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"""Blocking and non-blocking HTTP client interfaces.
This module defines a common interface shared by two implementations,
``simple_httpclient`` and ``curl_httpclient``. Applications may either
instantiate their chosen implementation class directly or use the
`AsyncHTTPClient` class from this module, which selects an implementation
that can be overridden with the `AsyncHTTPClient.configure` method.
The default implementation is ``simple_httpclient``, and this is expected
to be suitable for most users' needs. However, some applications may wish
to switch to ``curl_httpclient`` for reasons such as the following:
* ``curl_httpclient`` has some features not found in ``simple_httpclient``,
including support for HTTP proxies and the ability to use a specified
network interface.
* ``curl_httpclient`` is more likely to be compatible with sites that are
not-quite-compliant with the HTTP spec, or sites that use little-exercised
features of HTTP.
* ``curl_httpclient`` is faster.
* ``curl_httpclient`` was the default prior to Tornado 2.0.
Note that if you are using ``curl_httpclient``, it is highly
recommended that you use a recent version of ``libcurl`` and
``pycurl``. Currently the minimum supported version of libcurl is
7.22.0, and the minimum version of pycurl is 7.18.2. It is highly
recommended that your ``libcurl`` installation is built with
asynchronous DNS resolver (threaded or c-ares), otherwise you may
encounter various problems with request timeouts (for more
information, see
and comments in
To select ``curl_httpclient``, call `AsyncHTTPClient.configure` at startup::
from __future__ import absolute_import, division, print_function
import functools
import time
import weakref
from tornado.concurrent import TracebackFuture
from tornado.escape import utf8, native_str
from tornado import httputil, stack_context
from tornado.ioloop import IOLoop
from tornado.util import Configurable
class HTTPClient(object):
"""A blocking HTTP client.
This interface is provided for convenience and testing; most applications
that are running an IOLoop will want to use `AsyncHTTPClient` instead.
Typical usage looks like this::
http_client = httpclient.HTTPClient()
response = http_client.fetch("")
except httpclient.HTTPError as e:
# HTTPError is raised for non-200 responses; the response
# can be found in e.response.
print("Error: " + str(e))
except Exception as e:
# Other errors are possible, such as IOError.
print("Error: " + str(e))
def __init__(self, async_client_class=None, **kwargs):
self._io_loop = IOLoop(make_current=False)
if async_client_class is None:
async_client_class = AsyncHTTPClient
self._async_client = async_client_class(self._io_loop, **kwargs)
self._closed = False
def __del__(self):
def close(self):
"""Closes the HTTPClient, freeing any resources used."""
if not self._closed:
self._closed = True
def fetch(self, request, **kwargs):
"""Executes a request, returning an `HTTPResponse`.
The request may be either a string URL or an `HTTPRequest` object.
If it is a string, we construct an `HTTPRequest` using any additional
kwargs: ``HTTPRequest(request, **kwargs)``
If an error occurs during the fetch, we raise an `HTTPError` unless
the ``raise_error`` keyword argument is set to False.
response = self._io_loop.run_sync(functools.partial(
self._async_client.fetch, request, **kwargs))
return response
class AsyncHTTPClient(Configurable):
"""An non-blocking HTTP client.
Example usage::
def handle_response(response):
if response.error:
print("Error: %s" % response.error)
http_client = AsyncHTTPClient()
http_client.fetch("", handle_response)
The constructor for this class is magic in several respects: It
actually creates an instance of an implementation-specific
subclass, and instances are reused as a kind of pseudo-singleton
(one per `.IOLoop`). The keyword argument ``force_instance=True``
can be used to suppress this singleton behavior. Unless
``force_instance=True`` is used, no arguments other than
``io_loop`` should be passed to the `AsyncHTTPClient` constructor.
