Add Pool.is_closing() method (#973)

Author: singingwolfboy

Diff for: asyncpg/pool.py

@@ -446,6 +446,13 @@ async def _initialize(self):
 
                 await asyncio.gather(*connect_tasks)
 
+    def is_closing(self):
+        """Return ``True`` if the pool is closing or is closed.
+
+        .. versionadded:: 0.28.0
+        """
+        return self._closed or self._closing
+
     def get_size(self):
         """Return the current number of connections in this pool.
 

Diff for: tests/test_pool.py

@@ -740,6 +740,17 @@ async def test_pool_size_and_capacity(self):
                         self.assertEqual(pool.get_size(), 3)
                         self.assertEqual(pool.get_idle_size(), 0)
 
+    async def test_pool_closing(self):
+        async with self.create_pool() as pool:
+            self.assertFalse(pool.is_closing())
+            await pool.close()
+            self.assertTrue(pool.is_closing())
+
+        async with self.create_pool() as pool:
+            self.assertFalse(pool.is_closing())
+            pool.terminate()
+            self.assertTrue(pool.is_closing())
+
     async def test_pool_handles_transaction_exit_in_asyncgen_1(self):
         pool = await self.create_pool(database='postgres',
                                       min_size=1, max_size=1)