maurice munoz <[EMAIL PROTECTED]> asks:
> > How fast is CGI(perl) compared to Servlets.
> > How is that determined.?
The typical servlet article or book just blithely states that
servlets are much faster than CGI scripts. The original servlet white
paper Sun released mentioned some of the cases where CGI scripts might
be as fast or faster, but it doesn't seem like anbody has actually
done any formal comparisons.
If you're asking how fast "CGI" per se is, compared to servlets,
the question doesn't make any sense. CGI is just a standard for how
to ask the web server to run a program and send the output to the
browser. You probably mean to ask, how fast are CGI scripts, compared
to java servlets. However, this also doesn't make any sense, because
CGI programs can be implemented in a huge variety of ways. They're
usually implemented in some flavor of scripting language, which has
lead to the common usage of the phrase "CGI script" to refer to CGI
programs. But CGIs can be written in Perl, C, C++, Cobol, Fortran,
even Java :-).
Okay, so assuming that you're talking about the mainstream of CGI
programming, like Perl, Python, etc, the answer in a large part still
depends on how the CGI scripts are implemented, and how they're run.
Leave aside issues of how the particular programmer chose to structure
the code. Any demo can be rigged, as the recent Microsoft-funded
Mindcraft comparison between Linux and NT demonstrated. Give me a
skilled Perl coder and a skilled Java coder and I'll have both of them
code pathological approaches that will surely lose compared to normal
scripts or servlets. Likewise, have one code in a "moderate" fashion
while the other goes all-out to optimize and I'll bet I can have either
one win.
So assume the programs are both designed and coded in a
moderately sensible way. The speed issue usually boils down to a
number of factors, only one of which is how the speed of the "typical"
language implementation:
The Perl crowd, for example, maintains that Perl is often as fast
as well-coded C for doing text-intensive stuff - and of course, not
every C coder is going to be able to write code up to that level of
quality. Of course, I've never seen any statistical studies and proof
of this fact, either. I did hear vague rumors last week that somebody
did a study that showed Perl code loses to Java code (not CGI scripts,
just plain code) in most cases, but again, I don't know the details -
for all I know, the "most cases" doesn't include the stuff used for
80% of CGI scripting.
Other factors that have an impact are the circumstances of how
the program is started, whether it's kept in memory, when compilation
happens, where the interpreter or virtual machine that runs the
program needs to be loaded, whether the program needs to open
connections to any resources (like database handles) or can get them
from a pool or keep persistent resources, and so forth.
Since CGI scripts are typically written in Perl and start from
scratch for every request, there are a number of factors we might
assume are present: forking a process to run the script, loading the
script file, loading in the the Perl interpreter, loading any modules
required by the script, loading any resources (opening database
handles), and then finally actually running the script, doing whatever
it does, sending the results back to the user, and then throwing all of
that away to start over again next time.
Servlet proponents point out, quite rightly, that all of that
takes up a heck of a lot of resources - and time. However, Perl
proponents point out that some fairly common techniques and tools -
like mod_perl, which makes the perl interpreter part of the webserver,
and fastCGI, which runs the CGI scripts as a separate server the
webserver can hand off CGI requests to, both of them providing tools
for persistent resources (usually database handles) and running
scripts as daemons - will deal with most of the above issues.
On the flip side, writing a simple "standard" CGI script in Perl
is quite easy and fast; because you're throwing everything away after
running the script, you don't have to worry nearly as much about
things like memory leaks, allocating and deallocating variables, etc.
Compared to a servlet, CGI scripts are a snap to write. However, when
you switch to writing CGI scripts to run as daemons under mod_perl or
fastCGI, with persistent data and resource pooling, writing a perl
script is significantly trickier - kind of like writing a servlet.
Steven J. Owens
[EMAIL PROTECTED]
[EMAIL PROTECTED]
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