Rename Snippet client v2's startup sequence steps (#806)

Rename the startup sequence steps (hopefully) for the better.

2 files changed, 92 insertions, 135 deletions

diff --git a/mobly/snippet/client_base.py b/mobly/snippet/client_base.py
index 8fdd6c9..31e99dc 100644
--- a/mobly/snippet/client_base.py
+++ b/mobly/snippet/client_base.py
@@ -38,13 +38,11 @@ The JSON RPC protocol expected by this module is:
               or returned void.>,
     'callback': <Required. String that represents a callback ID used to
                 identify events associated with a particular CallbackHandler
-                object, `null` if this is not a async RPC.>,
+                object, `null` if this is not an asynchronous RPC.>,
   }
 """
 
 import abc
-import contextlib
-import enum
 import json
 import threading
 import time
@@ -59,14 +57,6 @@ _MAX_RPC_RESP_LOGGING_LENGTH = 1024
 RPC_RESPONSE_REQUIRED_FIELDS = ('id', 'error', 'result', 'callback')
 
 
-class StartServerStages(enum.Enum):
-  """The stages for the starting server process."""
-  BEFORE_STARTING_SERVER = 1
-  DO_START_SERVER = 2
-  BUILD_CONNECTION = 3
-  AFTER_STARTING_SERVER = 4
-
-
 class ClientBase(abc.ABC):
   """Base class for JSON RPC clients that connect to snippet servers.
 
@@ -107,14 +97,13 @@ class ClientBase(abc.ABC):
   def __del__(self):
     self.close_connection()
 
-  def start_server(self):
-    """Starts the server on the remote device and connects to it.
+  def initialize(self):
+    """Initializes the snippet client to interact with the remote device.
 
-    This process contains four stages:
-      - before_starting_server: prepares for starting the server.
-      - do_start_server: starts the server on the remote device.
-      - build_connection: builds a connection with the server.
-      - after_starting_server: does the things after the server is available.
+    This function contains following stages:
+      1. preparing to start the snippet server.
+      2. starting the snippet server on the remote device.
+      3. making a connection to the snippet server.
 
     After this, the self.host_port and self.device_port attributes must be
     set.
@@ -127,55 +116,42 @@ class ClientBase(abc.ABC):
       errors.ServerStartError: when failed to start the snippet server.
     """
 
-    @contextlib.contextmanager
-    def _execute_one_stage(stage):
-      """Context manager for executing one stage.
-
-      Args:
-        stage: StartServerStages, the stage which is running under this
-          context manager.
-
-      Yields:
-        None.
-      """
-      self.log.debug('[START_SERVER] Running the stage %s.', stage.name)
-      yield
-      self.log.debug('[START_SERVER] Finished the stage %s.', stage.name)
-
-    self.log.debug('Starting the server.')
+    self.log.debug('Initializing the snippet package %s.', self.package)
     start_time = time.perf_counter()
 
-    with _execute_one_stage(StartServerStages.BEFORE_STARTING_SERVER):
-      self.before_starting_server()
+    self.log.debug('Preparing to start the snippet server of %s.', self.package)
+    self.before_starting_server()
 
     try:
-      with _execute_one_stage(StartServerStages.DO_START_SERVER):
-        self.do_start_server()
-
-      with _execute_one_stage(StartServerStages.BUILD_CONNECTION):
-        self._build_connection()
+      self.log.debug('Starting the snippet server of %s.', self.package)
+      self.start_server()
 
