Re: [dispatch] Potential incoming work: web push for IMAP, CalDAV and CardDAV

[Michael Toomim <[e-mail]>]

Thank you very much for your early comments!

Julian:
> 
> Hmm. I think you'll need to work on the proper labeling of things. Even
> if the client opts into this format, the Content-Type will still have to
> describe the overall payload.

Hm, I think I see where you're coming from.  Here's the example in my mind:

Request:
     GET /animated-braid.gif
     Subscribe

Response:
     OK 200
     Subscribe
     Cache-Control: no-cache
     Patch-Type: braid-patch(bytes, sync9(array))
     ---- Part 1
     Content-Type: image/gif
     Patch-Type: braid-patch(bytes, sync9(array))
     Content-Length: 1239

     [100:200] = <binary data>
     ---- Part 2
     Content-Type: image/gif
     Patch-Type: braid-patch(bytes, sync9(array))
     Content-Length: 62638

     [348:887] = <binary data>

I think you're saying that the Content-Type of each part should need to describe the BODY of each part.  Why is that necessary?  I would imagine that it would only impact a cache, but we rule out caches with no-cache unless they understand the patch format.

It seems to me that the Content-Type *could* conceivably describe the semantic content of the resource, even though its updates are described with a particular Patch-Type.  Similar to how Range Requests don't change the Content-Type, even though they are only sending a small patch of the object in the BODY.

> You're basically inventing a new payload format that can wrap multiple
> payloads. But then we already have multipart/*; it really seems to me
> you should be using that instead.

I'm open to using multipart/*.  Are there any advantages to it?  It requires the sender to come up with a unique separator string, which means they need to scan all messages before choosing the separator to wrap them with.  It seems simpler to just use Content-Length: N to communicate how to break apart multiple messages, and as a bonus, you can stream the data and process just one message at a time.

Thank you very much for your early comments!