My New URL Shortening Service

Joshua, Koen and I were discussing URL shortening services (tinyurl, bit.ly, is.gd, etc.) over lunch this week, and so I decided to write my own (UrlShrink) available here: http://www.barneyb.com/applications/urlshrink/app/

It's ludicriously simple.  I opted for memory storage (think Mailinator) instead of a database for performance reasons.  With the load I anticipate, I think it'll be a deciding factor.  I've also included stable URL generation (which I don't know that any other service does), so if you try to shorten the same URL repeatedly, you'll get the same result every time.  As well as being more user friendly, this further increases performance because it prevents artificial bloat to the keyspace, thereby making searches marginally faster.

The app is all CFML, aside from an Alias and couple RewriteRules to make the URLs pretty.  Here are the rules:

Alias   /applications/urlshrink/app /home/www/urlshrink
RewriteRule ^(/applications/urlshrink/app)/geturl   $1/geturl.cfm   [PT]
RewriteRule ^(/applications/urlshrink/app)/shorturl/([^/]*) $1/forward.cfm?key=$2   [PT]

And here's the CFML (in five files) in case anyone else is interested in running their own service:

Application.cfm:
----------------
<cfapplication name="urlshrink" sessionmanagement="false" />
<cfset urlRoot = "http://www.barneyb.com/applications/urlshrink/app" />
<cfif NOT structKeyExists(application, "forwardLookup")>
        <cfset application.forwardLookup = {} />
        <cfset application.reverseLookup = {} />
</cfif>

index.cfm:
----------
<cfoutput>
<h1>UrlShrink</h1>
</cfoutput>
<cfinclude template="frm_shrink.cfm" />

frm_shrink.cfm:
---------------
<cfoutput>
<p>To make a shorter URL, just paste your long URL here and hit "Go!".
</p>
<form method="post" action="#urlRoot#/geturl">
URL:
<input name="url" size="50" />
<input type="submit" value="Go!" />
</form>
</cfoutput>

geturl.cfm:
-----------
<cfif structKeyExists(application.reverseLookup, form.url)>
        <cfset key = application.reverseLookup[form.url] />
        <cfset newUrl = urlRoot & "/shorturl/" & key />
<cfelse>
        <cfset key = hash(form.url, "SHA-256") />
        <cfset newUrl = urlRoot & "/shorturl/" & key />
        <cfif len(form.url) GT len(newUrl)>
                <cfset key = hash(form.url, "SHA-512") />
                <cfset newUrl = urlRoot & "/shorturl/" & key />
        </cfif>
        <cfset application.forwardLookup[key] = form.url />
        <cfset application.reverseLookup[form.url] = key />
</cfif>
<cfset percentSavings = -1 * (len(newUrl) - len(form.url)) / len(form.url) * 100 />
<cfoutput>
<h1>UrlShrink</h1>
<p>Your shortened URL is:
</p>
<p><a href="#newUrl#" style="white-space:nowrap;">#newUrl#</a>
</p>
<p>You've reduced the length of your URL by an exceptional #numberFormat(percentSavings, ".0")#%!
</p>
<h2>Shrink Another?</h2>
<cfinclude template="frm_shrink.cfm" />
</cfoutput>

forward.cfm:
------------
<cfparam name="url.key" default="" />
<cfif structKeyExists(url, "key") AND structKeyExists(application.forwardLookup, url.key)>
        <cflocation url="#application.forwardLookup[url.key]#" addtoken="false" />
<cfelse>
        <cfoutput>
        <h1>UrlShrink</h1>
        <p>The URL you're visiting isn't recognized.  Perhaps you'd like to shrink your own?
        </p>
        <cfinclude template="frm_shrink.cfm" />
        </cfoutput>
</cfif>

Total size is 1,901 bytes; that's pretty respectable for such a full-featured app.