nixos/librenms: add socket auth for mysql

This allows librenms to use socket authentication to the mysql package out of the box if installed under
the same username, avoiding complex DB password initialization steps.

nixos/modules/services/monitoring/librenms.nix

@@ -16,7 +16,8 @@ let
     upload_max_filesize = 100M
     date.timezone = "${config.time.timeZone}"
   '';
-  phpIni = pkgs.runCommand "php.ini" {
+  phpIni = pkgs.runCommand "php.ini"
+    {
       inherit (package) phpPackage;
       inherit phpOptions;
       preferLocalBuild = true;
@@ -47,7 +48,8 @@ let
     ${lib.optionalString (cfg.extraConfig != null) cfg.extraConfig}
   '';
 
-in {
+in
+{
   options.services.librenms = with lib; {
     enable = mkEnableOption "LibreNMS network monitoring system";
 
@@ -191,7 +193,8 @@ in {
     nginx = mkOption {
       type = types.submodule (
         recursiveUpdate
-          (import ../web-servers/nginx/vhost-options.nix { inherit config lib; }) {}
+          (import ../web-servers/nginx/vhost-options.nix { inherit config lib; })
+          { }
       );
       default = { };
       example = literalExpression ''
@@ -240,6 +243,7 @@ in {
         default = "localhost";
         description = ''
           Hostname or IP of the MySQL/MariaDB server.
+          Ignored if 'socket' is defined.
         '';
       };
 
@@ -248,6 +252,7 @@ in {
         default = 3306;
         description = ''
           Port of the MySQL/MariaDB server.
+          Ignored if 'socket' is defined.
         '';
       };
 
@@ -264,15 +269,28 @@ in {
         default = "librenms";
         description = ''
           Name of the user on the MySQL/MariaDB server.
+          Ignored if 'socket' is defined.
         '';
       };
 
       passwordFile = mkOption {
-        type = types.path;
+        type = types.nullOr types.path;
+        default = null;
         example = "/run/secrets/mysql.pass";
         description = ''
           A file containing the password for the user of the MySQL/MariaDB server.
           Must be readable for the LibreNMS user.
+          Ignored if 'socket' is defined, mandatory otherwise.
+        '';
+      };
+
+      socket = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        example = "/run/mysqld/mysqld.sock";
+        description = ''
+          A unix socket to mysql, accessible by the librenms user.
+          Useful when mysql is on the localhost.
         '';
       };
     };
@@ -483,13 +501,15 @@ in {
         EnvironmentFile = lib.mkIf (cfg.environmentFile != null) [ cfg.environmentFile ];
         User = cfg.user;
         Group = cfg.group;
-        ExecStartPre = lib.mkIf cfg.database.createLocally [ "!${pkgs.writeShellScript "librenms-db-init" ''
+        ExecStartPre = lib.mkIf cfg.database.createLocally [
+          "!${pkgs.writeShellScript "librenms-db-init" ''
           DB_PASSWORD=$(cat ${cfg.database.passwordFile} | tr -d '\n')
           echo "ALTER USER '${cfg.database.username}'@'localhost' IDENTIFIED BY '$DB_PASSWORD';" | ${pkgs.mariadb}/bin/mysql
           ${lib.optionalString cfg.useDistributedPollers ''
             echo "ALTER USER '${cfg.database.username}'@'%' IDENTIFIED BY '$DB_PASSWORD';" | ${pkgs.mariadb}/bin/mysql
           ''}
-        ''}"];
+        ''}"
+        ];
       };
       script = ''
         set -euo pipefail
@@ -516,13 +536,24 @@ in {
         ${lib.optionalString (cfg.useDistributedPollers || cfg.distributedPoller.enable) ''
           echo "CACHE_DRIVER=memcached" >> ${cfg.dataDir}/.env
         ''}
+        echo "DB_DATABASE=${cfg.database.database}" >> ${cfg.dataDir}/.env
+      ''
+      + (
+        if ! isNull cfg.database.socket
+        then ''
+          # use socket connection
+          echo "DB_SOCKET=${cfg.database.socket}" >> ${cfg.dataDir}/.env
+        ''
+        else ''
+          # use TCP connection
           echo "DB_HOST=${cfg.database.host}" >> ${cfg.dataDir}/.env
           echo "DB_PORT=${toString cfg.database.port}" >> ${cfg.dataDir}/.env
-        echo "DB_DATABASE=${cfg.database.database}" >> ${cfg.dataDir}/.env
           echo "DB_USERNAME=${cfg.database.username}" >> ${cfg.dataDir}/.env
           echo -n "DB_PASSWORD=" >> ${cfg.dataDir}/.env
           cat ${cfg.database.passwordFile} >> ${cfg.dataDir}/.env
-
+        ''
+      )
+      + ''
         # clear cache after update
         OLD_VERSION=$(cat ${cfg.dataDir}/version)
         if [[ $OLD_VERSION != "${package.version}" ]]; then
@@ -560,9 +591,11 @@ in {
 
     services.cron = {
       enable = true;
-      systemCronJobs = let
+      systemCronJobs =
+        let
           env = "PHPRC=${phpIni}";
-      in [
+        in
+        [
           # based on crontab provided by LibreNMS
           "33 */6 * * * ${cfg.user} ${env} ${package}/cronic ${package}/discovery-wrapper.py 1"
           "*/5 * * * * ${cfg.user} ${env} ${package}/discovery.php -h new >> /dev/null 2>&1"