AWS Solution Architect Associate Exam Study Notes: 10,000 Foot Overview

 

These notes were written while working through the A Cloud Guru AWS Certified Solutions Architect - Associate online course. These notes are partly from the videos, and also from various other online sources. Primarily, they’re notes for me, but you might find them useful too.

Since the AWS platform is changing so quickly, it’s possible that some of these notes may be out of date, so please take that into consideration if you are reading them.

 

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Setting web.config defaultProxy with Powershell for debugging .NET web services

 

Fiddler is an awesome tool for debugging web services. For the last 10 years, I’ve been using it virtually every working day for web service debugging in scenarios such as:

  • Capturing HTTP requests as they travel through a distributed system, which you have set up on your local development machine.
  • Intercepting and modifying HTTP requests, essentially performing a local man-in-the-middle interception. This is particularly useful if want to modify HTTP requests to simulate functionality which isn’t currently present, modify HTTP headers, etc.
  • Replaying captured requests - useful if you are debugging the way a web service behaves, given a specific request; capture the request, and replay it as many times as you need in order to debug the error.

If you’re doing any work with web services, Fiddler is definitly worth considering. Setting it up is fairly straightfoward

By default, Fiddler can update your browser proxy to route through the Fiddler proxy, which is, by default on port 8888, and will capture requests between Chrome/Firefox/Safari/etc, and your web app.

What if you’re debugging locally, and want to intercept .NET services which call other web services? i.e. Web Browser -> Web App -> Service1 -> Service2 (the one you want to debug)? This can be done by setting defaultProxy in web.config. In this case, since we want to debug Service2, we’d set defaultProxy in Service2’s web.config file.

i.e.

<configuration>
 <system.net>
  <defaultProxy>
   <proxy bypassonlocal="false" usesystemdefault="true" />
  </defaultProxy>
 </system.net>
</configuration>

With one of the distributed apps I frequently work with, I was setting, and resetting the web.config defaultProxy fairly frequently. To save some effort, I wrote a script to automate the change.

 

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dotnet new causing segmentation fault on Debian Linux

 

Earlier this evening I installed .NET core preview 2 on Debian Sid, and tried to create a new project via the dotnet new command, only to get a segmention fault error message:

[email protected]:~/git/testproject$ dotnet new console
Segmentation fault

In this instance, the segmentation fault on creation of a new project was is due to .NET Core telemetry being incompatible with version 1.1 of OpenSSL.

 

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Writing a method that takes an integer, and returns it's factorial

 

Sometimes, when being interviewed for a job as a software developer, you’ll be asked a question such as “write a method that takes an integer as a parameter, and returns it’s factorial.”

For example, the factorial of 3 is represented as “3!”, which is calculated via 3*2*1, which equals 6. 4! is 4*3*2*1, which is 24, etc.

Putting aside whether these kinds of questions should be asked in an interview, if they’re asking you this, there’s a fairly high likelihood they’re asking for you to show that you understand recursion. If that’s the case, no problem, something like this will calculate the factorial:

let rec factorial n =
    match n with
    | 0 | 1 -> 1
    | n when n > 0 && n <= 12 -> n * factorial (n - 1)
    | _ -> failwith "Parameter n is out of the supported range. Must be between 0 and 12."

This can be run in the F# interactive shell via:

> factorial 3;;
val it : int = 6

But what if they want to find out whether you:

  1. Understand recursion, and…
  2. Know when you can avoid recursion, and just write simple methods instead.

 

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CloudFlare S3 Website Error: 502 - Bad Gateway

 

I recently migrated my mattbutton.com blog away from Wordpress hosting in favor of a static site generated by Hugo, hosted on Amazon S3.

Initially, I hosted the static site via Aerobatic.io, who recently removed their free tier, and started charging $15 per month for hosting with a custom domain.. 50% more than the $10 per month I was previously paying for Hostgator Wordpress hosting. Unless I have certain specific requirements, I can’t justfy that kind of cost to host a static site.

Aerobatic.io are using Amazon S3 and Amazon CloudFront behind the scenes, so I decided to cut out the middle-man, set it up myself, and save nearly $15 per month.

Setting up the S3 bucket to host my site was fine. For the CDN/SSL side of things I initially tried using CloudFront because most of the AWS Hugo Hosting, HowTo guides were using it.

When trying to set up CloudFront via my personal AWS account, I got an error saying a distribution already exists for mattbutton.com. The reason for this error is because Aerobatic.io had already created a CloudFront distribution pointing to their own S3 bucket. CloudFront isn’t an option for me until Aerobatic.io delete their mattbutton.com CloudFront distribution.

I still wanted to use SSL, and had decided on setting up mattbutton.com with it mainly out of interest, partly because Google uses HTTPS as a ranking signal, and partly because Chrome will eventually show a Not Secure warning for all pages served over HTTP.

Since AWS CloudFront wasn’t an option, I decided on using the CloudFlare free plan for SSL and CDN. Everything went well, until I encountered a CloudFlare 502 Bad Gateway error page:

Cloudflare 502 Bad Gateway

I wasn’t having any luck searching for a solution to this error for this particular error. Fortunately, there’s a simple fix, if you know what you’re looking for, and you’re happy with the trade-offs involved.

 

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Toastmasters Role Templates

 

I joined a Toastmasters public speaking club back in November 2016. There are lots of resources out there, I found they were fragemented, and none really resonated my personal style of speaking, especially for the club I’m in, which adheres to the Toastmasters structure and rules, yet has a much more natural speaking than other clubs I’ve visited.

After performing each of the roles several times (Chair, Grammarian, Table Topics Master, etc) I found it useful to build up, and revise templates as my skill and personal style evolved. Below are my current templates, which I will update over time:

 

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Searching for Whale Sharks in Koh Tao, Thailand

 

I spent two weeks in late August on the island of Koh Tao, which is located in the eastern Gulf of Thailand.

The weather was perfect. Every day, I’d head out on the boat to go scuba diving at various dive sites around the island. I’d been a qualified diver for several months prior, so no training was needed, and I signed up for the fun dives, where we would be taken on underwater tours by a guide called a dive master.

I was planning on diving virtually every day around the beautiful island of Koh Tao. In particular, I was hoping to see some big sea creatures such as the Whale Shark.

 

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