327 lines
11 KiB
Python
327 lines
11 KiB
Python
# Copyright 2014 Google Inc. All rights reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Batch updates / deletes of storage buckets / blobs.
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See: https://cloud.google.com/storage/docs/json_api/v1/how-tos/batch
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"""
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from email.encoders import encode_noop
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from email.generator import Generator
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from email.mime.application import MIMEApplication
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from email.mime.multipart import MIMEMultipart
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from email.parser import Parser
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import io
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import json
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import httplib2
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import six
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from gcloud.exceptions import make_exception
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from gcloud.storage.connection import Connection
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class MIMEApplicationHTTP(MIMEApplication):
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"""MIME type for ``application/http``.
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Constructs payload from headers and body
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:type method: str
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:param method: HTTP method
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:type uri: str
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:param uri: URI for HTTP request
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:type headers: dict
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:param headers: HTTP headers
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:type body: str or None
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:param body: HTTP payload
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"""
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def __init__(self, method, uri, headers, body):
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if isinstance(body, dict):
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body = json.dumps(body)
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headers['Content-Type'] = 'application/json'
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headers['Content-Length'] = len(body)
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if body is None:
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body = ''
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lines = ['%s %s HTTP/1.1' % (method, uri)]
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lines.extend(['%s: %s' % (key, value)
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for key, value in sorted(headers.items())])
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lines.append('')
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lines.append(body)
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payload = '\r\n'.join(lines)
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if six.PY2:
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# email.message.Message is an old-style class, so we
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# cannot use 'super()'.
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MIMEApplication.__init__(self, payload, 'http', encode_noop)
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else: # pragma: NO COVER Python3
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super_init = super(MIMEApplicationHTTP, self).__init__
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super_init(payload, 'http', encode_noop)
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class NoContent(object):
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"""Emulate an HTTP '204 No Content' response."""
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status = 204
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class _FutureDict(object):
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"""Class to hold a future value for a deferred request.
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Used by for requests that get sent in a :class:`Batch`.
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"""
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@staticmethod
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def get(key, default=None):
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"""Stand-in for dict.get.
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:type key: object
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:param key: Hashable dictionary key.
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:type default: object
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:param default: Fallback value to dict.get.
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:raises: :class:`KeyError` always since the future is intended to fail
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as a dictionary.
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"""
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raise KeyError('Cannot get(%r, default=%r) on a future' % (
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key, default))
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def __getitem__(self, key):
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"""Stand-in for dict[key].
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:type key: object
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:param key: Hashable dictionary key.
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:raises: :class:`KeyError` always since the future is intended to fail
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as a dictionary.
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"""
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raise KeyError('Cannot get item %r from a future' % (key,))
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def __setitem__(self, key, value):
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"""Stand-in for dict[key] = value.
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:type key: object
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:param key: Hashable dictionary key.
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:type value: object
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:param value: Dictionary value.
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:raises: :class:`KeyError` always since the future is intended to fail
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as a dictionary.
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"""
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raise KeyError('Cannot set %r -> %r on a future' % (key, value))
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class Batch(Connection):
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"""Proxy an underlying connection, batching up change operations.
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:type client: :class:`gcloud.storage.client.Client`
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:param client: The client to use for making connections.
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"""
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_MAX_BATCH_SIZE = 1000
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def __init__(self, client):
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super(Batch, self).__init__()
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self._client = client
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self._requests = []
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self._target_objects = []
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def _do_request(self, method, url, headers, data, target_object):
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"""Override Connection: defer actual HTTP request.
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Only allow up to ``_MAX_BATCH_SIZE`` requests to be deferred.
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:type method: str
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:param method: The HTTP method to use in the request.
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:type url: str
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:param url: The URL to send the request to.
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:type headers: dict
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:param headers: A dictionary of HTTP headers to send with the request.
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:type data: str
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:param data: The data to send as the body of the request.
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:type target_object: object or :class:`NoneType`
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:param target_object: This allows us to enable custom behavior in our
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batch connection. Here we defer an HTTP request
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and complete initialization of the object at a
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later time.
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:rtype: tuple of ``response`` (a dictionary of sorts)
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and ``content`` (a string).
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:returns: The HTTP response object and the content of the response.
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"""
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if len(self._requests) >= self._MAX_BATCH_SIZE:
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raise ValueError("Too many deferred requests (max %d)" %
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self._MAX_BATCH_SIZE)
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self._requests.append((method, url, headers, data))
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result = _FutureDict()
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self._target_objects.append(target_object)
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if target_object is not None:
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target_object._properties = result
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return NoContent(), result
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def _prepare_batch_request(self):
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"""Prepares headers and body for a batch request.
