Searching all Craigslist.org Cities

March 31, 2005

If you've ever used Craigslist.org-- a fantastic and rather odd resource-- you may have noticed that it's heavily biased towards per-city searches. This is a pain if you want to do a national search across all cities that Craigslist.org operates sites for. A while back, I found a web page offering an all-city search, but I wasn't happy with the performance. And now it's been perma-banned by the Craigslist.org brass, so.. time to roll up my sleeves and implement my own improved Craigslist.org "all cities" jobs search.

My search is dramatically faster than Chovy's, because I use HTTP compressed queries and progressive Response.Write and Response.Flush output rendering as the queries are returned. This is one of my major beefs with ASP.NET; there's no way to do any kind of progressive page rendering using the ASP.NET architecture. (And no, iframes do not count.) The entire page renders to a buffer, then-- and only then-- it is all displayed at once. Not exactly an ideal web experience if you're building large pages.

Progressive output is particularly critical for a long-running web page process like this one. Otherwise you'd be sitting there looking at a whole lot of nothing until all ~30 cities were queried. Technically it takes the same amount of time, but there's a huge psychological difference between seeing immediate, if partial, results, and waiting the same amount of time looking at a blank screen. I always try my best to design for progressive rendering, even in Windows Forms.

Interestingly, I had to disable IIS6 dynamic compression to get Response.Flush to behave as expected. The good news is that disabling IIS6 compression can be done on a per-website per-folder basis:

I used the following commands from the \Inetpub\AdminScripts directory:

cscript adsutil.vbs set w3svc/{site#}/root/{vdir name}/DoStaticCompression False
cscript adsutil.vbs set w3svc/{site#}/root/{vdir name}/DoDynamicCompression False

To get the {site#}, click on the "Web Sites" node in the IIS manager and note the "Identifier" number in the right-hand Detail pane for the top-level website that contains the NTD application.

My favorite Craigslist posting, by the way, is this one.