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# Copyright 2014, Inc. or its affiliates. All Rights Reserved.
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
# or in the "license" file accompanying this file. This file is
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
import logging
import functools
from botocore import waiter, xform_name
from botocore.auth import AUTH_TYPE_MAPS
from botocore.awsrequest import prepare_request_dict
from import ClientMethodDocstring
from import PaginatorDocstring
from botocore.exceptions import ClientError, DataNotFoundError
from botocore.exceptions import OperationNotPageableError
from botocore.exceptions import UnknownSignatureVersionError
from botocore.hooks import first_non_none_response
from botocore.model import ServiceModel
from botocore.paginate import Paginator
from botocore.utils import CachedProperty
from botocore.utils import get_service_module_name
from botocore.utils import S3RegionRedirector
from botocore.utils import S3ArnParamHandler
from botocore.utils import S3EndpointSetter
from botocore.args import ClientArgsCreator
from botocore import UNSIGNED
# Keep this imported. There's pre-existing code that uses
# "from botocore.client import Config".
from botocore.config import Config
from botocore.history import get_global_history_recorder
from botocore.discovery import (
EndpointDiscoveryHandler, EndpointDiscoveryManager,
from botocore.retries import standard
from botocore.retries import adaptive
logger = logging.getLogger(__name__)
history_recorder = get_global_history_recorder()
class ClientCreator(object):
"""Creates client objects for a service."""
def __init__(self, loader, endpoint_resolver, user_agent, event_emitter,
retry_handler_factory, retry_config_translator,
response_parser_factory=None, exceptions_factory=None,
self._loader = loader
self._endpoint_resolver = endpoint_resolver
self._user_agent = user_agent
self._event_emitter = event_emitter
self._retry_handler_factory = retry_handler_factory
self._retry_config_translator = retry_config_translator
self._response_parser_factory = response_parser_factory
self._exceptions_factory = exceptions_factory
# TODO: Migrate things away from scoped_config in favor of the
# config_store. The config store can pull things from both the scoped
# config and environment variables (and potentially more in the
# future).
self._config_store = config_store
def create_client(self, service_name, region_name, is_secure=True,
endpoint_url=None, verify=None,
credentials=None, scoped_config=None,
responses = self._event_emitter.emit(
'choose-service-name', service_name=service_name)
service_name = first_non_none_response(responses, default=service_name)
service_model = self._load_service_model(service_name, api_version)
cls = self._create_client_class(service_name, service_model)
endpoint_bridge = ClientEndpointBridge(
self._endpoint_resolver, scoped_config, client_config,
client_args = self._get_client_args(
service_model, region_name, is_secure, endpoint_url,
verify, credentials, scoped_config, client_config, endpoint_bridge)
service_client = cls(**client_args)
service_client, endpoint_bridge, endpoint_url, client_config,
service_client, endpoint_url, client_config
return service_client
def create_client_class(self, service_name, api_version=None):
service_model = self._load_service_model(service_name, api_version)
return self._create_client_class(service_name, service_model)
def _create_client_class(self, service_name, service_model):
class_attributes = self._create_methods(service_model)
py_name_to_operation_name = self._create_name_mapping(service_model)
class_attributes['_PY_TO_OP_NAME'] = py_name_to_operation_name
bases = [BaseClient]
service_id = service_model.service_id.hyphenize()
'creating-client-class.%s' % service_id,
class_name = get_service_module_name(service_model)
cls = type(str(class_name), tuple(bases), class_attributes)
return cls
def _load_service_model(self, service_name, api_version=None):
json_model = self._loader.load_service_model(service_name, 'service-2',
service_model = ServiceModel(json_model, service_name=service_name)
return service_model
def _register_retries(self, client):
retry_mode = client.meta.config.retries['mode']
if retry_mode == 'standard':
elif retry_mode == 'adaptive':
elif retry_mode == 'legacy':
def _register_v2_standard_retries(self, client):
max_attempts = client.meta.config.retries.get('total_max_attempts')
kwargs = {'client': client}
if max_attempts is not None:
kwargs['max_attempts'] = max_attempts
def _register_v2_adaptive_retries(self, client):
def _register_legacy_retries(self, client):
endpoint_prefix = client.meta.service_model.endpoint_prefix
service_id = client.meta.service_model.service_id
service_event_name = service_id.hyphenize()