The implementation subclass as well as arguments to its
constructor can be set with the static method `configure()`
All `AsyncHTTPClient` implementations support a ``defaults``
keyword argument, which can be used to set default values for
`HTTPRequest` attributes. For example::
None, defaults=dict(user_agent="MyUserAgent"))
# or with force_instance:
client = AsyncHTTPClient(force_instance=True,
.. versionchanged:: 4.1
The ``io_loop`` argument is deprecated.
def configurable_base(cls):
return AsyncHTTPClient
def configurable_default(cls):
from tornado.simple_httpclient import SimpleAsyncHTTPClient
return SimpleAsyncHTTPClient
def _async_clients(cls):
attr_name = '_async_client_dict_' + cls.__name__
if not hasattr(cls, attr_name):
setattr(cls, attr_name, weakref.WeakKeyDictionary())
return getattr(cls, attr_name)
def __new__(cls, io_loop=None, force_instance=False, **kwargs):
io_loop = io_loop or IOLoop.current()
if force_instance:
instance_cache = None
instance_cache = cls._async_clients()
if instance_cache is not None and io_loop in instance_cache:
return instance_cache[io_loop]
instance = super(AsyncHTTPClient, cls).__new__(cls, io_loop=io_loop,
# Make sure the instance knows which cache to remove itself from.
# It can't simply call _async_clients() because we may be in
# __new__(AsyncHTTPClient) but instance.__class__ may be
# SimpleAsyncHTTPClient.
instance._instance_cache = instance_cache
if instance_cache is not None:
instance_cache[instance.io_loop] = instance
return instance
def initialize(self, io_loop, defaults=None):
self.io_loop = io_loop
self.defaults = dict(HTTPRequest._DEFAULTS)
if defaults is not None:
self._closed = False
def close(self):
"""Destroys this HTTP client, freeing any file descriptors used.
This method is **not needed in normal use** due to the way
that `AsyncHTTPClient` objects are transparently reused.
``close()`` is generally only necessary when either the
`.IOLoop` is also being closed, or the ``force_instance=True``
argument was used when creating the `AsyncHTTPClient`.
No other methods may be called on the `AsyncHTTPClient` after
if self._closed:
self._closed = True
if self._instance_cache is not None:
if self._instance_cache.get(self.io_loop) is not self:
raise RuntimeError("inconsistent AsyncHTTPClient cache")
del self._instance_cache[self.io_loop]
def fetch(self, request, callback=None, raise_error=True, **kwargs):
"""Executes a request, asynchronously returning an `HTTPResponse`.
The request may be either a string URL or an `HTTPRequest` object.
If it is a string, we construct an `HTTPRequest` using any additional
kwargs: ``HTTPRequest(request, **kwargs)``
This method returns a `.Future` whose result is an
`HTTPResponse`. By default, the ``Future`` will raise an
`HTTPError` if the request returned a non-200 response code
(other errors may also be raised if the server could not be
contacted). Instead, if ``raise_error`` is set to False, the
response will always be returned regardless of the response
If a ``callback`` is given, it will be invoked with the `HTTPResponse`.
In the callback interface, `HTTPError` is not automatically raised.
Instead, you must check the response's ``error`` attribute or
call its `~HTTPResponse.rethrow` method.
if self._closed:
raise RuntimeError("fetch() called on closed AsyncHTTPClient")
if not isinstance(request, HTTPRequest):
request = HTTPRequest(url=request, **kwargs)
if kwargs:
raise ValueError("kwargs can't be used if request is an HTTPRequest object")
# We may modify this (to add Host, Accept-Encoding, etc),
# so make sure we don't modify the caller's object. This is also
# where normal dicts get converted to HTTPHeaders objects.
request.headers = httputil.HTTPHeaders(request.headers)
request = _RequestProxy(request, self.defaults)
future = TracebackFuture()
if callback is not None:
callback = stack_context.wrap(callback)
def handle_future(future):
exc = future.exception()
if isinstance(exc, HTTPError) and exc.response is not None:
response = exc.response
elif exc is not None:
response = HTTPResponse(
request, 599, error=exc,
request_time=time.time() - request.start_time)
response = future.result()
self.io_loop.add_callback(callback, response)
def handle_response(response):
if raise_error and response.error:
self.fetch_impl(request, handle_response)
return future
def fetch_impl(self, request, callback):
raise NotImplementedError()
def configure(cls, impl, **kwargs):
"""Configures the `AsyncHTTPClient` subclass to use.
