~justin-fathomdb/nova/justinsb-openstack-api-volumes

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<title>Twisted Documentation: Reactor Overview</title>

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<h1 class="title">Reactor Overview</h1>

<div class="toc"><ol><li><a href="#auto0">Reactor Basics</a></li><li><a href="#auto1">Using the reactor object</a></li></ol></div>

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<p>

This HOWTO introduces the Twisted reactor, describes the basics of the

reactor and links to the various reactor interfaces.

</p>

<h2>Reactor Basics<a name="auto0"/></h2>

<p>The reactor is the core of the event loop within Twisted -- the loop

which drives applications using Twisted. The event loop is a programming

construct that waits for and dispatches events or messages in a program.

It works by calling some internal or external "event provider", which

generally blocks until an event has arrived, and then calls the relevant

event handler ("dispatches the event"). The reactor provides basic

interfaces to a number of services, including network communications,

threading, and event dispatching.

</p>

<p>

For information about using the reactor and the Twisted event loop, see:

</p>

<ul>

<li>the event dispatching howtos: <a href="time.html" shape="rect">Scheduling</a> and <a href="defer.html" shape="rect">Using Deferreds</a>;</li>

<li>the communication howtos: <a href="servers.html" shape="rect">TCP

servers</a>, <a href="clients.html" shape="rect">TCP clients</a>, <a href="udp.html" shape="rect">UDP networking</a> and <a href="process.html" shape="rect">Using

processes</a>; and</li>

<li><a href="threading.html" shape="rect">Using threads</a>.</li>

</ul>

<p>There are multiple implementations of the reactor, each

modified to provide better support for specialized features

over the default implementation. More information about these

and how to use a particular implementation is available via

<a href="choosing-reactor.html" shape="rect">Choosing a Reactor</a>.</p>

<p>

Twisted applications can use the interfaces in <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.application.service.html" title="twisted.application.service">twisted.application.service</a></code> to configure and run the

application instead of using

boilerplate reactor code. See <a href="application.html" shape="rect">Using Application</a> for an introduction to

Application.

</p>

<h2>Using the reactor object<a name="auto1"/></h2>

<p>You can get to the <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.reactor.html" title="twisted.internet.reactor">reactor</a></code> object using the following code:</p>

<pre class="python"><p class="py-linenumber">1

</p><span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span>.<span class="py-src-variable">internet</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">reactor</span>

</pre>

<p>The reactor usually implements a set of interfaces, but

depending on the chosen reactor and the platform, some of

the interfaces may not be implemented:</p>

<ul>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorCore.html" title="twisted.internet.interfaces.IReactorCore">IReactorCore</a></code>: Core (required) functionality.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorFDSet.html" title="twisted.internet.interfaces.IReactorFDSet">IReactorFDSet</a></code>: Use FileDescriptor objects.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorProcess.html" title="twisted.internet.interfaces.IReactorProcess">IReactorProcess</a></code>: Process management. Read the

<a href="process.html" shape="rect">Using Processes</a> document for

more information.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorSSL.html" title="twisted.internet.interfaces.IReactorSSL">IReactorSSL</a></code>: SSL networking support.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorTCP.html" title="twisted.internet.interfaces.IReactorTCP">IReactorTCP</a></code>: TCP networking support. More information

can be found in the <a href="servers.html" shape="rect">Writing Servers</a>

and <a href="clients.html" shape="rect">Writing Clients</a> documents.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorThreads.html" title="twisted.internet.interfaces.IReactorThreads">IReactorThreads</a></code>: Threading use and management. More

information can be found within <a href="threading.html" shape="rect">Threading In Twisted</a>.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorTime.html" title="twisted.internet.interfaces.IReactorTime">IReactorTime</a></code>: Scheduling interface. More information

can be found within <a href="time.html" shape="rect">Scheduling Tasks</a>.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorUDP.html" title="twisted.internet.interfaces.IReactorUDP">IReactorUDP</a></code>: UDP networking support. More information

can be found within <a href="udp.html" shape="rect">UDP Networking</a>.</li>

<li><code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.internet.interfaces.IReactorUNIX.html" title="twisted.internet.interfaces.IReactorUNIX">IReactorUNIX</a></code>: UNIX socket support.</li>

</ul>

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