CategoryReact

Don’t worry, Heimdall will watch over all your microservices.

TL;DR : I wrote a service registry tool, named Heimdall, go and fork it!

Long version: almost every time I am working on a piece of code I get stuck on something and after a while I get new ideas for new projects. This may lead to a huge number of useless git repos, each one with a partially functional software, but it also pushes me to work on new things each day.

This time I was working on a super-secret project (that I will of course share very soon) based on a nice microservices architecture and I soon realized I needed some kind of Service Registry. The project was quite small so I was not really interested in a complex tool like a router with load balancing functions or similia so I decided to code the thing myself.

For the ones of you that don’t know what a Service Registry is and what it does, allow me to give you some context.
Imagine you’re a client that needs to consume some APIs. You could of course use a configuration file for storing the endpoints but in case you’re cloud-based, urls can change often.

Also, what if you want some nice features like multiple instances, autoscaling and load balancing?

The answer is simple: use a registry! 

Every service will register itself during initialization, allowing clients to query the registry and know the endpoint (possibly the best one).

I found this concept pretty useful so I decided to create a poor man’s version myself, using ASP.NET Core, MongoDB and React and I named it Heimdall, the guardian god of the Norse mythology .
The list of features for now is very scarce, you can just register a service, add/remove endpoints and query, but I have a full roadmap ready 🙂

Oh and I also added help pages using Swagger !

Recording of Webinar Introduction to React & Typescript available

Last Saturday I had the chance to run my first webinar, thanks to my friend and ex-colleague Lalit Kale and the folks from Indiamentor.

We discussed about React, pros and cons, why should someone use it instead of AngularJS (for example eh, no puns intended) and how to setup the dev environment. Then I showed a small demo of a hello-world-like application made with Typescript using Visual Studio Code.

Later the same day, the Indiamentor team has also uploaded on Youtube the complete recording:

Unfortunately due to some obscure technical reasons, the streaming software decided to stop updating the screenshare after a couple of slides, so in the video you won’t see the second part of the presentation. However, I used Google Presentations to create my deck, so here’s the link 🙂

I had a very good time preparing the slides and talking to the audience, even if I wasn’t actually seeing anyone. I am really starting to think that maybe I could prepare some coding or software architecture lessons and begin running some (online) courses.

Data pagination with NodeJS and React

TL;DR:

here’s the link to the GitHub repo.

Some time ago, in one of my articles I showed a way to paginate your data using WebAPI on the server and AngularJS on client-side. Funnily enough I wrote that post exactly two years ago, I just noticed it while writing this. Well, turns out a lot of people is still searching for it, so now, after two years, I have decided to write another couple of notes but with a different tech stack.

Yes, of course, I could have used the same backend from the old article, but where’s the fun in that?

Enter NodeJS and React!

So, let’s start with the server first. As you can see from the sources, I used Typescript this time. To be honest, I don’t feel “safe” while writing Javascript code, even with lots of unit tests. Having some form of “strongly-typed” language is a little bit of relief, at least for the .NET coder in me.

The architecture is very simple: we have an express application with just one Route ( /api/products/ ) exposing a GET action which reads from a Repository the paged list of available products. Due to the nature of the example, I decided to keep things simple and not add any kind of IoC container, just to avoid to overcomplicate the code.

I have also added two middlewares, one to console.log() all the incoming requests and the other to allow CORS for a specific domain ( eg. our client application ). In case you need to refresh your memory, here’s a nice article about NodeJS middlewares.

The core concept that you can see from the Products API is to return an object that exposes the list of Products along with some infos like the total number of pages, the total Products count and the current page number.

Let’s talk about the client now.

I was definitely not disappointed discovering that the learning curve for React is actually very, very low. Coming from the Angular world, I was expecting more difficulties, but in a matter of hours I have been able to setup my dev env with Typescript ( wanna know how?  ) and start coding my components.

Oh yes, don’t miss my webinar this Saturday! I’ll do a quick introduction about Typescript and React.

Ideally, I could have served the client part directly from the NodeJS application, but I preferred to keep everything separated. Yeah, I had to activate CORS, but it’s not really a big deal. Also, it makes everything more “microservices-oriented“, which is becoming more and more an hype these days. In my mind, for that kind of architecture you should have two servers talking, but bear with me.

In our small demo, the client is using a service to read the products, displays them in a table and renders a pager at the bottom. As you can easily notice, I am using the fetch() polyfill to perform the AJAX request.

Also, to make things more interesting, in this case I am using an IoC container, Inversify, to handle dependencies. However, since Components are instantiated directly by the React engine we cannot use constructor injection but have to revert to property injection….which in this case is handled by the @lazyInject decorator. I’ll write another post about the subject in the upcoming future.

For now, if you enjoy the example, don’t forget to write a comment!

Webinar: introduction to React & Typescript – again!

Due to the huge amount of registrations, me and the folks at Indiamentors have decided to postpone the Introduction to React & Typescript webinar to Saturday September 17th at 6:30 IST .

As I told you before, this webinar is going to be an introduction about React,  how to setup your dev environment and how to write your first piece of React code.
I’ll show you a small demo and at the end we’re going to have a nice Q&A session.

Here’s the agenda:

  • Why React?
  • Let’s get started!
  • React Components
  • Properties and State
  • Webpack
  • Demo

Make sure to register and reserve your seat!

Webinar: Introduction to React and Typescript

Just a quick update: thanks to my good friend Lalit Kale who invited me, I will be running a webinar this Saturday about React and Typescript.

It’s going to be an introduction about how to setup your dev environment and how to write your first piece of React code.  Absolutely no rocket science involved, we’ll discuss about pros and cons, there will be a quick demo and I’m sure it will be fun (at least for me).

It will be at 6:30pm IST . As you may have guessed, most of the audience is in India, also because I’m doing this in partnership with Indiamentor.

Here’s the link for the registration.

Don’t miss it!

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