feature: add DAL interface (#587)

Author: ran-isenberg

.github/workflows/codeql-analysis.yml

@@ -2,11 +2,13 @@
     "cSpell.words": [
         "appconfig",
         "Codecov",
+        "getlogin",
         "getuid",
         "mkdocs",
         "mypy",
         "ranisenberg",
         "runtimes",
+        "Stubber",
         "yapf"
     ]
 }

.vscode/settings.json

@@ -8,6 +8,12 @@ show_column_numbers = True
 show_error_codes = True
 show_error_context = True
 
+
+# Disable specific error codes in the 'tests' package
+[mypy-tests.*]
+disable_error_code = annotation-unchecked
+allow_untyped_defs = True
+
 [mypy-jmespath]
 ignore_missing_imports=True
 
@@ -23,6 +29,9 @@ ignore_missing_imports = True
 [mypy-botocore]
 ignore_missing_imports = True
 
+[mypy-botocore.stub]
+ignore_missing_imports = True
+
 [mypy-botocore.response]
 ignore_missing_imports = True
 

mypy.ini

@@ -1,37 +1,10 @@
-import uuid
-
-import boto3
-from botocore.exceptions import ClientError
-from cachetools import TTLCache, cached
-from mypy_boto3_dynamodb import DynamoDBServiceResource
-from mypy_boto3_dynamodb.service_resource import Table
-from pydantic import ValidationError
+from abc import ABC, abstractmethod
 
 from service.dal.schemas.db import OrderEntry
-from service.handlers.utils.observability import logger, tracer
-from service.schemas.exceptions import InternalServerException
-
-
-# cache dynamodb connection data for no longer than 5 minutes
-@cached(cache=TTLCache(maxsize=1, ttl=300))
-def _get_db_handler(table_name: str) -> Table:
-    dynamodb: DynamoDBServiceResource = boto3.resource('dynamodb')
-    return dynamodb.Table(table_name)
 
 
-@tracer.capture_method(capture_response=False)
-def create_order_in_db(table_name: str, customer_name: str, order_item_count: int) -> OrderEntry:
-    order_id = str(uuid.uuid4())
-    logger.info('trying to save order', extra={'order_id': order_id})
-    try:
-        entry = OrderEntry(order_id=order_id, customer_name=customer_name, order_item_count=order_item_count)
-        logger.info('opening connection to dynamodb table', extra={'table_name': table_name})
-        table: Table = _get_db_handler(table_name)
-        table.put_item(Item=entry.dict())
-    except (ClientError, ValidationError) as exc:
-        error_msg = 'failed to create order'
-        logger.exception(error_msg, extra={'exception': str(exc), 'customer_name': customer_name})
-        raise InternalServerException(error_msg) from exc
+class DalHandler(ABC):
 
-    logger.info('finished create order', extra={'order_id': order_id, 'order_item_count': order_item_count, 'customer_name': customer_name})
-    return entry
+    @abstractmethod
+    def create_order_in_db(self, customer_name: str, order_item_count: int) -> OrderEntry:
+        ...  # pragma: no cover

poetry.lock

@@ -0,0 +1,42 @@
+import uuid
+
+import boto3
+from botocore.exceptions import ClientError
+from cachetools import TTLCache, cached
+from mypy_boto3_dynamodb import DynamoDBServiceResource
+from mypy_boto3_dynamodb.service_resource import Table
+from pydantic import ValidationError
+
+from service.dal.db_handler import DalHandler
+from service.dal.schemas.db import OrderEntry
+from service.handlers.utils.observability import logger, tracer
+from service.schemas.exceptions import InternalServerException
+
+
+class DynamoDalHandler(DalHandler):
+
+    def __init__(self, table_name: str):
+        self.table_name = table_name
+
+    # cache dynamodb connection data for no longer than 5 minutes
+    @cached(cache=TTLCache(maxsize=1, ttl=300))
+    def _get_db_handler(self) -> Table:
+        dynamodb: DynamoDBServiceResource = boto3.resource('dynamodb')
+        return dynamodb.Table(self.table_name)
+
+    @tracer.capture_method(capture_response=False)
+    def create_order_in_db(self, customer_name: str, order_item_count: int) -> OrderEntry:
+        order_id = str(uuid.uuid4())
+        logger.info('trying to save order', extra={'order_id': order_id})
+        try:
+            entry = OrderEntry(order_id=order_id, customer_name=customer_name, order_item_count=order_item_count)
+            logger.info('opening connection to dynamodb table', extra={'table_name': self.table_name})
+            table: Table = self._get_db_handler()
+            table.put_item(Item=entry.dict())
+        except (ClientError, ValidationError) as exc:
+            error_msg = 'failed to create order'
+            logger.exception(error_msg, extra={'exception': str(exc), 'customer_name': customer_name})
+            raise InternalServerException(error_msg) from exc
+
+        logger.info('finished create order', extra={'order_id': order_id, 'order_item_count': order_item_count, 'customer_name': customer_name})
+        return entry

service/dal/db_handler.py

@@ -43,7 +43,7 @@ def create_order(event: Dict[str, Any], context: LambdaContext) -> Dict[str, Any
         logger.error('event failed input validation', extra={'error': str(exc)})
         return build_response(http_status=HTTPStatus.BAD_REQUEST, body={})
 
