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celery


			
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    <li>Background Processing
    <li>Distributed
    <li>Asynchronous/Synchronous
    <li>Concurrency
    <li>Periodic Tasks
    <li>Retries
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<h1>Celery 1.0 has been released!</a></h1>
<p>We&#8217;re happy to announce the release of Celery 1.0.</p>
<div class="section" id="what-is-it">
<h2>What is it?</h2>
<p>Celery is a task queue/job queue based on distributed message passing.
It is focused on real-time operation, but supports scheduling as well.</p>
<p>The execution units, called tasks, are executed concurrently on one or
more worker servers. Tasks can execute asynchronously (in the background) or synchronously
(wait until ready).</p>
<p>Celery is already used in production to process millions of tasks a day.</p>
<p>Celery was originally created for use with Django, but is now usable
from any Python project. It can
also operate with other languages via webhooks.</p>
<p>The recommended message broker is <a class="reference external" href="http://rabbitmq.org">RabbitMQ</a>, but support for Redis or
database is also available.</p>
<div class="section" id="features">
<h3>Features</h3>
<p>See <a class="reference external" href="http://ask.github.com/celery/getting-started/introduction.html#features">http://ask.github.com/celery/getting-started/introduction.html#features</a></p>
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<div class="section" id="stable-api">
<h2>Stable API</a></h2>
<p>From this version on the public API is considered stable. This means there won&#8217;t
be any backwards incompatible changes in new minor versions. Changes to the
API will be deprecated; so, for example, if we decided to remove a function
that existed in Celery 1.0:</p>
<ul class="simple">
<li>Celery 1.2 will contain a backwards-compatible replica of the function which
will raise a <tt class="docutils literal"><span class="pre">PendingDeprecationWarning</span></tt>.
This warning is silent by default; you need to explicitly turn on display
of these warnings.</li>
<li>Celery 1.4 will contain the backwards-compatible replica, but the warning
will be promoted to a full-fledged <tt class="docutils literal"><span class="pre">DeprecationWarning</span></tt>. This warning
is loud by default, and will likely be quite annoying.</li>
<li>Celery 1.6 will remove the feature outright.</li>
</ul>
<p>See the <a class="reference external" href="http://ask.github.com/celery/internals/deprecation.html">Celery Deprecation Timeline</a> for a list of pending removals.</p>
</div>
<div class="section" id="what-s-new">
<h2>What&#8217;s new?</h2>
<ul>
<li><p class="first">Task decorators</p>
<blockquote>
<p>Write tasks as regular functions and decorate them.
There are both <tt class="xref docutils literal"><span class="pre">task()</span></tt>, and <tt class="xref docutils literal"><span class="pre">periodic_task()</span></tt> decorators.</p>
</blockquote>
</li>
<li><p class="first">Tasks are automatically registered</p>
<blockquote>
<p>Registering the tasks manually was getting tedious, so now you don&#8217;t have
to anymore. You can still do it manually if you need to, just
disable <tt class="xref docutils literal"><span class="pre">Task.autoregister</span></tt>. The concept of abstract task classes
has also been introduced, this is like django models, where only the
subclasses of an abstract task is registered.</p>
</blockquote>
</li>
<li><p class="first">Events</p>
<blockquote>
<p>If enabled, the worker will send events, telling you what tasks it
executes, their results, and how long it took to execute them. It also
sends out heartbeats, so listeners are able to detect nonfunctional
workers. This is the basis for the new real-time web monitor we&#8217;re working on
(<a class="reference external" href="http://github.com/ask/celerymon/">celerymon</a>)</p>
</blockquote>
</li>
</ul>
<ul>
<li><p class="first">Rate limiting</p>
<blockquote>
<p>Global and per task rate limits. 10 tasks a second? or one an hour? You
decide. It&#8217;s using the awesome <a class="reference external" href="http://en.wikipedia.org/wiki/Token_bucket">token bucket algorithm</a>, which is
commonly used for network traffic shaping. It accounts for bursts of
activity, so your workers won&#8217;t be bored by having nothing to do.</p>
</blockquote>
</li>
</ul>
<ul>
<li><p class="first">New periodic task service.</p>
<blockquote>
<p>Periodic tasks are no longer dispatched by <tt class="docutils literal"><span class="pre">celeryd</span></tt>, but instead by a
separate service called <tt class="docutils literal"><span class="pre">celerybeat</span></tt>. This is an optimized, centralized
service dedicated to your periodic tasks, which means you don&#8217;t have to
worry about deadlocks or race conditions any more. But that does mean you
