stockholm/krebs/3modules/cachecache.nix

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{ pkgs, config, lib, ... }:
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# fork of https://gist.github.com/rycee/f495fc6cc4130f155e8b670609a1e57b
# related: https://github.com/nh2/nix-binary-cache-proxy
with lib;
let
cfg = config.krebs.cachecache;
nginxCfg = config.services.nginx;
cacheFallbackConfig = {
proxyPass = "$upstream_endpoint";
extraConfig = ''
# Default is HTTP/1, keepalive is only enabled in HTTP/1.1.
proxy_http_version 1.1;
# Remove the Connection header if the client sends it, it could
# be "close" to close a keepalive connection
proxy_set_header Connection "";
# Needed for CloudFront.
proxy_ssl_server_name on;
proxy_set_header Host $proxy_host;
proxy_cache nix_cache_cache;
proxy_cache_valid 200 302 60m;
proxy_cache_valid 404 1m;
expires max;
add_header Cache-Control $nix_cache_cache_header always;
'';
};
in
{
options = {
krebs.cachecache = {
enable = mkEnableOption "Nix binary cache cache";
virtualHost = mkOption {
type = types.str;
default = "nix-cache";
description = ''
Name of the nginx virtualhost to use and setup. If null, do
not setup any virtualhost.
'';
};
enableSSL = mkOption {
type = types.bool;
default = true;
description = ''
enable SSL via letsencrypt. Requires working dns resolution and open
internet tls port.
'';
};
resolver = mkOption {
type = types.str;
description = "Address of DNS resolver.";
default = "8.8.8.8 ipv6=off";
example = "127.0.0.1 ipv6=off";
};
cacheDir = mkOption {
type = types.str;
default = "/var/cache/nix-cache-cache";
description = ''
Where nginx should store cached data.
'';
};
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indexFile = mkOption {
type = types.path;
default = pkgs.writeText "myindex" "<html>hello world</html>";
description = ''
Path to index.html file.
'';
};
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maxSize = mkOption {
type = types.str;
default = "50g";
description = "Maximum cache size.";
};
};
};
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config = mkIf cfg.enable {
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networking.firewall.allowedTCPPorts = [ 80 443 ];
systemd.services.nginx.preStart = ''
mkdir -p ${cfg.cacheDir} /srv/www/nix-cache-cache
chmod 700 ${cfg.cacheDir} /srv/www/nix-cache-cache
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ln -fs ${cfg.indexFile} /srv/www/nix-cache-cache/index.html
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chown ${nginxCfg.user}:${nginxCfg.group} \
${cfg.cacheDir} /srv/www/nix-cache-cache
'';
services.nginx = {
enable = true;
appendHttpConfig = ''
proxy_cache_path ${cfg.cacheDir}
levels=1:2
keys_zone=nix_cache_cache:100m
max_size=${cfg.maxSize}
inactive=365d
use_temp_path=off;
# Cache only success status codes; in particular we don't want
# to cache 404s. See https://serverfault.com/a/690258/128321.
map $status $nix_cache_cache_header {
200 "public";
302 "public";
default "no-cache";
}
'';
virtualHosts.${cfg.virtualHost} = {
addSSL = cfg.enableSSL;
enableACME = cfg.enableSSL;
extraConfig = ''
# Using a variable for the upstream endpoint to ensure that it is
# resolved at runtime as opposed to once when the config file is loaded
# and then cached forever (we don't want that):
# see https://tenzer.dk/nginx-with-dynamic-upstreams/
# This fixes errors like
#
# nginx: [emerg] host not found in upstream "upstream.example.com"
#
# when the upstream host is not reachable for a short time when
# nginx is started.
resolver ${cfg.resolver} valid=10s;
set $upstream_endpoint https://cache.nixos.org;
'';
locations."/" =
{
root = "/srv/www/nix-cache-cache";
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index = "index.html";
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extraConfig = ''
expires max;
add_header Cache-Control $nix_cache_cache_header always;
# Ask the upstream server if a file isn't available
# locally.
error_page 404 = @fallback;
# Don't bother logging the above 404.
log_not_found off;
'';
};
locations."@fallback" = cacheFallbackConfig;
# We always want to copy cache.nixos.org's nix-cache-info
# file, and ignore our own, because `nix-push` by default
# generates one without `Priority` field, and thus that file
# by default has priority 50 (compared to cache.nixos.org's
# `Priority: 40`), which will make download clients prefer
# `cache.nixos.org` over our binary cache.
locations."= /nix-cache-info" = cacheFallbackConfig;
};
};
};
}