Update app configuration

Why these changes are being introduced:

In most CLI and lambda apps we have used a Config class approach for app
configuration.  Additionally, there has been kind of a fuzzy line for the lambda
template specifically between "cold-start" (when Lambda function is initialized) and "hot" (when Lambda is fielding requests without fully shutting down) configurations.

How this addresses that need:
* Adds Config class
* Updates main lambda entrypoint file to have cold-start configurations (e.g.
logging and Sentry) and very little hot configuration
* Tests are updated to reflect new central Config class

Side effects of this change:
* None

Relevant ticket(s):
* None

Author: ghukill

lambdas/config.py

@@ -0,0 +1,106 @@
+import logging
+import os
+
+import sentry_sdk
+from sentry_sdk.integrations.aws_lambda import AwsLambdaIntegration
+
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.DEBUG)
+
+
+class Config:
+    REQUIRED_ENV_VARS = (
+        "WORKSPACE",
+        "SENTRY_DSN",
+    )
+    OPTIONAL_ENV_VARS = ("WARNING_ONLY_LOGGERS",)
+
+    def check_required_env_vars(self) -> None:
+        """Method to raise exception if required env vars not set."""
+        missing_vars = [var for var in self.REQUIRED_ENV_VARS if not os.getenv(var)]
+        if missing_vars:
+            message = f"Missing required environment variables: {', '.join(missing_vars)}"
+            raise OSError(message)
+
+    @property
+    def workspace(self) -> str | None:
+        return os.getenv("WORKSPACE")
+
+    @property
+    def sentry_dsn(self) -> str | None:
+        dsn = os.getenv("SENTRY_DSN")
+        if dsn and dsn.strip().lower() != "none":
+            return dsn
+        return None
+
+
+def configure_logger(
+    root_logger: logging.Logger,
+    *,
+    verbose: bool = False,
+    warning_only_loggers: str | None = None,
+) -> str:
+    """Configure application via passed application root logger.
+
+    If verbose=True, 3rd party libraries can be quite chatty.  For convenience, they can
+    be set to WARNING level by either passing a comma seperated list of logger names to
+    'warning_only_loggers' or by setting the env var WARNING_ONLY_LOGGERS.
+    """
+    if verbose:
+        root_logger.setLevel(logging.DEBUG)
+        logging_format = (
+            "%(asctime)s %(levelname)s %(name)s.%(funcName)s() "
+            "line %(lineno)d: %(message)s"
+        )
+    else:
+        root_logger.setLevel(logging.INFO)
+        logging_format = "%(asctime)s %(levelname)s %(name)s.%(funcName)s(): %(message)s"
+
+    warning_only_loggers = os.getenv("WARNING_ONLY_LOGGERS", warning_only_loggers)
+    if warning_only_loggers:
+        for name in warning_only_loggers.split(","):
+            logging.getLogger(name).setLevel(logging.WARNING)
+
+    # Clear any existing handlers to prevent duplication in AWS Lambda environment
+    # where container may be reused between invocations
+    for handler in root_logger.handlers[:]:
+        root_logger.removeHandler(handler)
+
+    handler = logging.StreamHandler()
+    handler.setFormatter(logging.Formatter(logging_format))
+    root_logger.addHandler(handler)
+
+    return (
+        f"Logger '{root_logger.name}' configured with level="
+        f"{logging.getLevelName(root_logger.getEffectiveLevel())}"
+    )
+
+
+def configure_dev_logger(
+    warning_only_loggers: str = ",".join(  # noqa: FLY002
+        ["asyncio", "botocore", "urllib3", "boto3", "smart_open"]
+    ),
+) -> None:
+    """Invoke to setup DEBUG level console logging for development work."""
+    os.environ["WARNING_ONLY_LOGGERS"] = warning_only_loggers
+    root_logger = logging.getLogger()
+    configure_logger(root_logger, verbose=True)
+
+
+def configure_sentry() -> None:
+    CONFIG = Config()  # noqa: N806
+    env = CONFIG.workspace
+    if CONFIG.sentry_dsn:
+        sentry_sdk.init(
+            dsn=CONFIG.sentry_dsn,
+            environment=env,
+            integrations=[
+                AwsLambdaIntegration(),
+            ],
+            traces_sample_rate=1.0,
+        )
+        logger.info(
+            "Sentry DSN found, exceptions will be sent to Sentry with env=%s", env
+        )
+    else:
+        logger.info("No Sentry DSN found, exceptions will not be sent to Sentry")

lambdas/my_function.py

@@ -1,33 +1,24 @@
 import json
 import logging
-import os
 
-import sentry_sdk
-from sentry_sdk.integrations.aws_lambda import AwsLambdaIntegration
+from lambdas.config import Config, configure_logger, configure_sentry
 