have to make sure only one instance of this service is running at any one
time.</p>
</blockquote>
<p><strong>TIP:</strong> If you&#8217;re only running a single <tt class="docutils literal"><span class="pre">celeryd</span></tt> server, you can embed
<tt class="docutils literal"><span class="pre">celerybeat</span></tt> inside it. Just add the <tt class="docutils literal"><span class="pre">--beat</span></tt> argument.</p>
</li>
<li><p class="first">Broadcast commands</p>
<blockquote>
<p>If you change your mind and don&#8217;t want to run a task after all, you
now have the option to revoke it.</p>
<p>Also, you can rate limit tasks or even shut down the worker remotely.</p>
<p>It doesn&#8217;t have many commands yet, but we&#8217;re waiting for broadcast
commands to reach its full potential, so please share your ideas
if you have any.</p>
</blockquote>
</li>
<li><p class="first">Multiple queues</p>
<blockquote>
<p>The worker is able to receive tasks on multiple queues at once.
This opens up a lot of new possibilities when combined with the impressive
routing support in AMQP.</p>
</blockquote>
</li>
<li><p class="first">Platform agnostic message format.</p>
<p>The message format has been standardized and is now using the ISO-8601 format
for dates instead of Python <tt class="docutils literal"><span class="pre">datetime</span></tt> objects. This means you can write task
consumers in other languages than Python (<tt class="docutils literal"><span class="pre">eceleryd</span></tt> anyone?)</p>
</li>
<li><p class="first">Timely</p>
<p>Periodic tasks are now scheduled on the clock, i.e. <tt class="docutils literal"><span class="pre">timedelta(hours=1)</span></tt>
means every hour at :00 minutes, not every hour from the server starts.
To revert to the previous behavior you have the option to enable
<tt class="xref docutils literal"><span class="pre">PeriodicTask.relative</span></tt>.</p>
</li>
<li><p class="first">... and a lot more!</p>
</li>
</ul>
<p>To read about these and other changes in detail, please refer to
the <a class="reference external" href="http://ask.github.com/celery/changelog.html">changelog</a>. This document contains crucial information for those
upgrading from a previous version of Celery, so be sure to read the entire
change set before you continue.</p>
<p><strong>TIP:</strong> If you install the <tt class="xref docutils literal"><span class="pre">setproctitle</span></tt> module you can see which
task each worker process is currently executing in <tt class="docutils literal"><span class="pre">ps</span></tt> listings.
Just install it using pip: <tt class="docutils literal"><span class="pre">pip</span> <span class="pre">install</span> <span class="pre">setproctitle</span></tt>.</p>
</div>
<div class="section" id="resources">
<h2>Resources</h2>
<ul class="simple">
<li>Homepage: <a class="reference external" href="http://celeryproject.org">http://celeryproject.org</a></li>
<li>Download: <a class="reference external" href="http://pypi.python.org/pypi/celery">http://pypi.python.org/pypi/celery</a></li>
<li>Documentation: <a class="reference external" href="http://celeryproject.org/docs/">http://celeryproject.org/docs/</a></li>
<li>Changelog: <a class="reference external" href="http://celeryproject.org/docs/changelog.html">http://celeryproject.org/docs/changelog.html</a></li>
<li>Code: <a class="reference external" href="http://github.com/ask/celery/">http://github.com/ask/celery/</a></li>
<li>FAQ: <a class="reference external" href="http://ask.github.com/celery/faq.html">http://ask.github.com/celery/faq.html</a></li>
<li>Mailing-list: <a class="reference external" href="http://groups.google.com/group/celery-users">http://groups.google.com/group/celery-users</a></li>
<li>IRC: #celery on irc.freenode.net.</li>
</ul>
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      <span class="newsitem">
      <h2>1.0 is in beta.</h2>
      <h4>By Ask on 08.02.2010</h4>
      <p>1.0 is scheduled to be released this week! Please help us test the latest
      <a href="http://github.com/ask/celery/tarball/v1.0.0-pre4">release
          candiate</a> to make this happen. To upgrade from an earlier
      version, please read the <a href="http://ask.github.com/celery/changelog.html">changelog</a>.
      <hr>
      </span>

      <span class="newsitem">
      <h2>New website.</h2>
      <h4>By Ask on 08.02.2010</h4>
      <p>We finally got a home page. Big thanks to <a href="http://helmersworks.com">Jan Henrik Helmers</a>
      <hr>
      </span>

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     <div class="iStretch">Copyright (c) 2009-2010, <a href="http://twitter.com/asksol">Ask Solem</a> and
         <a href="http://github.com/ask/celery/blob/master/AUTHORS">contributors</a>.<br>
 Page design by <a href="http://www.helmersworks.com/">Jan Henrik Helmers</a>
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