As anybody who has run a growing website or blog knows, response time is going to get worse with the more users you have visiting your site. The users come from all angles, RSS feeds, homepage visits, search engine visits, people sealing your static files that you host, and pretty much anything else that can be served over HTTP. The solution to this problem is to off load your static content on to a Content Delivery Network or CDN. CDN providers cost a lot of money though, so it is nothing for us mere mortals with one server can afford.

But thanks to Google anyone can now run their own CDN for free on Googles servers. Lucky for you and me Google has made the process really painless and you can even have the CDN under you own domain name. In my case static.coderjournal.com.

What Is A Content Delivery Network?

According to Wikipedia:

A content delivery network or content distribution network (CDN) is a system of computers networked together across the Internet that cooperate transparently to deliver content most often for the purpose of improving performance, scalability, and cost efficiency, to end users. The first web content based CDNs were Speedera, Sandpiper, Mirror Image and Skycache, followed by Akamai and Digital Island.

Basically it is a network of computers around the world that serves your content to the end user closest to one of those many servers around the world. This method of delivery cuts down on server overload, DNS hops, and delivery time.

When sites like Microsoft, Yahoo, Google, or Amazon delivery content they use Content Delivery Networks (CDN’s) to host most of their content, especially static files such as images, stylesheets, downloads and anything else you can think of. The reason they do this is to reduce load on their application servers, that serve dynamic content, such as PHP or ASP.NET pages.

What Is Google App Engine?

So you may ask what is Google App Engine:

Google App Engine lets you run your web applications on Google’s infrastructure. App Engine applications are easy to build, easy to maintain, and easy to scale as your traffic and data storage needs grow. With App Engine, there are no servers to maintain: You just upload your application, and it’s ready to serve your users.

You can serve your app using a free domain name on the appspot.com domain, or use Google Apps to serve it from your own domain. You can share your application with the world, or limit access to members of your organization.

App Engine costs nothing to get started. Sign up for a free account, and you can develop and publish your application for the world to see, at no charge and with no obligation. A free account can use up to 500MB of persistent storage and enough CPU and bandwidth for about 5 million page views a month.

Google has also announced a very very affordable price plan that any mere mortal can afford. They are not ready to start charging people yet, but here are the details:

• $0.10 – $0.12 per CPU core-hour
• $0.15 – $0.18 per GB-month of storage
• $0.11 – $0.13 per GB outgoing bandwidth
• $0.09 – $0.11 per GB incoming bandwidth

How do I setup my own CDN using Google App Engine?

To use Google App Engine you need to do a couple things that readies you computer to publish your static content to Google. Please take note that my setup is for Windows, but you can easily modify the process for any other OS.

Setup

1. You need to download and install Python on your computer. You may already have it if you are using a Unix environment (i.e. Linux or Mac OS X). If you need to download it or would just like to check to see if it is up to date, please visit http://www.python.org/download/ and download the correct version for you operating system.
2. Install Python to c:\Program Files\ (all my scripts that I have designed to make the publishing to Google are going to be using this path).
3. You will also need Google App Engine SDK which is available at http://code.google.com/appengine/downloads.html. Download the version that is for you OS. Note that the SDK will check for the Python install, so make sure you install it before the SDK.
4. Sign up for Google App Engine at http://appengine.google.com/, you will need a valid Google account. I suggest you sign up for a Google Apps account and use that as your Google account. Why I suggest this will become apparent later on.
5. Once you are done with the setup process you need to create an application. Click the “Create an Application” and give your application a name (called “application identifier”). This is a unique name for all Google App Engine applications. For example I set my application identifier to “coderjournal”. Click though to the next part of the application, if this is your first time registering an application you need to specify your cell phone number and confirm your account with a SMS code that Google sends you.

Publish To Your CDN

1. Download my publishing files, hosted on my CDN, at http://static.coderjournal.com/downloads/coderjournal-cdn.zip
2. Create a directory on your computer specifically for you CDN files. My directory is c:\websites\static.coderjournal.com. Fill this directory with all your static files you want hosted on your CDN. Fill it full of all your css, downloads, flash, images, javascripts, videos, and anything else you want hosted.
3. Unzip the files I provided to you in step 1 into the directory you created in step 2.
4. Next we need to edit the YAML configuration file. Open the app.yaml file in your favorite text editor and change application: coderjournal to application: {your application identifier}.
5. Next go down and edit your static directories, in mine I have css, downloads, flash, images, and js. You can create your own by just modifying the ones I put in the file.
6. If you installed the Google App Engine SDK in the default directory and Python in c:\Program Files\ then skip to step 7. The next part is also required if you are using the x64 version of Windows, because Google App Engine SDK installs in c:\Program Files (x86)\. So change the paths in publish-cdn-coderjournal.bat to your actual paths.
7. Now double click on publish-cdn-coderjournal.bat and a command window will display. Fill in your Google account and password that you used to sign up for the Google App Engine account. And you content will start to publish.
8. You now have you own private CDN that can be accessed at http://application-identifier.appspot.com.