-      with _execute_one_stage(StartServerStages.AFTER_STARTING_SERVER):
-        self.after_starting_server()
+      self.log.debug('Making a connection to the snippet server of %s.',
+                     self.package)
+      self._make_connection()
 
     except Exception:
-      self.log.error('[START SERVER] Error occurs when starting the server.')
+      self.log.error(
+          'Error occurred trying to start and connect to the snippet server '
+          'of %s.', self.package)
       try:
         self.stop_server()
       except Exception:  # pylint: disable=broad-except
         # Only prints this exception and re-raises the original exception
-        self.log.exception('[START_SERVER] Failed to stop server because of '
-                           'new exception.')
+        self.log.exception(
+            'Failed to stop the snippet server of %s after failure to start '
+            'and connect.', self.package)
 
       raise
 
-    self.log.debug('Snippet %s started after %.1fs on host port %d.',
-                   self.package,
-                   time.perf_counter() - start_time, self.host_port)
+    self.log.debug(
+        'Snippet package %s initialized after %.1fs on host port %d.',
+        self.package,
+        time.perf_counter() - start_time, self.host_port)
 
   @abc.abstractmethod
   def before_starting_server(self):
-    """Prepares for starting the server.
+    """Performs the preparation steps before starting the remote server.
 
     For example, subclass can check or modify the device settings at this
     stage.
@@ -186,45 +162,43 @@ class ClientBase(abc.ABC):
     """
 
   @abc.abstractmethod
-  def do_start_server(self):
+  def start_server(self):
     """Starts the server on the remote device.
 
     The client has completed the preparations, so the client calls this
     function to start the server.
     """
 
-  def _build_connection(self):
-    """Proxy function of build_connection.
+  def _make_connection(self):
+    """Proxy function of make_connection.
 
-    This function resets the RPC id counter before calling `build_connection`.
+    This function resets the RPC id counter before calling `make_connection`.
     """
     self._counter = self._id_counter()
-    self.build_connection()
+    self.make_connection()
 
   @abc.abstractmethod
-  def build_connection(self):
-    """Builds a connection with the server on the remote device.
+  def make_connection(self):
+    """Makes a connection to the snippet server on the remote device.
 
-    The command to start the server has been already sent before calling this
-    function. So the client builds a connection to it and sends a handshake
-    to ensure the server is available for upcoming RPCs.
+    This function makes a connection to the server and sends a handshake
+    request to ensure the server is available for upcoming RPCs.
+
+    There are two types of connections used by snippet clients:
+    * The client makes a new connection each time it needs to send an RPC.
+    * The client makes a connection in this stage and uses it for all the RPCs.
+      In this case, the client should implement `close_connection` to close
+      the connection.
 
     This function uses self.host_port for communicating with the server. If
     self.host_port is 0 or None, this function finds an available host port to
-    build connection and set self.host_port to the found port.
+    make the connection and set self.host_port to the found port.
 
     Raises:
       errors.ProtocolError: something went wrong when exchanging data with the
         server.
     """
 
-  @abc.abstractmethod
-  def after_starting_server(self):
-    """Does the things after the server is available.
-
-    For example, subclass can get device information from the server.
-    """
-
   def __getattr__(self, name):
     """Wrapper for python magic to turn method calls into RPCs."""
 
@@ -273,11 +247,11 @@ class ClientBase(abc.ABC):
 
     Raises:
       errors.ServerRestoreConnectionError: when failed to restore the connection
-        with the snippet server.
+        to the snippet server.
     """
 
   def _rpc(self, rpc_func_name, *args, **kwargs):
-    """Sends a RPC to the server.
+    """Sends an RPC to the server.
 
     Args:
       rpc_func_name: str, the name of the snippet function to execute on the
@@ -325,7 +299,7 @@ class ClientBase(abc.ABC):
     """Checks whether the server is still running.
 
     If the server is not running, it throws an error. As this function is called
-    each time the client tries to send a RPC, this should be a quick check
+    each time the client tries to send an RPC, this should be a quick check
     without affecting performance. Otherwise it is fine to not check anything.
 
