Commit graph

4 commits

Author SHA1 Message Date
sterni
d485ebf01a fix(bubblegum): import lib from the new correct place
Since cl/2910 depot has no lib attribute anymore. Import it from the
depot fix point via depot.third_party.nixpkgs.lib to avoid passing
another argument and enlargening the shebang further.

Change-Id: I3c719eba38a5ceb36689ebf0409bd19d4f46a609
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3050
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
2021-04-20 08:42:58 +00:00
sterni
386afdc794 feat(web/bubblegum): allow passing status as an int
The whole pass the name of the status as a string thing was mostly born
out of an overeager use of yants. It is still very neat especially for
common cases like "OK", so we'll keep it, but also allow passing the
integer variant of the status as well which probably feels more natural
for a lot of people, especially over getting the casing right for
"I'm a teapot".

Change-Id: I3f012a291447ef385efdd28132292a8b331998c0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2850
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
2021-04-05 10:54:32 +00:00
sterni
1c0f89f4ca feat(web/bubblegum): report some errors to the user via HTTP
We can actually catch some errors that may be generated in bubblegum
applications where we can report them to the user in a way that doesn't
require curl -vv:

* Type errors in the status argument: By removing yants completely we
  not only (presumably) gain some performance, but also the ability to
  return an internal server error on an unexpected type instead of
  throwing.

* User generated evaluation errors: by using builtins.tryEval we can
  catch throws and asserts the user inserted when generating the body
  and report to the user that something went wrong. To do: also support
  for the headers.

Change-Id: I8363b9825c6c730e624eb8016a5482d63cbc1890
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2849
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
2021-04-05 10:54:32 +00:00
sterni
93a746aaaa 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 <mail@tazj.in>
2021-04-01 18:50:36 +00:00