Using Your Own Domain (Optional)

1. If you created your own Google App as suggested up in Setup step 4, you can create your own custom domain for your CDN. If you didn’t, don’t worry just create one, and follow the steps below.
2. Go to the dashboard of your Google Apps and click “Add more services”.
3. Under other services you will see Google App Engine and a place to enter your application identifier. Enter you application identifier and click “Add It Now”.
4. It will take you to the next page where you enter in the domain you want for your CDN, I suggest something simple like static.yoursite.com.
5. Then you just need to follow the steps for adding a CNAME to your DNS and you are ready to go with you custom domain.

How do I use my own CDN?

Well this is the cool part! You just use the absolute path to your files. For example if you wanted to host the image to your right you would just use the following in your HTML:

Potential Gotcha: I forgot to mention that currently the files hosted statically are case-sensitive. I have reported this issue to Google, hopefully they will correct it soon. http://code.google.com/p/googleappengine/issues/detail?id=466

<img src="http://static.coderjournal.com/images/ideapipe-logo.png" />

It is really that simple. Now comes the cool part that I need your help with, and proof that this is really a true CDN. I would like to see how many different IP Addresses my CDN points to. So far I was able to find the following IP addresses:

• 72.14.207.121
• 64.233.179.121
• 66.249.91.121

That point to:

static.coderjournal.com

To see what IP Address you get on your local machine just pull up the command prompt and type:

ping static.coderjournal.com

Please report your findings in the comments below. I am sure everybody would love to see how big Google’s CDN really is.

I was having a conversation with my best friend a few days ago and we got on the subject of our preferences for how URL’s are rendered for blogs.

I fall on the side of lowercase letters and hyphens splitting the words:

http://www.somesite.com/2008/05/my-url-preference-is-like-this/

He falls on the side of title case lettering and no hyphens splitting the words:

http://www.somesite.com/2008/05/HisURLPreferenceIsLikeThis/

He has his reasons I have mine, I just think mine are more valid. Sorry Al that is my opinion. I am going to layout why I think mine are more valid, with an example from Celebrity Jeopardy. For those of you who aren’t familiar with this famous skit:

Celebrity Jeopardy! was a recurring sketch on Saturday Night Live. It parodies the Celebrity Jeopardy! edition of the television game show Jeopardy! where celebrities compete and the game’s level of difficulty is significantly reduced. Thirteen sketches have been aired to date, two per season from 1996 to 2002, and one in 2005.

Before I get to my commentary lets first watch this excerpt from Saturday Night Live’s Celebrity Jeopardy!:

I really tried to find a good example of one of the famous Sean Connery mess ups in a legal video sharing site, but none of them had anything usable. The skit I was really looking for was the famous “An Album Cover” where Sean Connery pronounces it as “Anal Bum Cover”.

As you can see Norm MacDonald playing the character of Burt Reynolds transforms the category in Celebrity Jeopordy!, on purpose for comedy reasons. In my analogy Google is going to be the Burt Reynolds of your search, however instead of finding the wrong words on purpose it is going to do it because it is a dumb machine that does what it is asked even if the results are not contextually accurate.

Notice in the image above, in the highlighted words, Google finds both “An Album Cover” and “Anal Bum Cover”. This is because Google understands that the words you may be looking for don’t always fall in the same order and spacing as the exact phase you are looking for. This is something that SEO experts have known for a long and try to control so that their content shows in the top spot for the keywords they designed in to the page.

If you don’t control your URL, which is one of the highest ranking keywords on your site. You could end up decreasing the effectiveness of your keywords, as an almost duplicate keyword penalty. Granted I don’t know if something like this exists as a penalty, but when you are dealing with SEO it never hurts to be as careful and precise as possible.

So again I ask which URL would you rather have? Now knowing how a URL can be misconstrued :

http://www.somesite.com/2008/05/an-album-cover/

http://www.somesite.com/2008/05/AnAlbumCover/

So this is my way of saying be careful what your URL spells out, you may get unintended search rankings that you may not want, or you may offend a person who reads the URL wrong. Either way it is always good to control your environment with in reasonable means to make sure the message is received as you were intending it.

note: There are other factors in play that yielded the search results above.  However one thing that you will notice is that none of the URL’s were falsely highlighted, that is because they used a non-whitespace character to break up the words.

First off I would like to say that many of my readers are very intelligent, they picked up on a one line sentence in my last post about my new design and Coder Journal switching from Linux to Windows.

I also moved hosts from GoDaddy’s shared Linux hosting. To GoDaddy’s virtual dedicated hosting on Windows. This proved difficult since URL Rewriting isn’t currently built in to IIS 6.0 like it is in Apache. I will talk a little about this setup in a later post.

Switching from Linux to Windows wasn’t the part that really intrigued many of them, it happens every day so why would it? It was the fact that I was able to get the same level of URL Rewriting out of IIS 6.0 as I was out of Apache’s mod_rewrite and still be able to make WordPress look and function like it was running on Apache.

So to get started I just want to say, while I know there are other solutions out there to get WordPress hosted on IIS with the exact same outcome as what I am going to present below. I did this for the following reasons:

1. I am a .NET guy and I love developing software that is popular on other platforms on .NET just to see if it can be done.
2. I also believe in Eating One’s Own Dog Food, and the URL Rewriter and Reverse Proxy that I am presenting below, and that is used in Coder Journal, is my own creation.

