openstack/deb-python-eventlet
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wsgi: Add "100 Continue" response documentation

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Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>
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Tushar Gohad
2014-08-26 22:09:50 -07:00
parent e18b30b119
commit e9486899e0
1 changed files with 41 additions and 0 deletions
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doc/modules/wsgi.rst
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@@ -72,3 +72,44 @@ Post hooks are useful when code needs to be executed after a response has been
fully sent to the client (or when the client disconnects early). One example is
for more accurate logging of bandwidth used, as client disconnects use less
bandwidth than the actual Content-Length.
"100 Continue" Response Headers
-------------------------------
Eventlet's WSGI server supports sending (optional) headers with HTTP "100 Continue"
provisional responses. This is useful in such cases where a WSGI server expects
to complete a PUT request as a single HTTP request/response pair, and also wants to
communicate back to client as part of the same HTTP transaction. An example is
where the HTTP server wants to pass hints back to the client about characteristics
of data payload it can accept. As an example, an HTTP server may pass a hint in a
header the accompanying "100 Continue" response to the client indicating it can or
cannot accept encrypted data payloads, and thus client can make the encrypted vs
unencrypted decision before starting to send the data).
This works well for WSGI servers as the WSGI specification mandates HTTP
expect/continue mechanism (PEP333).
To define the "100 Continue" response headers, one may call
:func:`set_hundred_continue_response_header` on :samp:`env['wsgi.input']`
as shown in the following example::
from eventlet import wsgi
import eventlet
def wsgi_app(env, start_response):
# Define "100 Continue" response headers
env['wsgi.input'].set_hundred_continue_response_headers(
[('Hundred-Continue-Header-1', 'H1'),
('Hundred-Continue-Header-k', 'Hk')])
# The following read() causes "100 Continue" response to
# the client. Headers 'Hundred-Continue-Header-1' and
# 'Hundred-Continue-Header-K' are sent with the response
# following the "HTTP/1.1 100 Continue\r\n" status line
text = env['wsgi.input'].read()
start_response('200 OK', [('Content-Length', str(len(text)))])
return [text]
You can find a more elaborate example in the file:
``tests/wsgi_test.py``, :func:`test_024a_expect_100_continue_with_headers`.