[ZDP] Addition to seperate parts of zope architecture

[Tom Deprez]

ZServer

Previously we were talking that Zope could be used with almost every
WebServer (cgi enabled) on the planet and here we are, talking about a
server layer. Oh no, we weren't talking rubbish in the previous paragraphs.
It's still possible to use Zope with another webserver, although you might
loose some flexibility, like FTP. Now you may think that this the bottleneck
of Zope: 'You can use another webserver, but you loose some of the benifits,
so we push you to use the ZServer'... On the contrary! It is even possible
to make a construction so that ZServer acts as a layer between Apache and
ZServer. And this set-up, gives you the benefits of both worlds: i.e. with
Apache, you can still publish 'normal' web-sites and you can use the extra
benefits which Apache offers, like virtual servers etc. On the other hand
however, thanks to ZServer, you can access Zope through FTP and WebDav.
Isn't this a beauty? However, how beautifull it may sound at first, if
you're a beginner, I would advice you to wait for creating such
constructions... because it asks for several settings. So, at first I would
advise you to only use ZServer (or if you're already experienced with
another WebServer, used that instead). Why do I advise you to use ZServer if
you're a beginner? Well, ZServer is easy installed, almost no configuration.
And that's a releave if your a totally beginner. Ever installed Apache? It's
great, but you've to set several configuration files and therefor you need
to know a lot of things...

That said, we can actually talk about ZServer. ZServer wasn't there with the
first release of Zope. It's precessor is called ZopeHTTPServer which is a
simple Python based webserver. And if I may give my advise, it would be even
better to install ZopeHTTPServer than ZServer. ZopeHTTPServer needs totally
no configuration! And it works immediately. Offcourse, there is also another
side of the coin: it can't do everything! For instance, it can only publish
via HTTP and can only publish one module at a time. And it has no support
for thread pools. To overcome these problems, a successor is created, named
ZServer. ZServer itself is based on Medusa, which is created by Sam Rushing
and by which the Zope creaters have an agreement with. Also Medusa is a
Python server framework. Besides getting rid of the limitations of
ZopeHTTPServer, ZServer gives HTTP, FTP, WebDav and PCGI access. Other
protocols will probably follow (eg. FastCGI). So, ZServer is not only an
HTTP Server, like Apache, it is more. But then again Apache is very
specialised as a HTTP Server.

If you need more information on the provided protocols, then you can read
the following paragraphs

FTP Support

What is so special about this FTP support? Well, FTP support can become very
handy when creating your website. Instead of getting the rendered document,
because that's what you get you use the HTTP protocol, you get the contents
of the document. Besides this benefit, you get all other FTP protocol
benefits (like navigating the object hierachy with 'cd' command), next to
the things you can also do when working with HTTP protocol (e.g. replacing
content of Documents, Images and files. Creating or Deleting them).

WebDav Support

At the moment, WebDav is a relative newly protocol. It's almost nowhere
implemented... that it is implemented in Zope, only gives you an idea how
fast Zope is growing and updated! Basically, WebDav is an extension to the
HTTP/1.1 protocol. It uses some extra HTTP commands, like 'OPTIONS' to
implement it's functionality. Traditional webservers block commands they
don't recognize (even Apache needs a patch to allow these extensions of the
HTTP protocpm), instead of propagating the command to Zope, resulting in
breaking WebDav. Note however, that blocking of unrecognised commands is a
good policy. It surely makes everything much safer. In simple words WebDav
means that you can open an URL as a Web Folder. Its just like you would open
a local folder on your computer, but now this folder resides somewhere on
the net.

PCGI Support

The PCGI support enables the possibility to forward request from another web
server to ZServer. The other web server is then in charge of controlling the
CGI environment and HTTP headers. So this means that you're not using
ZServer for HTTP requests. Although you at that moment don't have to manage
the ZServer environment, you have to manage the environment of the other web
server which can impose a large overhead if you're not acquinted with that
one. However, it can give you the benefits of both worlds (see one of
previous paragraphs).


Tom.