Detect EOF signaling remote server closed connection

httpx/dispatch/http11.py

@@ -166,6 +166,9 @@ async def _receive_event(self, timeout: TimeoutConfig = None) -> H11Event:
                     )
                 except OSError:  # pragma: nocover
                     data = b""
+                if self.h11_state.their_state == h11.SEND_RESPONSE and data == b"":
+                    # the server closed a keep-alive connection
+                    raise NotConnected
                 self.h11_state.receive_data(data)
             else:
                 break

tests/dispatch/test_connection_pools.py

@@ -131,3 +131,21 @@ async def test_premature_response_close(server):
         await response.close()
         assert len(http.active_connections) == 0
         assert len(http.keepalive_connections) == 0
+
+
+@pytest.mark.asyncio
+async def test_keepalive_connection_closed_by_server_is_reestablished(server):
+    """
+    Upon keep-alive connection closed by remote a new connection should be reestablished.
+    """
+    async with httpx.ConnectionPool() as http:
+        response = await http.request("GET", "http://127.0.0.1:8000/")
+        await response.read()
+
+        await server.shutdown()  # shutdown the server to close the keep-alive connection
+        await server.startup()
+
+        response = await http.request("GET", "http://127.0.0.1:8000/")
+        await response.read()
+        assert len(http.active_connections) == 0
+        assert len(http.keepalive_connections) == 1

tests/test_multipart.py

@@ -10,11 +10,11 @@
     CertTypes,
     Client,
     Dispatcher,
-    multipart,
     Request,
     Response,
     TimeoutTypes,
     VerifyTypes,
+    multipart,
 )