structure saas with tools
This commit is contained in:
Davidson Gomes
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# Copyright 2017 Google Inc.
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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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"""Shared utilities used by both downloads and uploads."""
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from __future__ import absolute_import
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import base64
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import hashlib
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import logging
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import random
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import warnings
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from urllib.parse import parse_qs
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from urllib.parse import urlencode
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from urllib.parse import urlsplit
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from urllib.parse import urlunsplit
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from google.resumable_media import common
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RANGE_HEADER = "range"
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CONTENT_RANGE_HEADER = "content-range"
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CONTENT_ENCODING_HEADER = "content-encoding"
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_SLOW_CRC32C_WARNING = (
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"Currently using crcmod in pure python form. This is a slow "
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"implementation. Python 3 has a faster implementation, `google-crc32c`, "
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"which will be used if it is installed."
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)
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_GENERATION_HEADER = "x-goog-generation"
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_HASH_HEADER = "x-goog-hash"
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_STORED_CONTENT_ENCODING_HEADER = "x-goog-stored-content-encoding"
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_MISSING_CHECKSUM = """\
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No {checksum_type} checksum was returned from the service while downloading {}
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(which happens for composite objects), so client-side content integrity
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checking is not being performed."""
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_LOGGER = logging.getLogger(__name__)
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def do_nothing():
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"""Simple default callback."""
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def header_required(response, name, get_headers, callback=do_nothing):
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"""Checks that a specific header is in a headers dictionary.
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Args:
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response (object): An HTTP response object, expected to have a
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``headers`` attribute that is a ``Mapping[str, str]``.
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name (str): The name of a required header.
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get_headers (Callable[Any, Mapping[str, str]]): Helper to get headers
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from an HTTP response.
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callback (Optional[Callable]): A callback that takes no arguments,
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to be executed when an exception is being raised.
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Returns:
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str: The desired header.
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Raises:
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~google.resumable_media.common.InvalidResponse: If the header
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is missing.
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"""
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headers = get_headers(response)
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if name not in headers:
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callback()
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raise common.InvalidResponse(
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response, "Response headers must contain header", name
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)
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return headers[name]
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def require_status_code(response, status_codes, get_status_code, callback=do_nothing):
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"""Require a response has a status code among a list.
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Args:
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response (object): The HTTP response object.
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status_codes (tuple): The acceptable status codes.
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get_status_code (Callable[Any, int]): Helper to get a status code
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from a response.
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callback (Optional[Callable]): A callback that takes no arguments,
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to be executed when an exception is being raised.
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Returns:
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int: The status code.
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Raises:
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~google.resumable_media.common.InvalidResponse: If the status code
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is not one of the values in ``status_codes``.
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"""
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status_code = get_status_code(response)
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if status_code not in status_codes:
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if status_code not in common.RETRYABLE:
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callback()
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raise common.InvalidResponse(
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response,
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"Request failed with status code",
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status_code,
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"Expected one of",
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*status_codes
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)
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return status_code
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def calculate_retry_wait(base_wait, max_sleep, multiplier=2.0):
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"""Calculate the amount of time to wait before a retry attempt.
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Wait time grows exponentially with the number of attempts, until
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``max_sleep``.
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A random amount of jitter (between 0 and 1 seconds) is added to spread out
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retry attempts from different clients.
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Args:
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base_wait (float): The "base" wait time (i.e. without any jitter)
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that will be multiplied until it reaches the maximum sleep.
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max_sleep (float): Maximum value that a sleep time is allowed to be.
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multiplier (float): Multiplier to apply to the base wait.
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Returns:
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Tuple[float, float]: The new base wait time as well as the wait time
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to be applied (with a random amount of jitter between 0 and 1 seconds
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added).
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"""
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new_base_wait = multiplier * base_wait
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if new_base_wait > max_sleep:
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new_base_wait = max_sleep
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jitter_ms = random.randint(0, 1000)
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return new_base_wait, new_base_wait + 0.001 * jitter_ms
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def _get_crc32c_object():
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"""Get crc32c object
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Attempt to use the Google-CRC32c package. If it isn't available, try
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to use CRCMod. CRCMod might be using a 'slow' varietal. If so, warn...
