Source code for runway.lookups.handlers.cfn

"""Retrieve a value from CloudFormation Stack Outputs.

The query syntax for this lookup is ``<stack-name>.<output-name>``.
When specifying the output name, be sure to use the *Logical ID* of
the output; not the *Export.Name*.

"""
from __future__ import annotations

import json
import logging
from typing import TYPE_CHECKING, Any, Dict, NamedTuple, Optional, Union, cast

from botocore.exceptions import ClientError

from ...cfngin.exceptions import StackDoesNotExist
from ...exceptions import OutputDoesNotExist
from .base import LookupHandler

if TYPE_CHECKING:
    from mypy_boto3_cloudformation.client import CloudFormationClient

    from ...cfngin.providers.aws.default import Provider
    from ...context import CfnginContext, RunwayContext

LOGGER = logging.getLogger(__name__)
TYPE_NAME = "cfn"


[docs]class OutputQuery(NamedTuple): """Output query NamedTuple.""" stack_name: str output_name: str
[docs]class CfnLookup(LookupHandler): """CloudFormation Stack Output lookup."""
[docs] @staticmethod def should_use_provider(args: Dict[str, str], provider: Optional[Provider]) -> bool: """Determine if the provider should be used for the lookup. This will open happen when the lookup is used with CFNgin. Args: args: Parsed arguments provided to the lookup. provider: CFNgin provider. """ if provider: if args.get("region") and provider.region != args["region"]: LOGGER.debug("not using provider; requested region does not match") return False LOGGER.debug("using provider") return True return False
[docs] @staticmethod def get_stack_output(client: CloudFormationClient, query: OutputQuery) -> str: """Get CloudFormation Stack output. Args: client: Boto3 CloudFormation client. query: What to get. """ LOGGER.debug("describing stack: %s", query.stack_name) stack = client.describe_stacks(StackName=query.stack_name)["Stacks"][0] outputs = { # these should always exist even though the schema says they are not required output["OutputKey"]: output["OutputValue"] # type: ignore for output in stack.get("Outputs", []) } LOGGER.debug("%s stack outputs: %s", stack["StackName"], json.dumps(outputs)) return outputs[query.output_name]
[docs] @classmethod def handle( # pylint: disable=arguments-differ cls, value: str, context: Union[CfnginContext, RunwayContext], *, provider: Optional[Provider] = None, **_: Any, ) -> Any: """Retrieve a value from CloudFormation Stack outputs. Args: value: The value passed to the Lookup. context: The current context object. provider: AWS provider. Returns: Result of the query. Raises: OutputDoesNotExist: Output does not exist on the Stack provided and default was not provided. """ raw_query, args = cls.parse(value) try: query = OutputQuery(*raw_query.split(".")) except TypeError as exc: raise ValueError( f'query must be <stack-name>.<output-name>; got "{raw_query}"' ) from exc try: # dict is not perserved in mock call so it must be a copy of # args for testing to function correctly if cls.should_use_provider(args.copy(), provider): # this will only happen when used from cfngin result = cast("Provider", provider).get_output( query.stack_name, query.output_name ) else: cfn_client = context.get_session(region=args.get("region")).client( "cloudformation" ) result = cls.get_stack_output(cfn_client, query) except (ClientError, KeyError, StackDoesNotExist) as exc: # StackDoesNotExist is only raised by provider if "default" in args: LOGGER.debug( "unable to resolve lookup for CloudFormation Stack " 'output "%s"; using default', raw_query, exc_info=True, ) args.pop("load", None) # don't load a default value result = args.pop("default") elif isinstance(exc, (ClientError, StackDoesNotExist)): raise else: raise OutputDoesNotExist(query.stack_name, query.output_name) from exc return cls.format_results(result, **args)