# First, we load the entire retry config for all services,
# then pull out just the information we need.
original_config = self._loader.load_data('_retry')
if not original_config:
retries = self._transform_legacy_retries(client.meta.config.retries)
retry_config = self._retry_config_translator.build_retry_config(
endpoint_prefix, original_config.get('retry', {}),
original_config.get('definitions', {}),
logger.debug("Registering retry handlers for service: %s",
handler = self._retry_handler_factory.create_retry_handler(
retry_config, endpoint_prefix)
unique_id = 'retry-config-%s' % service_event_name
'needs-retry.%s' % service_event_name, handler,
def _transform_legacy_retries(self, retries):
if retries is None:
copied_args = retries.copy()
if 'total_max_attempts' in retries:
copied_args = retries.copy()
copied_args['max_attempts'] = (
copied_args.pop('total_max_attempts') - 1)
return copied_args
def _get_retry_mode(self, client, config_store):
client_retries = client.meta.config.retries
if client_retries is not None and \
client_retries.get('mode') is not None:
return client_retries['mode']
return config_store.get_config_variable('retry_mode') or 'legacy'
def _register_endpoint_discovery(self, client, endpoint_url, config):
if endpoint_url is not None:
# Don't register any handlers in the case of a custom endpoint url
# Only attach handlers if the service supports discovery
if client.meta.service_model.endpoint_discovery_operation is None:
events =
service_id = client.meta.service_model.service_id.hyphenize()
enabled = False
if config and config.endpoint_discovery_enabled is not None:
enabled = config.endpoint_discovery_enabled
elif self._config_store:
enabled = self._config_store.get_config_variable(
if enabled:
manager = EndpointDiscoveryManager(client)
handler = EndpointDiscoveryHandler(manager)
handler.register(events, service_id)
def _register_s3_events(self, client, endpoint_bridge, endpoint_url,
client_config, scoped_config):
if client.meta.service_model.service_name != 's3':
S3RegionRedirector(endpoint_bridge, client).register()
client.meta, client_config, scoped_config)
def _set_s3_presign_signature_version(self, client_meta,
client_config, scoped_config):
# This will return the manually configured signature version, or None
# if none was manually set. If a customer manually sets the signature
# version, we always want to use what they set.
provided_signature_version = _get_configured_signature_version(
's3', client_config, scoped_config)
if provided_signature_version is not None:
# Check to see if the region is a region that we know about. If we
# don't know about a region, then we can safely assume it's a new
# region that is sigv4 only, since all new S3 regions only allow sigv4.
# The only exception is aws-global. This is a pseudo-region for the
# global endpoint, we should respect the signature versions it
# supports, which includes v2.
regions = self._endpoint_resolver.get_available_endpoints(
's3', client_meta.partition)
if client_meta.region_name != 'aws-global' and \
client_meta.region_name not in regions:
# If it is a region we know about, we want to default to sigv2, so here
# we check to see if it is available.
endpoint = self._endpoint_resolver.construct_endpoint(
's3', client_meta.region_name)
signature_versions = endpoint['signatureVersions']
if 's3' not in signature_versions:
# We now know that we're in a known region that supports sigv2 and
# the customer hasn't set a signature version so we default the
# signature version to sigv2.
'choose-signer.s3', self._default_s3_presign_to_sigv2)
def _default_s3_presign_to_sigv2(self, signature_version, **kwargs):
Returns the 's3' (sigv2) signer if presigning an s3 request. This is
intended to be used to set the default signature version for the signer
to sigv2.
:type signature_version: str
:param signature_version: The current client signature version.
:type signing_name: str
:param signing_name: The signing name of the service.
