Tag: aws

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Interrelated personal side projects can be a goldmine of learning opportunities

Some people struggle to find ideas for working on side/personal software development projects for learning (and fun!). I’ve kept a running list of ideas in an online notebook and if I’m struggling for an idea for a new project I refer back to this list.

Over the past couple of years I stumbled across a series of inter-related projects that’s been a goldmine of learning opportunities, from frontend to backend to serverless.

This series of projects started with a question “Can you solve a problem without understanding the problem?”. tl;dr? No. The problem for this activity was solving Sudoku puzzles, and you can read more about this here:

Can you develop code to effectively solve a problem without understanding the problem first? (writing code to solve Sudoku puzzles)

This lead to the next step, researching more about exact cover problems, and how they can be solved with well established algorithms:

Revisiting Donald Knuth’s Algorithm X and Dancing Links to solve Sudoku puzzles

After building an implementation of Donald Knuth’s Algorithm X, I packaged it up as an AWS Lambda, and then built a React frontend for it:

Building a React frontend for my AWS Lambda Sudoku solver

I have one other project in progress for the frontend, replacing Flux with Redux. I’m still working on that one.

After building my solver and the frontend, I starting thinking about how to generate new puzzles. This is in progress here: https://github.com/kevinhooke/sudoku-generator

If you’re generating new puzzles you also need a way to grade the difficulty of puzzles. The unusual thing about this is there’s no established algorithm for grading the complexity of Sudoku puzzles, they’re typically graded by applying human solving techniques, so this led to this: https://github.com/kevinhooke/sudoku-human-grader

This string of related projects has kept me busy of the past couple of years. Not every idea will lead to a series of related projects like this, but if you can find an idea that does, it will keep you busy with plenty of problems to solve and many learning opportunities.

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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

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node.js, node-oracledb and Oracle Instant Client

To access an Oracle DB from an AWS Lambda function developed with node.js, you need to package you Lambda with shared libraries from Oracle’s Instant Client. The install instructions are here ( http://oracle.github.io/node-oracledb/INSTALL.html#quickstart ) but the only part that is really needed is the download location (since there’s no specific instructions for bundling the libs with an AWS Lambda): https://www.oracle.com/database/technologies/instant-client/linux-x86-64-downloads.html

Not all the Oracle Instant Client files are needed. From this older npm module to automate the packaging of the required libraries, I used this same list of required libraries:

libclntshcore.so.19.1
libclntsh.so.19.1
libmql1.so
libipc1.so
libnnz19.so
libons.so (not packaged in current Instant Client)
libociicus.so
libaio.so (from separate download - see next step)

libaio – if you’re on a Linux platform you can ‘apt-get install libaio’ or similar, but building my Lambda on a Mac I had to manually download the package and extract just the .so file from here (download the Arch Linux x64 package): https://pkgs.org/download/libaio

Put these in a /lib dir and zip up the folder and files. Use this to create a Lambda Layer.

For the Lambda itself install the node.js module for the api:

npm install –save node-oracledb

For examples in api usage, see the examples here: https://github.com/oracle/node-oracledb/tree/master/examples

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Installing Oracle Instant Client and Tools in an AWS EC2

I’m using the AWS Amazon Linux 2 AMI on my EC2. To download the Oracle Instant Client get the download urls for the instant client and instant client tools from: https://www.oracle.com/database/technologies/instant-client/linux-x86-64-downloads.html

Download using curl and install with rpm:

curl instant-client-url-from-page-above --output instant-client.rpm
rpm -i instant-client.rpm
curl instant-client-tools-from-page-above --output instant-client-tools.rpm
rpm -i instant-client-tools.rpm

To connect using sql-plus:

sqlplus 'admin@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=your-instance-endpoint.rds.amazonaws.com)(PORT=1521))(CONNECT_DATA=(SID=your-db-name)))'

Enter password when prompted.

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