``AsyncHTTPClient()`` actually creates an instance of a subclass.
This method may be called with either a class object or the
fully-qualified name of such a class (or ``None`` to use the default,
If additional keyword arguments are given, they will be passed
to the constructor of each subclass instance created. The
keyword argument ``max_clients`` determines the maximum number
of simultaneous `~AsyncHTTPClient.fetch()` operations that can
execute in parallel on each `.IOLoop`. Additional arguments
may be supported depending on the implementation class in use.
super(AsyncHTTPClient, cls).configure(impl, **kwargs)
class HTTPRequest(object):
"""HTTP client request object."""
# Default values for HTTPRequest parameters.
# Merged with the values on the request object by AsyncHTTPClient
# implementations.
_DEFAULTS = dict(
def __init__(self, url, method="GET", headers=None, body=None,
auth_username=None, auth_password=None, auth_mode=None,
connect_timeout=None, request_timeout=None,
if_modified_since=None, follow_redirects=None,
max_redirects=None, user_agent=None, use_gzip=None,
network_interface=None, streaming_callback=None,
header_callback=None, prepare_curl_callback=None,
proxy_host=None, proxy_port=None, proxy_username=None,
proxy_password=None, proxy_auth_mode=None,
allow_nonstandard_methods=None, validate_cert=None,
ca_certs=None, allow_ipv6=None, client_key=None,
client_cert=None, body_producer=None,
expect_100_continue=False, decompress_response=None,
r"""All parameters except ``url`` are optional.
:arg string url: URL to fetch
:arg string method: HTTP method, e.g. "GET" or "POST"
:arg headers: Additional HTTP headers to pass on the request
:type headers: `~tornado.httputil.HTTPHeaders` or `dict`
:arg body: HTTP request body as a string (byte or unicode; if unicode
the utf-8 encoding will be used)
:arg body_producer: Callable used for lazy/asynchronous request bodies.
It is called with one argument, a ``write`` function, and should
return a `.Future`. It should call the write function with new
data as it becomes available. The write function returns a
`.Future` which can be used for flow control.
Only one of ``body`` and ``body_producer`` may
be specified. ``body_producer`` is not supported on
``curl_httpclient``. When using ``body_producer`` it is recommended
to pass a ``Content-Length`` in the headers as otherwise chunked
encoding will be used, and many servers do not support chunked
encoding on requests. New in Tornado 4.0
:arg string auth_username: Username for HTTP authentication
:arg string auth_password: Password for HTTP authentication
:arg string auth_mode: Authentication mode; default is "basic".
Allowed values are implementation-defined; ``curl_httpclient``
supports "basic" and "digest"; ``simple_httpclient`` only supports
:arg float connect_timeout: Timeout for initial connection in seconds,
default 20 seconds
:arg float request_timeout: Timeout for entire request in seconds,
default 20 seconds
:arg if_modified_since: Timestamp for ``If-Modified-Since`` header
:type if_modified_since: `datetime` or `float`
:arg bool follow_redirects: Should redirects be followed automatically
or return the 3xx response? Default True.
:arg int max_redirects: Limit for ``follow_redirects``, default 5.
:arg string user_agent: String to send as ``User-Agent`` header
:arg bool decompress_response: Request a compressed response from
the server and decompress it after downloading. Default is True.
New in Tornado 4.0.
:arg bool use_gzip: Deprecated alias for ``decompress_response``
since Tornado 4.0.
:arg string network_interface: Network interface to use for request.
``curl_httpclient`` only; see note below.
:arg callable streaming_callback: If set, ``streaming_callback`` will
be run with each chunk of data as it is received, and
``HTTPResponse.body`` and ``HTTPResponse.buffer`` will be empty in
the final response.
:arg callable header_callback: If set, ``header_callback`` will
be run with each header line as it is received (including the
first line, e.g. ``HTTP/1.0 200 OK\r\n``, and a final line
containing only ``\r\n``. All lines include the trailing newline
characters). ``HTTPResponse.headers`` will be empty in the final
response. This is most useful in conjunction with
``streaming_callback``, because it's the only way to get access to
header data while the request is in progress.
