Faster Web Applications with SCGI
Once you're comfortable writing programs using SCGI, you may want to try adapting existing applications to use it. Some well-known Web applications, such as MoinMoin (a wiki) and Trac (a wiki-based collaborative development environment), are implemented as Python modules. Both of these examples come with CGI scripts in Python that can be called from Apache. The CGI scripts are very short; they really don't do anything except import the application's modules and invoke a function on them.
If you find an application like that, all you really need to do to make it work with SCGI is take that little bit of Python code and move it into a produce() method, as in the examples you've seen here. If you have SCGI 1.12 or newer, you also might want to take a look at an alternative SCGIHandler method, produce_cgilike().
That's about all we have room for. If you wonder about how the CGI parameters work, try looking at the CGI standard, which calls them “request meta-variables” (see Resources).
Finally, a word of warning. You'll notice that the last example program dies horribly if you fail to pass the expected arguments. The SCGI server replaces the failing processes, so in this case, there's no real problem. But, this should remind you how careful you need to be when writing Web applications. Never trust the input you receive from outside! If a program can be crashed, someone can probably subvert it or take it out of action. People all over the world do that sort of thing for fun or profit, so take the risk seriously.
SCGI Downloads: quixote.python.ca/releases
SCGI Home Page: www.mems-exchange.org/software/scgi
CGI Standard: ftp.rfc-editor.org/in-notes/rfc3875.txt
More on SCGI with Python and Apache2: thaiopensource.org/development/suriyan/wiki/UsingScgi
Perl Interface: search.cpan.org/~vipercode/SCGI/lib/SCGI.pm
Lisp Interface: randallsquared.com/download/scgi
Jeroen Vermeulen works for the Open Source Department of the Thai Software Industry Promotion Agency. He's currently working on Suriyan, a server system for those who don't have time for server systems.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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- Managing Linux Using Puppet
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
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