-    metrics.add_metric(name='ValidEvents', unit=MetricUnit.Count, value=1)
+    metrics.add_metric(name='ValidCreateOrderEvents', unit=MetricUnit.Count, value=1)
     try:
         response: CreateOrderOutput = handle_create_request(
             customer_name=input.customer_name,

service/dal/dynamo_dal_handler.py

@@ -1,11 +1,18 @@
-from service.dal.db_handler import create_order_in_db
+from functools import lru_cache
+
+from service.dal.dynamo_dal_handler import DynamoDalHandler
 from service.dal.schemas.db import OrderEntry
 from service.handlers.schemas.dynamic_configuration import FeatureFlagsNames
 from service.handlers.utils.dynamic_configuration import get_dynamic_configuration_store
 from service.handlers.utils.observability import logger, tracer
 from service.schemas.output import CreateOrderOutput
 
 
+@lru_cache
+def get_dynamodb_dal_handler(table_name: str) -> DynamoDalHandler:
+    return DynamoDalHandler(table_name)
+
+
 @tracer.capture_method(capture_response=False)
 def handle_create_request(customer_name: str, order_item_count: int, table_name: str) -> CreateOrderOutput:
     logger.info('starting to handle create request', extra={'order_item_count': order_item_count, 'customer_name': customer_name})
@@ -24,7 +31,7 @@ def handle_create_request(customer_name: str, order_item_count: int, table_name:
         default=False,
     )
     logger.debug('premium feature flag value', extra={'premium': premium})
-
-    order: OrderEntry = create_order_in_db(table_name, customer_name, order_item_count)
+    dal_handler: DynamoDalHandler = get_dynamodb_dal_handler(table_name)
+    order: OrderEntry = dal_handler.create_order_in_db(customer_name, order_item_count)
     # convert from db entry to output, they won't always be the same
     return CreateOrderOutput(customer_name=order.customer_name, order_item_count=order.order_item_count, order_id=order.order_id)

service/handlers/create_order.py

@@ -4,8 +4,9 @@
 
 import boto3
 from aws_lambda_powertools.utilities.feature_flags.exceptions import SchemaValidationError
-from botocore.exceptions import ClientError
+from botocore.stub import Stubber
 
+from service.dal.dynamo_dal_handler import DynamoDalHandler
 from service.handlers.create_order import create_order
 from service.handlers.schemas.input import Input
 from tests.utils import generate_api_gw_event, generate_context
@@ -64,17 +65,15 @@ def test_handler_200_ok(mocker, table_name: str):
     assert response['Item']['order_item_count'] == order_item_count
 
 
-def test_internal_server_error(mocker):
-
-    def db_mock_function(table_name: str):
-        raise ClientError(error_response={}, operation_name='put_item')
-
-    db_mock = mocker.patch('service.dal.db_handler._get_db_handler')
-    db_mock.side_effect = db_mock_function
+def test_internal_server_error():
+    db_handler: DynamoDalHandler = DynamoDalHandler('table')
+    table = db_handler._get_db_handler()
+    stubber = Stubber(table.meta.client)
+    stubber.add_client_error(method='put_item', service_error_code='ValidationException')
+    stubber.activate()
     body = Input(customer_name='RanTheBuilder', order_item_count=5)
     response = create_order(generate_api_gw_event(body.dict()), generate_context())
     assert response['statusCode'] == HTTPStatus.INTERNAL_SERVER_ERROR
-    db_mock.assert_called
 
 
 def test_handler_bad_request(mocker):

service/logic/handle_create_request.py

@@ -1,17 +1,15 @@
 import pytest
-from botocore.exceptions import ClientError
+from botocore.stub import Stubber
 
-from service.dal.db_handler import create_order_in_db
+from service.dal.dynamo_dal_handler import DynamoDalHandler
 from service.schemas.exceptions import InternalServerException
 
 
-def test_raise_exception(mocker):
-
-    def db_mock_function(table_name: str):
-        raise ClientError(error_response={}, operation_name='put_item')
-
-    db_mock = mocker.patch('service.dal.db_handler._get_db_handler')
-    db_mock.side_effect = db_mock_function
+def test_raise_exception():
+    db_handler: DynamoDalHandler = DynamoDalHandler('table')
+    table = db_handler._get_db_handler()
+    stubber = Stubber(table.meta.client)
+    stubber.add_client_error(method='put_item', service_error_code='ValidationException')
+    stubber.activate()
     with pytest.raises(InternalServerException):
-        create_order_in_db(table_name='table', customer_name='customer', order_item_count=5)
-    db_mock.assert_called
+        db_handler.create_order_in_db(customer_name='customer', order_item_count=5)