:arg callable prepare_curl_callback: If set, will be called with
a ``pycurl.Curl`` object to allow the application to make additional
``setopt`` calls.
:arg string proxy_host: HTTP proxy hostname. To use proxies,
``proxy_host`` and ``proxy_port`` must be set; ``proxy_username``,
``proxy_pass`` and ``proxy_auth_mode`` are optional. Proxies are
currently only supported with ``curl_httpclient``.
:arg int proxy_port: HTTP proxy port
:arg string proxy_username: HTTP proxy username
:arg string proxy_password: HTTP proxy password
:arg string proxy_auth_mode: HTTP proxy Authentication mode;
default is "basic". supports "basic" and "digest"
:arg bool allow_nonstandard_methods: Allow unknown values for ``method``
argument? Default is False.
:arg bool validate_cert: For HTTPS requests, validate the server's
certificate? Default is True.
:arg string ca_certs: filename of CA certificates in PEM format,
or None to use defaults. See note below when used with
:arg string client_key: Filename for client SSL key, if any. See
note below when used with ``curl_httpclient``.
:arg string client_cert: Filename for client SSL certificate, if any.
See note below when used with ``curl_httpclient``.
:arg ssl.SSLContext ssl_options: `ssl.SSLContext` object for use in
``simple_httpclient`` (unsupported by ``curl_httpclient``).
Overrides ``validate_cert``, ``ca_certs``, ``client_key``,
and ``client_cert``.
:arg bool allow_ipv6: Use IPv6 when available? Default is true.
:arg bool expect_100_continue: If true, send the
``Expect: 100-continue`` header and wait for a continue response
before sending the request body. Only supported with
.. note::
When using ``curl_httpclient`` certain options may be
inherited by subsequent fetches because ``pycurl`` does
not allow them to be cleanly reset. This applies to the
``ca_certs``, ``client_key``, ``client_cert``, and
``network_interface`` arguments. If you use these
options, you should pass them on every request (you don't
have to always use the same values, but it's not possible
to mix requests that specify these options with ones that
use the defaults).
.. versionadded:: 3.1
The ``auth_mode`` argument.
.. versionadded:: 4.0
The ``body_producer`` and ``expect_100_continue`` arguments.
.. versionadded:: 4.2
The ``ssl_options`` argument.
.. versionadded:: 4.5
The ``proxy_auth_mode`` argument.
# Note that some of these attributes go through property setters
# defined below.
self.headers = headers
if if_modified_since:
self.headers["If-Modified-Since"] = httputil.format_timestamp(
self.proxy_host = proxy_host
self.proxy_port = proxy_port
self.proxy_username = proxy_username
self.proxy_password = proxy_password
self.proxy_auth_mode = proxy_auth_mode
self.url = url
self.method = method
self.body = body
self.body_producer = body_producer
self.auth_username = auth_username
self.auth_password = auth_password
self.auth_mode = auth_mode
self.connect_timeout = connect_timeout
self.request_timeout = request_timeout
self.follow_redirects = follow_redirects
self.max_redirects = max_redirects
self.user_agent = user_agent
if decompress_response is not None:
self.decompress_response = decompress_response
self.decompress_response = use_gzip
self.network_interface = network_interface
self.streaming_callback = streaming_callback
self.header_callback = header_callback
self.prepare_curl_callback = prepare_curl_callback
self.allow_nonstandard_methods = allow_nonstandard_methods
self.validate_cert = validate_cert
self.ca_certs = ca_certs
self.allow_ipv6 = allow_ipv6
self.client_key = client_key
self.client_cert = client_cert
self.ssl_options = ssl_options
self.expect_100_continue = expect_100_continue
self.start_time = time.time()
def headers(self):
return self._headers
def headers(self, value):
if value is None:
self._headers = httputil.HTTPHeaders()
self._headers = value
def body(self):
return self._body
def body(self, value):
self._body = utf8(value)
def body_producer(self):
return self._body_producer
def body_producer(self, value):
self._body_producer = stack_context.wrap(value)
def streaming_callback(self):
return self._streaming_callback
def streaming_callback(self, value):
self._streaming_callback = stack_context.wrap(value)
def header_callback(self):
return self._header_callback
def header_callback(self, value):
self._header_callback = stack_context.wrap(value)
def prepare_curl_callback(self):
return self._prepare_curl_callback
def prepare_curl_callback(self, value):
self._prepare_curl_callback = stack_context.wrap(value)
class HTTPResponse(object):
"""HTTP Response object.
