RWS: Refactor loading of configuration

Simplify it and bring it closer to how CMS itself loads its
configuration.

Author: gollux

cmsranking/Config.py

@@ -68,30 +68,27 @@ def __init__(self):
             sys.exit(1)
         self.log_dir = os.path.join(self.base_dir, 'log/ranking')
         self.lib_dir = os.path.join(self.base_dir, 'lib/ranking')
-        self.conf_paths = [os.path.join(self.base_dir, 'etc/cms_ranking.toml')]
 
-        # Allow users to override config file path using environment
+        # Default config file path can be overridden using environment
         # variable 'CMS_RANKING_CONFIG'.
-        if CMS_RANKING_CONFIG_ENV_VAR in os.environ:
-            self.conf_paths = [os.environ[CMS_RANKING_CONFIG_ENV_VAR]]
+        default_config_file = os.path.join(self.base_dir, 'etc/cms_ranking.toml')
+        self.config_file = os.environ.get('CMS_RANKING_CONFIG', default_config_file)
 
     def get(self, key):
         """Get the config value for the given key.
 
         """
         return getattr(self, key)
 
-    def load(self, config_override_fobj=None):
-        """Look for config files on disk and load them.
+    def load(self, config_override: str | None = None):
+        """Load the configuration file.
 
         """
-        # If a command-line override is given it is used exclusively.
-        if config_override_fobj is not None:
-            if not self._load_one(config_override_fobj):
-                sys.exit(1)
-        else:
-            if not self._load_many(self.conf_paths):
-                sys.exit(1)
+
+        config_file = config_override if config_override is not None else self.config_file
+        if not self._load_config(config_file):
+            logging.critical(f'Cannot load configuration file {config_file}')
+            sys.exit(1)
 
         try:
             os.makedirs(self.lib_dir)
@@ -110,58 +107,39 @@ def load(self, config_override_fobj=None):
 
         add_file_handler(self.log_dir)
 
-    def _load_many(self, conf_paths: list[str]) -> bool:
-        """Load the first existing config file among the given ones.
-
-        Take a list of paths where config files may reside and attempt
-        to load the first one that exists.
-
-        conf_paths: paths of config file candidates, from most
-            to least prioritary.
-        returns: whether loading was successful.
-
-        """
-        for conf_path in conf_paths:
-            try:
-                with open(conf_path, "rb") as conf_fobj:
-                    logger.info("Using config file %s.", conf_path)
-                    return self._load_one(conf_fobj)
-            except FileNotFoundError:
-                # If it doesn't exist we just skip to the next one.
-                pass
-            except OSError as error:
-                logger.critical("Unable to access config file %s: [%s] %s.",
-                                conf_path, errno.errorcode[error.errno],
-                                os.strerror(error.errno))
-                return False
-        tried = " ".join(conf_paths)
-        logging.warning(f"No configuration file found, tried: {tried}. "
-                        "Falling back to default values.")
-        return True
-
-    def _load_one(self, conf_fobj: typing.BinaryIO) -> bool:
+    def _load_config(self, path: str) -> bool:
         """Populate config parameters from the given file.
 
         Parse it as TOML and store in self all configuration properties
         it defines. Log critical message and return False if anything
         goes wrong or seems odd.
 
-        conf_fobj: the config file.
+        path: the path of the TOML config file.
         returns: whether parsing was successful.
 
         """
-        # Parse config file.
+        # Load config file.
         try:
-            data = tomllib.load(conf_fobj)
-        except ValueError:
-            logger.critical("Config file is invalid TOML.")
+            with open(path, 'rb') as f:
+                data = tomllib.load(f)
+        except FileNotFoundError:
+            logger.debug("Couldn't find config file %s (maybe you need to "
+                         "convert it from cms_ranking.conf to cms_ranking.toml?).", path)
+            return False
+        except OSError as error:
+            logger.warning("I/O error while opening file %s: [%s] %s",
+                           path, errno.errorcode[error.errno],
+                           os.strerror(error.errno))
+            return False
+        except ValueError as error:
+            logger.warning("Invalid syntax in file %s: %s", path, error)
             return False
 
         # Store every config property.
         for key, value in data.items():
-            if not hasattr(self, key):
-                logger.critical("Invalid field %s in config file, maybe a "
-                                "typo?", key)
-                return False
-            setattr(self, key, value)
+            if hasattr(self, key):
+                setattr(self, key, value)
+            else:
+                logger.warning("Unrecognized key %s in config!", key)
+
         return True

cmsranking/RankingWebServer.py

@@ -526,7 +526,7 @@ def main() -> int:
     """
     parser = argparse.ArgumentParser(
         description="Ranking for CMS.")
-    parser.add_argument("--config", type=argparse.FileType("rb"),
+    parser.add_argument("--config", type=str,
                         help="override config file")
     parser.add_argument("-d", "--drop", action="store_true",
                         help="drop the data already stored")