# Copyright 2012-2014 Amazon.com, 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
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
import logging
import time
import jmespath
from botocore.docs.docstring import WaiterDocstring
from botocore.utils import get_service_module_name
from . import xform_name
from .exceptions import ClientError, WaiterConfigError, WaiterError
logger = logging.getLogger(__name__)
def create_waiter_with_client(waiter_name, waiter_model, client):
"""
:type waiter_name: str
:param waiter_name: The name of the waiter. The name should match
the name (including the casing) of the key name in the waiter
model file (typically this is CamelCasing).
:type waiter_model: botocore.waiter.WaiterModel
:param waiter_model: The model for the waiter configuration.
:type client: botocore.client.BaseClient
:param client: The botocore client associated with the service.
:rtype: botocore.waiter.Waiter
:return: The waiter object.
"""
single_waiter_config = waiter_model.get_waiter(waiter_name)
operation_name = xform_name(single_waiter_config.operation)
operation_method = NormalizedOperationMethod(
getattr(client, operation_name)
)
# Create a new wait method that will serve as a proxy to the underlying
# Waiter.wait method. This is needed to attach a docstring to the
# method.
def wait(self, **kwargs):
Waiter.wait(self, **kwargs)
wait.__doc__ = WaiterDocstring(
waiter_name=waiter_name,
event_emitter=client.meta.events,
service_model=client.meta.service_model,
service_waiter_model=waiter_model,
include_signature=False,
)
# Rename the waiter class based on the type of waiter.
waiter_class_name = str(
'%s.Waiter.%s'
% (get_service_module_name(client.meta.service_model), waiter_name)
)
# Create the new waiter class
documented_waiter_cls = type(waiter_class_name, (Waiter,), {'wait': wait})
# Return an instance of the new waiter class.
return documented_waiter_cls(
waiter_name, single_waiter_config, operation_method
)
def is_valid_waiter_error(response):
error = response.get('Error')
if isinstance(error, dict) and 'Code' in error:
return True
return False
class NormalizedOperationMethod:
def __init__(self, client_method):
self._client_method = client_method
def __call__(self, **kwargs):
try:
return self._client_method(**kwargs)
except ClientError as e:
return e.response
class WaiterModel:
SUPPORTED_VERSION = 2
def __init__(self, waiter_config):
"""
Note that the WaiterModel takes ownership of the waiter_config.
It may or may not mutate the waiter_config. If this is a concern,
it is best to make a copy of the waiter config before passing it to
the WaiterModel.
:type waiter_config: dict
:param waiter_config: The loaded waiter config
from the <service>*.waiters.json file. This can be
obtained from a botocore Loader object as well.
"""
self._waiter_config = waiter_config['waiters']
# These are part of the public API. Changing these
# will result in having to update the consuming code,
# so don't change unless you really need to.
version = waiter_config.get('version', 'unknown')
self._verify_supported_version(version)
self.version = version
self.waiter_names = list(sorted(waiter_config['waiters'].keys()))
def _verify_supported_version(self, version):
if version != self.SUPPORTED_VERSION:
raise WaiterConfigError(
error_msg=(
"Unsupported waiter version, supported version "
"must be: %s, but version of waiter config "
"is: %s" % (self.SUPPORTED_VERSION, version)
)
)
def get_waiter(self, waiter_name):
try:
single_waiter_config = self._waiter_config[waiter_name]
except KeyError:
raise ValueError("Waiter does not exist: %s" % waiter_name)
return SingleWaiterConfig(single_waiter_config)
class SingleWaiterConfig:
"""Represents the waiter configuration for a single waiter.
A single waiter is considered the configuration for a single
value associated with a named waiter (i.e TableExists).
"""
def __init__(self, single_waiter_config):
self._config = single_waiter_config
# These attributes are part of the public API.
self.description = single_waiter_config.get('description', '')
# Per the spec, these three fields are required.
self.operation = single_waiter_config['operation']
self.delay = single_waiter_config['delay']
self.max_attempts = single_waiter_config['maxAttempts']
@property
def acceptors(self):
acceptors = []
for acceptor_config in self._config['acceptors']:
acceptor = AcceptorConfig(acceptor_config)
acceptors.append(acceptor)
return acceptors
class AcceptorConfig:
def __init__(self, config):
self.state = config['state']
self.matcher = config['matcher']
self.expected = config['expected']
self.argument = config.get('argument')
self.matcher_func = self._create_matcher_func()
@property
def explanation(self):
if self.matcher == 'path':
return 'For expression "{}" we matched expected path: "{}"'.format(
self.argument,
self.expected,
)
elif self.matcher == 'pathAll':
return (
'For expression "%s" all members matched excepted path: "%s"'
% (self.argument, self.expected)
)
elif self.matcher == 'pathAny':
return (
'For expression "%s" we matched expected path: "%s" at least once'
% (self.argument, self.expected)
)
elif self.matcher == 'status':
return 'Matched expected HTTP status code: %s' % self.expected
elif self.matcher == 'error':
return 'Matched expected service error code: %s' % self.expected
else:
return (
'No explanation for unknown waiter type: "%s"' % self.matcher
)
def _create_matcher_func(self):
