feat: fix bugs in shutdown and add `stop` (#4)

postgresql_watcher/watcher.py

diff --git a/postgresql_watcher/watcher.py b/postgresql_watcher/watcher.py
index 818b38a..50ff524 100644
--- a/postgresql_watcher/watcher.py
+++ b/postgresql_watcher/watcher.py
@@ -50,7 +50,6 @@
             logger (Optional[Logger], optional): Custom logger to use. Defaults to None.
         """
         self.update_callback = None
-        self.parent_conn = None
         self.host = host
         self.port = port
         self.user = user
@@ -83,7 +82,7 @@
         self._cleanup_connections_and_processes()
 
         self.parent_conn, self.child_conn = Pipe()
-        self.subscription_proces = Process(
+        self.subscription_process = Process(
             target=casbin_channel_subscription,
             args=(
                 self.child_conn,
@@ -109,9 +108,12 @@
         self,
         timeout=20, # seconds
     ):
-        if not self.subscription_proces.is_alive():
+        if self.subscription_process is None:
+            self._create_subscription_process(start_listening=False)
+
+        if not self.subscription_process.is_alive():
             # Start listening to messages
-            self.subscription_proces.start()
+            self.subscription_process.start()
             # And wait for the Process to be ready to listen for updates
             # from PostgreSQL
             timeout_time = time() + timeout
@@ -124,6 +126,9 @@
                     raise PostgresqlWatcherChannelSubscriptionTimeoutError(timeout)
                 sleep(1 / 1000)  # wait for 1 ms
 
+    def stop(self):
+        self._cleanup_connections_and_processes()
+
     def _cleanup_connections_and_processes(self) -> None:
         # Clean up potentially existing Connections and Processes
         if self.parent_conn is not None:
@@ -132,8 +137,9 @@
         if self.child_conn is not None:
             self.child_conn.close()
             self.child_conn = None
-        if self.subscription_process is not None:
+        if self.subscription_process is not None and self.subscription_process.pid is not None:
             self.subscription_process.terminate()
+            self.subscription_process.join()
             self.subscription_process = None
 
     def set_update_callback(self, update_handler: Optional[Callable[[None], None]]):

tests/test_postgresql_watcher.py

diff --git a/tests/test_postgresql_watcher.py b/tests/test_postgresql_watcher.py
index d3f9d70..5311ccb 100644
--- a/tests/test_postgresql_watcher.py
+++ b/tests/test_postgresql_watcher.py
@@ -50,7 +50,7 @@
             assert isinstance(pg_watcher.parent_conn, connection.PipeConnection)
         else:
             assert isinstance(pg_watcher.parent_conn, connection.Connection)
-        assert isinstance(pg_watcher.subscription_proces, context.Process)
+        assert isinstance(pg_watcher.subscription_process, context.Process)
 
     def test_update_single_pg_watcher(self):
         pg_watcher = get_watcher("test_update_single_pg_watcher")
@@ -115,6 +115,28 @@
         self.assertFalse(main_watcher.should_reload())
         self.assertTrue(handler.call_count == 0)
 
+    def test_stop_and_restart(self):
+        channel_name = "test_stop_and_restart"
+        pg_watcher = get_watcher(channel_name)
+
+        # Verify initially started
+        self.assertTrue(pg_watcher.subscription_process.is_alive())
+
+        # Stop the watcher
+        pg_watcher.stop()
+        self.assertIsNone(pg_watcher.subscription_process)
+
+        # Restart the watcher
+        pg_watcher.start()
+
+        # Verify resources are recreated and process is alive
+        self.assertTrue(pg_watcher.subscription_process.is_alive())
+
+        # Verify it still works after restart
+        pg_watcher.update()
+        sleep(CASBIN_CHANNEL_SELECT_TIMEOUT * 2)
+        self.assertTrue(pg_watcher.should_reload())
+
 
 if __name__ == "__main__":
     main()