Add a method DockerService.Load to SystemService. (#198)

The method will load a tar image to docker engine (equivalent to the CLI docker load)

The API is needed for implementing gnoi.containerz.deploy, where we deploy a docker image to the network device.

host_modules/docker_service.py

@@ -251,3 +251,26 @@ def run(self, image, command, kwargs):
             return errno.ENOENT, "Image {} not found.".format(image)
         except Exception as e:
             return 1, "Failed to run image {}: {}".format(image, str(e))
+
+    @host_service.method(
+        host_service.bus_name(MOD_NAME), in_signature="s", out_signature="is"
+    )
+    def load(self, image):
+        """
+        Load a Docker image from a tar archive.
+
+        Args:
+            image (str): The path to the tar archive containing the Docker image.
+
+        Returns:
+            tuple: A tuple containing the exit code (int) and a message indicating the result of the operation.
+        """
+        try:
+            client = docker.from_env()
+            with open(image, 'rb') as image_tar:
+                client.images.load(image_tar)
+            return 0, "Image {} has been loaded.".format(image)
+        except FileNotFoundError:
+            return errno.ENOENT, "File {} not found.".format(image)
+        except Exception as e:
+            return 1, "Failed to load image {}: {}".format(image, str(e))

tests/host_modules/docker_service_test.py

@@ -287,3 +287,34 @@ def test_docker_run_fail_non_empty_command(
             docker_service = DockerService(MOD_NAME)
             rc, msg = docker_service.run("docker-syncd-brcm:latest", "rm -rf /", {})
         assert rc == errno.EPERM, "Return code is wrong"
+
+    @mock.patch("dbus.SystemBus")
+    @mock.patch("dbus.service.BusName")
+    @mock.patch("dbus.service.Object.__init__")
+    def test_docker_load_success(self, MockInit, MockBusName, MockSystemBus):
+        mock_docker_client = mock.Mock()
+        mock_docker_client.images.load.return_value = ["loaded_image"]
+
+        with mock.patch("builtins.open", mock.mock_open(read_data="data")) as MockOpen, \
+             mock.patch.object(docker, "from_env", return_value=mock_docker_client):
+            docker_service = DockerService(MOD_NAME)
+            rc, _ = docker_service.load("image.tar")
+
+        assert rc == 0, "Return code is wrong"
+        mock_docker_client.images.load.assert_called_once_with(MockOpen.return_value)
+        MockOpen.assert_called_once_with("image.tar", "rb")
+
+    @mock.patch("dbus.SystemBus")
+    @mock.patch("dbus.service.BusName")
+    @mock.patch("dbus.service.Object.__init__")
+    def test_docker_load_file_not_found(self, MockInit, MockBusName, MockSystemBus):
+        mock_docker_client = mock.Mock()
+
+        with mock.patch("builtins.open", mock.mock_open()) as MockOpen, \
+             mock.patch.object(docker, "from_env", return_value=mock_docker_client):
+            MockOpen.side_effect = FileNotFoundError
+            docker_service = DockerService(MOD_NAME)
+            rc, _ = docker_service.load("non_existent_image.tar")
+
+        assert rc == errno.ENOENT, "Return code is wrong"
+        MockOpen.assert_called_once_with("non_existent_image.tar", "rb")