+# ---------------------------------------
+# One-time, Lambda cold start setup
+# ---------------------------------------
+CONFIG = Config()
+
+root_logger = logging.getLogger()
+log_config_message = configure_logger(root_logger)
 logger = logging.getLogger(__name__)
-logger.setLevel(logging.DEBUG)
+logger.info(log_config_message)
 
-env = os.getenv("WORKSPACE")
-if sentry_dsn := os.getenv("SENTRY_DSN"):
-    sentry = sentry_sdk.init(
-        dsn=sentry_dsn,
-        environment=env,
-        integrations=[
-            AwsLambdaIntegration(),
-        ],
-        traces_sample_rate=1.0,
-    )
-    logger.info("Sentry DSN found, exceptions will be sent to Sentry with env=%s", env)
-else:
-    logger.info("No Sentry DSN found, exceptions will not be sent to Sentry")
+configure_sentry()
 
 
+# ---------------------------------------
+# Lambda handler entrypoint
+# ---------------------------------------
 def lambda_handler(event: dict) -> str:
-    if not os.getenv("WORKSPACE"):
-        unset_workspace_error_message = "Required env variable WORKSPACE is not set"
-        raise RuntimeError(unset_workspace_error_message)
-
     logger.debug(json.dumps(event))
-
     return "You have successfully called this lambda!"

pyproject.toml

@@ -55,7 +55,6 @@ ignore = [
     "PLR0912",
     "PLR0913",
     "PLR0915",
-    "S320",
     "S321",
 ]
 

tests/test_config.py

@@ -0,0 +1,36 @@
+# ruff: noqa: N806
+from unittest.mock import patch
+
+import pytest
+
+from lambdas.config import Config, configure_sentry
+
+
+def test_config_configures_sentry_if_dsn_present(caplog, monkeypatch):
+    monkeypatch.setenv("SENTRY_DSN", "https://[email protected]/123456")
+    with patch("sentry_sdk.init") as mock_init:
+        configure_sentry()
+        mock_init.assert_called_once()
+        assert (
+            "Sentry DSN found, exceptions will be sent to Sentry with env=test"
+            in caplog.text
+        )
+
+
+def test_config_doesnt_configure_sentry_if_dsn_not_present(caplog, monkeypatch):
+    monkeypatch.delenv("SENTRY_DSN", raising=False)
+    configure_sentry()
+    assert "No Sentry DSN found, exceptions will not be sent to Sentry" in caplog.text
+
+
+def test_config_missing_required_env_vars(monkeypatch):
+    monkeypatch.delenv("WORKSPACE")
+    with pytest.raises(
+        OSError, match="Missing required environment variables: WORKSPACE"
+    ):
+        Config().check_required_env_vars()
+
+
+def test_config_env_var_dot_notation(monkeypatch):
+    CONFIG = Config()
+    assert CONFIG.workspace == "test"

tests/test_my_function.py

@@ -1,30 +1,5 @@
-from importlib import reload
-
-import pytest
-
 from lambdas import my_function
 
 
-def test_my_function_configures_sentry_if_dsn_present(caplog, monkeypatch):
-    monkeypatch.setenv("SENTRY_DSN", "https://[email protected]/123456")
-    reload(my_function)
-    assert (
-        "Sentry DSN found, exceptions will be sent to Sentry with env=test" in caplog.text
-    )
-
-
-def test_my_function_doesnt_configure_sentry_if_dsn_not_present(caplog, monkeypatch):
-    monkeypatch.delenv("SENTRY_DSN", raising=False)
-    reload(my_function)
-    assert "No Sentry DSN found, exceptions will not be sent to Sentry" in caplog.text
-
-
-def test_lambda_handler_missing_workspace_env_raises_error(monkeypatch):
-    monkeypatch.delenv("WORKSPACE", raising=False)
-    with pytest.raises(RuntimeError) as error:
-        my_function.lambda_handler({})
-    assert "Required env variable WORKSPACE is not set" in str(error)
-
-
 def test_my_function():
     assert my_function.lambda_handler({}) == "You have successfully called this lambda!"