rethinkdb service: initial implementation

nixos/modules/services/databases/rethinkdb.nix

@@ -0,0 +1,110 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.rethinkdb;
+  rethinkdb = cfg.package;
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    services.rethinkdb = {
+
+      enable = mkOption {
+        default = false;
+        description = "Whether to enable the RethinkDB server.";
+      };
+
+      #package = mkOption {
+      #  default = pkgs.rethinkdb;
+      #  description = "Which RethinkDB derivation to use.";
+      #};
+
+      user = mkOption {
+        default = "rethinkdb";
+        description = "User account under which RethinkDB runs.";
+      };
+
+      group = mkOption {
+        default = "rethinkdb";
+        description = "Group which rethinkdb user belongs to.";
+      };
+
+      dbpath = mkOption {
+        default = "/var/db/rethinkdb";
+        description = "Location where RethinkDB stores its data, 1 data directory per instance.";
+      };
+
+      pidpath = mkOption {
+        default = "/var/run/rethinkdb";
+        description = "Location where each instance's pid file is located.";
+      };
+
+      #cfgpath = mkOption {
+      #  default = "/etc/rethinkdb/instances.d";
+      #  description = "Location where RethinkDB stores it config files, 1 config file per instance.";
+      #};
+
+      # TODO: currently not used by our implementation.
+      #instances = mkOption {
+      #  type = types.attrsOf types.str;
+      #  default = {};
+      #  description = "List of named RethinkDB instances in our cluster.";
+      #};
+
+    };
+
+  };
+
+  ###### implementation
+  config = mkIf config.services.rethinkdb.enable {
+
+    environment.systemPackages = [ rethinkdb ];
+
+    systemd.services.rethinkdb = {
+      description = "RethinkDB server";
+
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+
+      serviceConfig = {
+        # TODO: abstract away 'default', which is a per-instance directory name
+        #       allowing end user of this nix module to provide multiple instances,
+        #       and associated directory per instance
+        ExecStart = "${rethinkdb}/bin/rethinkdb -d ${cfg.dbpath}/default";
+        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
+        User = cfg.user;
+        Group = cfg.group;
+        PIDFile = "${cfg.pidpath}/default.pid";
+        PermissionsStartOnly = true;
+      };
+
+      preStart = ''
+        if ! test -e ${cfg.dbpath}; then
+            install -d -m0755 -o ${cfg.user} -g ${cfg.group} ${cfg.dbpath}
+            install -d -m0755 -o ${cfg.user} -g ${cfg.group} ${cfg.dbpath}/default
+            chown -R ${cfg.user}:${cfg.group} ${cfg.dbpath}
+        fi
+        if ! test -e "${cfg.pidpath}/default.pid"; then
+            install -D -o ${cfg.user} -g ${cfg.group} /dev/null "${cfg.pidpath}/default.pid"
+        fi
+      '';
+    };
+
+    users.extraUsers.rethinkdb = mkIf (cfg.user == "rethinkdb")
+      { name = "rethinkdb";
+        description = "RethinkDB server user";
+      };
+
+    users.extraGroups = optionalAttrs (cfg.group == "rethinkdb") (singleton
+      { name = "rethinkdb";
+      });
+
+  };
+
+}