As of January 1, 2020 this library no longer supports Python 2 on the latest released version. Library versions released prior to that date will continue to be available. For more information please visit Python 2 support on Google Cloud.

Source code for google.resumable_media.requests.download

# Copyright 2017 Google Inc.
#
# 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.

"""Support for downloading media from Google APIs."""

import urllib3.response

from google.resumable_media import _download
from google.resumable_media import common
from google.resumable_media import _helpers
from google.resumable_media.requests import _request_helpers


_CHECKSUM_MISMATCH = u"""\
Checksum mismatch while downloading:

  {}

The X-Goog-Hash header indicated an {checksum_type} checksum of:

  {}

but the actual {checksum_type} checksum of the downloaded contents was:

  {}
"""


[docs]class Download(_request_helpers.RequestsMixin, _download.Download): """Helper to manage downloading a resource from a Google API. "Slices" of the resource can be retrieved by specifying a range with ``start`` and / or ``end``. However, in typical usage, neither ``start`` nor ``end`` is expected to be provided. Args: media_url (str): The URL containing the media to be downloaded. stream (IO[bytes]): A write-able stream (i.e. file-like object) that the downloaded resource can be written to. start (int): The first byte in a range to be downloaded. If not provided, but ``end`` is provided, will download from the beginning to ``end`` of the media. end (int): The last byte in a range to be downloaded. If not provided, but ``start`` is provided, will download from the ``start`` to the end of the media. headers (Optional[Mapping[str, str]]): Extra headers that should be sent with the request, e.g. headers for encrypted data. checksum Optional([str]): The type of checksum to compute to verify the integrity of the object. The response headers must contain a checksum of the requested type. If the headers lack an appropriate checksum (for instance in the case of transcoded or ranged downloads where the remote service does not know the correct checksum) an INFO-level log will be emitted. Supported values are "md5", "crc32c" and None. The default is "md5". Attributes: media_url (str): The URL containing the media to be downloaded. start (Optional[int]): The first byte in a range to be downloaded. end (Optional[int]): The last byte in a range to be downloaded. """ def _write_to_stream(self, response): """Write response body to a write-able stream. .. note: This method assumes that the ``_stream`` attribute is set on the current download. Args: response (~requests.Response): The HTTP response object. Raises: ~google.resumable_media.common.DataCorruption: If the download's checksum doesn't agree with server-computed checksum. """ # `_get_expected_checksum()` may return None even if a checksum was # requested, in which case it will emit an info log _MISSING_CHECKSUM. # If an invalid checksum type is specified, this will raise ValueError. expected_checksum, checksum_object = _helpers._get_expected_checksum( response, self._get_headers, self.media_url, checksum_type=self.checksum ) with response: # NOTE: In order to handle compressed streams gracefully, we try # to insert our checksum object into the decompression stream. If # the stream is indeed compressed, this will delegate the checksum # object to the decoder and return a _DoNothingHash here. local_checksum_object = _add_decoder(response.raw, checksum_object) body_iter = response.iter_content( chunk_size=_request_helpers._SINGLE_GET_CHUNK_SIZE, decode_unicode=False ) for chunk in body_iter: self._stream.write(chunk) local_checksum_object.update(chunk) if expected_checksum is None: return else: actual_checksum = _helpers.prepare_checksum_digest(checksum_object.digest()) if actual_checksum != expected_checksum: msg = _CHECKSUM_MISMATCH.format( self.media_url, expected_checksum, actual_checksum, checksum_type=self.checksum.upper(), ) raise common.DataCorruption(response, msg)
[docs] def consume( self, transport, timeout=( _request_helpers._DEFAULT_CONNECT_TIMEOUT, _request_helpers._DEFAULT_READ_TIMEOUT, ), ): """Consume the resource to be downloaded. If a ``stream`` is attached to this download, then the downloaded resource will be written to the stream. Args: transport (~requests.Session): A ``requests`` object which can make authenticated requests. timeout (Optional[Union[float, Tuple[float, float]]]): The number of seconds to wait for the server response. Depending on the retry strategy, a request may be repeated several times using the same timeout each time. Can also be passed as a tuple (connect_timeout, read_timeout). See :meth:`requests.Session.request` documentation for details. Returns: ~requests.Response: The HTTP response returned by ``transport``. Raises: ~google.resumable_media.common.DataCorruption: If the download's checksum doesn't agree with server-computed checksum. ValueError: If the current :class:`Download` has already finished. """ method, url, payload, headers = self._prepare_request() # NOTE: We assume "payload is None" but pass it along anyway. request_kwargs = { u"data": payload, u"headers": headers, u"retry_strategy": self._retry_strategy, u"timeout": timeout, } if self._stream is not None: request_kwargs[u"stream"] = True result = _request_helpers.http_request(transport, method, url, **request_kwargs) self._process_response(result) if self._stream is not None: self._write_to_stream(result) return result