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:rtype: tuple (dict, str)
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:returns: The pair of headers and body of the batch request to be sent.
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:raises: :class:`ValueError` if no requests have been deferred.
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"""
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if len(self._requests) == 0:
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raise ValueError("No deferred requests")
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multi = MIMEMultipart()
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for method, uri, headers, body in self._requests:
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subrequest = MIMEApplicationHTTP(method, uri, headers, body)
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multi.attach(subrequest)
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# The `email` package expects to deal with "native" strings
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if six.PY3: # pragma: NO COVER Python3
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buf = io.StringIO()
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else:
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buf = io.BytesIO()
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generator = Generator(buf, False, 0)
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generator.flatten(multi)
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payload = buf.getvalue()
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# Strip off redundant header text
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_, body = payload.split('\n\n', 1)
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return dict(multi._headers), body
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def _finish_futures(self, responses):
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"""Apply all the batch responses to the futures created.
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:type responses: list of (headers, payload) tuples.
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:param responses: List of headers and payloads from each response in
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the batch.
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:raises: :class:`ValueError` if no requests have been deferred.
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"""
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# If a bad status occurs, we track it, but don't raise an exception
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# until all futures have been populated.
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exception_args = None
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if len(self._target_objects) != len(responses):
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raise ValueError('Expected a response for every request.')
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for target_object, sub_response in zip(self._target_objects,
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responses):
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resp_headers, sub_payload = sub_response
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if not 200 <= resp_headers.status < 300:
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exception_args = exception_args or (resp_headers,
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sub_payload)
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elif target_object is not None:
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target_object._properties = sub_payload
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if exception_args is not None:
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raise make_exception(*exception_args)
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def finish(self):
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"""Submit a single `multipart/mixed` request w/ deferred requests.
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:rtype: list of tuples
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:returns: one ``(headers, payload)`` tuple per deferred request.
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"""
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headers, body = self._prepare_batch_request()
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url = '%s/batch' % self.API_BASE_URL
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# Use the private ``_connection`` rather than the public
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# ``.connection``, since the public connection may be this
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# current batch.
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response, content = self._client._connection._make_request(
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'POST', url, data=body, headers=headers)
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responses = list(_unpack_batch_response(response, content))
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self._finish_futures(responses)
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return responses
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def current(self):
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"""Return the topmost batch, or None."""
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return self._client.current_batch
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def __enter__(self):
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self._client._push_batch(self)
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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try:
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if exc_type is None:
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self.finish()
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finally:
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self._client._pop_batch()
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def _generate_faux_mime_message(parser, response, content):
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"""Convert response, content -> (multipart) email.message.
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Helper for _unpack_batch_response.
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"""
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# We coerce to bytes to get consitent concat across
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# Py2 and Py3. Percent formatting is insufficient since
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# it includes the b in Py3.
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if not isinstance(content, six.binary_type):
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content = content.encode('utf-8')
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content_type = response['content-type']
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if not isinstance(content_type, six.binary_type):
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content_type = content_type.encode('utf-8')
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faux_message = b''.join([
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b'Content-Type: ',
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content_type,
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b'\nMIME-Version: 1.0\n\n',
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content,
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])
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if six.PY2:
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return parser.parsestr(faux_message)
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else: # pragma: NO COVER Python3
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return parser.parsestr(faux_message.decode('utf-8'))
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def _unpack_batch_response(response, content):
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"""Convert response, content -> [(headers, payload)].
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Creates a generator of tuples of emulating the responses to
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:meth:`httplib2.Http.request` (a pair of headers and payload).
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:type response: :class:`httplib2.Response`
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:param response: HTTP response / headers from a request.
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:type content: str
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:param content: Response payload with a batch response.
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:rtype: generator
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:returns: A generator of header, payload pairs.
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"""
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parser = Parser()
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message = _generate_faux_mime_message(parser, response, content)
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if not isinstance(message._payload, list):
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raise ValueError('Bad response: not multi-part')
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for subrequest in message._payload:
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status_line, rest = subrequest._payload.split('\n', 1)
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_, status, _ = status_line.split(' ', 2)
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sub_message = parser.parsestr(rest)
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payload = sub_message._payload
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ctype = sub_message['Content-Type']
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msg_headers = dict(sub_message._headers)
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msg_headers['status'] = status
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headers = httplib2.Response(msg_headers)
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if ctype and ctype.startswith('application/json'):
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payload = json.loads(payload)
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yield headers, payload
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