config: Implement singleton pattern

Signed-off-by: Phoevos Kalemkeris <[email protected]>

Author: phoevos

cogstack_model_gateway/common/config.py

@@ -69,30 +69,35 @@ def to_dict(self):
         }
 
 
-def load_config() -> Config:
-    """Load configuration from the provided JSON file and environment variables."""
-    try:
-        with open(CONFIG_FILE) as f:
-            config = json.load(f)
-    except FileNotFoundError:
-        print(f"Config file {CONFIG_FILE} not found.")
-        raise
-    except json.JSONDecodeError:
-        print(f"Config file {CONFIG_FILE} is not a valid JSON file.")
-        raise
-
-    load_dotenv()
-    config["env"] = {
-        var.replace(ACCEPTED_ENVIRONMENT_VARIABLE_PREFIX, "", 1).lower(): value
-        for var in ACCEPTED_ENVIRONMENT_VARIABLES
-        if (value := os.getenv(var))
-    }
-    log.info(f"Loaded config: {config}")
-    return Config(config)
+_config_instance: Config = None
 
 
-config = load_config()
+def load_config() -> Config:
+    """Load configuration from the provided JSON file and environment variables."""
+    global _config_instance
+    if _config_instance is None:
+        try:
+            with open(CONFIG_FILE) as f:
+                config = json.load(f)
+        except FileNotFoundError:
+            log.error(f"Config file {CONFIG_FILE} not found.")
+            raise
+        except json.JSONDecodeError:
+            log.error(f"Config file {CONFIG_FILE} is not a valid JSON file.")
+            raise
+
+        load_dotenv()
+        config["env"] = {
+            var.replace(ACCEPTED_ENVIRONMENT_VARIABLE_PREFIX, "", 1).lower(): value
+            for var in ACCEPTED_ENVIRONMENT_VARIABLES
+            if (value := os.getenv(var))
+        }
+        log.info(f"Loaded config: {config}")
+        _config_instance = Config(config)
+    return _config_instance
 
 
 def get_config() -> Config:
-    return config
+    if _config_instance is None:
+        raise RuntimeError("Config not initialized. Call load_config() first.")
+    return _config_instance

cogstack_model_gateway/gateway/main.py

@@ -3,7 +3,7 @@
 
 from fastapi import FastAPI
 
-from cogstack_model_gateway.common.config import config
+from cogstack_model_gateway.common.config import load_config
 from cogstack_model_gateway.common.db import DatabaseManager
 from cogstack_model_gateway.common.object_store import ObjectStoreManager
 from cogstack_model_gateway.common.queue import QueueManager
@@ -18,7 +18,7 @@
 async def lifespan(app: FastAPI):
     log.info("Initializing database and queue connections")
 
-    global config
+    config = load_config()
     dbm = DatabaseManager(
         user=config.env.db_user,
         password=config.env.db_password,

tests/unit/common/test_config.py

@@ -63,7 +63,7 @@ def test_config_set():
     assert config.nested.inner_key == "inner_value"
 
 
-@patch("cogstack_model_gateway.common.config.config", new=Config({"key": "value"}))
+@patch("cogstack_model_gateway.common.config._config_instance", new=Config({"key": "value"}))
 def test_get_config():
     config = get_config()
     assert isinstance(config, Config)
@@ -73,6 +73,7 @@ def test_get_config():
 @patch("builtins.open", new_callable=mock_open, read_data='{"key": "value"}')
 @patch("os.getenv", side_effect=lambda k, d=None: TEST_ENV_VARS.get(k, d))
 @patch("cogstack_model_gateway.common.config.load_dotenv")
+@patch("cogstack_model_gateway.common.config._config_instance", new=None)
 def test_load_config(mock_load_dotenv, mock_getenv, mock_open):
     config = load_config()
     assert isinstance(config, Config)
@@ -87,6 +88,7 @@ def test_load_config(mock_load_dotenv, mock_getenv, mock_open):
 @patch("builtins.open", new_callable=mock_open, read_data='{"key": "value"}')
 @patch("os.getenv", side_effect=lambda k, d=None: None)
 @patch("cogstack_model_gateway.common.config.load_dotenv")
+@patch("cogstack_model_gateway.common.config._config_instance", new=None)
 def test_load_config_no_env_vars(mock_load_dotenv, mock_getenv, mock_open):
     config = load_config()
     assert isinstance(config, Config)