:return: 's3' if the request is an s3 presign request, None otherwise
for suffix in ['-query', '-presign-post']:
if signature_version.endswith(suffix):
return 's3' + suffix
def _get_client_args(self, service_model, region_name, is_secure,
endpoint_url, verify, credentials,
scoped_config, client_config, endpoint_bridge):
args_creator = ClientArgsCreator(
self._event_emitter, self._user_agent,
self._response_parser_factory, self._loader,
self._exceptions_factory, config_store=self._config_store)
return args_creator.get_client_args(
service_model, region_name, is_secure, endpoint_url,
verify, credentials, scoped_config, client_config, endpoint_bridge)
def _create_methods(self, service_model):
op_dict = {}
for operation_name in service_model.operation_names:
py_operation_name = xform_name(operation_name)
op_dict[py_operation_name] = self._create_api_method(
py_operation_name, operation_name, service_model)
return op_dict
def _create_name_mapping(self, service_model):
# py_name -> OperationName, for every operation available
# for a service.
mapping = {}
for operation_name in service_model.operation_names:
py_operation_name = xform_name(operation_name)
mapping[py_operation_name] = operation_name
return mapping
def _create_api_method(self, py_operation_name, operation_name,
def _api_call(self, *args, **kwargs):
# We're accepting *args so that we can give a more helpful
# error message than TypeError: _api_call takes exactly
# 1 argument.
if args:
raise TypeError(
"%s() only accepts keyword arguments." % py_operation_name)
# The "self" in this scope is referring to the BaseClient.
return self._make_api_call(operation_name, kwargs)
_api_call.__name__ = str(py_operation_name)
# Add the docstring to the client method
operation_model = service_model.operation_model(operation_name)
docstring = ClientMethodDocstring(
example_prefix='response = client.%s' % py_operation_name,
_api_call.__doc__ = docstring
return _api_call
class ClientEndpointBridge(object):
"""Bridges endpoint data and client creation
This class handles taking out the relevant arguments from the endpoint
resolver and determining which values to use, taking into account any
client configuration options and scope configuration options.
This class also handles determining what, if any, region to use if no
explicit region setting is provided. For example, Amazon S3 client will
utilize "us-east-1" by default if no region can be resolved."""
DEFAULT_ENDPOINT = '{service}.{region}'
_DUALSTACK_ENABLED_SERVICES = ['s3', 's3-control']
def __init__(self, endpoint_resolver, scoped_config=None,
client_config=None, default_endpoint=None,
self.service_signing_name = service_signing_name
self.endpoint_resolver = endpoint_resolver
self.scoped_config = scoped_config
self.client_config = client_config
self.default_endpoint = default_endpoint or self.DEFAULT_ENDPOINT
def resolve(self, service_name, region_name=None, endpoint_url=None,
region_name = self._check_default_region(service_name, region_name)
resolved = self.endpoint_resolver.construct_endpoint(
service_name, region_name)
# If we can't resolve the region, we'll attempt to get a global
# endpoint for non-regionalized services (iam, route53, etc)
if not resolved:
# TODO: fallback partition_name should be configurable in the
# future for users to define as needed.
resolved = self.endpoint_resolver.construct_endpoint(
service_name, region_name, partition_name='aws')
if resolved:
return self._create_endpoint(
resolved, service_name, region_name, endpoint_url, is_secure)
return self._assume_endpoint(service_name, region_name,
endpoint_url, is_secure)
def _check_default_region(self, service_name, region_name):
if region_name is not None:
return region_name
# Use the client_config region if no explicit region was provided.
if self.client_config and self.client_config.region_name is not None:
return self.client_config.region_name
def _create_endpoint(self, resolved, service_name, region_name,
endpoint_url, is_secure):
explicit_region = region_name is not None
region_name, signing_region = self._pick_region_values(
resolved, region_name, endpoint_url)
if endpoint_url is None:
if self._is_s3_dualstack_mode(service_name):
endpoint_url = self._create_dualstack_endpoint(
service_name, region_name,
resolved['dnsSuffix'], is_secure, explicit_region)
# Use the sslCommonName over the hostname for Python 2.6 compat.
hostname = resolved.get('sslCommonName', resolved.get('hostname'))
endpoint_url = self._make_url(hostname, is_secure,
resolved.get('protocols', []))
signature_version = self._resolve_signature_version(
service_name, resolved)
signing_name = self._resolve_signing_name(service_name, resolved)
return self._create_result(
service_name=service_name, region_name=region_name,
signing_region=signing_region, signing_name=signing_name,
endpoint_url=endpoint_url, metadata=resolved,
def _is_s3_dualstack_mode(self, service_name):
if service_name not in self._DUALSTACK_ENABLED_SERVICES:
