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