Discover YepCode technology stack

We decided that the YepCode technology stack would take advantage of the latest technological advances based on our experience from previous projects.

As you might have seen in one of the previous posts, some years ago we created a similar project for a big corporate. That project was a monolith web application, that included an engine to run processes written in Groovy. In that case, every piece of code was created using JEE technologies.

That was a great project, that is still widely used with great profit for that company. But, as we started YepCode from scratch, we wanted to take advantage of the latest cutting-edge technologies.

Divide et impera… microservices to the rescue!

The planning process for building the YepCode technology stack was thorough.
 
We had no doubt about the benefits of creating YepCode using microservices instead of a monolithic architecture: scalability, resources efficiency, automating (CI/CD), reliability, isolated and bulletproof environments, maintenance,…
 

In the following image, you can see YepCode current microservices architecture diagram. In the next sections, we’ll do an overview of one to tell you about technologies, responsibilities and communications between them.

YepCode microservices stack
YepCode microservices stack

Before starting, a little bit of DDD, testing, hexagonal architecture, git branching model, CI/CD…

As you may suppose, in YepCode we are code lovers, and we like to create software using high-quality standards. Some of the principles we apply on every YepCode layer are:

  • DDD: We need to understand that Software is not just about code. Domain-Driven Design makes sure that every person involved in the project speaks the same language. Sometimes it’s hard to communicate but once broken that barrier, information flows and doesn’t get lost.
    DDD provides a guide to strategic and tactical design. Strategic focus on business values and tactical on building a battle-tested domain model.
    DDD also e
    mphasizes practices like continuous integration. This ensures the integrity of the entire project, allowing potential problems to be detected on the fly.
  • Testing: We want every piece of code to be fully tested. We know that’s kind of ideal but we do our best. Every feature has its unit, integration, acceptance and smoke tests. Develop a function without any test is not acceptable for us.
  • Git branching model: Another of our main Goals is agility. For that reason, we choose trunk-based development as our branching model. With this model, we ensure that we work in the main branch almost all the time. And, of course, the main is always production-ready.
  • CI/CD: We rely on Bitbucket to implement our CI/CD cycles. With each pull request, all tests are executed. After a merge into the master branch, new docker images are generated and published to our private docker registry. Finally, our Kubernetes cluster picks them to deploy the new versions.

Hey, are you still there? Don’t lose focus. We are talking about the YepCode technology stack, so let’s start with our web-client

YepCode users only need a web browser to use the platform. We choose NextJS as our frontend framework because we love it! Probably you already know this but NextJS is based on ReactJS. It helps us with tedious initial and production ReactJS configurations.

This is one of our core technologies for other projects, and the team has wide expertise using it. In the past, we had worked a lot with Ruby On Rails or JEE templates frameworks. But in this case, we pick this framework that allows us to quickly achieve any needed feature.

We also use TailwindCSS to help us managing styles. We could use some preprocessor directly like Sass but that requires a lot of effort to start and maintain. TailwindCSS does all for us. With very little effort we maintain our code clean and we are very agile.

We are fortunate to have a great design staff that ensures that the user experience and design are under control in every change. To do that, we rely on Figma, which allows us to share and discuss any new feature before starting to implement it.

And, what about the APIs?

When was the time to pick our API language, although there are some other options, we were discussing go for a Rest API or a GraphQL API. And the second one won. We are pretty comfortable with that decision. We enjoy the flexibility that queries and mutations provide, only requesting the necessary information in each React component.

Our idea is to open this API to be able to use the full YepCode power as a backend service. In this way, other clients could schedule executions, create processes, review logs,…

The backend microservices

The component that serves the GraphQL API acting as an entry point, is a JEE web application, mainly based on the Spring framework stack. This service is the only one opened to the internet, so it’s also responsible to receive external webhook requests.

The engine microservice is in charge of reading and store from the database any information that the executors may need. It’s subscribed to MQ queues where executors publish events (logs, statistics, execution results,…). And also publish events with the executions that need to be processed.

Another critical microservice is the scheduler. This microservice is in charge of schedule processes and prepare executions to be started at any configured time (defined by a fixed start time or using a cron expression).

The components in charge of running the process executions are the executors. They receive MQ messages with all the needed information to run a process (source code, parameters, credentials,…). And publish events to report how the processes have finished.

How AAA has been solved?

We don’t like to reinvent the wheel, and since we have been using Keycloak as an identity and access management solution for years, we are continuing that approach. This open-source project is our core for authentication, authorization and accounting.

Persistence: MongoDB to the rescue

Another big decision (maybe one of the greatest dilemmas in every software application), is which solution to use for store the data. A relational database could be used. But the documents that we have to store are quite large, and the most common retrieval is by key. So, we decided to choose a NoSQL database that stores information in JSON documents as the best option.

Among all the great software projects that fit that NoSQL approach, we pick MongoDB. Mainly by the experience we had with it and because it’s one of the core solutions present on the high availability cluster where YepCode runs.

And what about the metal that allows running all this stuff

We have also been working with Docker and Kubernetes solutions for years, and we are pretty comfortable with them. So with YepCode, we keep on with that DevOps solutions.
 
In our cluster, we enjoy high availability features. Each microservice can scale to accommodate any increased workload. In addition, we have high availability and redundancy in the persistence layer, but we prefer to tell you about this in another article 🤓