From 93a746aaaa092ffc3e7eb37e1df30bfd3a28435f Mon Sep 17 00:00:00 2001 From: sterni Date: Sun, 21 Feb 2021 12:57:40 +0100 Subject: feat(web/bubblegum): nix CGI programming framework 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 --- web/bubblegum/examples/hello.nix | 80 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 web/bubblegum/examples/hello.nix (limited to 'web/bubblegum/examples/hello.nix') diff --git a/web/bubblegum/examples/hello.nix b/web/bubblegum/examples/hello.nix new file mode 100644 index 000000000000..881426bd1212 --- /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: "
  • ${v.title}
    • ") + routes); + + template = { title, content, ... }: '' + + + + + ${title} + + + +
    +

    //web/bubblegum

    +

    example app

    +
    +
    + +
    +
    +

    ${content}

    +
    + + ''; + + response = routes."${pathInfo}" or notFound; + +in + respond response.status { + "Content-type" = "text/html"; + } (template response) -- cgit 1.4.1