     Raises:
diff --git a/tests/mobly/snippet/client_base_test.py b/tests/mobly/snippet/client_base_test.py
index 4da74d6..3eb6521 100755
--- a/tests/mobly/snippet/client_base_test.py
+++ b/tests/mobly/snippet/client_base_test.py
@@ -26,7 +26,7 @@ from mobly.snippet import errors
 def _generate_fix_length_rpc_response(
     response_length,
     template='{"id": 0, "result": "%s", "error": null, "callback": null}'):
-  """Generates a RPC response string with specified length.
+  """Generates an RPC response string with specified length.
 
   This function generates a random string and formats the template with the
   generated random string to get the response string. This function formats
@@ -66,13 +66,10 @@ class FakeClient(client_base.ClientBase):
   def before_starting_server(self):
     pass
 
-  def do_start_server(self):
+  def start_server(self):
     pass
 
-  def build_connection(self):
-    pass
-
-  def after_starting_server(self):
+  def make_connection(self):
     pass
 
   def restore_server_connection(self, port=None):
@@ -103,70 +100,56 @@ class ClientBaseTest(unittest.TestCase):
     self.client.host_port = 12345
 
   @mock.patch.object(FakeClient, 'before_starting_server')
-  @mock.patch.object(FakeClient, 'do_start_server')
-  @mock.patch.object(FakeClient, '_build_connection')
-  @mock.patch.object(FakeClient, 'after_starting_server')
-  def test_start_server_stage_order(self, mock_after_func, mock_build_conn_func,
-                                    mock_do_start_func, mock_before_func):
-    """Test that starting server runs its stages in expected order."""
+  @mock.patch.object(FakeClient, 'start_server')
+  @mock.patch.object(FakeClient, '_make_connection')
+  def test_init_server_stage_order(self, mock_make_conn_func, mock_start_func,
+                                   mock_before_func):
+    """Test that initialization runs its stages in expected order."""
     order_manager = mock.Mock()
     order_manager.attach_mock(mock_before_func, 'mock_before_func')
-    order_manager.attach_mock(mock_do_start_func, 'mock_do_start_func')
-    order_manager.attach_mock(mock_build_conn_func, 'mock_build_conn_func')
-    order_manager.attach_mock(mock_after_func, 'mock_after_func')
+    order_manager.attach_mock(mock_start_func, 'mock_start_func')
+    order_manager.attach_mock(mock_make_conn_func, 'mock_make_conn_func')
 
-    self.client.start_server()
+    self.client.initialize()
 
     expected_call_order = [
         mock.call.mock_before_func(),
-        mock.call.mock_do_start_func(),
-        mock.call.mock_build_conn_func(),
-        mock.call.mock_after_func(),
+        mock.call.mock_start_func(),
+        mock.call.mock_make_conn_func(),
     ]
     self.assertListEqual(order_manager.mock_calls, expected_call_order)
 
   @mock.patch.object(FakeClient, 'stop_server')
   @mock.patch.object(FakeClient, 'before_starting_server')
-  def test_start_server_before_starting_server_fail(self, mock_before_func,
-                                                    mock_stop_server):
-    """Test starting server's stage before_starting_server fails."""
+  def test_init_server_before_starting_server_fail(self, mock_before_func,
+                                                   mock_stop_server):
+    """Test before_starting_server stage of initialization fails."""
     mock_before_func.side_effect = Exception('ha')
 
     with self.assertRaisesRegex(Exception, 'ha'):
-      self.client.start_server()
+      self.client.initialize()
     mock_stop_server.assert_not_called()
 
   @mock.patch.object(FakeClient, 'stop_server')
-  @mock.patch.object(FakeClient, 'do_start_server')
-  def test_start_server_do_start_server_fail(self, mock_do_start_func,
-                                             mock_stop_server):
-    """Test starting server's stage do_start_server fails."""
-    mock_do_start_func.side_effect = Exception('ha')
+  @mock.patch.object(FakeClient, 'start_server')
+  def test_init_server_start_server_fail(self, mock_start_func,
+                                         mock_stop_server):
+    """Test start_server stage of initialization fails."""
+    mock_start_func.side_effect = Exception('ha')
 
     with self.assertRaisesRegex(Exception, 'ha'):
-      self.client.start_server()
+      self.client.initialize()
     mock_stop_server.assert_called()
 
