스케쥴러 시작/정기 기능 추가

app/services/modbus/polling_service.rb

@@ -2,9 +2,9 @@ module Modbus
   class PollingService
     class << self
       def start
-        return if @thread&.alive?
+        return if $modbus_polling_threads.any?(&:alive?)
 
-        @thread = Thread.new do
+        thread = Thread.new do
           puts "[#{Time.current}] Modbus polling service 시작됨"
           last_logged_hour = nil
           loop do
@@ -32,14 +32,17 @@ module Modbus
             end
           end
         end
+        $modbus_polling_threads << thread
       end
 
       def stop
-        if @thread
-          @thread.exit
-          @thread = nil
-          puts "[#{Time.now}] Modbus polling service 중지됨"
-        end
+        $modbus_polling_threads.each { |t| t.kill if t.alive? }
+        $modbus_polling_threads.clear
+        puts "[#{Time.now}] Modbus polling service 중지됨"
+      end
+
+      def running?
+        $modbus_polling_threads.any?(&:alive?)
       end
     end
   end