1.1 A Brief History of the Web
No book on web technology would be complete without a brief look at
how the World Wide Web (WWW) has become as popular as it is today.
The Web has come a long way since the days when the first hypertext
documents were sent over the Internet. In 1989, when the physicists
at the CERN laboratory
proposed the idea of sharing research information between researchers
using hypertext documents, they had no idea how big the Web would
grow or how essential it would become to daily life for much of the
industrialized world. The Web is now an accepted part of our
vernacular.It took a while for the benefits of using the Web to become clear to
others outside of CERN, but as we all know, it eventually erupted
into what we use today. From its beginnings, the Web was designed for
dealing with static documents, but it was a natural progression to
want the ability to generate document content dynamically. The
Common Gateway
Interface (CGI) was created to do that very thing. CGI is
a standard that allows web servers to interact with external
applications in such a way that hypertext pages no longer have to be
static. A CGI program can retrieve results from a database and insert
those results as a table in a hypertext document. Likewise, data
entered into a hypertext page can be inserted into the database. This
technology opened up infinite possibilities and, in fact, started the
Internet craze of the mid-1990s and today.Although CGI applications are
very good at what they do, there are some serious limitations to this
approach. For one thing, CGI applications are very
resource-intensive. A new operating system (OS) heavyweight process
is created to handle every request that comes from a browser. Once
the CGI script is finished executing, the process has to be reclaimed
by the OS. This constant starting and stopping of heavyweight
processes is terribly inefficient. You can imagine how bad the
response time might be if hundreds of concurrent users were making
requests to the same web application. Another major limitation of CGI
is that it's difficult to link to other stages of
request processing, because it is running in a separate process from
the web server. This makes it difficult to handle things such as
authorization, workflow, and logging.A few alternatives to standard CGI applications have been put
forward. One alternative is
FastCGI,
a language-independent extension to CGI that doesn't
have the same process model as standard CGI. It's
able to create a single heavyweight process for each FastCGI program,
allowing multiple requests to run within the same process space.
However, when clients interact concurrently with the same FastCGI
program, the program needs to create a pool of processes to handle
each request. This is not much better than standard CGI. Another
problem with FastCGI applications is that they're
only as portable as the languages in which they are written. Other
alternatives to CGI include
mod_perl for
Apache, NSAPI for
Netscape, and ISAPI
for Microsoft's IIS web server. While these
solutions often offer better performance and scalability than
standard CGI programs, they still have portability issues.In 1997, while the Java language was experiencing tremendous growth
and use by application developers, the Java Servlet technology was
created. This new web technology opened up an entirely new avenue for
web developers to explore. |
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