nixpkgs/modules/services/databases/mysql.nix

{pkgs, config, ...}:

###### interface
let
  inherit (pkgs.lib) mkOption mkIf;

  options = {
    services = {
      mysql = {
        enable = mkOption {
          default = false;
          description = "
            Whether to enable the MySQL server.
          ";
        };
        
        port = mkOption {
          default = "3306";
          description = "Port of MySQL"; 
        };
        
        user = mkOption {
          default = "mysql";
          description = "User account under which MySQL runs";
        };
        
        dataDir = mkOption {
          default = "/var/mysql";
          description = "Location where MySQL stores its table files";
        };
        
        logError = mkOption {
          default = "/var/log/mysql_err.log";
          description = "Location of the MySQL error logfile";
        };
        
        pidDir = mkOption {
          default = "/var/run/mysql";
          description = "Location of the file which stores the PID of the MySQL server";
        };
      };
    };
  };
in

###### implementation

let

  cfg = config.services.mysql;

  mysql = pkgs.mysql;

  pidFile = "${cfg.pidDir}/mysqld.pid";

  mysqldOptions =
    "--user=${cfg.user} --datadir=${cfg.dataDir} " +
    "--log-error=${cfg.logError} --pid-file=${pidFile}";

in


mkIf config.services.mysql.enable {
  require = [
    options
  ];

  users = {
    extraUsers = [
      { name = "mysql";
        description = "MySQL server user";
      }
    ];
  };

  services = {
    extraJobs = [{
      name = "mysql";
      

      extraPath = [mysql];
      
      job = ''
        description "MySQL server"

        stop on shutdown

        start script
            if ! test -e ${cfg.dataDir}; then
                mkdir -m 0700 -p ${cfg.dataDir}
                chown -R ${cfg.user} ${cfg.dataDir}
                ${mysql}/bin/mysql_install_db ${mysqldOptions}
            fi

            mkdir -m 0700 -p ${cfg.pidDir}
            chown -R ${cfg.user} ${cfg.pidDir}
        end script

        respawn ${mysql}/bin/mysqld ${mysqldOptions}

        stop script
            pid=$(cat ${pidFile})
            kill "$pid"
            ${mysql}/bin/mysql_waitpid "$pid" 1000
        end script
      '';
    }];
  };
}