296 lines
11 KiB
Python
296 lines
11 KiB
Python
"""
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This module provides a pool manager that uses Google App Engine's
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`URLFetch Service <https://cloud.google.com/appengine/docs/python/urlfetch>`_.
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Example usage::
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from urllib3 import PoolManager
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from urllib3.contrib.appengine import AppEngineManager, is_appengine_sandbox
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if is_appengine_sandbox():
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# AppEngineManager uses AppEngine's URLFetch API behind the scenes
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http = AppEngineManager()
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else:
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# PoolManager uses a socket-level API behind the scenes
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http = PoolManager()
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r = http.request('GET', 'https://google.com/')
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There are `limitations <https://cloud.google.com/appengine/docs/python/\
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urlfetch/#Python_Quotas_and_limits>`_ to the URLFetch service and it may not be
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the best choice for your application. There are three options for using
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urllib3 on Google App Engine:
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1. You can use :class:`AppEngineManager` with URLFetch. URLFetch is
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cost-effective in many circumstances as long as your usage is within the
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limitations.
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2. You can use a normal :class:`~urllib3.PoolManager` by enabling sockets.
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Sockets also have `limitations and restrictions
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<https://cloud.google.com/appengine/docs/python/sockets/\
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#limitations-and-restrictions>`_ and have a lower free quota than URLFetch.
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To use sockets, be sure to specify the following in your ``app.yaml``::
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env_variables:
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GAE_USE_SOCKETS_HTTPLIB : 'true'
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3. If you are using `App Engine Flexible
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<https://cloud.google.com/appengine/docs/flexible/>`_, you can use the standard
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:class:`PoolManager` without any configuration or special environment variables.
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"""
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from __future__ import absolute_import
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import logging
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import os
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import warnings
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from ..packages.six.moves.urllib.parse import urljoin
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from ..exceptions import (
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HTTPError,
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HTTPWarning,
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MaxRetryError,
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ProtocolError,
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TimeoutError,
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SSLError
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)
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from ..packages.six import BytesIO
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from ..request import RequestMethods
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from ..response import HTTPResponse
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from ..util.timeout import Timeout
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from ..util.retry import Retry
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try:
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from google.appengine.api import urlfetch
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except ImportError:
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urlfetch = None
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log = logging.getLogger(__name__)
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class AppEnginePlatformWarning(HTTPWarning):
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pass
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class AppEnginePlatformError(HTTPError):
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pass
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class AppEngineManager(RequestMethods):
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"""
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Connection manager for Google App Engine sandbox applications.
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This manager uses the URLFetch service directly instead of using the
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emulated httplib, and is subject to URLFetch limitations as described in
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the App Engine documentation `here
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<https://cloud.google.com/appengine/docs/python/urlfetch>`_.
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Notably it will raise an :class:`AppEnginePlatformError` if:
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* URLFetch is not available.
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* If you attempt to use this on App Engine Flexible, as full socket
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support is available.
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* If a request size is more than 10 megabytes.
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* If a response size is more than 32 megabtyes.
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* If you use an unsupported request method such as OPTIONS.
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Beyond those cases, it will raise normal urllib3 errors.
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"""
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def __init__(self, headers=None, retries=None, validate_certificate=True,
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urlfetch_retries=True):
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if not urlfetch:
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raise AppEnginePlatformError(
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"URLFetch is not available in this environment.")
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if is_prod_appengine_mvms():
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raise AppEnginePlatformError(
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"Use normal urllib3.PoolManager instead of AppEngineManager"
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"on Managed VMs, as using URLFetch is not necessary in "
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"this environment.")
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warnings.warn(
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"urllib3 is using URLFetch on Google App Engine sandbox instead "
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"of sockets. To use sockets directly instead of URLFetch see "
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"https://urllib3.readthedocs.io/en/latest/reference/urllib3.contrib.html.",
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AppEnginePlatformWarning)
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RequestMethods.__init__(self, headers)
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self.validate_certificate = validate_certificate
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self.urlfetch_retries = urlfetch_retries
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self.retries = retries or Retry.DEFAULT
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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# Return False to re-raise any potential exceptions
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return False
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def urlopen(self, method, url, body=None, headers=None,
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retries=None, redirect=True, timeout=Timeout.DEFAULT_TIMEOUT,
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**response_kw):
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retries = self._get_retries(retries, redirect)
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try:
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follow_redirects = (
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redirect and
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retries.redirect != 0 and
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retries.total)
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response = urlfetch.fetch(
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url,
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payload=body,
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method=method,
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headers=headers or {},
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allow_truncated=False,
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follow_redirects=self.urlfetch_retries and follow_redirects,
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deadline=self._get_absolute_timeout(timeout),
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validate_certificate=self.validate_certificate,
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)
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except urlfetch.DeadlineExceededError as e:
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raise TimeoutError(self, e)
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except urlfetch.InvalidURLError as e:
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if 'too large' in str(e):
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raise AppEnginePlatformError(
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"URLFetch request too large, URLFetch only "
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"supports requests up to 10mb in size.", e)
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raise ProtocolError(e)
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except urlfetch.DownloadError as e:
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if 'Too many redirects' in str(e):
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raise MaxRetryError(self, url, reason=e)
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raise ProtocolError(e)
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except urlfetch.ResponseTooLargeError as e:
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raise AppEnginePlatformError(
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"URLFetch response too large, URLFetch only supports"
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"responses up to 32mb in size.", e)
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except urlfetch.SSLCertificateError as e:
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raise SSLError(e)
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except urlfetch.InvalidMethodError as e:
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raise AppEnginePlatformError(
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"URLFetch does not support method: %s" % method, e)
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http_response = self._urlfetch_response_to_http_response(
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response, retries=retries, **response_kw)
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# Handle redirect?
