We’re living in an age where technologies are switching standards are changing all the time. You forget to read Medium/Stackoverflow/Reddit and you found there are at least five (5) new industry standards that are taking the place of the existing ones that you know (those that have been releasing something like a year ago 🙂 ).
Do you still remember the old ages when SOAP was the unbeatable format? How much time did we spend building our SOAP Services in our enterprises? REST replace it as the new standard.. but just a few years and we’re back in a new battle just for synchronous communication: gRPC, GraphQL, are here to conquer everything again. It is crazy, huh?
But the situation is similar to asynchronous communication. Asynchronous communication has been here for a long time. Even, a long time before the terms Event-Driven Architecture or Streaming was really a “cool” term or a thing you be aware of.
We’ve been using these patterns for so long in our companies. Big enterprises have been using this model into their enterprise integrations for so long. Pub/Sub based protocols and technologies like TIBCO Rendezvous has been using since the late 90, and then we also incorporate more standards approaches like JMS using a different kind of servers to have all these event-based communications.
But now with the cloud-native revolution, the need for distributed computing, more agility, more scalability, centralized solutions are not valid anymore, and we’ve seen an explosion in the number of options to communicate based on these patterns.
You could think that this is the same situation as we were discussing at the beginning of this article regarding REST predominance and new cutting-edge technologies trying to replace it, but this is something quite different. Because experience has told us that a single size doesn’t fit all.
You cannot find a single technology or component that can provide all the communication needs that you need for all your use-cases. You can name any technology or protocol that you want: Kafka, Pulsar, JMS, MQTT, AMQP, Thrift, FTL, and so on.
Think about each of them and you probably will find some use-cases that one technology plays better than the others, so it makes no sense to just trying to find a single technology solution to cover all the needs. What it is needed is more a polyglot approach when you have different technologies that play well together and use the one that works best for your use case (the right tool for the right job approach) as we’re doing for the different technologies we’re deploying in our cluster.
Probably we’re not going to use the same technology to do a Machine Learning based Microservice, than a Streaming Application, right? The same principle applies here.
But the problem here when we try to talk about different technologies playing together is about standardization. If we think about REST, gRPC, or GraphQL even that they’re different they play based some common grounds. They rely on the same base HTTP protocol for a standard so it is easy to support all of them in the same architecture.
But this is not true with the technologies about Asynchronous Communication. And I’d like to focus on standardization and specification today. And that’s what AsyncAPI Initiative is trying to solve. And to define what AsyncAPI is I’d like to use their own words from their official website:
AsyncAPI is an open source initiative that seeks to improve the current state of Event-Driven Architectures (EDA). Our long-term goal is to make working with EDA’s as easy as it is to work with REST APIs. That goes from documentation to code generation, from discovery to event management. Most of the processes you apply to your REST APIs nowadays would be applicable to your event-driven/asynchronous APIs too.
So, their goal is to provide a set of tools to have a better world in all those EDA architectures that all companies have or starting to have at this moment and everything pivots around one thing: The OpenAPI Specification.
Similar to the OpenAPI specification it allows us to define a common interface for our EDA Interfaces and the most important part is that this is multi-channel. So the same specification can be used for your MQTT-based API or your Kafka API. Let’s take a look at how it looks like this AsyncAPI Specification:
As you can see it is very similar to the OpenAPI 3.0 and they already done that with the purpose to ease the transition between OpenAPI 3.0 and AsyncAPI and also to try to join both worlds together: It is more about just API, no matter if they’re synchronous or asynchronous and provide the same benefits regarding the ecosystem from one to the other.
Show me the code!!
But let’s stop talking and let’s start coding and to do that I’d like to use one of the tools that in my view has the greater support for AsyncAPI, and that’s it Project Flogo.
Probably you remember some of the different posts I’ve been done regarding Project Flogo and TIBCO Flogo Enterprise as a great technology to use for your microservices development (low-code/all-code approach, Golang based, a lot of connectors and open source extensions as well).
But today we’re going to use it to create our first AsyncAPI compliant microservice. And we’re going to rely on that because it provides a set of extensions to support the AsyncAPI initiative as you can see here:
So the first thing that we’re going to do is to create our AsyncAPI definition and to do it simpler, we’re going to use the sample one that we have available in the OpenAsync API with a simple change: We’re going to change from AMQP protocol to Kafka protocol because this is cool these days, isn’t it? 😉
title: Hello world application
description: This is "My Company" broker.
- user-password: 
description: The date and time a message was sent.
As you can see something simple. Two operations “hello” and “goodbye” with easy payload:
- name: Name that we’re going to use for the greeting.
- sentAt: The date and time a message was sent.
So the first thing we’re going to do is to create a Flogo Application that complies to that AsyncAPI specification:
git clone https://github.com/project-flogo/asyncapi.git cd asyncapi/ go install
Now we have the generator installer so we only need to execute and provide our YML as the input in the following command:
asyncapi -input helloworld.yml -type flogodescriptor
And we will create a HelloWorld application for us, that we need to tweak a little bit. Only to make you be up & running quickly, I’m just sharing the code in my GitHub repository that you can borrow from them (But I really encourage you to take the time to take a look at the code to see the beauty of the Flogo App Development 🙂 )
Now, that we already have the app, we have just a simple dummy application that allows us to receive the message that complies with the specification, and in our case just log the payload, which can be our starting point to build our new Event-Driven Microservices compliant with AsyncAPI.
So, let’s try it but to do so, we need a few things. First of all, we need a Kafka server running and to do that in a quick way we’re going to leverage on the following docker-compose.yml file:
And to run that we just need to fire the following command from the same folder we have this file named as docker-compose.yml:
docker-compose up -d
And after doing that, we just need a sample application and what better that use Flogo again to create it but this time, let’s use the Graphical Viewer to create it right away:
So we need just to configure the Publish Kafka activity to provide the broker (localhost:9092), the topic (hello) and the message :
"name": "hello world",
And that’s it! Let’s run it!!!:
First we start the AsyncAPI Flogo Microservice:
And then we just launch the tester, that is going to send the same message each minute, as you can see in the picture below:
And each time we sent that message, is going to be received in our Async API Flogo Microservice:
So, I hope this first introduction to the AsyncAPI world has been of the interest of you, but don’t forget to take a look at more resources in their own website: