects to /database-6753f4a/table.json

So we always redirect to the version with the truncated hash in the URL.

[simonw]

https://stackoverflow.com/a/18134919/6083 is a good answer about how many characters of the hash are needed to be unique. I say we default to 7 characters, like git does - but allow extras to be configured.

[simonw]

Can I take advantage of HTTP/2 so even if you get redirected I start serving you the correct resource straight away?

[simonw]

Looks like the easiest way to implement HTTP/2 server push today is to run behind Cloudflare and use this:

Link: </asset/to/push.js>; rel=preload; as=script

https://blog.cloudflare.com/announcing-support-for-http-2-server-push-2/

Here's the W3C draft: https://w3c.github.io/preload/

From https://w3c.github.io/preload/#as-attribute it looks like I should use as=fetch if the content is intended for consumption by fetch() or XMLHTTPRequest.

Unclear if I should throw as=fetch crossorigin in there. Need to experiment on that.

[simonw]

Here's what the homepage of cloudflare.com does (with newlines added within the link header for clarity):

$ curl -i 'https://www.cloudflare.com/' 
HTTP/1.1 200 OK
Date: Mon, 23 Oct 2017 21:45:58 GMT
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
link:
    </vendor/bitdashplayer.min.css>; rel=preload; as=style,
    </vendor/bitdash-controls.min.css>; rel=preload; as=style,
    </video/marketing-video/cloudflare-marketing-video.mpd>; rel=preload,
    </video/marketing-video/cloudflare-marketing-video.m3u8>; rel=preload,
    </video/marketing-video/video_0_800000/dash/init.mp4>; rel=preload; as=video,
    </video/marketing-video/audio_0_128000/dash/init.mp4>; rel=preload; as=video,
    </video/marketing-video/video_0_800000/dash/segment_0.m4s>; rel=preload; as=video,
    </video/marketing-video/audio_0_128000/dash/segment_0.m4s>; rel=preload; as=video,
    </video/new-short-optimized-22.mp4>; rel=preload; as=video,
    </video/marketing-video/poster.jpg>; rel=preload; as=image

The original header looked like this:

link: </vendor/bitdashplayer.min.css>; rel=preload; as=style, </vendor/bitdash-controls.min.css>; rel=preload; as=style, </video/marketing-video/cloudflare-marketing-video.mpd>; rel=preload, </video/marketing-video/cloudflare-marketing-video.m3u8>; rel=preload, </video/marketing-video/video_0_800000/dash/init.mp4>; rel=preload; as=video, </video/marketing-video/audio_0_128000/dash/init.mp4>; rel=preload; as=video, </video/marketing-video/video_0_800000/dash/segment_0.m4s>; rel=preload; as=video, </video/marketing-video/audio_0_128000/dash/segment_0.m4s>; rel=preload; as=video, </video/new-short-optimized-22.mp4>; rel=preload; as=video, </video/marketing-video/poster.jpg>; rel=preload; as=image