   @mock.patch.object(FakeClient, 'stop_server')
-  @mock.patch.object(FakeClient, '_build_connection')
-  def test_start_server_build_connection_fail(self, mock_build_conn_func,
-                                              mock_stop_server):
-    """Test starting server's stage _build_connection fails."""
-    mock_build_conn_func.side_effect = Exception('ha')
-
-    with self.assertRaisesRegex(Exception, 'ha'):
-      self.client.start_server()
-    mock_stop_server.assert_called()
-
-  @mock.patch.object(FakeClient, 'stop_server')
-  @mock.patch.object(FakeClient, 'after_starting_server')
-  def test_start_server_after_starting_server_fail(self, mock_after_func,
-                                                   mock_stop_server):
-    """Test starting server's stage after_starting_server fails."""
-    mock_after_func.side_effect = Exception('ha')
+  @mock.patch.object(FakeClient, '_make_connection')
+  def test_init_server_make_connection_fail(self, mock_make_conn_func,
+                                            mock_stop_server):
+    """Test _make_connection stage of initialization fails."""
+    mock_make_conn_func.side_effect = Exception('ha')
 
     with self.assertRaisesRegex(Exception, 'ha'):
-      self.client.start_server()
+      self.client.initialize()
     mock_stop_server.assert_called()
 
   @mock.patch.object(FakeClient, 'check_server_proc_running')
@@ -177,9 +160,9 @@ class ClientBaseTest(unittest.TestCase):
   def test_rpc_stage_dependencies(self, mock_handle_resp, mock_decode_resp_str,
                                   mock_send_request, mock_gen_request,
                                   mock_precheck):
-    """Test the internal dependencies when sending a RPC.
+    """Test the internal dependencies when sending an RPC.
 
-    When sending a RPC, it calls multiple functions in specific order, and
+    When sending an RPC, it calls multiple functions in specific order, and
     each function uses the output of the previously called function. This test
     case checks above dependencies.
 
@@ -191,7 +174,7 @@ class ClientBaseTest(unittest.TestCase):
       mock_gen_request: the mock function of FakeClient._gen_rpc_request.
       mock_precheck: the mock function of FakeClient.check_server_proc_running.
     """
-    self.client.start_server()
+    self.client.initialize()
 
     expected_response_str = ('{"id": 0, "result": 123, "error": null, '
                              '"callback": null}')
@@ -226,8 +209,8 @@ class ClientBaseTest(unittest.TestCase):
   def test_rpc_precheck_fail(self, mock_handle_resp, mock_decode_resp_str,
                              mock_send_request, mock_gen_request,
                              mock_precheck):
-    """Test when RPC precheck fails it will skip sending RPC."""
-    self.client.start_server()
+    """Test when RPC precheck fails it will skip sending the RPC."""
+    self.client.initialize()
     mock_precheck.side_effect = Exception('server_died')
 
     with self.assertRaisesRegex(Exception, 'server_died'):
@@ -239,7 +222,7 @@ class ClientBaseTest(unittest.TestCase):
     mock_decode_resp_str.assert_not_called()
 
   def test_gen_request(self):
-    """Test generating a RPC request.
+    """Test generating an RPC request.
 
