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:
> Ji??,
>
> 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, Ji?? Moravec <jiri.c.moravec at
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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