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batch.py
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/
batch.py
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# Copyright 2014 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License 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.
"""Batch updates / deletes of storage buckets / blobs.
See https://cloud.google.com/storage/docs/json_api/v1/how-tos/batch
"""
from email.encoders import encode_noop
from email.generator import Generator
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart
from email.parser import Parser
import io
import json
import requests
from google.cloud import _helpers
from google.cloud import exceptions
from google.cloud.storage._http import Connection
from google.cloud.storage.constants import _DEFAULT_TIMEOUT
class MIMEApplicationHTTP(MIMEApplication):
"""MIME type for ``application/http``.
Constructs payload from headers and body
:type method: str
:param method: HTTP method
:type uri: str
:param uri: URI for HTTP request
:type headers: dict
:param headers: HTTP headers
:type body: str
:param body: (Optional) HTTP payload
"""
def __init__(self, method, uri, headers, body):
if isinstance(body, dict):
body = json.dumps(body)
headers["Content-Type"] = "application/json"
headers["Content-Length"] = len(body)
if body is None:
body = ""
lines = ["%s %s HTTP/1.1" % (method, uri)]
lines.extend(
["%s: %s" % (key, value) for key, value in sorted(headers.items())]
)
lines.append("")
lines.append(body)
payload = "\r\n".join(lines)
super().__init__(payload, "http", encode_noop)
class _FutureDict(object):
"""Class to hold a future value for a deferred request.
Used by for requests that get sent in a :class:`Batch`.
"""
@staticmethod
def get(key, default=None):
"""Stand-in for dict.get.
:type key: object
:param key: Hashable dictionary key.
:type default: object
:param default: Fallback value to dict.get.
:raises: :class:`KeyError` always since the future is intended to fail
as a dictionary.
"""
raise KeyError("Cannot get(%r, default=%r) on a future" % (key, default))
def __getitem__(self, key):
"""Stand-in for dict[key].
:type key: object
:param key: Hashable dictionary key.
:raises: :class:`KeyError` always since the future is intended to fail
as a dictionary.
"""
raise KeyError("Cannot get item %r from a future" % (key,))
def __setitem__(self, key, value):
"""Stand-in for dict[key] = value.
:type key: object
:param key: Hashable dictionary key.
:type value: object
:param value: Dictionary value.
:raises: :class:`KeyError` always since the future is intended to fail
as a dictionary.
"""
raise KeyError("Cannot set %r -> %r on a future" % (key, value))
class _FutureResponse(requests.Response):
"""Reponse that returns a placeholder dictionary for a batched requests."""
def __init__(self, future_dict):
super(_FutureResponse, self).__init__()
self._future_dict = future_dict
self.status_code = 204
def json(self):
return self._future_dict
@property
def content(self):
return self._future_dict
class Batch(Connection):
"""Proxy an underlying connection, batching up change operations.
:type client: :class:`google.cloud.storage.client.Client`
:param client: The client to use for making connections.
"""
_MAX_BATCH_SIZE = 1000
def __init__(self, client):
api_endpoint = client._connection.API_BASE_URL
client_info = client._connection._client_info
super(Batch, self).__init__(
client, client_info=client_info, api_endpoint=api_endpoint
)
self._requests = []
self._target_objects = []
def _do_request(
self, method, url, headers, data, target_object, timeout=_DEFAULT_TIMEOUT
):
"""Override Connection: defer actual HTTP request.
Only allow up to ``_MAX_BATCH_SIZE`` requests to be deferred.
:type method: str
:param method: The HTTP method to use in the request.
:type url: str
:param url: The URL to send the request to.
:type headers: dict
:param headers: A dictionary of HTTP headers to send with the request.
:type data: str
:param data: The data to send as the body of the request.
:type target_object: object
:param target_object:
(Optional) This allows us to enable custom behavior in our batch
connection. Here we defer an HTTP request and complete
initialization of the object at a later time.
:type timeout: float or tuple
:param timeout:
(Optional) The amount of time, in seconds, to wait
for the server response. See: :ref:`configuring_timeouts`
:rtype: tuple of ``response`` (a dictionary of sorts)
and ``content`` (a string).
:returns: The HTTP response object and the content of the response.
"""
if len(self._requests) >= self._MAX_BATCH_SIZE:
raise ValueError(
"Too many deferred requests (max %d)" % self._MAX_BATCH_SIZE
)
self._requests.append((method, url, headers, data, timeout))
result = _FutureDict()
self._target_objects.append(target_object)
if target_object is not None:
target_object._properties = result
return _FutureResponse(result)
def _prepare_batch_request(self):
"""Prepares headers and body for a batch request.