     Test that _gen_rpc_request returns a string represents a JSON dict
     with all required fields.
@@ -270,7 +253,7 @@ class ClientBaseTest(unittest.TestCase):
       self.client._decode_response_string_and_validate_format(0, None)
 
   def test_rpc_response_missing_fields(self):
-    """Test parsing a RPC response that misses some required fields."""
+    """Test parsing an RPC response that misses some required fields."""
     mock_resp_without_id = '{"result": 123, "error": null, "callback": null}'
     with self.assertRaisesRegex(
         errors.ProtocolError,
@@ -300,7 +283,7 @@ class ClientBaseTest(unittest.TestCase):
           10, mock_resp_without_callback)
 
   def test_rpc_response_error(self):
-    """Test parsing a RPC response with a non-empty error field."""
+    """Test parsing an RPC response with a non-empty error field."""
     mock_resp_with_error = {
         'id': 10,
         'result': 123,
@@ -343,7 +326,7 @@ class ClientBaseTest(unittest.TestCase):
       mock_handle_callback.assert_not_called()
 
   def test_rpc_response_id_mismatch(self):
-    """Test parsing a RPC response with wrong id."""
+    """Test parsing an RPC response with a wrong id."""
     right_id = 5
     wrong_id = 20
     resp = f'{{"id": {right_id}, "result": 1, "error": null, "callback": null}}'
@@ -358,7 +341,7 @@ class ClientBaseTest(unittest.TestCase):
     mock_log = mock.Mock()
     self.client.log = mock_log
     self.client.set_snippet_client_verbose_logging(True)
-    self.client.start_server()
+    self.client.initialize()
 
     resp = _generate_fix_length_rpc_response(
         client_base._MAX_RPC_RESP_LOGGING_LENGTH * 2)
@@ -372,7 +355,7 @@ class ClientBaseTest(unittest.TestCase):
     mock_log = mock.Mock()
     self.client.log = mock_log
     self.client.set_snippet_client_verbose_logging(False)
-    self.client.start_server()
+    self.client.initialize()
 
     resp = _generate_fix_length_rpc_response(
         int(client_base._MAX_RPC_RESP_LOGGING_LENGTH // 2))
@@ -386,7 +369,7 @@ class ClientBaseTest(unittest.TestCase):
     mock_log = mock.Mock()
     self.client.log = mock_log
     self.client.set_snippet_client_verbose_logging(False)
-    self.client.start_server()
+    self.client.initialize()
 
     resp = _generate_fix_length_rpc_response(
         client_base._MAX_RPC_RESP_LOGGING_LENGTH)
@@ -400,7 +383,7 @@ class ClientBaseTest(unittest.TestCase):
     mock_log = mock.Mock()
     self.client.log = mock_log
     self.client.set_snippet_client_verbose_logging(False)
-    self.client.start_server()
+    self.client.initialize()
 
     max_len = client_base._MAX_RPC_RESP_LOGGING_LENGTH
     resp = _generate_fix_length_rpc_response(max_len * 40)
@@ -414,7 +397,7 @@ class ClientBaseTest(unittest.TestCase):
   @mock.patch.object(FakeClient, 'send_rpc_request')
   def test_rpc_call_increment_counter(self, mock_send_request):
     """Test that with each RPC call the counter is incremented by 1."""
-    self.client.start_server()
+    self.client.initialize()
     resp = '{"id": %d, "result": 123, "error": null, "callback": null}'
     mock_send_request.side_effect = (resp % (i,) for i in range(10))
 
@@ -424,9 +407,9 @@ class ClientBaseTest(unittest.TestCase):
     self.assertEqual(next(self.client._counter), 10)
 
   @mock.patch.object(FakeClient, 'send_rpc_request')
-  def test_build_connection_reset_counter(self, mock_send_request):
-    """Test that _build_connection resets the counter to zero."""
-    self.client.start_server()
+  def test_init_connection_reset_counter(self, mock_send_request):
+    """Test that _make_connection resets the counter to zero."""
+    self.client.initialize()
     resp = '{"id": %d, "result": 123, "error": null, "callback": null}'
     mock_send_request.side_effect = (resp % (i,) for i in range(10))
 
@@ -434,7 +417,7 @@ class ClientBaseTest(unittest.TestCase):
       self.client.some_rpc()
 
     self.assertEqual(next(self.client._counter), 10)
-    self.client._build_connection()
+    self.client._make_connection()
     self.assertEqual(next(self.client._counter), 0)