allow setting config from individual env variables

docs/sanic/config.md

@@ -29,6 +29,14 @@ In general the convention is to only have UPPERCASE configuration parameters. Th
 
 There are several ways how to load configuration.
 
+### From environment variables.
+
+Any variables defined with the `SANIC_` prefix will be applied to the sanic config. For example, setting `SANIC_REQUEST_TIMEOUT` will be loaded by the application automatically. You can pass the `load_vars` boolean to the Sanic constructor to override that:
+
+```python
+app = Sanic(load_vars=False)
+```
+
 ### From an Object
 
 If there are a lot of configuration values and they have sensible defaults it might be helpful to put them into a module:

sanic/app.py

@@ -25,7 +25,8 @@ from sanic.websocket import WebSocketProtocol, ConnectionClosed
 
 class Sanic:
 
-    def __init__(self, name=None, router=None, error_handler=None):
+    def __init__(self, name=None, router=None, error_handler=None,
+                 load_env=True):
         # Only set up a default log handler if the
         # end-user application didn't set anything up.
         if not logging.root.handlers and log.level == logging.NOTSET:
@@ -44,7 +45,7 @@ class Sanic:
         self.name = name
         self.router = router or Router()
         self.error_handler = error_handler or ErrorHandler()
-        self.config = Config()
+        self.config = Config(load_env=load_env)
         self.request_middleware = deque()
         self.response_middleware = deque()
         self.blueprints = {}

sanic/config.py

@@ -1,9 +1,10 @@
 import os
 import types
 
+SANIC_PREFIX = 'SANIC_'
 
 class Config(dict):
-    def __init__(self, defaults=None):
+    def __init__(self, defaults=None, load_env=True):
         super().__init__(defaults or {})
         self.LOGO = """
                  ▄▄▄▄▄
@@ -29,6 +30,9 @@ class Config(dict):
         self.REQUEST_MAX_SIZE = 100000000  # 100 megababies
         self.REQUEST_TIMEOUT = 60  # 60 seconds
 
+        if load_env:
+            self.load_environment_vars()
+
     def __getattr__(self, attr):
         try:
             return self[attr]
@@ -90,3 +94,13 @@ class Config(dict):
         for key in dir(obj):
             if key.isupper():
                 self[key] = getattr(obj, key)
+
+    def load_environment_vars(self):
+        for k, v in os.environ.items():
+            """
+            Looks for any SANIC_ prefixed environment variables and applies
+            them to the configuration if present.
+            """
+            if k.startswith(SANIC_PREFIX):
+                _, config_key = k.split(SANIC_PREFIX, 1)
+                self[config_key] = v

tests/test_config.py

@@ -16,6 +16,17 @@ def test_load_from_object():
     assert app.config.CONFIG_VALUE == 'should be used'
     assert 'not_for_config' not in app.config
 
+def test_auto_load_env():
+    environ["SANIC_TEST_ANSWER"] = "42"
+    app = Sanic()
+    assert app.config.TEST_ANSWER == "42"
+    del environ["SANIC_TEST_ANSWER"]
+
+def test_auto_load_env():
+    environ["SANIC_TEST_ANSWER"] = "42"
+    app = Sanic(load_env=False)
+    assert getattr(app.config, 'TEST_ANSWER', None) == None
+    del environ["SANIC_TEST_ANSWER"]
 
 def test_load_from_file():
     app = Sanic('test_load_from_file')