tin oscillator

Kubernetes-native configuration with .NET Core

Fri, 30 Mar 2018 00:00:00 +0000

Traditionally, containerised applications have gotten their configuration from environment variables or configuration files mounted into the container. But since containers (including their environment variables and mounts) are effectively immutable, changing the configuration requires that the container is re-created.

For static configuration, this is fine, but for dynamic configuration you’re better off using something like Consul K/V or a database for your configuration data.

And if you’re hosting your application in Kubernetes, you now have an additional option :-)

Kubernetes configuration resources

Kubernetes provides 2 primary mechanisms for configuring applications:

ConfigMaps
Secrets

ConfigMap

...

How does Intellisense work?

Sat, 30 Sep 2017 00:00:00 +0000

What is Intellisense?

Many modern editors have features to make life easier when working code, markup, and other types of structured text. Collectively, Microsoft calls these features “Intellisense” and they include features such as quick-info and parameter-help tooltips, completions, go-to-definition, and many more.

Many of us use it every day, but have you ever wondered what’s going on behind the scenes to make it happen?

First stop: types of Intellisense

Intellisense features can be roughly divided into 2 categories:

Contextual
Can include information from elsewhere, but...

Exporting environment variables from Python to Bash

Wed, 14 Jun 2017 01:24:00 +0000

Environment variables are used almost everywhere, but they’re somewhat painful to deal with when you need to set them from something other than the current shell’s scripting language.

The problem is that each process has its own set of environment variables, and while these will be passed to child processes (when they’re launched), a child process can never affect its parent’s environment.

This is by design (the other way lies madness), but it does make it difficult to export environment variables whose values come (for example) from a Python script.

I recently had to write a Python script to parse...

Building modules for PowerShell Core

Sun, 19 Feb 2017 22:48:00 +0000

Want to skip ahead to the sample module code?

As a developer I’ve long been a fan of Powershell; while there are other shells out there (such as Xonsh) that can do similar things, I tend to keep coming back to PowerShell as an automation language on Windows. Not only does it have a relatively large library of modules available for automating almost every aspect of Windows and related technologies, but the language itself is also surprisingly sophisticated; take parameter sets, for example:

Cmdlets are a lot like functions; they take parameters, and return outputs. What uniquely identifies...

Go: Generics? No. Amplified types? Yes!

Thu, 08 Dec 2016 03:48:00 +0000

I’ve spent a fair bit of time recently working on a Terraform provider for Dimension Data CloudControl. One of the bigger pain-points I’ve found is that for a system like Terraform (where schemas are really only known at runtime), you can’t avoid passing things around as interface{}.

Go doesn’t do generics

Go seems to have managed to get along OK without generics, but the lack of them does make things a little inconvenient sometimes. For one thing, I find myself spending a lot of time writing code like this:

func getTags(

Writing a Terraform provider (part 3)
Sun, 20 Nov 2016 05:18:00 +0000
   Part 1  Part 2  Part 3  
 
 
 Acceptance tests
 As with any software that has dependencies on external systems, the question of how to write automated acceptance tests for a Terraform provider can be a little tricky (usually the systems you depend on are sufficiently complex that it’s not practical to mock them).
 Although you might be able to get away with using a record / playback proxy to simulate remote APIs, these systems tend to be very stateful and when you combine this with Terraform’s only-semi-deterministic ordering of commands to external...


Writing a Terraform provider (part 2)
Sun, 13 Nov 2016 02:43:00 +0000
   Part 1  Part 2  Part 3  
 
 
 The Terraform extensibility model
 Terraform encapsulates functionality for communicating with various back-end systems into 2 basic abstractions: Providers and Provisioners.
 Providers
 A provider is the component responsible for implementing one or more resource types by interacting with resources via APIs on behalf of Terraform (and then exposing this information in a format that Terraform can use).
 External providers
 Providers such as our ddcloud provider are not part of Terraform; they are not supported by Hashicorp, and must be installed alongside Terraform before...


Writing a Terraform provider (part 1)
Sat, 12 Nov 2016 10:18:00 +0000
   Part 1  Part 2  Part 3  
 
 
 A couple of months ago, I started writing a provider for Terraform (a declarative configuration-management tool for infrastructure).
 The goal was to get Terraform talking to Dimension Data CloudControl, the control plane for our cloud compute facilities (the Managed Cloud Platform, or MCP).
 As it turns out, you need to put a fair bit of thought into the design of your driver.
 Terraform’s conceptual model
 In my opinion one of the best design choices made by Hashicorp, when they created Terraform, was...


New role at work
Fri, 11 Nov 2016 22:53:00 +0000
Wow. Just… wow. It’s been more than a year since my last post. I have no idea how the time got away from me.
 In the end, this was what drove me to seek a new role at work. So I’m no longer running our platform team, but am instead now responsible for driving our open-source projects. I can honestly say that I’ve gone from dreading each day of work to loving my job :)
 The best things about my new role:
  Multi-language
 Multi-platform
 Getting to engage with the broader community
 Focus is on invention / innovation;...


Modelling concurrency in Akka.NET
Sun, 20 Mar 2016 22:09:31 +0000
As a toolkit, Akka is useful for several reasons. In this series, the primary focus will be on how it can be used to model concurrency. 
 This is the second in of a series of posts on Akka.NET and my experience of using it to re-implement one of the core parts of my employer’s platform. You can find the other parts here:
  Part 1 - Adventures with Akka.NET
 
 The actor model
 Akka is based on the actor model. Without plagiarising Wikipedia too deeply, here’s a summary of the salient points:
  An actor is...