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"""
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try:
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import google_crc32c # type: ignore
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crc_obj = google_crc32c.Checksum()
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except ImportError:
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try:
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import crcmod # type: ignore
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crc_obj = crcmod.predefined.Crc("crc-32c")
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_is_fast_crcmod()
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except ImportError:
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raise ImportError("Failed to import either `google-crc32c` or `crcmod`")
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return crc_obj
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def _is_fast_crcmod():
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# Determine if this is using the slow form of crcmod.
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nested_crcmod = __import__(
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"crcmod.crcmod",
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globals(),
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locals(),
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["_usingExtension"],
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0,
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)
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fast_crc = getattr(nested_crcmod, "_usingExtension", False)
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if not fast_crc:
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warnings.warn(_SLOW_CRC32C_WARNING, RuntimeWarning, stacklevel=2)
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return fast_crc
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def _get_metadata_key(checksum_type):
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if checksum_type == "md5":
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return "md5Hash"
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else:
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return checksum_type
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def prepare_checksum_digest(digest_bytestring):
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"""Convert a checksum object into a digest encoded for an HTTP header.
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Args:
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bytes: A checksum digest bytestring.
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Returns:
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str: A base64 string representation of the input.
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"""
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encoded_digest = base64.b64encode(digest_bytestring)
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# NOTE: ``b64encode`` returns ``bytes``, but HTTP headers expect ``str``.
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return encoded_digest.decode("utf-8")
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def _get_expected_checksum(response, get_headers, media_url, checksum_type):
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"""Get the expected checksum and checksum object for the download response.
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Args:
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response (~requests.Response): The HTTP response object.
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get_headers (callable: response->dict): returns response headers.
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media_url (str): The URL containing the media to be downloaded.
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checksum_type Optional(str): The checksum type to read from the headers,
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exactly as it will appear in the headers (case-sensitive). Must be
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"md5", "crc32c" or None.
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Returns:
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Tuple (Optional[str], object): The expected checksum of the response,
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if it can be detected from the ``X-Goog-Hash`` header, and the
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appropriate checksum object for the expected checksum.
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"""
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if checksum_type not in ["md5", "crc32c", None]:
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raise ValueError("checksum must be ``'md5'``, ``'crc32c'`` or ``None``")
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elif checksum_type in ["md5", "crc32c"]:
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headers = get_headers(response)
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expected_checksum = _parse_checksum_header(
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headers.get(_HASH_HEADER), response, checksum_label=checksum_type
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)
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if expected_checksum is None:
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msg = _MISSING_CHECKSUM.format(
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media_url, checksum_type=checksum_type.upper()
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)
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_LOGGER.info(msg)
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checksum_object = _DoNothingHash()
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else:
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if checksum_type == "md5":
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checksum_object = hashlib.md5()
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else:
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checksum_object = _get_crc32c_object()
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else:
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expected_checksum = None
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checksum_object = _DoNothingHash()
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return (expected_checksum, checksum_object)
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def _get_uploaded_checksum_from_headers(response, get_headers, checksum_type):
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"""Get the computed checksum and checksum object from the response headers.
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Args:
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response (~requests.Response): The HTTP response object.
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get_headers (callable: response->dict): returns response headers.
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checksum_type Optional(str): The checksum type to read from the headers,
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exactly as it will appear in the headers (case-sensitive). Must be
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"md5", "crc32c" or None.
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Returns:
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Tuple (Optional[str], object): The checksum of the response,
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if it can be detected from the ``X-Goog-Hash`` header, and the
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appropriate checksum object for the expected checksum.
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"""
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if checksum_type not in ["md5", "crc32c", None]:
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raise ValueError("checksum must be ``'md5'``, ``'crc32c'`` or ``None``")
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elif checksum_type in ["md5", "crc32c"]:
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headers = get_headers(response)
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remote_checksum = _parse_checksum_header(
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headers.get(_HASH_HEADER), response, checksum_label=checksum_type
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)
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else:
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remote_checksum = None
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return remote_checksum
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def _parse_checksum_header(header_value, response, checksum_label):
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"""Parses the checksum header from an ``X-Goog-Hash`` value.
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.. _header reference: https://cloud.google.com/storage/docs/\
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xml-api/reference-headers#xgooghash
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Expects ``header_value`` (if not :data:`None`) to be in one of the three
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following formats:
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* ``crc32c=n03x6A==``
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* ``md5=Ojk9c3dhfxgoKVVHYwFbHQ==``
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* ``crc32c=n03x6A==,md5=Ojk9c3dhfxgoKVVHYwFbHQ==``
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See the `header reference`_ for more information.
