Get default config values from environment

server/config.py

@@ -156,14 +156,22 @@ def __init__(self):
         self.QUEUE_POP_TIME_MOVING_AVG_SIZE = 5
 
         self._defaults = {
-            key: value for key, value in vars(self).items() if key.isupper()
+            key: value
+            for key, value in vars(self).items()
+            if key.isupper()
         }
 
         self._callbacks: dict[str, Callable] = {}
         self.refresh()
 
     def refresh(self) -> None:
         new_values = self._defaults.copy()
+        # Add fallback values from environment.
+        # NOTE: Only works for string values!
+        for key in new_values:
+            value = os.getenv(key)
+            if value is not None:
+                new_values[key] = value
 
         config_file = os.getenv("CONFIGURATION_FILE")
         if config_file is not None:

tests/unit_tests/test_configuration_refresh.py

@@ -22,12 +22,27 @@ async def config_service(monkeypatch):
 async def test_configuration_refresh(monkeypatch):
     config.refresh()
     assert config.DB_PASSWORD == "banana"
+    assert config.DB_LOGIN == "root"
+
     monkeypatch.setenv("CONFIGURATION_FILE", "tests/data/refresh_conf.yaml")
     assert config.DB_PASSWORD == "banana"
 
+    # Values in config file will override defaults
+    config.refresh()
+    assert config.DB_PASSWORD == "apple"
+    assert config.DB_LOGIN == "root"
+
+    # Values in config file will override environment
+    monkeypatch.setenv("DB_PASSWORD", "plantain")
     config.refresh()
+    assert config.DB_PASSWORD == "apple"
+    assert config.DB_LOGIN == "root"
 
+    # Values in environment will override defaults
+    monkeypatch.setenv("DB_LOGIN", "beet")
+    config.refresh()
     assert config.DB_PASSWORD == "apple"
+    assert config.DB_LOGIN == "beet"
 
 
 async def test_config_refresh_file_not_found(monkeypatch):
@@ -80,7 +95,7 @@ async def test_config_callback_on_change(config_service, monkeypatch):
 
 
 @fast_forward(20)
-async def test_config_no_callback_without_change(config_service, monkeypatch):
+async def test_config_no_callback_without_change(config_service):
     callback = mock.Mock()
     config.register_callback("DB_PASSWORD", callback)
     assert config.DB_PASSWORD == "banana"