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ServiceStarter Tutorial: Controlling Services

This article is a tutorial for a new utility ServiceStarter. The purpose of ServiceStarter is to control the lifecycle of independent services, ensuring that services start and stop in the correct order and predictably degrade if a required service fails at runtime. This tutorial is based upon a notional order processing system connected to an exchange.

As background, this is my Christmas project. Due to a COVID-cancelled skiing holiday, I was left with time on my hands. A friend, who is building an event-driven HFT trading system, asked me to help solve the problem of starting and stopping trading services in a predictable order.  The solution morphed into the ServiceStarter project.

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Spring Webflux: EventLoop vs Thread Per Request Model

Spring Webflux Introduction

Spring Webflux has been introduced as part of Spring 5, and with this, it started to support Reactive Programming. It uses an asynchronous programming model. The use of reactive programming makes applications highly scalable to support high request load over a period of time.

What Problem It Solved Compared With Spring MVC

Spring MVC uses a Synchronous Programming model, where each request has been mapped to a thread and which is responsible to take the response back to the request socket. Cases where applications make some network calls like, fetch data from a database, fetch a response from another application, file read/write etc., a request thread has to wait to get the desired response. 

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Reactive Messaging Examples for Quarkus

Quarkus provides several different reactive messaging capabilities. The open-source project cloud-native-starter uses some of these capabilities in a sample application which is described in this article.

There a several easy to follow Quarkus guides about the topic 'reactive messaging'. Tutorials are great, but the best way to learn new technologies is for me is to use them in simple applications. That's why I've come up with a simple scenario.

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Getting Started With Spring Cloud Gateway

In this article, we will integrate spring cloud gateway with a microservice-based architecture application using spring cloud. In the process, we will use spring cloud gateway as a gateway provider, Netflix Eureka as a discovery server, with circuit breaker pattern using Netflix Hystrix.

Let's quickly get started with the implementation of it.