# An acceptor function is a callable that takes a single value. The
# parsed AWS response. Note that the parsed error response is also
# provided in the case of errors, so it's entirely possible to
# handle all the available matcher capabilities in the future.
# There's only three supported matchers, so for now, this is all
# contained to a single method. If this grows, we can expand this
# out to separate methods or even objects.
if self.matcher == 'path':
return self._create_path_matcher()
elif self.matcher == 'pathAll':
return self._create_path_all_matcher()
elif self.matcher == 'pathAny':
return self._create_path_any_matcher()
elif self.matcher == 'status':
return self._create_status_matcher()
elif self.matcher == 'error':
return self._create_error_matcher()
else:
raise WaiterConfigError(
error_msg="Unknown acceptor: %s" % self.matcher
)
def _create_path_matcher(self):
expression = jmespath.compile(self.argument)
expected = self.expected
def acceptor_matches(response):
if is_valid_waiter_error(response):
return
return expression.search(response) == expected
return acceptor_matches
def _create_path_all_matcher(self):
expression = jmespath.compile(self.argument)
expected = self.expected
def acceptor_matches(response):
if is_valid_waiter_error(response):
return
result = expression.search(response)
if not isinstance(result, list) or not result:
# pathAll matcher must result in a list.
# Also we require at least one element in the list,
# that is, an empty list should not result in this
# acceptor match.
return False
for element in result:
if element != expected:
return False
return True
return acceptor_matches
def _create_path_any_matcher(self):
expression = jmespath.compile(self.argument)
expected = self.expected
def acceptor_matches(response):
if is_valid_waiter_error(response):
return
result = expression.search(response)
if not isinstance(result, list) or not result:
# pathAny matcher must result in a list.
# Also we require at least one element in the list,
# that is, an empty list should not result in this
# acceptor match.
return False
for element in result:
if element == expected:
return True
return False
return acceptor_matches
def _create_status_matcher(self):
expected = self.expected
def acceptor_matches(response):
# We don't have any requirements on the expected incoming data
# other than it is a dict, so we don't assume there's
# a ResponseMetadata.HTTPStatusCode.
status_code = response.get('ResponseMetadata', {}).get(
'HTTPStatusCode'
)
return status_code == expected
return acceptor_matches
def _create_error_matcher(self):
expected = self.expected
def acceptor_matches(response):
# When the client encounters an error, it will normally raise
# an exception. However, the waiter implementation will catch
# this exception, and instead send us the parsed error
# response. So response is still a dictionary, and in the case
# of an error response will contain the "Error" and
# "ResponseMetadata" key.
return response.get("Error", {}).get("Code", "") == expected
return acceptor_matches
class Waiter:
def __init__(self, name, config, operation_method):
"""
:type name: string
:param name: The name of the waiter
:type config: botocore.waiter.SingleWaiterConfig
:param config: The configuration for the waiter.
:type operation_method: callable
:param operation_method: A callable that accepts **kwargs
and returns a response. For example, this can be
a method from a botocore client.
"""
self._operation_method = operation_method
# The two attributes are exposed to allow for introspection
# and documentation.
self.name = name
self.config = config
def wait(self, **kwargs):
acceptors = list(self.config.acceptors)
current_state = 'waiting'
# pop the invocation specific config
config = kwargs.pop('WaiterConfig', {})
sleep_amount = config.get('Delay', self.config.delay)
max_attempts = config.get('MaxAttempts', self.config.max_attempts)
last_matched_acceptor = None
num_attempts = 0
while True:
response = self._operation_method(**kwargs)
num_attempts += 1
for acceptor in acceptors:
if acceptor.matcher_func(response):
last_matched_acceptor = acceptor
current_state = acceptor.state
break
else:
# If none of the acceptors matched, we should
# transition to the failure state if an error
# response was received.
if is_valid_waiter_error(response):
# Transition to a failure state, which we
# can just handle here by raising an exception.
raise WaiterError(
name=self.name,
reason='An error occurred (%s): %s'
% (
response['Error'].get('Code', 'Unknown'),
response['Error'].get('Message', 'Unknown'),
),
last_response=response,
)
if current_state == 'success':
logger.debug(
"Waiting complete, waiter matched the " "success state."
)
return
if current_state == 'failure':
reason = 'Waiter encountered a terminal failure state: %s' % (
acceptor.explanation
)
raise WaiterError(
name=self.name,
reason=reason,
last_response=response,
)
if num_attempts >= max_attempts:
if last_matched_acceptor is None:
reason = 'Max attempts exceeded'
else:
reason = (
'Max attempts exceeded. Previously accepted state: %s'
% (acceptor.explanation)
)
raise WaiterError(
name=self.name,
reason=reason,
last_response=response,
)
time.sleep(sleep_amount)