What This Post Covers

This post is meant to provide an insight in to a technology, Reverse Proxy, that many developers are unaware of and it will be demonstrated through the eyes of my blog and how it works in regards to WordPress/IIS 6.0. Some of the basics will be covered such as the working of a URL Rewriter and Reverse Proxy. This post will not cover how to code a URL Rewriter or Reverse Proxy in C#. The reader should also have a basic understanding of how RegEx, HTTP, and URL Rewriters.

The Problem

On IIS 6.0, and previous versions, due to a lack of any standardized URL Rewriting process built in, so developers have to take nice visitor and SEO friendly URL’s like this:

http://www.coderjournal.com/2008/02/10/sample-post/

And make IIS 6.0 compatible ugly URL’s, which may or may not be SEO friendly, and neither URL is as visitor friendly as the one above.

http://www.coderjournal.com/?p=123
http://www.coderjournal.com/index.php/2008/02/10/sample-post/

My Solution Used On Coder Journal

The solution I choose was influenced by a number of factors, a couple that will change for the better when IIS 7.0 is released. The factors are:

• I need to run PHP for WordPress.
• I need to run FastCGI for IIS 6.0 to get the best performance out of PHP.
• .NET and PHP run separate from each other, so I cannot use a .NET URL Rewriter to control which PHP file is chosen to run. (This changes in IIS 7.0 with Integrated Pipelines)
• I need to pass all requests to www.coderjournal.com through .NET, which has a performance loss for rendering static files such as image, and text files. (This changes in IIS 7.0 with Integrated Pipelines)
• I need to keep the URL’s friendly for visitors and SEO.

So because of what I listed above I needed to create two web servers to host www.coderjournal.com, which I will talk about later on in this article. One of the servers is the public interface to www.coderjournal.com, which I will call frontend, and the other is the Backend WordPress web server, which I will call backend that only handles standard WordPress with the ugly URL’s listed above, this one is not public. The picture will demonstrate the structure better than I can explain.

As you can see, from the above picture, all requests to WordPress are handled by the frontend server for this blog. This all happens through a technique known as Reverse Proxy.

A reverse proxy dispatches in-bound network traffic to a set of servers, presenting a single interface to the caller. For example, a reverse proxy could be used for load balancing a cluster of web servers. In contrast, a forward proxy acts as a proxy for out-bound traffic. For example, an ISP may use a proxy to forward HTTP traffic from its clients to external web servers on the internet; it may also cache the results to improve performance.

So with out going in to a deep explanation of how I was able to accomplish the reverse proxy, basically for every request that comes in to frontend server that meets a certain criteria I make another HTTP web request to the backend server and then write it’s response back to the original frontend server request.

Step 1 – Setting Up .NET to Process All Requests

Setup your frontend server to process everything through the .NET framework.

1. Open IIS and right-click on the website and select Properties.
2. Click the Configuration button under Application Settings section
3. Click the Insert… button to create a new wildcard mapping
4. Set the executable textbox to aspnet_isapi.dll file location.
   for .net 2.0, 3.0, 3.5: C:WindowsMicrosoft.NETFrameworkv2.0.50727aspnet_isapi.dll
5. Make sure the checkbox Verify that file exists is not checked.
6. Press OK to confirm and close all the windows.

Step 2 – Install PHP/WordPress

Just follow this article on IIS.NET for installing PHP/WordPress on IIS 6.0. You may also want to install FastCGI, I recommend this, but it is optional.

Step 3 – Setting Up the URL Rewriter and Reverse Proxy Rules

The criteria for the requests are put inside the URL Rewriter Rules files. But before the proxy request is made, I must check to make sure the file being requested doesn’t already exist on the frontend server. If it does exist on the frontend server I don’t want to make a reverse proxy request. The following is the code used to do that.

# any file that exists just return it
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^(.*) $1 [L]

Then after I check to make sure the file doesn’t exist on the frontend server I make the request to the backend using the following rules.

# proxy all connections through to the backend server
RewriteRule ^(/[0-9]{4}/.*) http://backend/index.php$1 [P]
RewriteRule ^(/tags/.*) http://backend/index.php$1 [NC,P]
RewriteRule ^(/topics/.*) http://backend/index.php$1 [NC,P]
RewriteRule ^(/author/.*) http://backend/index.php$1 [NC,P]
RewriteRule ^(/comments/feed/.*) http://backend/index.php$1 [NC,P]
RewriteRule ^(/page/.*) http://backend/index.php$1 [NC,P]
RewriteRule ^(.*) http://backend$1 [P]

Conclusions

To get the exact same setup as I have, you will need the following software, which is all free for download:

• Managed Fusion URL Rewrite and Reverse Proxy
• GoDaddy Virtual Dedicated Windows Server
• FastCGI for IIS 6.0
• PHP 5.2+ for Windows
• Latest Version of WordPress
• MySQL 5.0+

As always if you have any questions about the setup or the performance please post them below in the comments and I will answer them and or update the post as needed.

Happy Coding.