[docs]class RawDownload(_request_helpers.RawRequestsMixin, _download.Download): """Helper to manage downloading a raw resource from a Google API. "Slices" of the resource can be retrieved by specifying a range with ``start`` and / or ``end``. However, in typical usage, neither ``start`` nor ``end`` is expected to be provided. Args: media_url (str): The URL containing the media to be downloaded. stream (IO[bytes]): A write-able stream (i.e. file-like object) that the downloaded resource can be written to. start (int): The first byte in a range to be downloaded. If not provided, but ``end`` is provided, will download from the beginning to ``end`` of the media. end (int): The last byte in a range to be downloaded. If not provided, but ``start`` is provided, will download from the ``start`` to the end of the media. headers (Optional[Mapping[str, str]]): Extra headers that should be sent with the request, e.g. headers for encrypted data. checksum Optional([str]): The type of checksum to compute to verify the integrity of the object. The response headers must contain a checksum of the requested type. If the headers lack an appropriate checksum (for instance in the case of transcoded or ranged downloads where the remote service does not know the correct checksum) an INFO-level log will be emitted. Supported values are "md5", "crc32c" and None. The default is "md5". Attributes: media_url (str): The URL containing the media to be downloaded. start (Optional[int]): The first byte in a range to be downloaded. end (Optional[int]): The last byte in a range to be downloaded. """ def _write_to_stream(self, response): """Write response body to a write-able stream. .. note: This method assumes that the ``_stream`` attribute is set on the current download. Args: response (~requests.Response): The HTTP response object. Raises: ~google.resumable_media.common.DataCorruption: If the download's checksum doesn't agree with server-computed checksum. """ # `_get_expected_checksum()` may return None even if a checksum was # requested, in which case it will emit an info log _MISSING_CHECKSUM. # If an invalid checksum type is specified, this will raise ValueError. expected_checksum, checksum_object = _helpers._get_expected_checksum( response, self._get_headers, self.media_url, checksum_type=self.checksum ) with response: body_iter = response.raw.stream( _request_helpers._SINGLE_GET_CHUNK_SIZE, decode_content=False ) for chunk in body_iter: self._stream.write(chunk) checksum_object.update(chunk) response._content_consumed = True if expected_checksum is None: return else: actual_checksum = _helpers.prepare_checksum_digest(checksum_object.digest()) if actual_checksum != expected_checksum: msg = _CHECKSUM_MISMATCH.format( self.media_url, expected_checksum, actual_checksum, checksum_type=self.checksum.upper(), ) raise common.DataCorruption(response, msg)
[docs] def consume( self, transport, timeout=( _request_helpers._DEFAULT_CONNECT_TIMEOUT, _request_helpers._DEFAULT_READ_TIMEOUT, ), ): """Consume the resource to be downloaded. If a ``stream`` is attached to this download, then the downloaded resource will be written to the stream. Args: transport (~requests.Session): A ``requests`` object which can make authenticated requests. timeout (Optional[Union[float, Tuple[float, float]]]): The number of seconds to wait for the server response. Depending on the retry strategy, a request may be repeated several times using the same timeout each time. Can also be passed as a tuple (connect_timeout, read_timeout). See :meth:`requests.Session.request` documentation for details. Returns: ~requests.Response: The HTTP response returned by ``transport``. Raises: ~google.resumable_media.common.DataCorruption: If the download's checksum doesn't agree with server-computed checksum. ValueError: If the current :class:`Download` has already finished. """ method, url, payload, headers = self._prepare_request() # NOTE: We assume "payload is None" but pass it along anyway. result = _request_helpers.http_request( transport, method, url, data=payload, headers=headers, retry_strategy=self._retry_strategy, stream=True, timeout=timeout, ) self._process_response(result) if self._stream is not None: self._write_to_stream(result) return result
[docs]class ChunkedDownload(_request_helpers.RequestsMixin, _download.ChunkedDownload): """Download a resource in chunks from a Google API. Args: media_url (str): The URL containing the media to be downloaded. chunk_size (int): The number of bytes to be retrieved in each request. stream (IO[bytes]): A write-able stream (i.e. file-like object) that will be used to concatenate chunks of the resource as they are downloaded. start (int): The first byte in a range to be downloaded. If not provided, defaults to ``0``. end (int): The last byte in a range to be downloaded. If not provided, will download to the end of the media. headers (Optional[Mapping[str, str]]): Extra headers that should be sent with each request, e.g. headers for data encryption key headers. Attributes: media_url (str): The URL containing the media to be downloaded. start (Optional[int]): The first byte in a range to be downloaded. end (Optional[int]): The last byte in a range to be downloaded. chunk_size (int): The number of bytes to be retrieved in each request. Raises: ValueError: If ``start`` is negative. """
