Using Route 53 to create subdomain names for your projects

If you create and deploy your own software projects to the cloud, at some point you probably end up with a number of things deployed to various places and unless you spend time maintaining your bookmarks to all these projects, it becomes hard to keep track after a while.

One of the interesting things about Route 53 is that you can create A records that resolve to IP addresses either within AWS or hosted elsewhere. If you have you own domain setup in Route 53, you can easily create subdomains with A records pointing to where ever these projects are hosted. e.g.

example1.youdomain.com -> x.x.x.x

example2.yourdomain.com -> y.y.y.y

A while back I deployed my Sudoku Solver React app to an S3 bucket hosting the website, and I can never remember the S3 endpoint name. But using a Route 53 Alias to the S3 endpoint, you can create whatever subdomain you need to point to the target resource. Here’s what it looks like setting up an alias:

Notes:

  • when you click in the Alias Target box you should see your S3 bucket already listed (if not, check you’ve enabled Static Website Hosting)
  • the recordset name must be identical to the first part of your bucket name (e.g. ‘example’)
  • the S3 bucket name must be the subdomain name plus full domain, e.g. example.yourdomain.com

Where’s my ESXi Console (or, booting from a DVD by mistake)

I had a need to install and setup a Windows 8 VM. I have an original install DVD, so attached a USB DVD to my HP DL380 server and was planning on setting up a VM installed from the DVD. Some time later waiting for the ESXi console to be available, it was not responding and wondered what was going on. Started up the Remote Console option from iLO and found that the server had booted from the DVD. Yeah, that’s not gonna work 🙂

Sudoku and Exact Cover problems

Sudoku is an example of an Exact Cover problem and can be solved by picking a subset of candidate rows from the exact cover matrix that satisfy all of the constraints for the complete grid.

I explored building an implementation of Donald Knuth’s Algorithm X using Dancing Links as a Sudoku solver, which you can read more about here.

For a 9×9 Sudoku puzzle, a candidate grid has x possible candidates, by y constraints.

For a 9×9 grid using numbers 1 through 9, there are:

9 rows x 9 columns x 9 (values 1 through 9) = 729

… possible candidate values for the cells.

For 4 constraints applied to every cell in the 9×9 grid, there are

9 rows x 9 columns x 4 constraints = 324

… constraints to be met.

If you fill a grid where a 1 represents a met constraint by that candidate and 0 is unmet, if you zoom out far enough the table looks like this:

To see how a matrix like this is used together with Donald Knuth’s Algorithm X and Dancing Links, see my previous post here.