Dear Simon and Jeroen,
thank you for your answers. I have to reiterate that I am out of my
depth in here. My knowledge of http is clicking links and not much
beyond that.
I will definitely look into `webutils` and `Rserve`.
One of the reason why I brought this issue is that I have a static site
generator that uses the pkg `servr` to serve the static site locally,
before I push it to github pages.
This allowed me to remove some 12 dependencies.
For this, the internal R webserver seems to be completely sufficient and
I thought that it would be nice to have this functionality without it
being "illegal" (i.e., replacing internal function)
and possibly documented so that the limitations are clear.
As for the limitations, IMHO when implemented as I did (Sys.sleep(Inf),
setting path, and reset on exit), it behaves like most shiny apps I saw,
or many apps in general.
So when I think about it as kind of user interface within browser
instead of written in something like tcl/tk instead of a part of
internet infrastructure, it feels quite sufficient to me.
Lately, I have been quite minimalist and I found a great joy finding
that base is quite bit more powerful than people often think so, so I am
quite happy finding out that the internal R server is fully sufficient
for me,
but can't speak for other people and their intended use.
So we can leave it at that. Maybe in few more years when I am more
familiar with web architecture and R internals, I can make a better
argument, hopefully followed with some rad code.
-- Jirka
On 6/12/24 20:05, Simon Urbanek wrote:
Jiří,
in a sense there are two quite different issue that you are touching upon. On
one hand, your request for exposing the http server is something I was pretty
much expecting. In order to judge the appetite for it I have included the
support for custom handlers back then as inofficial API specifically so that if
anyone cares we could work on refining it (really only Jeff and Hadley ever
asked and/or provided feedback). But I would argue over time it became more
clear that it's probably not the way to go.
The real problem is that we don't really want to "just" expose the server
because of the implications that you mentioned indirectly: the server is deliberately run
in the current R session - which is pretty much exactly what we want for the help system,
but it is something that is in most cases undesirable for several reasons. Firstly,
normal R user does not expect http requests to mess with their analysis (e.g. changing
the working directory would certainly not be welcome), so we don't want random code to
execute and interfere with user's work. Secondly, http services are usually expected to
be scalable and not interfere with each other - which is not possible directly here with
the server as-is since it is fully serial within the user's session. What is truly
desired strongly depends on the use-case: some applications would prefer a forked session
for each connection, other may want co-operation in a separate environment. It is all
doable, but beyond the scope of R's internal http server.
Moreover the internal http server is based on the Rserve package and you always
have much larger flexibility there. There are also higher level abstractions
like RestRserve. So if you like the internal server then you can seamlessly use
Rserve as the API was derived from there. Of course there are other
alternatives in package space like httpuv. We typically don't want to fold
things into core R unless it's absolutely necessary - i.e., if they can happily
live in package space.
In short, I'm still not convinced that you really want to use the built-in
sever. Although it is a fully featured http server, it was included for a very
specific purpose, and it's not clear that it would be a good fit for other
purposes.
That said, I'm interested in ideas about what users would want to use it for.
There may be use-cases which do fit the design so we could make it happen. I
would recommend looking at Rserve first, because anything implemented there is
trivial to add to R (as it is the same code base) if it would make sense. So
I'm open to suggestions, but they should be centered around what cannot be done
already.
Cheers,
Simon
On Dec 5, 2024, at 2:43 PM, Jiří Moravec <jiri.c.mora...@gmail.com> wrote:
R has a native HTTP server that is used for serving R help pages interactively,
at least on the loopback device (127.0.0.1)
But all of the working are internal, not exposed to user and not documented.
This is quite shame since the server seems to be fully capable of handling
basic tasks,
be it serving static websites or even interactively processing queries.
This was previously noticed by Jeffry Horner, the author of the Rook package.
I am just a guy who found it interesting.
The basic working is as follows:
User needs to either overwrite the internal `tools:::httpd` function or add
their hook into the internal environment tools:::.httpd.handlers.env.
In the former case, the user will be of a full control of the server, in the
later case, the `app` will be hooked to `/custom/app` instead.
All that is needed then is to run the interactive help that starts the
webserver.
Based on the breadcrumbs left on the way, I was able to write a server that
emulates much more complex `servr` package that I have previously used to test
locally my blog.
https://gist.github.com/J-Moravec/497d71f4a4b7a204235d093b3fa69cc3
You can see that I am forced to do some illegal procedures:
* tools:::httpd needs to be replaced
* the server doesn't have knowledge of a directory so setwd needs to be set
* the function must not end, otherwise the directory is changed during the
server lifetime (and depends on the current working directory)
I would like to suggest and probe for willingness to expose the native http
server.
This would include:
* de-hardcoding the server so that we can register other functions not just
httpd
* exporting many functions and renaming them (such as mime_type)
* writing better interfaces, `startDynamicHelp` is kind of hard to work with,
something like httpd_start(dir, fun, port), httpd_stop(port) and
httpd_status(port) would be much cleaner.
I would like to say that I have no idea what I am doing, I don't understand
webtech or the internal implementation, so if there are reasons why this isn't
a great idea...
I am happy to make a PR for the R part.
https://github.com/wch/r-source/blob/trunk/src/library/tools/R/dynamicHelp.R
The C part with the R's C internals look to me like a black magic and I don't
feel confident enough.
https://github.com/wch/r-source/blob/trunk/src/modules/internet/Rhttpd.c
See this old stackoverflow answer, where someone was looking for `python -m
SimpleHTTPServer 8080`
https://stackoverflow.com/q/12636764/4868692
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