How can I enable Caddy plugins in NixOS? - nix

Question

I've just started playing with NixOS, and have so far managed to edit /etc/nixos/configuration.nix in my NixOS 18.09 VM to have PHP-FPM and the Caddy webserver enabled.
{ config, pkgs, ... }:
{
imports = [ <nixpkgs/nixos/modules/installer/virtualbox-demo.nix> ];
users = {
mutableUsers = false;
groups = {
caddy = { };
php-project = { };
};
users = {
hello = {
group = "php-project";
};
};
};
environment.systemPackages = [
pkgs.htop
pkgs.httpie
pkgs.php # for PHP CLI
];
services.caddy = {
enable = true;
email = "david#example.com";
agree = true;
config = ''
(common) {
gzip
header / -Server
header / -X-Powered-By
}
:8080 {
root /var/www/hello
fastcgi / /run/phpfpm/hello.sock php
log syslog
import common
}
'';
};
services.phpfpm = {
phpOptions = ''
date.timezone = "Europe/Berlin"
'';
poolConfigs = {
hello = ''
user = hello
listen = /run/phpfpm/hello.sock
; ...
pm.max_requests = 500
'';
};
};
}
A PHP-processed response is available at at localhost:8080. (Yay!)
To enable Caddy plugins when compiling from source, Go imports are added to caddy's run.go, e.g.:
_ "github.com/mholt/caddy/caddyhttp" // plug in the HTTP server type
// This is where other plugins get plugged in (imported)
_ "github.com/nicolasazrak/caddy-cache" // added to use another plugin
)
How can I set such line insertion to be performed after the source is downloaded and before the build takes place? (If this is a reasonable approach when using Nix?)
The NixOS 18.09 caddy package.
The NixOS 18.09 caddy service.
I believe that when writing a package a builder script (Bash or otherwise) can be assigned, and I'm thinking the line insertion could be done in it. But I'm lost as to how to assign a script to an existing package in this situation (override an attribute/use an overlay?) and where to put the script on the disk.
Status update
I've been doing some reading on customising packages in general and it sounds like overlays might be what I need. However, I don't seem to be able to get my overlay evaluated.
I'm using overriding of the package name as a test as it's simpler than patching code.
Overlay attempt 1
/etc/nixos/configuration.nix:
{ config, pkgs, options, ... }:
{
imports = [ <nixpkgs/nixos/modules/installer/virtualbox-demo.nix> ];
nix.nixPath = options.nix.nixPath.default ++ [
"nixpkgs-overlays=/etc/nixos/overlays-compat/"
];
# ...
}
/etc/nixos/overlays-compat/overlays.nix:
self: super:
with super.lib;
let
# Using the nixos plumbing that's used to evaluate the config...
eval = import <nixpkgs/nixos/lib/eval-config.nix>;
# Evaluate the config,
paths = (eval {modules = [(import <nixos-config>)];})
# then get the `nixpkgs.overlays` option.
.config.nixpkgs.overlays
;
in
foldl' (flip extends) (_: super) paths self
/etc/nixos/overlays-compat/caddy.nix:
self: super:
{
caddy = super.caddy.override {
name = "caddy-override";
};
}
Overlay attempt 2
/etc/nixos/configuration.nix:
nixpkgs.overlays = [ (self: super: {
caddy = super.caddy.override {
name = "caddy-override";
};
} ) ];
error: anonymous function at /nix/store/mr5sfmz6lm5952ch5q6v49563wzylrkx-nixos-18.09.2327.37694c8cc0e/nixos/pkgs/servers/caddy/default.nix:1:1 called with unexpected argument 'name', at /nix/store/mr5sfmz6lm5952ch5q6v49563wzylrkx-nixos-18.09.2327.37694c8cc0e/nixos/lib/customisation.nix:69:12
overrideAttrs
I previously managed to override the package name with this:
{ config, pkgs, options, ... }:
let
caddyOverride = pkgs.caddy.overrideAttrs (oldAttrs: rec {
name = "caddy-override-v${oldAttrs.version}";
});
in {
{
# ...
services.caddy = {
package = caddyOverride;
# ...
}
}
I could see in htop that the caddy binary was in a folder called /nix/store/...-caddy-override-v0.11.0-bin/. But I understand that overriding in this way has been superseded by overlays.

Answer 1

In order to add plugins to Caddy, it seems that the method is to modify the source.
You will need to adapt the Nixpkgs expression for Caddy to make that possible. That can be done outside the Nixpkgs tree, using services.caddy.package = callPackage ./my-caddy.nix {} for example, or by forking the Nixpkgs repository and pointing your NIX_PATH to your clone.

Answer 2

There is an issue for Caddy plugins: https://github.com/NixOS/nixpkgs/issues/14671
PR welcome!