[MirageOS-devel] Dispatching boilerplate and the tutorial

[Drup <drupyog+caml@xxxxxxxx>]

The mirage guide presents nice and simple unikernels in the first 
tutorial[1], which is a very gentle introduction to mirage things, and 
then suddenly drop you into this: 
https://github.com/mirage/mirage-www/tree/master/src
The intention seems to be to present the config.ml and makes you try 
various configurations, but I don't think it works that well: people are 
going to try to understand dispatch(_tls).ml, because that's where most 
of the meat is, and these files are a bit messy, to say the least.
The next tutorials are not really related to mirage (CI, opam, 
profiling), so it is pretty much the end note of the mirage guide.
I see various issues:
1) mirage-www is not minimalistic. Now that mirage-seal is here (and in 
particular the static files[2]), maybe that should be used instead
2) Defining a unikernel that serves stuff to the web is a good amount of 
boilerplate. Also, considering the amount of indirections, this 
boilerplate is not obvious for a beginner. The main file is basically 
100 lines of plumbing to be able to call the dispatch function. This 
boilerplate is now embedded into mirage-seal which is very good, but I 
think it should be put into a small reusable library.
To add insult to injury, some of this plumbing is responsible for 
setting up the tls chain, and we all know this code should really not be 
done by the end user (regardless of how easy it is, by comparison).
3) The tutorial doesn't really explain the relation between various 
libraries that you end up using, in particular how the various cohttp 
things fit into the grand scheme.
I wonder how feasible it is to define various new modules/combinators 
that are usable in the config files, such as a fully setup HTTP(S) 
*server* stack, or a crunch device (without the need to redefine 
read_fs[3] everywhere ...). The main issue I see is that it adds even 
more things in mirage/mirage-types....

[1]: https://mirage.io/wiki/hello-world
[2]: https://github.com/mirage/mirage-seal/tree/master/static
[3]: 
https://github.com/mirage/mirage-www/blob/master/src/dispatch.ml#L71-L77

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