How do I connect up my Amazon EC2 instances without manually modifying config files?

Question

I have a three-tier Windows-based web application bundled into 3 AMIs on Amazon EC2 that I use for load testing.

• An ASP.NET web application on IIS
• An .NET application server
• SQL Server

After I launch them, the config files of each tier needs modifying to update the IP addresses.

At the moment I am doing this manually: I connect to the webserver instance via remote desktop and modify the config file to point to the new IP of the application server instance. Then I do the same with the application server to change the IP in the connection string.

This must be a common requirement and I must be missing something obvious. There must be a better way!

• I could use Elastic IP addresses, but these machines are only provisioned for a couple of hours at a time, and I would be charged for the addresses when they were NOT in use (which would be most of the time).

• Is there some way of persistently naming the machines? Can I somehow get all the machines on the same network and use machine names instead of IP addresses?

• I could write some nifty PowerShell script that would perform the modifications remotely. Is there an example somewhere?

• I could use a dynamic IP address service . I'm not sure if this would have any negative effect on performance or availability... Are there any downsides to this approach?

• I could install some sort of self-configuring service on each machine (which connects to S3? SNS? SimpleDB?) to publish/retrieve the addresses of the other machines and update the config files automatically. Is there an example somewhere?

What is best practice?

Answer 1

You could use Amazon Virtual Private Cloud (Amazon VPC) . You have a private subnet where you can assign an IP address to an instance , but it may require launching an instance from command line to assign IP . VPC is charged the same way as EC2.