WSGI, CGI, Framework “A”, … and Apache

For the past week I have been attempting to implement a Django framework properly utilizing WSGI to prototype and develop webapps fast on a VPS I have running CentOS 7 and Apache 2.4 with cPanel/WHM. As with everything backend on a Terminal emulator on a one man team, it was a pain in the ass. I definitely learned a lot along the way towards my “helloworld.py”:

Although, there isn’t anything that beats a properly configured VPS/dedicated web server except for my potato. Jussst kidding. Obviously.

Anyways, I came across this Quora answer while sprucing up the brief knowledge of the topic I can confidently say isn’t too much at all. Obviously wanting to get over with the installation procedure while learning a buck or two worth of knowledge comes unfortunately and unusually–but usually–at the last minute or after the fact.

Say no more to newbie backend pains regarding the following, and it’s all no thanks to obscure, indirect explanations that fragment all these concepts from each other. Here it goes.

How WSGI, CGI, and the frameworks are all connected ?

Apache listens on port 80. It gets an HTTP request. It parses the request to find a way to respond. Apache has a LOT of choices for responding. One way to respond is to use CGI to run a script. Another way to respond is to simply serve a file.

In the case of CGI, Apache prepares an environment and invokes the script through the CGI protocol. This is a standard Unix Fork/Exec situation — the CGI subprocess inherits an OS environment including the socket and stdout. The CGI subprocess writes a response, which goes back to Apache; Apache sends this response to the browser.

CGI is primitive and annoying. Mostly because it forks a subprocess for every request, and subprocess must exit or close stdout and stderr to signify end of response.

WSGI is an interface that is based on the CGI design pattern. It is not necessarily CGI — it does not have to fork a subprocess for each request. It can be CGI, but it doesn’t have to be.

WSGI adds to the CGI design pattern in several important ways. It parses the HTTP Request Headers for you and adds these to the environment. It supplies any POST-oriented input as a file-like object in the environment. It also provides you a function that will formulate the response, saving you from a lot of formatting details.

What do I need to know / install / do if I want to run a web framework (say web.py or cherrypy) on my basic CGI configuration ?

Recall that forking a subprocess is expensive. There are two ways to work around this.

  1. Embeddedmod_wsgi or mod_python embeds Python inside Apache; no process is forked. Apache runs the Django application directly.
  2. Daemonmod_wsgi or mod_fastcgi allows Apache to interact with a separate daemon (or “long-running process”), using the WSGI protocol. You start your long-running Django process, then you configure Apache’s mod_fastcgi to communicate with this process.

Note that mod_wsgi can work in either mode: embedded or daemon.

When you read up on mod_fastcgi, you’ll see that Django uses flup to create a WSGI-compatible interface from the information provided by mod_fastcgi. The pipeline works like this.

Apache -> mod_fastcgi -> FLUP (via FastCGI protocol) -> Django (via WSGI protocol)

Django has several “django.core.handlers” for the various interfaces.

For mod_fastcgi, Django provides a manage.py runfcgi that integrates FLUP and the handler.

For mod_wsgi, there’s a core handler for this.

How to install WSGI support ?

Follow these instructions.

http://code.google.com/p/modwsgi/wiki/IntegrationWithDjango

For background see this

http://docs.djangoproject.com/en/dev/howto/deployment/#howto-deployment-index

Source: http://stackoverflow.com/questions/219110/how-python-web-frameworks-wsgi-and-cgi-fit-together

 

Web DOJO

Full Page Image (now you have a spankin’ website…that only took 1 image and 18 seconds.) Proof of concept below:

  1. pdag.io/lol/1.html
  2. pdag.io/lol/2.html
  3. pdag.io/lol/3.html
  4. pdag.io/lol/4.html

FULL SCREEN OVERLAY NAVIGATION (super cool) & THIS

Accordian (Great for Product Description Teasers and more)

Responsive Tables (Great for dynamically updated content, HTML)

Modal Image

Verticle Tabs (Product Tour example/applicable)

Pagination (!)

Simple To-Do List

Animated Buttons

Pop-ups AND Tooltips (Great way to guide customers to do things)

File Copy (PHP)

Parallax Scrolling (Great for a long, one page form.) In addition with “Center Website”

ALERTS (CLEAN AND IMPOSSIBLE TO MISS, Effective communication to visitor)

Clean Syntactic Sugar, Back to Basics Website

Image Overlay (yeah, screw paying for WordPress price gouging plugin, JK, this is on a WP site)

Image Blur/Grayscale/Coloring (CSS) (who needs photoshop?!)

 

Back/Forward Navigation

Height Equilibration

Hide & Show (element) / class

Table Sort (Javascript)

Thumbnail Preview (great for reviewing uploaded image and email inclusions)

Coming Soon Landing Page

Image processing … e.g. gold mine of amazing modules.

CSS Switch

Snackbar

Cards ’nuff said

Avatar

John Doe

Architect & Engineer

Clean Pricing Table

  • Basic
  • $ 9.99 / year
  • 10GB Storage
  • 10 Emails
  • 10 Domains
  • 1GB Bandwidth
  • Sign Up

Responsive Modal Login Form (Awesome)

Basic Contact Form (PHP)

Personal Card (Great for personal website)


global $wp_query; //class

Internet Black Hole

http://www.caida.org/projects/network_telescope/

Originating from “a globally routed /8 network (approximately 1/256th of all IPv4 Internet addresses) that carries almost no legitimate traffic…traffic destined to darkspace has evolved to include longer-duration, low-intensity events intended to establish and maintain botnets.”

“By monitoring these unsolicited responses, researchers can identify denial-of-service attack victims and infer information about the volume of the attack, the bandwidth of the victim, the location of the victim, and the types of services the attacker targets.”

“Scans are automated, semi-automated, and manual attempts to locate exploitable computers on the Internet.” – nmap scripting

“The scan traffic often differs from other types of traffic visible on the network telescope because it is not driven by chance.” – port and address range scanning /24

“Rather, the attacker’s byzantine motives in selecting scan targets appear arbitrary from the perspective of the recipient of the scan.” –  TCP-SYN/TCP-ACK/ICMP/SCTP/UDP/etc pings

“The UCSD Network Telescope observes many types of scans continually, including ping based scans for the existence of a device at a given IP address, sequential scans of ports on a single IP address, methodical scans for a single or a small number of vulnerable ports sequentially through an IP address range, and even scans utilizing TCP resets.”

Related: Serious Vulnerabilities Patched in CUPS Printing Service (og)

https://wiki.debian.org/AirPrint

Real-time graphs:

http://www.caida.org/data/realtime/passive/?monitor=equinix-sanjose-dirA&row=timescales&col=sources&sources=app&graphs_sing=ts&counters_sing=bits&timescales=24&timescales=168&timescales=672&timescales=17520