Microservices With Spring Boot, Part 1 — Getting Started

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This guide will help you learn the basics of microservices and microservices architectures. We will also start looking at a basic implementation of a microservice with Spring Boot.

We will create a couple of microservices and get them to talk to each other using Eureka Naming Server and Ribbon for client-side load balancing.

This is a 5-part article series. In part 1 of this series, let's introduce the concept of microservices and understand how to create great microservices with Spring Boot and Spring Cloud.

Microservices with Spring Boot

What You Will Learn

Resources Overview

In this guide, we will create a Student Resource exposing three services using the proper URIs and HTTP methods:

Microservices Overview - A Big Picture

In this series of articles, we would create two microservices:

Do not worry if you are not clear about a few things. The idea is to give a big picture before we get our hands dirty and create the microservices step by step.

Forex Service

Forex Service (FS) is the Service Provider. It provides currency exchange values for various currency. Let's assume that it talks to a Forex Exchange and provides the current conversion value between currencies.

An example request and response is shown below:

GET to http://localhost:8000/currency-exchange/from/EUR/to/INR

The request above is the currency exchange value for EUR to INR. In the response, conversionMultiple is 75. We will talk about port in the response a little later.

Currency Conversion Service

Currency Conversion Service (CCS) can convert a bucket of currencies into another currency. It uses the Forex Service to get current currency exchange values. CCS is the Service Consumer.

An example request and response is shown below:

GET to http://localhost:8100/currency-converter/from/EUR/to/INR/quantity/10000

{
  id: 10002,
  from: "EUR",
  to: "INR",
  conversionMultiple: 75,
  port: 8000,
}

The request above is to find the value of 10000 EUR in INR. The totalCalculatedAmount is 750000 INR.

The diagram below shows the communication between CCS and FS.

Eureka Naming Server and Ribbon

Based on the load, we can have multiple instances of the Currency Conversion Service and the Forex Service running.

The number of instances for each service might vary with time. Below picture shows a specific instance where there are five instances of the Forex Service.

What needs to happen in the above situation is load should be uniformly distributed among these five instances.

In this series of articles, we will use Ribbon for Load Balancing and Eureka Naming server for registering all microservices.  Do not worry if you are not clear about a few things. The idea is to give a big picture before we get our hands dirty and create the microservices step by step.

What Is a Monolith Application?

Have you ever worked on a project

These are typical characteristics of a monolithic application. Monolith applications are typically huge - more 100,000 line of code. In some instances even more than million lines of code. Monoliths are characterized by

Typical challenges include

Microservices

Microservice architectures evolved as a solution to the scalability and innovation challenges with monolithic architectures.

There are a number of definitions proposed for microservices:

Small autonomous services that work together. - Sam Newman

Developing a single application as a suite of small services each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API. These services are built around business capabilities and independently deployable by fully automated deployment machinery. There is a bare minimum of centralized management of these services, which may be written in different programming languages and use different data storage technologies. - James Lewis and Martin Fowler

While there is no single accepted definition for microservices, for me, there are a few important characteristics:

What Does Microservice Architecture Look Like?

This is how a monolith would look. One application for everything:

This is how the same application would look like when developed using microservices architecture.

Microservice architectures involve a number of small, well-designed components interacting with messages.

Advantages of Microservices

Advantages of microservices include

Challenges With Microservice Architectures

While developing a number of smaller components might look easy, there are a number of inherent complexities that are associated with microservices architectures. Let's look at some of the challenges:

Solutions to Challenges with Microservice Architectures

Spring Boot

Spring Boot enables building production-ready applications quickly and provides non-functional features:

Spring Cloud

Spring Cloud provides solutions to cloud-enable your microservices. It leverages and builds on top of some of the Cloud solutions opensourced by Netflix (Netflix OSS).

Important Spring Cloud Modules

In this series of articles, we will create two microservices:

The diagram below shows the communication between CCS and FS. We would establish communication between these two components.

We would want to be able to dynamically scale up and scale down the number of instances of each of these services.

And the number of instances for each service might vary with time. Below picture shows a specific instance where there are 5 instances of the Forex Service.

Implementing a solution for dynamic scale up and down needs to answer two questions

Because we want this to be dynamic, we cannot hardcode the URLs of FS in CCS. That's why we bring in a Naming Server.

All instances of the components (CCS and FS) register with the Eureka Naming Server. When FS needs to call the CCS, it will ask Eureka Naming Server for the active instances. We will use Ribbon to do Client Side Load Balancing between the different instances of FS.

A high-level sequence diagram of what would happen when there is a request from CCS to FS is shown below:

Next in this series of articles:

 

 

 

 

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