Introduction to Microservices
Microservices are small, self-reliant services that work with each other to achieve a complex business goal. These services are independent and complete such that they can be built by various development teams, using different programming languages and data stores. Microservices are scalable individually and can be deployed automatically. They are easy to maintain and provide greater fault tolerance as compared to monolithic services. Yet, they are loosely coupled and are capable of interacting with each other to achieve the goals of a larger application.
Various tools are available in the market so that you can build software using a microservices architecture. Spring Cloud and Spring Boot are popular Java microservices frameworks.
Spring Boot is an opinionated application development platform built using the Spring framework that is used to develop Java web applications. At the same time, it is customizable, and you can configure it based on your requirements. Basic aspects of the spring cloud tutorial will be discussed in this blog.
Microservices Using Spring Boot and Spring Cloud
This Spring Cloud tutorial provides a basic overview of building a simple microservices application using Spring Boot and Spring Cloud. Further, the tutorial provides links to relevant documentation that will help you achieve your learning goals. You will need to do the following:
1. Create a New Service Using Spring Boot by Using the Spring Initializer
According to the spring cloud tutorial, the first step is to create a project structure using the Spring Initializer. The initializer provides a quick way of adding all dependencies that you need for your project. For example, you can choose the Maven project, Java, and Spring Boot version 2.0.0. Maven projects require a group ID and Artefact ID, similar to package and class in Java.
You will also need to choose dependencies, for example, Web (to start developing web applications), DevTools (makes it easy to develop applications), Actuator (to monitor the app), and Config Client ( to connect the application to the Spring Config server). Once you have selected all the options, you will generate the project. To learn more, refer to Starting with Spring Initializer on the Building a RESTful Web Service resource. Refer to Spring Data JPA to learn how to connect to the database.
2. Ensure Service Naming and Discovery
All microservices are required to be registered to discover when another service in the architecture is looking for them. For example, a specific service may want to find all instances of another service re-running in a particular environment. In this spring cloud tutorial, you will learn that the naming server stores the information about all the services and their instances and provides the information to those seeking it. Thus, it helps in the process of service discovery. To learn more about service registration and discovery, refer to Microservice Registration and Discovery with Spring Cloud and Netflix’s Eureka.
3. Invoke Other Microservices
With Spring Cloud, several calls are required to be made to other components and services. This is achieved by using Feign that takes the complexity out of the process by enabling you to write web service clients easier. To learn more, refer to Spring Cloud Open Feign.
4. Ensure Load Balancing
As per this spring cloud tutorial, Feign also provides integration with Ribbon, a client-side load balancing framework. The Ribbon helps use the Feign configuration to distribute calls and balance them between all the instances of a service that another service wants to connect with. Refer to Client Side Load Balancing with Ribbon and Spring Cloud to learn more.
5. Manage Microservices Configuration Centrally by Using Spring Cloud Config Server
According to this spring cloud tutorial an application uses multiple microservices, multiple environments for these microservices, and also, various instances of these services running in the environments. The Spring Configuration Server provides a centralized location to store the configuration information related to all such instances of microservices.
As a result, this configuration is available in one place and is required to be used by any service in the architecture. To manage configuration centrally, you will define properties related to a new service, and then connect the associated Spring Config server by using Git as the code repository. To learn more, refer to the documentation Spring Config Overview. To learn how to connect Spring Config with Git, refer to Spring Cloud Config.
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6. Establish Security with Spring Cloud
In a microservices architecture, where hundreds of microservices work together, it is essential to have checks on authentication and authorization. Other than security, there are considerations such as metrics, limits, and so on. An API Gateway makes it possible to implement features that are common to all services.
For example, Zuul Server is an API Gateway application that handles requests and performs dynamic routing of microservices applications. Refer to Spring Cloud Gateway to learn more in this spring cloud tutorial.
7. Enable Fault Tolerance
An important consideration while implementing microservices is that if one component stops working, the entire application can come to a halt. Hystrix framework helps build fault-tolerant microservices using which you can gracefully upgrade functionality when a method call fails. This enables a microservice to continue operating when a related service fails, preventing the failure from cascading and giving the failing service time to recover.
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Hopefully, this Spring Cloud tutorial will serve as an essential starting point to get you started.
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