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redirect_location = redirect and http_response.get_redirect_location()
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if redirect_location:
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# Check for redirect response
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if (self.urlfetch_retries and retries.raise_on_redirect):
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raise MaxRetryError(self, url, "too many redirects")
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else:
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if http_response.status == 303:
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method = 'GET'
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try:
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retries = retries.increment(method, url, response=http_response, _pool=self)
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except MaxRetryError:
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if retries.raise_on_redirect:
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raise MaxRetryError(self, url, "too many redirects")
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return http_response
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retries.sleep_for_retry(http_response)
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log.debug("Redirecting %s -> %s", url, redirect_location)
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redirect_url = urljoin(url, redirect_location)
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return self.urlopen(
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method, redirect_url, body, headers,
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retries=retries, redirect=redirect,
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timeout=timeout, **response_kw)
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# Check if we should retry the HTTP response.
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has_retry_after = bool(http_response.getheader('Retry-After'))
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if retries.is_retry(method, http_response.status, has_retry_after):
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retries = retries.increment(
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method, url, response=http_response, _pool=self)
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log.debug("Retry: %s", url)
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retries.sleep(http_response)
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return self.urlopen(
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method, url,
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body=body, headers=headers,
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retries=retries, redirect=redirect,
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timeout=timeout, **response_kw)
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return http_response
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def _urlfetch_response_to_http_response(self, urlfetch_resp, **response_kw):
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if is_prod_appengine():
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# Production GAE handles deflate encoding automatically, but does
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# not remove the encoding header.
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content_encoding = urlfetch_resp.headers.get('content-encoding')
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if content_encoding == 'deflate':
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del urlfetch_resp.headers['content-encoding']
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transfer_encoding = urlfetch_resp.headers.get('transfer-encoding')
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# We have a full response's content,
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# so let's make sure we don't report ourselves as chunked data.
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if transfer_encoding == 'chunked':
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encodings = transfer_encoding.split(",")
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encodings.remove('chunked')
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urlfetch_resp.headers['transfer-encoding'] = ','.join(encodings)
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return HTTPResponse(
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# In order for decoding to work, we must present the content as
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# a file-like object.
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body=BytesIO(urlfetch_resp.content),
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headers=urlfetch_resp.headers,
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status=urlfetch_resp.status_code,
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**response_kw
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)
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def _get_absolute_timeout(self, timeout):
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if timeout is Timeout.DEFAULT_TIMEOUT:
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return None # Defer to URLFetch's default.
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if isinstance(timeout, Timeout):
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if timeout._read is not None or timeout._connect is not None:
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warnings.warn(
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"URLFetch does not support granular timeout settings, "
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"reverting to total or default URLFetch timeout.",
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AppEnginePlatformWarning)
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return timeout.total
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return timeout
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def _get_retries(self, retries, redirect):
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if not isinstance(retries, Retry):
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retries = Retry.from_int(
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retries, redirect=redirect, default=self.retries)
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if retries.connect or retries.read or retries.redirect:
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warnings.warn(
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"URLFetch only supports total retries and does not "
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"recognize connect, read, or redirect retry parameters.",
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AppEnginePlatformWarning)
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return retries
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def is_appengine():
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return (is_local_appengine() or
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is_prod_appengine() or
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is_prod_appengine_mvms())
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def is_appengine_sandbox():
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return is_appengine() and not is_prod_appengine_mvms()
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def is_local_appengine():
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return ('APPENGINE_RUNTIME' in os.environ and
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'Development/' in os.environ['SERVER_SOFTWARE'])
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def is_prod_appengine():
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return ('APPENGINE_RUNTIME' in os.environ and
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'Google App Engine/' in os.environ['SERVER_SOFTWARE'] and
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not is_prod_appengine_mvms())
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def is_prod_appengine_mvms():
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return os.environ.get('GAE_VM', False) == 'true'
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