return False
# TODO: This normalization logic is duplicated from the
# ClientArgsCreator class. Consolidate everything to
# ClientArgsCreator. _resolve_signature_version also has similarly
# duplicated logic.
client_config = self.client_config
if client_config is not None and client_config.s3 is not None and \
'use_dualstack_endpoint' in client_config.s3:
# Client config trumps scoped config.
return client_config.s3['use_dualstack_endpoint']
if self.scoped_config is None:
return False
enabled = self.scoped_config.get('s3', {}).get(
'use_dualstack_endpoint', False)
if enabled in [True, 'True', 'true']:
return True
return False
def _create_dualstack_endpoint(self, service_name, region_name,
dns_suffix, is_secure, explicit_region):
if not explicit_region and region_name == 'aws-global':
# If the region_name passed was not explicitly set, default to
# us-east-1 instead of the modeled default aws-global. Dualstack
# does not support aws-global
region_name = 'us-east-1'
hostname = '{service}.dualstack.{region}.{dns_suffix}'.format(
service=service_name, region=region_name,
# Dualstack supports http and https so were hardcoding this value for
# now. This can potentially move into the endpoints.json file.
return self._make_url(hostname, is_secure, ['http', 'https'])
def _assume_endpoint(self, service_name, region_name, endpoint_url,
if endpoint_url is None:
# Expand the default hostname URI template.
hostname = self.default_endpoint.format(
service=service_name, region=region_name)
endpoint_url = self._make_url(hostname, is_secure,
['http', 'https'])
logger.debug('Assuming an endpoint for %s, %s: %s',
service_name, region_name, endpoint_url)
# We still want to allow the user to provide an explicit version.
signature_version = self._resolve_signature_version(
service_name, {'signatureVersions': ['v4']})
signing_name = self._resolve_signing_name(service_name, resolved={})
return self._create_result(
service_name=service_name, region_name=region_name,
signing_region=region_name, signing_name=signing_name,
signature_version=signature_version, endpoint_url=endpoint_url,
def _create_result(self, service_name, region_name, signing_region,
signing_name, endpoint_url, signature_version,
return {
'service_name': service_name,
'region_name': region_name,
'signing_region': signing_region,
'signing_name': signing_name,
'endpoint_url': endpoint_url,
'signature_version': signature_version,
'metadata': metadata
def _make_url(self, hostname, is_secure, supported_protocols):
if is_secure and 'https' in supported_protocols:
scheme = 'https'
scheme = 'http'
return '%s://%s' % (scheme, hostname)
def _resolve_signing_name(self, service_name, resolved):
# CredentialScope overrides everything else.
if 'credentialScope' in resolved \
and 'service' in resolved['credentialScope']:
return resolved['credentialScope']['service']
# Use the signingName from the model if present.
if self.service_signing_name:
return self.service_signing_name
# Just assume is the same as the service name.
return service_name
def _pick_region_values(self, resolved, region_name, endpoint_url):
signing_region = region_name
if endpoint_url is None:
# Do not use the region name or signing name from the resolved
# endpoint if the user explicitly provides an endpoint_url. This
# would happen if we resolve to an endpoint where the service has
# a "defaults" section that overrides all endpoint with a single
# hostname and credentialScope. This has been the case historically
# for how STS has worked. The only way to resolve an STS endpoint
# was to provide a region_name and an endpoint_url. In that case,
# we would still resolve an endpoint, but we would not use the
# resolved endpointName or signingRegion because we want to allow
# custom endpoints.
region_name = resolved['endpointName']
signing_region = region_name
if 'credentialScope' in resolved \
and 'region' in resolved['credentialScope']:
signing_region = resolved['credentialScope']['region']
return region_name, signing_region
def _resolve_signature_version(self, service_name, resolved):
configured_version = _get_configured_signature_version(
service_name, self.client_config, self.scoped_config)
if configured_version is not None:
return configured_version
# Pick a signature version from the endpoint metadata if present.
if 'signatureVersions' in resolved:
potential_versions = resolved['signatureVersions']
if service_name == 's3':
return 's3v4'
if 'v4' in potential_versions:
return 'v4'
# Now just iterate over the signature versions in order until we
# find the first one that is known to Botocore.
for known in potential_versions:
if known in AUTH_TYPE_MAPS:
return known
raise UnknownSignatureVersionError(
class BaseClient(object):
