Added config dependency provider

docs/built_in_dependencies.rst

@@ -0,0 +1,15 @@
+.. _built_in_dependencies:
+
+Built-in Dependencies
+=====================
+
+Nameko includes some commonly used :ref:`dependency_injection`. This section introduces them and gives brief examples of their usage.
+
+.. _config_dependency:
+
+Config
+------
+
+Config is a simple dependency provider for accessing configuration values runtime, see :ref:`running_a_service`.
+
+.. literalinclude:: examples/config_dependency.py

docs/cli.rst

@@ -3,6 +3,8 @@ Command Line Interface
 
 Nameko ships with a command line interface to make hosting and interacting with services as easy as possible.
 
+.. _running_a_service:
+
 Running a Service
 -----------------
 
@@ -43,6 +45,8 @@ and providing a simple YAML configuration file:
 
 The ``LOGGING`` entry is passed to :func:`logging.config.dictConfig` and should conform to the schema for that call.
 
+Config values can be accessed via the built-in :ref:`config_dependency` dependency provider.
+
 
 Environment variable substitution
 ---------------------------------

docs/examples/config_dependency.py

@@ -0,0 +1,13 @@
+from nameko.dependencies import Config
+from nameko.rpc import rpc
+
+
+class Service:
+
+    name = "test_config"
+
+    config = Config()
+
+    @rpc
+    def get_max_workers(self):
+        return self.config.get("max_workers")

docs/examples/test/test_examples.py

@@ -7,7 +7,7 @@
 
 from nameko.standalone.events import event_dispatcher
 from nameko.standalone.rpc import ClusterRpcProxy, ServiceRpcProxy
-from nameko.testing.services import entrypoint_waiter
+from nameko.testing.services import entrypoint_waiter, entrypoint_hook
 
 
 class TestHttp(object):
@@ -281,3 +281,18 @@ def test_websocket_rpc(self, container_factory, web_config, websocket):
 
         ws = websocket()
         assert ws.rpc('echo', value=u"hellø") == u'hellø'
+
+
+class TestConfig:
+
+    def test_can_get_config_value(self, container_factory, empty_config):
+        from examples.config_dependency import Service
+
+        config = empty_config.copy()
+        config["max_workers"] = 123
+
+        container = container_factory(Service, config)
+        container.start()
+
+        with entrypoint_hook(container, "get_max_workers") as get_max_workers:
+            assert 123 == get_max_workers()

docs/index.rst

@@ -56,6 +56,7 @@ This section covers most things you need to know to create and run your own Name
    installation
    cli
    built_in_extensions
+   built_in_dependencies
    community_extensions
    testing
    writing_extensions

nameko/dependencies.py

@@ -0,0 +1,12 @@
+""" Nameko built-in dependencies.
+"""
+
+from nameko.extensions import DependencyProvider
+
+
+class Config(DependencyProvider):
+    """ Dependency provider for accessing configuration values.
+    """
+
+    def get_dependency(self, worker_ctx):
+        return self.container.config.copy()

test/test_dependencies.py

@@ -0,0 +1,20 @@
+from mock import Mock, call, patch
+import pytest
+
+from nameko.dependencies import Config
+
+
+class TestConfig:
+
+    @pytest.yield_fixture(autouse=True)
+    def patch_container(self):
+        with patch.object(Config, 'container'):
+            yield
+
+    def test_get_dependency(self):
+        config = Config()
+
+        dependency = config.get_dependency(Mock(name='worker_ctx'))
+
+        assert config.container.config.copy.return_value == dependency
+        assert [call()] == config.container.config.copy.call_args_list