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Args:
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header_value (Optional[str]): The ``X-Goog-Hash`` header from
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a download response.
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response (~requests.Response): The HTTP response object.
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checksum_label (str): The label of the header value to read, as in the
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examples above. Typically "md5" or "crc32c"
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Returns:
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Optional[str]: The expected checksum of the response, if it
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can be detected from the ``X-Goog-Hash`` header; otherwise, None.
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Raises:
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~google.resumable_media.common.InvalidResponse: If there are
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multiple checksums of the requested type in ``header_value``.
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"""
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if header_value is None:
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return None
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matches = []
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for checksum in header_value.split(","):
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name, value = checksum.split("=", 1)
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# Official docs say "," is the separator, but real-world responses have encountered ", "
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if name.lstrip() == checksum_label:
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matches.append(value)
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if len(matches) == 0:
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return None
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elif len(matches) == 1:
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return matches[0]
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else:
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raise common.InvalidResponse(
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response,
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"X-Goog-Hash header had multiple ``{}`` values.".format(checksum_label),
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header_value,
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matches,
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)
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def _get_checksum_object(checksum_type):
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"""Respond with a checksum object for a supported type, if not None.
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Raises ValueError if checksum_type is unsupported.
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"""
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if checksum_type == "md5":
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return hashlib.md5()
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elif checksum_type == "crc32c":
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return _get_crc32c_object()
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elif checksum_type is None:
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return None
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else:
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raise ValueError("checksum must be ``'md5'``, ``'crc32c'`` or ``None``")
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def _parse_generation_header(response, get_headers):
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"""Parses the generation header from an ``X-Goog-Generation`` value.
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Args:
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response (~requests.Response): The HTTP response object.
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get_headers (callable: response->dict): returns response headers.
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Returns:
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Optional[long]: The object generation from the response, if it
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can be detected from the ``X-Goog-Generation`` header; otherwise, None.
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"""
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headers = get_headers(response)
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object_generation = headers.get(_GENERATION_HEADER, None)
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if object_generation is None:
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return None
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else:
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return int(object_generation)
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def _get_generation_from_url(media_url):
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"""Retrieve the object generation query param specified in the media url.
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Args:
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media_url (str): The URL containing the media to be downloaded.
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Returns:
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long: The object generation from the media url if exists; otherwise, None.
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"""
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_, _, _, query, _ = urlsplit(media_url)
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query_params = parse_qs(query)
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object_generation = query_params.get("generation", None)
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if object_generation is None:
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return None
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else:
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return int(object_generation[0])
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def add_query_parameters(media_url, query_params):
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"""Add query parameters to a base url.
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Args:
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media_url (str): The URL containing the media to be downloaded.
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query_params (dict): Names and values of the query parameters to add.
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Returns:
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str: URL with additional query strings appended.
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"""
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if len(query_params) == 0:
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return media_url
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scheme, netloc, path, query, frag = urlsplit(media_url)
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params = parse_qs(query)
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new_params = {**params, **query_params}
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query = urlencode(new_params, doseq=True)
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return urlunsplit((scheme, netloc, path, query, frag))
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def _is_decompressive_transcoding(response, get_headers):
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"""Returns True if the object was served decompressed. This happens when the
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"x-goog-stored-content-encoding" header is "gzip" and "content-encoding" header
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is not "gzip". See more at: https://cloud.google.com/storage/docs/transcoding#transcoding_and_gzip
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Args:
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response (~requests.Response): The HTTP response object.
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get_headers (callable: response->dict): returns response headers.
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Returns:
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bool: Returns True if decompressive transcoding has occurred; otherwise, False.
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"""
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headers = get_headers(response)
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return (
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headers.get(_STORED_CONTENT_ENCODING_HEADER) == "gzip"
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and headers.get(CONTENT_ENCODING_HEADER) != "gzip"
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)
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class _DoNothingHash(object):
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"""Do-nothing hash object.
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Intended as a stand-in for ``hashlib.md5`` or a crc32c checksum
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implementation in cases where it isn't necessary to compute the hash.
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"""
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def update(self, unused_chunk):
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"""Do-nothing ``update`` method.
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Intended to match the interface of ``hashlib.md5`` and other checksums.
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Args:
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unused_chunk (bytes): A chunk of data.
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"""
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