ArcGIS Server 9.2, Working Around The Browser Limiting HTTP Connections!

Ok, so I was wanting to improve the performance of ArcGIS Server 9.2 even more! Yes more than than using cached services! I have a bundle of cached services and I am serving these up over the web. In order to do so it means certain things have to optimized so that its even quicker.

Firstly I generated my cache so that the images are a combination of JPEG and PNG8 files. This means they are smaller and fast for the user to download.

All good and it works really well, but I now point you to an article that Art Haddad wrote up a few months ago: http://artsplace.spaces.live.com/blog/cns!56D6C3AF278BFBAC!232.entry. He talks about how WinInet limits the number of simultaneous connections that it makes to a single HTTP server.

“WinInet limits the number of simultaneous connections that it makes to a single HTTP server. If you exceed this limit, the requests block until one of the current connections has completed. This is by design and is in agreement with the HTTP specification and industry standards.”

So I was looking at ways to work around this. As Art was testing you can change it locally on every machine but that’s not what we are wanting to do for a web based application. How does Microsoft Local Live and Google Maps address this problem? Well they create multiple domain names and serve the site and images up over these.

What do I mean by this? Have a look at a screenshot I took of Fiddler running on my machine while I was testing my application:

Click on the picture above to see it in a bigger size. Basically I created a bundle of domain names on our DNS servers. mcc1, mcc2, mcc3 and assigned ArcGIS Server to work with these. Now the different cached services I have running are served up over these three domain names making the application even faster and to the user! As mentioned above, this is the same way Microsoft Local Live and Google Maps work!

I’m currently looking at ways to make things even more faster. I have a few more ideas and I am trying to get around a few restrictions. So far its working really well. I’m very impressed! I will trying a bundle of things over the next couple days so will post more when I can If any one has feedback it will be good to hear.