# This is actually reassigned with the py->op_name mapping
# when the client creator creates the subclass. This value is used
# because calls such as client.get_paginator('list_objects') use the
# snake_case name, but we need to know the ListObjects form.
# xform_name() does the ListObjects->list_objects conversion, but
# we need the reverse mapping here.
def __init__(self, serializer, endpoint, response_parser,
event_emitter, request_signer, service_model, loader,
client_config, partition, exceptions_factory):
self._serializer = serializer
self._endpoint = endpoint
self._response_parser = response_parser
self._request_signer = request_signer
self._cache = {}
self._loader = loader
self._client_config = client_config
self.meta = ClientMeta(event_emitter, self._client_config,, service_model,
self._PY_TO_OP_NAME, partition)
self._exceptions_factory = exceptions_factory
self._exceptions = None
def __getattr__(self, item):
event_name = 'getattr.%s.%s' % (
self._service_model.service_id.hyphenize(), item
handler, event_response =
event_name, client=self)
if event_response is not None:
return event_response
raise AttributeError(
"'%s' object has no attribute '%s'" % (
self.__class__.__name__, item)
def _register_handlers(self):
# Register the handler required to sign requests.
service_id = self.meta.service_model.service_id.hyphenize()
'request-created.%s' % service_id,
def _service_model(self):
return self.meta.service_model
def _make_api_call(self, operation_name, api_params):
operation_model = self._service_model.operation_model(operation_name)
service_name = self._service_model.service_name
history_recorder.record('API_CALL', {
'service': service_name,
'operation': operation_name,
'params': api_params,
if operation_model.deprecated:
logger.debug('Warning: %s.%s() is deprecated',
service_name, operation_name)
request_context = {
'client_region': self.meta.region_name,
'client_config': self.meta.config,
'has_streaming_input': operation_model.has_streaming_input,
'auth_type': operation_model.auth_type,
request_dict = self._convert_to_request_dict(
api_params, operation_model, context=request_context)
service_id = self._service_model.service_id.hyphenize()
handler, event_response =
model=operation_model, params=request_dict,
request_signer=self._request_signer, context=request_context)
if event_response is not None:
http, parsed_response = event_response
http, parsed_response = self._make_request(
operation_model, request_dict, request_context)
http_response=http, parsed=parsed_response,
model=operation_model, context=request_context
if http.status_code >= 300:
error_code = parsed_response.get("Error", {}).get("Code")
error_class = self.exceptions.from_code(error_code)
raise error_class(parsed_response, operation_name)
return parsed_response
def _make_request(self, operation_model, request_dict, request_context):
return self._endpoint.make_request(operation_model, request_dict)
except Exception as e:
exception=e, context=request_context
def _convert_to_request_dict(self, api_params, operation_model,
api_params = self._emit_api_params(
api_params, operation_model, context)
request_dict = self._serializer.serialize_to_request(
api_params, operation_model)
if not self._client_config.inject_host_prefix:
request_dict.pop('host_prefix', None)
return request_dict
def _emit_api_params(self, api_params, operation_model, context):
# Given the API params provided by the user and the operation_model
# we can serialize the request to a request_dict.
operation_name =
# Emit an event that allows users to modify the parameters at the
# beginning of the method. It allows handlers to modify existing
# parameters or return a new set of parameters to use.
service_id = self._service_model.service_id.hyphenize()
responses =
params=api_params, model=operation_model, context=context)
api_params = first_non_none_response(responses, default=api_params)
event_name = (
params=api_params, model=operation_model, context=context)
return api_params
def get_paginator(self, operation_name):
"""Create a paginator for an operation.
:type operation_name: string
:param operation_name: The operation name. This is the same name
as the method name on the client. For example, if the
method name is ``create_foo``, and you'd normally invoke the
operation as ``client.create_foo(**kwargs)``, if the
``create_foo`` operation can be paginated, you can use the
call ``client.get_paginator("create_foo")``.
:raise OperationNotPageableError: Raised if the operation is not
pageable. You can use the ``client.can_paginate`` method to
check if an operation is pageable.
