EVOLUTION-MANAGER

Edit File: deployment.rst

Deployment ========== Nevow includes two major phases for deciding what HTML to render. :doc:`traversal` is the procedure by which a URL is mapped to a Python object which will perform the HTML generation. :ref:`glossary-page_rendering` is the process by which data objects are combined with an HTML template to produce the final output. Before any of this can take place, however, we must have an environment in which our Python code can run in response to an HTTP request, and HTML can be returned to the browser for rendering. This is called the :ref:`glossary-deployment_environment`. There are various deployment options for Nevow page code: - CGI: Simple deployment in almost any HTTP server - WSGI: A more complete and flexible way for deploying on many HTTP servers - Twisted.Web: A standalone application server process which includes a built-in HTTP server - Zomne: A small CGI which hands off HTTP requests to a long-running application server process, similar to FastCGI or SCGI CGI --- You can deploy Nevow on any webserver which uses the Common Gateway Interface. Using this method, your code is responsible for properly formatting and outputting the HTTP response headers, and Nevow is used only to generate the HTML body of your page. Here is the simplest possible CGI: .. code-block:: python #!/usr/bin/env python print "Content-type: text/plain\r\n\r\n", from nevow import rend, loaders class HelloWorld(rend.Page): docFactory = loaders.stan("Hello, world!") print HelloWorld().renderSynchronously() With this simple CGI you can use the Nevow template loaders and standard nevow template interpolation techniques in your CGIs. However, you do not get any :doc:`traversal` features, and you have to generate HTTP headers yourself. WSGI is a slightly higher-level deployment option which does not suffer these problems. Twisted.Web ----------- A convenient and powerful way to deploy Nevow applications is inside a process running the twisted.web HTTP server. With Python, Twisted, and Nevow installed, you have all you need to run a Web Application, with no other dependencies or external HTTP servers such as Apache required. Running your Nevow applications under twisted.web also gives you access to some of the more advanced "Live" features of Nevow, such as ``nevow.athena``. Currently, these modules require more control over the HTTP socket than CGI can provide. (This may change in the future.) Deploying a Nevow application under twisted.web requires a little more boilerplate, but can be considerably easier to set up than other deployment options because there are no external dependencies. Note that normally you should declare your Page classes in modules external to the twisted configuration file, but everything is included in one file here for brevity. Here is the minimal configuration file required to use Nevow with twisted.web: .. code-block:: python from nevow import rend, loaders, appserver class HelloWorld(rend.Page): docFactory = loaders.stan("Hello, world!") from twisted.application import service, internet application = service.Application("hello-world") internet.TCPServer(8080, appserver.NevowSite(HelloWorld())).setServiceParent(application) Save this file as "helloworld.tac" and start the server using the command: :: twistd -noy helloworld.tac Then visit your twisted.web server by viewing the url "http://localhost:8080/" in your browser. See the twistd man page for more information about what twistd is capable of, including daemonizing the HTTP server. Conclusion ---------- Nevow may be deployed in a number of environments, from the most restrictive to the most permissive. Writing a CGI can be an easy way to try out the Nevow templating mechanism, but can be slow. A long-running application server process can be a good way to get good performance as well as additional features such as in-memory server-side sessions, advanced automatic form handling with formless, and live page updating features such as nevow.athena. Which deployment option you choose will depend on the amount of control you have over your deployment environment, and what advanced features your application will require.