Marc Costello - Marc Costello

What is important to me in a role: 2022

I find it very useful to jot down what I value most and what I'm looking for in a role each year. This is the first time I have published it of course. I find it grounds me. It is all too easy to get swept away with the work

Faced with monolith to microservices. My thought process

This is essentially a list - A thought process to which I personally find useful when faced with pulling out chunks of a larger codebase. I like to think the approach is fairly practical and 'real world'. I'm primarily targeting those difficult areas, you know, the parts of the domain

c#

Async/await - Pitfall 2 - Synchronisation

In keeping with my previous post in this series, this one is about context synchronisation in .net web applications. There is no SynchronisationContext in .net core (.net 5+). Keep that in mind. When you await a task in the .net framework, once the task is complete, the default is to

c#

Async/await - Pitfall 1 - Blocking async calls

This is a topic which has indeed been well covered and done to death at this point. But I still find many people who frequently fall into misunderstanding and pitfalls when working with asynchronous behaviour; using async/await in .NET. I'm primarily writing this series of post in the context

Little socket services

Naturally in the past whenever I needed to interact with a long running process, whether it be an API or other such daemon, I've always built some sort of http api off the back of it. This usually involves at least one framework to handle http for me, not to

docker

Memory analysis of a Spring Boot application in docker - lessons learnt

I have a Spring Boot application running an embedded TomCat server, pretty basic... It's running inside a Docker container. If I was to $ docker run the image (without memory restrictions), this is what it looks like: docker ps ~677mb container for a fairly simple Spring Boot app?! Surely I'm not

f#

How functional programming helped me recognise patterns and concepts in mathematics

I've never been strong at mathematics, and to this day I don't believe you need to be a skilled mathematician to be a good developer, but as time has gone on I've found more and more value in being able to understand and implement algorithms and expressions, which are fundamentally

Modelling simple finite state machines in F#

State machines are found everywhere, whether they are fleshed out initially as such is a different matter. In an application it's common to see different states being represented as an enum, and the transitions replace the current state with the next based upon some logic. If we take an email

elixir

Elixir Connect4

elixirConnect4 repository At work, we use Connect4 as our technical test, which we send out to possible candidates. The candidate must write a working implementation of Connect4 as a console application. So there is no real focus on graphics, and to limit complexity (and the time it takes to build)

Code we talk and code we walk

Talking about code is hard. I genuinely find it much harder to persuade fellow peers of my approach to a problem than to actually write it. I'm sure there are the opposing types too - People who can talk about code much more proficiently than write it. I guess this

f#

A functional choice

To begin a story, a while back, I wanted to learn a functional programming language. I wanted to find out just how different the functional paradigm is to the imperative paradigm. Previously the closest I got to functional programming came from JavaScript, and I’ve always found it so much

javascript

Flux data-flow architecture

Flux is a unidirectional data flow architecture for building front end applications. Coined (and used) by Facebook Inc. Flux is a pattern, not a framework. You can implement Flux in any existing application, with or without React. Although React isn't technically a dependency - it is recommended. React's components are

Managing state in SPAs

Introduction Why is nobody talking about state management in Single page applications? There are endless posts, tutorials and resources (such as pluralsight) on building a SPA using frameworks such as AngularJs or EmberJs. I have yet to find one of them address or even mention state management. The web world

c#

C# 6 - What's good?

To get a full list of completed and planned features included with C# 6 / Rosyln take a look here It's great to see with Rosyln being build out in the open we get transparency on the new C# 6 features, because it's open source, you can download the code and

c#

Using Domain Events

An issue commonly encountered when working with DDD aggregates, is getting aggregates to interact; with each other, and other services around it. If you are unfamiliar with the aggregate pattern, Martin Fowler sums it up nicely. Transactions shouldn't happen between aggregates, they are separate contexts with separate concerns. However this

Flow

Psychologists call it Flow. Developers might refer to it as being in the zone, or wired in. Don't disrupt him Dave, he's in the zone! It's an interesting subject, especially looking at it from the angle of a programmer. So what is flow? Flow is a mental state. When a

Delving into new languages

I've always thought it important to explore other languages. To be taken out of your comfort zone is the most efficient way to improve in the least amount of time. As developers we should become comfortable with this feeling. The feeling that "I actually don't know anything" is

ddd

Handling immutable types (part 2)

You can read the first post of the series - Handling immutable types part 1 - If you haven't already. In my last post, I went on to explain some of the benefits of immutable types in your data structures. Which is great, but what happens when your types start

c#

Handling immutable types (part 1)

Immutable types are nice. We like immutable types. They are massively undervalued when building software. Many of us don't take the time to consider the purpose of the class we are creating and how it fits into the structure. Why immutable types? It is much easier to reason about a

OWIN

OWIN self-hosting using Nancy

One of the problems surrounding OWIN self-hosting currently, is that MVC is not compatible. Due to System.Web's tight integration with IIS. vNext will solve these issues, but what about now? I want the portability of OWIN self-hosting (using HttpListener) but I still have a need for a server side

c#

Procedural, not OO

Take this simple class public class Foo { public int SomeInt { get; set; } public string SomeString { get; set; } public Bar SomeBar { get; set; } public void DoSomeWork() { SomeString.Append(" Blah Blah"); SomeBar.BarMethod(); } } And initialise it like this: var foo = new Foo { SomeInt = 1, SomeString = "I'm a string", SomeBar = new Bar() }; foo.

c#

RAW and MEAN

RAW - RavenDb / Angular.js / WebApi MEAN - MongoDb / Express.js / Angular.js / NodeJs Both are considered full application stacks. With Angular.js in common. If I were creating any decent sized application, today, it would be a face off between these two stacks. I am excited about the MEAN

reflection

Newing up T

Parameterless constructor new() By far the most readable way to new up T. As long as your type has a parameterless constructor - you're good to go. It's also worth noting that this is just syntactic sugar - it's still very much reflection. You can implement this method very simply.

computing

From PC to Mac

I recently bought a Mac for home computing. Previously I owned an Alienware M17X R3. Beast of a machine - which I chose to buy over a Mac mostly because of gaming. I knew that the Alienware would be a much better gaming machine (obviously). I did have work to

How is your infrastructure layer holding up?

So how is the architecture of your software/web project holding up? If you were to attempt the project again, from the beginning, would you change your approach? This first came to my attention earlier this week, when a colleague approached, and asked if I could take a look at