:rtype: tuple (dict, str)
:returns: The pair of headers and body of the batch request to be sent.
:raises: :class:`ValueError` if no requests have been deferred.
"""
if len(self._requests) == 0:
raise ValueError("No deferred requests")
multi = MIMEMultipart()
# Use timeout of last request, default to _DEFAULT_TIMEOUT
timeout = _DEFAULT_TIMEOUT
for method, uri, headers, body, _timeout in self._requests:
subrequest = MIMEApplicationHTTP(method, uri, headers, body)
multi.attach(subrequest)
timeout = _timeout
buf = io.StringIO()
generator = Generator(buf, False, 0)
generator.flatten(multi)
payload = buf.getvalue()
# Strip off redundant header text
_, body = payload.split("\n\n", 1)
return dict(multi._headers), body, timeout
def _finish_futures(self, responses):
"""Apply all the batch responses to the futures created.
:type responses: list of (headers, payload) tuples.
:param responses: List of headers and payloads from each response in
the batch.
:raises: :class:`ValueError` if no requests have been deferred.
"""
# If a bad status occurs, we track it, but don't raise an exception
# until all futures have been populated.
exception_args = None
if len(self._target_objects) != len(responses): # pragma: NO COVER
raise ValueError("Expected a response for every request.")
for target_object, subresponse in zip(self._target_objects, responses):
if not 200 <= subresponse.status_code < 300:
exception_args = exception_args or subresponse
elif target_object is not None:
try:
target_object._properties = subresponse.json()
except ValueError:
target_object._properties = subresponse.content
if exception_args is not None:
raise exceptions.from_http_response(exception_args)
def finish(self):
"""Submit a single `multipart/mixed` request with deferred requests.
:rtype: list of tuples
:returns: one ``(headers, payload)`` tuple per deferred request.
"""
headers, body, timeout = self._prepare_batch_request()
url = "%s/batch/storage/v1" % self.API_BASE_URL
# Use the private ``_base_connection`` rather than the property
# ``_connection``, since the property may be this
# current batch.
response = self._client._base_connection._make_request(
"POST", url, data=body, headers=headers, timeout=timeout
)
# Raise exception if the top-level batch request fails
if not 200 <= response.status_code < 300:
raise exceptions.from_http_response(response)
responses = list(_unpack_batch_response(response))
self._finish_futures(responses)
return responses
def current(self):
"""Return the topmost batch, or None."""
return self._client.current_batch
def __enter__(self):
self._client._push_batch(self)
return self
def __exit__(self, exc_type, exc_val, exc_tb):
try:
if exc_type is None:
self.finish()
finally:
self._client._pop_batch()
def _generate_faux_mime_message(parser, response):
"""Convert response, content -> (multipart) email.message.
Helper for _unpack_batch_response.
"""
# We coerce to bytes to get consistent concat across
# Py2 and Py3. Percent formatting is insufficient since
# it includes the b in Py3.
content_type = _helpers._to_bytes(response.headers.get("content-type", ""))
faux_message = b"".join(
[b"Content-Type: ", content_type, b"\nMIME-Version: 1.0\n\n", response.content]
)
return parser.parsestr(faux_message.decode("utf-8"))
def _unpack_batch_response(response):
"""Convert requests.Response -> [(headers, payload)].
Creates a generator of tuples of emulating the responses to
:meth:`requests.Session.request`.
:type response: :class:`requests.Response`
:param response: HTTP response / headers from a request.
"""
parser = Parser()
message = _generate_faux_mime_message(parser, response)
if not isinstance(message._payload, list): # pragma: NO COVER
raise ValueError("Bad response: not multi-part")
for subrequest in message._payload:
status_line, rest = subrequest._payload.split("\n", 1)
_, status, _ = status_line.split(" ", 2)
sub_message = parser.parsestr(rest)
payload = sub_message._payload
msg_headers = dict(sub_message._headers)
content_id = msg_headers.get("Content-ID")
subresponse = requests.Response()
subresponse.request = requests.Request(
method="BATCH", url="contentid://{}".format(content_id)
).prepare()
subresponse.status_code = int(status)
subresponse.headers.update(msg_headers)
subresponse._content = payload.encode("utf-8")
yield subresponse