93 lines
3.8 KiB
Python
93 lines
3.8 KiB
Python
# Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"). You
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# may not use this file except in compliance with the License. A copy of
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# the License is located at
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#
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# http://aws.amazon.com/apache2.0/
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#
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# or in the "license" file accompanying this file. This file is
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# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
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# ANY KIND, either express or implied. See the License for the specific
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# language governing permissions and limitations under the License.
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"""Implements endpoint heuristics.
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This module implements the endpoint heuristics used by the AWS SDKs.
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In a nutshell, you give it some input data (a service name, a
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region name, and a scheme) and it gives you a complete url.
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"""
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from botocore.exceptions import UnknownEndpointError
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class EndpointResolver(object):
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_CONSTRAINT_FUNCS = {
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'startsWith': lambda x, y: str(x).startswith(y),
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'notStartsWith': lambda x, y: not str(x).startswith(y),
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'equals': lambda x, y: x == y,
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'notEquals': lambda x, y: x != y,
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'oneOf': lambda x, y: x in y
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}
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DEFAULT_SCHEME = 'https'
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def __init__(self, rules):
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self._rules = rules
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def get_rules_for_service(self, service_name):
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"""Return the rules for a given service.
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Note that the list returned is a reference to the actual list of
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rules used for the service. This list can be mutated to insert your
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own heuristic rules. You can also use a service name of ``_default``
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to get the list of default rules that are applied if no service
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name matches.
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"""
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return self._rules.get(service_name)
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def construct_endpoint(self, service_name, region_name, **kwargs):
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# We take **kwargs so that custom rules can be added that have
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# additional constraint keys that we don't know about.
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# We also need to fold the names used in the spec into **kwargs
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# so we can format the URI later.
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kwargs['service'] = service_name
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kwargs['region'] = region_name
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if 'scheme' not in kwargs:
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kwargs['scheme'] = self.DEFAULT_SCHEME
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service_rules = self._rules.get(service_name, [])
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endpoint = self._match_rules(service_rules, region_name, **kwargs)
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if endpoint is None:
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# If we didn't find any in the service section, try again
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# with the default section.
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endpoint = self._match_rules(self._rules.get('_default', []),
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region_name, **kwargs)
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if endpoint is None:
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raise UnknownEndpointError(service_name=service_name,
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region_name=region_name)
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return endpoint
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def _match_rules(self, service_rules, region_name, **kwargs):
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for rule in service_rules:
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if self._matches_rule(rule, region_name, **kwargs):
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return {'uri': rule['uri'].format(**kwargs),
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'properties': rule.get('properties', {})}
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# If we can't find any rules, then try again with the _default
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# section.
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def _matches_rule(self, rule, region_name, **kwargs):
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for constraint in rule.get('constraints', []):
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if not self._matches_constraint(constraint, **kwargs):
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return False
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return True
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def _matches_constraint(self, constraint, **kwargs):
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# Each constraint consists of an attribute in the first index (e.g.,
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# "scheme", "region", "service"), an assertion in the second index
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# (e.g., "startsWith", "equals", "oneOf"), and a value in the third
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# index (e.g., "us-east-1").
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x, func, y = (kwargs[constraint[0]],
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self._CONSTRAINT_FUNCS[constraint[1]],
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constraint[2])
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return func(x, y)
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