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/blog.nix | 134 +++++++++++++++++++++ web/bubblegum/examples/default.nix | 61 ++++++++++ web/bubblegum/examples/derivation-svg.nix | 11 ++ web/bubblegum/examples/hello.nix | 80 ++++++++++++ web/bubblegum/examples/posts/2021-04-01-hello.html | 3 + .../examples/posts/2021-04-02-a second post.html | 7 ++ 6 files changed, 296 insertions(+) create mode 100644 web/bubblegum/examples/blog.nix create mode 100644 web/bubblegum/examples/default.nix create mode 100644 web/bubblegum/examples/derivation-svg.nix create mode 100644 web/bubblegum/examples/hello.nix create mode 100644 web/bubblegum/examples/posts/2021-04-01-hello.html create mode 100644 web/bubblegum/examples/posts/2021-04-02-a second post.html (limited to 'web/bubblegum/examples') diff --git a/web/bubblegum/examples/blog.nix b/web/bubblegum/examples/blog.nix new file mode 100644 index 000000000000..f79ab0627e88 --- /dev/null +++ b/web/bubblegum/examples/blog.nix @@ -0,0 +1,134 @@ +{ depot, ... }: + +let + inherit (depot) + lib + ; + + inherit (depot.users.sterni.nix) + url + fun + string + ; + + inherit (depot.web.bubblegum) + pathInfo + scriptName + respond + absolutePath + ; + + # substituted using substituteAll in default.nix + blogdir = "@blogdir@"; + # blogdir = toString ./posts; # for local testing + + parseDate = post: + let + matched = builtins.match "/?([0-9]+)-([0-9]+)-([0-9]+)-.+" post; + in + if matched == null + then [ 0 0 0 ] + else builtins.map builtins.fromJSON matched; + + parseTitle = post: + let + matched = builtins.match "/?[0-9]+-[0-9]+-[0-9]+-(.+).html" post; + in + if matched == null + then "no title" + else builtins.head matched; + + dateAtLeast = a: b: + builtins.all fun.id + (lib.zipListsWith (partA: partB: partA >= partB) a b); + + byPostDate = a: b: + dateAtLeast (parseDate a) (parseDate b); + + posts = builtins.sort byPostDate + (builtins.attrNames + (lib.filterAttrs (_: v: v == "regular") + (builtins.readDir blogdir))); + + generic = { title, inner, ... }: '' + + + + + ${title} + + + + ${inner} + + + ''; + + index = posts: '' +
+

blog posts

+ +
+ ''; + + formatDate = + let + # Assume we never deal with years < 1000 + formatDigit = d: string.fit { + char = "0"; width = 2; + } (toString d); + in lib.concatMapStringsSep "-" formatDigit; + + post = title: post: '' +
+

${title}

+
+ ${builtins.readFile (blogdir + "/" + post)} +
+
+
+

Posted on ${formatDate (parseDate post)}

+ +
+ ''; + + validatePathInfo = pathInfo: + let + chars = string.toChars pathInfo; + in builtins.length chars > 1 + && !(builtins.elem "/" (builtins.tail chars)); + + response = + if pathInfo == "/" + then { + title = "blog"; + status = "OK"; + inner = index posts; + } + else if !(validatePathInfo pathInfo) + then { + title = "Bad Request"; + status = "Bad Request"; + inner = "No slashes in post names 😡"; + } + # CGI should already url.decode for us + else if builtins.pathExists (blogdir + "/" + pathInfo) + then rec { + title = parseTitle pathInfo; + status = "OK"; + inner = post title pathInfo; + } else { + title = "Not Found"; + status = "Not Found"; + inner = "

404 — not found

"; + }; +in + respond response.status { + "Content-type" = "text/html"; + } (generic response) diff --git a/web/bubblegum/examples/default.nix b/web/bubblegum/examples/default.nix new file mode 100644 index 000000000000..3f0f51db6369 --- /dev/null +++ b/web/bubblegum/examples/default.nix @@ -0,0 +1,61 @@ +{ depot, pkgs, lib, ... }: + +let + + scripts = [ + ./hello.nix + ./derivation-svg.nix + (substituteAll { + src = ./blog.nix; + # by making this a plain string this + # can be something outside the nix store! + blogdir = ./posts; + }) + ]; + + inherit (depot.nix) + writeExecline + runExecline + getBins + ; + + inherit (depot.web.bubblegum) + writeCGI + ; + + inherit (pkgs) + runCommandLocal + substituteAll + ; + + bins = (getBins pkgs.thttpd [ "thttpd" ]) + // (getBins pkgs.coreutils [ "printf" "cp" "mkdir" ]); + + webRoot = + let + copyScripts = lib.concatMap + (path: let + cgi = writeCGI { + # assume we are on NixOS since thttpd doesn't set PATH. + # using third_party.nix is tricky because not everyone + # has a tvix daemon running. + binPath = "/run/current-system/sw/bin"; + } path; + in [ + "if" [ bins.cp cgi "\${out}/${cgi.name}" ] + ]) scripts; + in runExecline.local "webroot" {} ([ + "importas" "out" "out" + "if" [ bins.mkdir "-p" "$out" ] + ] ++ copyScripts); + + port = 9000; + +in + writeExecline "serve-examples" {} [ + "foreground" [ + bins.printf "%s\n" "Running on http://localhost:${toString port}" + ] + "${bins.thttpd}" "-D" "-p" (toString port) "-l" "/dev/stderr" + "-c" "*.nix" "-d" webRoot + ] diff --git a/web/bubblegum/examples/derivation-svg.nix b/web/bubblegum/examples/derivation-svg.nix new file mode 100644 index 000000000000..a5f30a2bd155 --- /dev/null +++ b/web/bubblegum/examples/derivation-svg.nix @@ -0,0 +1,11 @@ +# Warning: this is *very* slow on the first request +{ depot, ... }: + +let + inherit (depot.web.bubblegum) + respond + ; +in + respond "OK" { + Content-type = "image/svg+xml"; + } (builtins.readFile "${depot.tvix.docs.svg}/component-flow.svg") 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) diff --git a/web/bubblegum/examples/posts/2021-04-01-hello.html b/web/bubblegum/examples/posts/2021-04-01-hello.html new file mode 100644 index 000000000000..3c58be7953f1 --- /dev/null +++ b/web/bubblegum/examples/posts/2021-04-01-hello.html @@ -0,0 +1,3 @@ +

    + This is it, the peak of cursed. +

    diff --git a/web/bubblegum/examples/posts/2021-04-02-a second post.html b/web/bubblegum/examples/posts/2021-04-02-a second post.html new file mode 100644 index 000000000000..050586c3029c --- /dev/null +++ b/web/bubblegum/examples/posts/2021-04-02-a second post.html @@ -0,0 +1,7 @@ +

    +

    +

    -- cgit 1.4.1