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-rw-r--r--krebs/3modules/cachecache.nix171
1 files changed, 171 insertions, 0 deletions
diff --git a/krebs/3modules/cachecache.nix b/krebs/3modules/cachecache.nix
new file mode 100644
index 000000000..989320480
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+++ b/krebs/3modules/cachecache.nix
@@ -0,0 +1,171 @@
+{ config, lib, ... }:
+
+
+# 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.
+ '';
+ };
+
+ # webRoot = mkOption {
+ # type = types.str;
+ # default = "/";
+ # description = ''
+ # Directory on virtual host that serves the cache. Must end in
+ # <literal>/</literal>.
+ # '';
+ # };
+
+ 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.
+ '';
+ };
+
+ maxSize = mkOption {
+ type = types.str;
+ default = "50g";
+ description = "Maximum cache size.";
+ };
+ };
+ };
+
+ config = mkIf cfg.enable {
+ 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
+ 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";
+ 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;
+ };
+ };
+ };
+}