Merge pull request #58 from joechild-pace/lazy-init

Add "lazy" connection option

.pre-commit-config.yaml

@@ -7,11 +7,13 @@ repos:
     -   id: check-merge-conflict
     -   id: fix-encoding-pragma
     -   id: flake8
--   repo: https://github.com/mattbennett/mirrors-isort.git
-    rev: master
+-   repo: https://github.com/PyCQA/isort
+    rev: 4.3.21
     hooks:
     - id: isort
 -   repo: https://github.com/ambv/black
     rev: 22.10.0
     hooks:
     - id: black
+      # TODO remove this when black is updated
+      additional_dependencies: [ 'click==8.0.4' ]

nameko_grpc/client.py

@@ -127,12 +127,16 @@ def __init__(
         compression_algorithm="none",
         compression_level="high",
         ssl=False,
+        lazy_startup=False,
     ):
         self.target = target
         self.stub = stub
         self.compression_algorithm = compression_algorithm
         self.compression_level = compression_level  # NOTE not used
         self.ssl = SslConfig(ssl)
+        self.lazy_startup = lazy_startup
+        self._channel_creation_lock = threading.Lock()
+        self._channel = None
 
     def spawn_thread(self, target, args=(), kwargs=None, name=None):
         raise NotImplementedError
@@ -144,11 +148,26 @@ def default_compression(self):
         return "identity"
 
     def start(self):
-        self.channel = ClientChannel(self.target, self.ssl, self.spawn_thread)
-        self.channel.start()
+        if not self.lazy_startup:
+            self._start_channel()
+
+    def _start_channel(self):
+        with self._channel_creation_lock:
+            if self._channel is None:
+                channel = ClientChannel(self.target, self.ssl, self.spawn_thread)
+                channel.start()
+                self._channel = channel
 
     def stop(self):
-        self.channel.stop()
+        if self._channel is not None:
+            self._channel.stop()
+            self._channel = None
+
+    @property
+    def channel(self):
+        if self._channel is None:
+            self._start_channel()
+        return self._channel
 
     def timeout(self, send_stream, response_stream, deadline):
         start = time.time()

test/conftest.py

@@ -352,18 +352,21 @@ def make(
         proto_name=None,
         compression_algorithm="none",
         compression_level="high",
+        lazy_startup=False,
+        service_url="//localhost:{}".format(grpc_port),
     ):
         if proto_name is None:
             proto_name = service_name
 
         stubs = load_stubs(proto_name)
         stub_cls = getattr(stubs, "{}Stub".format(service_name))
         client = Client(
-            "//localhost:{}".format(grpc_port),
+            service_url,
             stub_cls,
             compression_algorithm,
             compression_level,
             ssl_options,
+            lazy_startup=lazy_startup,
         )
         clients.append(client)
         return client.start()

test/test_basic.py

@@ -109,3 +109,30 @@ def generate_requests():
             ("A", 1),
             ("B", 2),
         ]
+
+
+class TestLazy:
+    def test_lazy_client(self, start_nameko_client, server, protobufs):
+        client = start_nameko_client("example", lazy_startup=True)
+        response = client.unary_unary(protobufs.ExampleRequest(value="A"))
+        assert response.message == "A"
+
+    # Note lack of server fixture
+    def test_lazy_client_does_not_connect_on_start(
+        self, start_nameko_client, protobufs, start_grpc_server
+    ):
+        client = start_nameko_client("example", lazy_startup=True)
+
+        with pytest.raises(ConnectionRefusedError):
+            client.unary_unary(protobufs.ExampleRequest(value="A"))
+
+        start_grpc_server("example")
+
+        # After starting the server, should now work
+        response = client.unary_unary(protobufs.ExampleRequest(value="A"))
+        assert response.message == "A"
+
+    # Note lack of server fixture
+    def test_nonlazy_client_connects_on_start(self, start_nameko_client, protobufs):
+        with pytest.raises(ConnectionRefusedError):
+            start_nameko_client("example", lazy_startup=False)