:rtype: L{botocore.paginate.Paginator}
:return: A paginator object.
if not self.can_paginate(operation_name):
raise OperationNotPageableError(operation_name=operation_name)
actual_operation_name = self._PY_TO_OP_NAME[operation_name]
# Create a new paginate method that will serve as a proxy to
# the underlying Paginator.paginate method. This is needed to
# attach a docstring to the method.
def paginate(self, **kwargs):
return Paginator.paginate(self, **kwargs)
paginator_config = self._cache['page_config'][
# Add the docstring for the paginate method.
paginate.__doc__ = PaginatorDocstring(
# Rename the paginator class based on the type of paginator.
paginator_class_name = str('%s.Paginator.%s' % (
# Create the new paginator class
documented_paginator_cls = type(
paginator_class_name, (Paginator,), {'paginate': paginate})
operation_model = self._service_model.operation_model(actual_operation_name)
paginator = documented_paginator_cls(
getattr(self, operation_name),
return paginator
def can_paginate(self, operation_name):
"""Check if an operation can be paginated.
:type operation_name: string
:param operation_name: The operation name. This is the same name
as the method name on the client. For example, if the
method name is ``create_foo``, and you'd normally invoke the
operation as ``client.create_foo(**kwargs)``, if the
``create_foo`` operation can be paginated, you can use the
call ``client.get_paginator("create_foo")``.
:return: ``True`` if the operation can be paginated,
``False`` otherwise.
if 'page_config' not in self._cache:
page_config = self._loader.load_service_model(
self._cache['page_config'] = page_config
except DataNotFoundError:
self._cache['page_config'] = {}
actual_operation_name = self._PY_TO_OP_NAME[operation_name]
return actual_operation_name in self._cache['page_config']
def _get_waiter_config(self):
if 'waiter_config' not in self._cache:
waiter_config = self._loader.load_service_model(
self._cache['waiter_config'] = waiter_config
except DataNotFoundError:
self._cache['waiter_config'] = {}
return self._cache['waiter_config']
def get_waiter(self, waiter_name):
"""Returns an object that can wait for some condition.
:type waiter_name: str
:param waiter_name: The name of the waiter to get. See the waiters
section of the service docs for a list of available waiters.
:returns: The specified waiter object.
:rtype: botocore.waiter.Waiter
config = self._get_waiter_config()
if not config:
raise ValueError("Waiter does not exist: %s" % waiter_name)
model = waiter.WaiterModel(config)
mapping = {}
for name in model.waiter_names:
mapping[xform_name(name)] = name
if waiter_name not in mapping:
raise ValueError("Waiter does not exist: %s" % waiter_name)
return waiter.create_waiter_with_client(
mapping[waiter_name], model, self)
def waiter_names(self):
"""Returns a list of all available waiters."""
config = self._get_waiter_config()
if not config:
return []
model = waiter.WaiterModel(config)
# Waiter configs is a dict, we just want the waiter names
# which are the keys in the dict.
return [xform_name(name) for name in model.waiter_names]
def exceptions(self):
if self._exceptions is None:
self._exceptions = self._load_exceptions()
return self._exceptions
def _load_exceptions(self):
return self._exceptions_factory.create_client_exceptions(
class ClientMeta(object):
"""Holds additional client methods.
This class holds additional information for clients. It exists for
two reasons:
* To give advanced functionality to clients
* To namespace additional client attributes from the operation
names which are mapped to methods at runtime. This avoids
ever running into collisions with operation names.
def __init__(self, events, client_config, endpoint_url, service_model,
method_to_api_mapping, partition): = events
self._client_config = client_config
self._endpoint_url = endpoint_url
self._service_model = service_model
self._method_to_api_mapping = method_to_api_mapping
self._partition = partition
def service_model(self):
return self._service_model
def region_name(self):
return self._client_config.region_name
def endpoint_url(self):
return self._endpoint_url
def config(self):
return self._client_config
def method_to_api_mapping(self):
return self._method_to_api_mapping
def partition(self):
return self._partition
def _get_configured_signature_version(service_name, client_config,
Gets the manually configured signature version.
:returns: the customer configured signature version, or None if no
signature version was configured.
# Client config overrides everything.
if client_config and client_config.signature_version is not None:
return client_config.signature_version
# Scoped config overrides picking from the endpoint metadata.
if scoped_config is not None:
# A given service may have service specific configuration in the
# config file, so we need to check there as well.
service_config = scoped_config.get(service_name)
if service_config is not None and isinstance(service_config, dict):
version = service_config.get('signature_version')
if version:
"Switching signature version for service %s "
"to version %s based on config file override.",
service_name, version)
return version
return None