* request: HTTPRequest object
* code: numeric HTTP status code, e.g. 200 or 404
* reason: human-readable reason phrase describing the status code
* headers: `tornado.httputil.HTTPHeaders` object
* effective_url: final location of the resource after following any
* buffer: ``cStringIO`` object for response body
* body: response body as bytes (created on demand from ``self.buffer``)
* error: Exception object, if any
* request_time: seconds from request start to finish
* time_info: dictionary of diagnostic timing information from the request.
Available data are subject to change, but currently uses timings
available from,
plus ``queue``, which is the delay (if any) introduced by waiting for
a slot under `AsyncHTTPClient`'s ``max_clients`` setting.
def __init__(self, request, code, headers=None, buffer=None,
effective_url=None, error=None, request_time=None,
time_info=None, reason=None):
if isinstance(request, _RequestProxy):
self.request = request.request
self.request = request
self.code = code
self.reason = reason or httputil.responses.get(code, "Unknown")
if headers is not None:
self.headers = headers
self.headers = httputil.HTTPHeaders()
self.buffer = buffer
self._body = None
if effective_url is None:
self.effective_url = request.url
self.effective_url = effective_url
if error is None:
if self.code < 200 or self.code >= 300:
self.error = HTTPError(self.code, message=self.reason,
self.error = None
self.error = error
self.request_time = request_time
self.time_info = time_info or {}
def body(self):
if self.buffer is None:
return None
elif self._body is None:
self._body = self.buffer.getvalue()
return self._body
def rethrow(self):
"""If there was an error on the request, raise an `HTTPError`."""
if self.error:
raise self.error
def __repr__(self):
args = ",".join("%s=%r" % i for i in sorted(self.__dict__.items()))
return "%s(%s)" % (self.__class__.__name__, args)
class HTTPError(Exception):
"""Exception thrown for an unsuccessful HTTP request.
* ``code`` - HTTP error integer error code, e.g. 404. Error code 599 is
used when no HTTP response was received, e.g. for a timeout.
* ``response`` - `HTTPResponse` object, if any.
Note that if ``follow_redirects`` is False, redirects become HTTPErrors,
and you can look at ``error.response.headers['Location']`` to see the
destination of the redirect.
def __init__(self, code, message=None, response=None):
self.code = code
self.message = message or httputil.responses.get(code, "Unknown")
self.response = response
super(HTTPError, self).__init__(code, message, response)
def __str__(self):
return "HTTP %d: %s" % (self.code, self.message)
# There is a cyclic reference between self and self.response,
# which breaks the default __repr__ implementation.
# (especially on pypy, which doesn't have the same recursion
# detection as cpython).
__repr__ = __str__
class _RequestProxy(object):
"""Combines an object with a dictionary of defaults.
Used internally by AsyncHTTPClient implementations.
def __init__(self, request, defaults):
self.request = request
self.defaults = defaults
def __getattr__(self, name):
request_attr = getattr(self.request, name)
if request_attr is not None:
return request_attr
elif self.defaults is not None:
return self.defaults.get(name, None)
return None
def main():
from tornado.options import define, options, parse_command_line
define("print_headers", type=bool, default=False)
define("print_body", type=bool, default=True)
define("follow_redirects", type=bool, default=True)
define("validate_cert", type=bool, default=True)
args = parse_command_line()
client = HTTPClient()
for arg in args:
response = client.fetch(arg,
except HTTPError as e:
if e.response is not None:
response = e.response
if options.print_headers:
if options.print_body:
if __name__ == "__main__":