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<title>asynwsgi: A light weight, asynchronous, pep-333/WSGI compatible http server</title> |
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<body> |
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<div class="document" id="asynwsgi-a-light-weight-asynchronous-pep-333-wsgi-compatible-http-server"> |
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<h1 class="title">asynwsgi: A light weight, asynchronous, pep-333/WSGI compatible http server</h1> |
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<table class="docinfo" frame="void" rules="none"> |
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<col class="docinfo-name" /> |
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<col class="docinfo-content" /> |
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<tbody valign="top"> |
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<tr class="field"><th class="docinfo-name">License:</th><td class="field-body">MIT</td> |
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</tr> |
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<tr class="field"><th class="docinfo-name">Project-Label:</th><td class="field-body">asynwsgi</td> |
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</tr> |
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<tr><th class="docinfo-name">Version:</th> |
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<td>0.4dev4-r436-service-api</td></tr> |
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<tr><th class="docinfo-name">Author:</th> |
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<td>Robin Bryce</td></tr> |
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<tr class="field"><th class="docinfo-name">Author-email:</th><td class="field-body"><a class="reference" href="mailto:robinbryce@gmail.com">robinbryce@gmail.com</a></td> |
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</tr> |
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<tr class="field"><th class="docinfo-name">Description:</th><td class="field-body">A suspiciously quick, pure python (2.5 only), asynchronous WSGI server, implemented using asynchronous I/O and non blocking sockets.</td> |
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</tr> |
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<tr><th class="docinfo-name">Copyright:</th> |
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<td><a class="first last reference" href="#copyright-c-2007-robin-bryce">Copyright (c) 2007 Robin Bryce</a></td></tr> |
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<tr class="field"><th class="docinfo-name">Classifiers:</th><td class="field-body">Development Status :: 2 - Pre-Alpha</td> |
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</tr> |
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<tr class="field"><th class="docinfo-name">Classifiers:</th><td class="field-body">Programming Language :: Python</td> |
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</tr> |
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</tbody> |
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</table> |
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<div class="abstract topic"> |
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<p class="topic-title first">Abstract</p> |
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<p>This work was started as an effort to better understand the impact of |
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different Python <a class="reference" href="http://www.python.org/dev/peps/pep-0333/">pep-333</a> WSGI application profiles on server |
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| 321 |
performance. This is still the focus of development. This server is NOT FOR |
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| 322 |
PRODUCTION USE. This server implementation owes a lot to several prior |
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| 323 |
works:</p> |
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<ul class="simple"> |
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| 325 |
<li>Josia Carlsons excelent <a class="reference" href="http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/440665">Asynchronous HTTP Server recipe</a>, and his <a class="reference" href="http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/442412">Simple web request benchmark</a></li> |
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| 326 |
<li><a class="reference" href="http://www.cherrypy.org/browser/tags/cherrypy-3.0.0/cherrypy/wsgiserver.py">CherryPy wsgiserver</a>, The standalone, threaded, wsgi implementation, provided with CherryPy 3.0</li> |
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| 327 |
<li>asyncore, and asyncore/chat from the Python stdlib</li> |
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| 328 |
</ul> |
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| 329 |
<p>Keep-Alive works for both HTTP/1.0 and HTTP/1.1 clients and is essential |
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| 330 |
for best performance.</p> |
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| 331 |
<p>The implementation requires Python 2.5, and (currently) linux and the |
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| 332 |
<cite>poll</cite> system call.</p> |
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| 333 |
<p>For documentation on using the dispatch mainloop and implementing |
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| 334 |
compatible dispatch targets see <a class="reference" href="doc/api/asynwsgi.dispatcher-module.html">asynwsgi.dispatcher</a> and |
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| 335 |
<a class="reference" href="doc/api/asynwsgi.tcpsocket-module.html">asynwsgi.tcpsocket</a></p> |
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| 336 |
<p>For the current server implementation see:</p> |
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| 337 |
<blockquote> |
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| 338 |
<tt class="docutils literal"><span class="pre">python</span> <span class="pre">-m</span> <span class="pre">asynwsgi.wsgiservice.server</span> <span class="pre">--help</span></tt></blockquote> |
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| 339 |
<p>For a minimal async http clients see:</p> |
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| 340 |
<pre class="literal-block"> |
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| 341 |
python -m asynwsgi.httpclient oneraw --help |
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| 342 |
python -m asynwsgi.httpclient bulkfetch --help |
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| 343 |
</pre> |
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| 344 |
<p>For profiling, use the --profile option of the server above |
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| 345 |
in conjunction with:</p> |
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| 346 |
<blockquote> |
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| 347 |
<tt class="docutils literal"><span class="pre">python</span> <span class="pre">-m</span> <span class="pre">asynwsgi.bench.http_processing</span> <span class="pre">--help</span></tt></blockquote> |
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| 348 |
<p>For a means to stress test the server on a single host see:</p> |
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| 349 |
<pre class="literal-block"> |
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| 350 |
python -m asynwsgi.bench.tool saturate --help |
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| 351 |
python -m asynwsgi.bench.tool bench --help |
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| 352 |
</pre> |
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| 353 |
<p>Both saturate and bench start a single server instance. saturate runs one |
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| 354 |
instance of a http_processing client while bench runs mutliple GET and POST |
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| 355 |
async client processes (http_processing instances with appropriate options) |
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| 356 |
against the same server instance.</p> |
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| 357 |
<p>For a means to generate and sustain a large number of pending connection |
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| 358 |
attempts with the server - Ie, MORE than the rate at wich the |
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| 359 |
server can accept those connections - see:</p> |
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| 360 |
<blockquote> |
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| 361 |
<tt class="docutils literal"><span class="pre">python</span> <span class="pre">-m</span> <span class="pre">asynwsgi.sclients.main</span> <span class="pre">--help</span></tt></blockquote> |
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| 362 |
