晋太元中,武陵人捕鱼为业。缘溪行,忘路之远近。忽逢桃花林,夹岸数百步,中无杂树,芳草鲜美,落英缤纷。渔人甚异之,复前行,欲穷其林。 林尽水源,便得一山,山有小口,仿佛若有光。便舍船,从口入。初极狭,才通人。复行数十步,豁然开朗。土地平旷,屋舍俨然,有良田、美池、桑竹之属。阡陌交通,鸡犬相闻。其中往来种作,男女衣着,悉如外人。黄发垂髫,并怡然自乐。 见渔人,乃大惊,问所从来。具答之。便要还家,设酒杀鸡作食。村中闻有此人,咸来问讯。自云先世避秦时乱,率妻子邑人来此绝境,不复出焉,遂与外人间隔。问今是何世,乃不知有汉,无论魏晋。此人一一为具言所闻,皆叹惋。余人各复延至其家,皆出酒食。停数日,辞去。此中人语云:“不足为外人道也。”(间隔 一作:隔绝) 既出,得其船,便扶向路,处处志之。及郡下,诣太守,说如此。太守即遣人随其往,寻向所志,遂迷,不复得路。 南阳刘子骥,高尚士也,闻之,欣然规往。未果,寻病终。后遂无问津者。
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"""
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 logging
import os
import warnings
from ..packages.six.moves.urllib.parse import urljoin
from ..exceptions import (
HTTPError,
HTTPWarning,
MaxRetryError,
ProtocolError,
TimeoutError,
SSLError
)
from ..packages.six import BytesIO
from ..request import RequestMethods
from ..response import HTTPResponse
from ..util.timeout import Timeout
from ..util.retry import Retry
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)
return HTTPResponse(
# In order for decoding to work, we must present the content as
# a file-like object.
body=BytesIO(urlfetch_resp.content),
headers=urlfetch_resp.headers,
status=urlfetch_resp.status_code,
**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
def is_appengine():
return (is_local_appengine() or
is_prod_appengine() or
is_prod_appengine_mvms())
def is_appengine_sandbox():
return is_appengine() and not is_prod_appengine_mvms()
def is_local_appengine():
return ('APPENGINE_RUNTIME' in os.environ and
'Development/' in os.environ['SERVER_SOFTWARE'])
def is_prod_appengine():
return ('APPENGINE_RUNTIME' in os.environ and
'Google App Engine/' in os.environ['SERVER_SOFTWARE'] and
not is_prod_appengine_mvms())
def is_prod_appengine_mvms():
return os.environ.get('GAE_VM', False) == 'true'