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| author | sterni <sternenseemann@systemli.org> | 2021-02-21T11·57+0100 |
|---|---|---|
| committer | sterni <sternenseemann@systemli.org> | 2021-04-01T18·50+0000 |
| commit | 93a746aaaa092ffc3e7eb37e1df30bfd3a28435f (patch) | |
| tree | 4197f3d5c7b5e2c4cdcb4be3dd1a17ed3ecc2ad7 /web/bubblegum/examples/hello.nix | |
| parent | 68f3ac64c4a2ae50dcb125f067692536f647e370 (diff) | |
feat(web/bubblegum): nix CGI programming framework r/2394
So here is what has been keeping me up at night: At some point I
realized that nix actually made a somewhat passable language for CGI
programming:
* That `builtins.getEnv` exists as one of the impurities of Nix is
perfect as environment variables are the main way of communication
from the web server to the CGI application.
* We can actually read from the filesystem via builtins.readDir and
builtins.readFile with bearable overhead if we avoid importing the
used paths into the nix store.
* Templating and routing are convenient to implement via indented strings
and attribute sets respectively.
Of course there are obvious limitation:
* The overhead of derivations is probably much to great for them to be
useful via IfD.
* Even without derivations, nix evaluation is very slow to the point
were a trivial application takes between 100ms and 400ms to produce a
response.
* We can't really cause effects other than producing a response which
makes it not viable for a lot of applications. There are some ways
around this:
* With a custom interpreter we could have streaming and multiplexed
I/O (using lazy lists emulated via attrsets) to cause such effects,
but it would probably perform terribly.
* We can use builtins.fetchurl to call other HTTP-based microservices,
but only in very limited constraints, i. e. only GET, no headers,
and only if the tarball ttl is set to 0 in the global nix.conf.
* Terrible error handling capabilities because builtins.tryEval actually
doesn't catch a lot of errors.
To prove that it actually works, there are some demo applications,
which I invite you to run and potentially break horribly:
nix-build -A web.bubblegum.examples && ./result
# navigate to http://localhost:9000
The setup uses thttpd and executes the nix CGI scripts using
users.sterni.nint which automatically passed `depot`, so they can
import the cgi library.
Change-Id: I3a22a749612211627e5f8301c31ec2e7a872812c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2746
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Diffstat (limited to 'web/bubblegum/examples/hello.nix')
| -rw-r--r-- | web/bubblegum/examples/hello.nix | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/web/bubblegum/examples/hello.nix b/web/bubblegum/examples/hello.nix new file mode 100644 index 0000000000..881426bd12 --- /dev/null +++ b/web/bubblegum/examples/hello.nix @@ -0,0 +1,80 @@ +{ depot, ... }: + +let + inherit (depot) + lib + ; + + inherit (depot.web.bubblegum) + pathInfo + respond + absolutePath + ; + + routes = { + "/" = { + status = "OK"; + title = "index"; + content = '' + Hello World! + ''; + }; + "/clock" = { + status = "OK"; + title = "clock"; + content = '' + It is ${toString builtins.currentTime}s since 1970-01-01 00:00 UTC. + ''; + }; + "/coffee" = { + status = "I'm a teapot"; + title = "coffee"; + content = '' + No coffee, I'm afraid + ''; + }; + }; + + notFound = { + status = "Not Found"; + title = "404"; + content = '' + This page doesn't exist. + ''; + }; + + navigation = + lib.concatStrings (lib.mapAttrsToList + (p: v: "<li><a href=\"${absolutePath p}\">${v.title}</a></li>") + routes); + + template = { title, content, ... }: '' + <!doctype html> + <html lang="en"> + <head> + <meta charset="utf-8"> + <title>${title}</title> + <style>a:link, a:visited { color: blue; }</style> + </head> + <body> + <hgroup> + <h1><code>//web/bubblegum</code></h1> + <h2>example app</h2> + </hgroup> + <header> + <nav> + <ul>${navigation}</ul> + </nav> + </header> + <main> + <p>${content}</p> + </main> + </body> + ''; + + response = routes."${pathInfo}" or notFound; + +in + respond response.status { + "Content-type" = "text/html"; + } (template response) |