<p>And take a look at the C10k site for a detailed explanation of what an |
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| 363 |
sclient is and what you can do with one.</p> |
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| 364 |
</div> |
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| 365 |
<blockquote id="copyright-c-2007-robin-bryce"> |
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| 366 |
<p>Copyright (c) 2007 Robin Bryce</p> |
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| 367 |
<p>Permission is hereby granted, free of charge, to any person obtaining a |
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| 368 |
copy of this software and associated documentation files (the "Software"), |
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| 369 |
to deal in the Software without restriction, including without limitation |
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| 370 |
the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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| 371 |
and/or sell copies of the Software, and to permit persons to whom the |
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| 372 |
Software is furnished to do so, subject to the following conditions:</p> |
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| 373 |
<p>The above copyright notice and this permission notice shall be included in |
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| 374 |
all copies or substantial portions of the Software.</p> |
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| 375 |
<p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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| 376 |
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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| 377 |
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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| 378 |
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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| 379 |
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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| 380 |
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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| 381 |
DEALINGS IN THE SOFTWARE.</p> |
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| 382 |
</blockquote> |
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| 383 |
<div class="contents topic"> |
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<p class="topic-title first"><a id="contents" name="contents">Contents</a></p> |
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<ul class="simple"> |
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<li><a class="reference" href="#wsgi-implementation-status" id="id1" name="id1">wsgi implementation status</a></li> |
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</ul> |
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</div> |
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<div class="section"> |
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<h1><a class="toc-backref" href="#id1" id="wsgi-implementation-status" name="wsgi-implementation-status">wsgi implementation status</a></h1> |
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<p>Certain aspects of the wsgi spec implementation may be neither complete or |
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correct. Development is currently focused on identifying how performance of |
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async servers is affected by aspects of the wsgi spec.</p> |
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<dl class="docutils"> |
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<dt><tt class="docutils literal"><span class="pre">wsgi.input</span></tt>:</dt> |
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<dd><ul class="first last"> |
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<li><p class="first">For Transfer-Encoding:chunks: read, readline etc are NOT SUPPORTED. The |
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only means to process the input is via the __iter__ method. See |
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<tt class="docutils literal"><span class="pre">asynwsgi.wsgiservice.server:wsgi_file_uploader</span></tt> for an example. The |
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yield pattern for __iter__ is also somewhat specialised. It is:</p> |
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<pre class="literal-block"> |
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[chunksz, datafirst] [data]* [chunksz, datafirst] [data]* ... [0 ''] |
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</pre> |
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<p>This pattern enables the server to deal with chunk boundaries on behalf of |
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your application with out incurring excessive buffering overhead.</p> |
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<p>The iterator will raise StopIteration <em>after</em> it has yielded the |
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terminating chunk. The future plan is to incorporate trailer headers into |
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this yield pattern but presently any trailer headers are silently droped |
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on the floor (this is actualy RFC 2616 compliant although not very |
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friendly).</p> |
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<p>Your application iterable is GUARANTEED only to be resumed if input.next() |
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has some data ready (either [chunksz, datafirst] or some/all of [data]*). |
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If on a subsequent iteration the server detects EAGAIN/EWOULDBLOCK then |
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input.next() will return <tt class="docutils literal"><span class="pre">wsgi.input_sentinel</span></tt>. If your application |
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sees this value it should simply yield it back to the server. So the |
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simplest idiom is:</p> |
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<pre class="literal-block"> |
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uploaded = cStringIO.StringIO() |
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content_length = 0 |
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for v in iter(environ['wsgi.input']): |
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if d is environ['wsgi.input_sentinel']): |
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yield d |
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continue |
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if not isinstance(d, str): |
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chunksz, d = d |
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content_length += chunksz |
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uploaded.write(d) |
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assert len(uploaded.getvalue()) == content_length |
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</pre> |
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<p>Note: wsgiservice.server has an example application interable that handles |
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POST with transfercoding:chunks and you can test this using:</p> |
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<pre class="literal-block"> |
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python -m asynwsg.bench.http_processing --synthesize-post=NCHUNKS\ |
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--chunksz=NBYTES http://localhost:8080/uploader/ |
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</pre> |
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</li> |
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<li><p class="first">POST suport where Transfer-Encoding header is absent or is set to 'none' |
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At present the server collects all the data into a cStringIO.StringIO |
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instance and does not invoke the application until <em>all</em> input has been |
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collected. (AND this is not particularly well tested at present)</p> |
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</li> |
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</ul> |
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</dd> |
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</dl> |
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</div> |
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</div> |
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</body> |
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</html> |
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