[docs] def consume_next_chunk( self, transport, timeout=( _request_helpers._DEFAULT_CONNECT_TIMEOUT, _request_helpers._DEFAULT_READ_TIMEOUT, ), ): """Consume the next chunk of the resource to be downloaded. Args: transport (~requests.Session): A ``requests`` object which can make authenticated requests. timeout (Optional[Union[float, Tuple[float, float]]]): The number of seconds to wait for the server response. Depending on the retry strategy, a request may be repeated several times using the same timeout each time. Can also be passed as a tuple (connect_timeout, read_timeout). See :meth:`requests.Session.request` documentation for details. Returns: ~requests.Response: The HTTP response returned by ``transport``. Raises: ValueError: If the current download has finished. """ method, url, payload, headers = self._prepare_request() # NOTE: We assume "payload is None" but pass it along anyway. result = _request_helpers.http_request( transport, method, url, data=payload, headers=headers, retry_strategy=self._retry_strategy, timeout=timeout, ) self._process_response(result) return result
[docs]class RawChunkedDownload(_request_helpers.RawRequestsMixin, _download.ChunkedDownload): """Download a raw resource in chunks from a Google API. Args: media_url (str): The URL containing the media to be downloaded. chunk_size (int): The number of bytes to be retrieved in each request. stream (IO[bytes]): A write-able stream (i.e. file-like object) that will be used to concatenate chunks of the resource as they are downloaded. start (int): The first byte in a range to be downloaded. If not provided, defaults to ``0``. end (int): The last byte in a range to be downloaded. If not provided, will download to the end of the media. headers (Optional[Mapping[str, str]]): Extra headers that should be sent with each request, e.g. headers for data encryption key headers. Attributes: media_url (str): The URL containing the media to be downloaded. start (Optional[int]): The first byte in a range to be downloaded. end (Optional[int]): The last byte in a range to be downloaded. chunk_size (int): The number of bytes to be retrieved in each request. Raises: ValueError: If ``start`` is negative. """
[docs] def consume_next_chunk( self, transport, timeout=( _request_helpers._DEFAULT_CONNECT_TIMEOUT, _request_helpers._DEFAULT_READ_TIMEOUT, ), ): """Consume the next chunk of the resource to be downloaded. Args: transport (~requests.Session): A ``requests`` object which can make authenticated requests. timeout (Optional[Union[float, Tuple[float, float]]]): The number of seconds to wait for the server response. Depending on the retry strategy, a request may be repeated several times using the same timeout each time. Can also be passed as a tuple (connect_timeout, read_timeout). See :meth:`requests.Session.request` documentation for details. Returns: ~requests.Response: The HTTP response returned by ``transport``. Raises: ValueError: If the current download has finished. """ method, url, payload, headers = self._prepare_request() # NOTE: We assume "payload is None" but pass it along anyway. result = _request_helpers.http_request( transport, method, url, data=payload, headers=headers, stream=True, retry_strategy=self._retry_strategy, timeout=timeout, ) self._process_response(result) return result
def _add_decoder(response_raw, checksum): """Patch the ``_decoder`` on a ``urllib3`` response. This is so that we can intercept the compressed bytes before they are decoded. Only patches if the content encoding is ``gzip``. Args: response_raw (urllib3.response.HTTPResponse): The raw response for an HTTP request. checksum (object): A checksum which will be updated with compressed bytes. Returns: object: Either the original ``checksum`` if ``_decoder`` is not patched, or a ``_DoNothingHash`` if the decoder is patched, since the caller will no longer need to hash to decoded bytes. """ encoding = response_raw.headers.get(u"content-encoding", u"").lower() if encoding != u"gzip": return checksum response_raw._decoder = _GzipDecoder(checksum) return _helpers._DoNothingHash() class _GzipDecoder(urllib3.response.GzipDecoder): """Custom subclass of ``urllib3`` decoder for ``gzip``-ed bytes. Allows a checksum function to see the compressed bytes before they are decoded. This way the checksum of the compressed value can be computed. Args: checksum (object): A checksum which will be updated with compressed bytes. """ def __init__(self, checksum): super(_GzipDecoder, self).__init__() self._checksum = checksum def decompress(self, data): """Decompress the bytes. Args: data (bytes): The compressed bytes to be decompressed. Returns: bytes: The decompressed bytes from ``data``. """ self._checksum.update(data) return super(_GzipDecoder, self).decompress(data)