Spring Cloud is a module in Spring which facilitates the RAD(Rapid Application Development) methodology to the Spring Framework. Through Spring cloud, we can rapidly build cloud-based allocation. With the help of Spring cloud, some general patterns in the distributed systems are built quickly.

Spring Cloud Tutorial For Beginners

What is Spring Cloud

Spring Cloud is considered as a framework used for developing strong cloud applications. It is also used for building Microservices applications. It is used for developing configuration management, cluster state, a control bus, intelligent routing, etc.

Spring Cloud Features

1. Service Discovery and intelligent routing

While developing microservices through service cloud, the main issue is handling main services like discovery service and configuration service. To deal with these issues, it makes every service depend on each other.

2. Service to Service calls

This feature discusses how a microservice communicates with other dependent services through a eureka server or service registry. The sequence of this communication is as follows:

  • Service registration
  • Registry Fetching
  • Discovering Downstream service.
  • Handling Ip addresses.
  • Calling remaining Endpoint

3. Leadership Election

This feature enables an application to work with another application through a third-party. It also provides a global ordering or global state without sacrificing existence.

4. Load balancing

Load balancing is applied to distribute network traffic to various servers. The main objective of load balancing is to optimise throughput, enhance efficiency, reduce response time, etc. 

5. Distributed configuration

To configure each instance of Microservices, we use a distributed configuration. 

6. Global Locks

It is used to assure that no two threads use the same resource concurrently. 

7. Distributed Messaging

Distributed Messaging gives the advantage of scalability, reliability and persistence.

Components of Spring Cloud

The components of Spring Cloud is as follows:

1. Configuration

This component provides client-side and server-side support for external configuration in distributed systems. The external properties of all applications can be handled through the config server. To store config, spring cloud config server uses SVN, Git, Vault, etc.

2. API Gateway

It allows sending API requests to connect services. It gives the library to develop an API gateway for spring MVC.

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3.Tracing

The other functionality of Spring cloud is distributed tracing. Tracing is used to get data from the application. Tracing can lead to more requests to different microservices. To allow tracing, we have to add “Spring Cloud Sleuth” to our project. Sleuth is accountable for storing timing. Timing is sent to Zipkin.

Zipkin is mainly designed to analyze latency problems. It reveals HTTP endpoint utilised for gathering input data. If we want to include tracing to our project, we have to add a spring-cloud-starter-Zipkin dependency.

4. CI Testing and Pipeline

Spring Cloud pipeline is a stubborn pipeline, and for every application, the pipeline is created automatically. Deploying, testing and building of different services are important to have a good cloud-native application.

Jenkins pipeline gives a collection of tools developed for modelling simple and sophisticated delivery pipeline as code. The Jenkinsfile is a test file used to store the definition of the pipeline.

5. Service Discovery

Service Discovery is used to identify the services and devices over the network. Service discovery tells us how microservices and applications link each other. In service discovery, we have two discovery patterns; they are:

   1. Client-side discovery:

    In client-side discovery, the client determines the network location of existing services. It uses a load-balancing algorithm to select the service from the existing services.

    2. Server-side Discovery

     In Server-side discovery, with the help of a load-balancer, the client renders an HTTP request to a service. The load balancer with the help of a server registry sends every request to the existing service instance.

6. Circuit Breakers

The library of Netflix named “ Hystrix” implements a circuit breaker pattern. Circuit breakers compute when the circuit should be opened and when it should be closed. When the entire services are closed, the circuit breaker will handle this situation. Circuit breakers contain three states; they are as follows:

  • Open-state
  • Closed-state
  • Half-open

7. Routing and Messaging

As the cloud application contains several microservices, so communication is essential. Spring cloud does communication with the help of HTTP requests or messaging.

Advantages of Spring Cloud

  • It allows one service to communicate with another service.
  • It is used to develop applications based on the cloud.
  • Its architecture is designed according to the microservice.
  • It adopts a spring boot model.

Let us see some of the Projects that use Spring Cloud

Primary Projects of Spring Cloud

1. Spring Cloud AWS

It is a section of the Spring cloud umbrella project. It allows simple integration with AWS(Amazon Web services).

2. Spring Cloud Stream

It is used for developing on-demand Microservices. It uses built-in spring idioms and best procedures to develop microservices. The main elements of Spring Cloud Stream are as follows:

  • Destination Binders: It is used to give incorporation with the extrinsic messaging systems.
  • Destination Bindings: It is used to reduce the gap between application provided producers and extrinsic messaging systems.
  • Message: It is considered as a data structure applied by consumers and producers to interact with Destination Binders.

3. Spring Cloud Cluster

It gives resources for developing a cluster property in a distributed system.

4. Spring Cloud Function

It allows the execution of business logic through functions. It is able to run independently or as Paas(Platform as a service).

5. Spring Cloud Sleuth

It is used for executing tracing solutions in distributed systems.

6. Spring Cloud Zookeeper

It gives service discovery and configuration management through apache zookeeper.

7. Spring Cloud CloudFoundry

It incorporates the pivotal cloud foundry with the application. It gives service discovery and simple implementation of OAuth2 and SSO.

8. Spring Cloud Config

It gives client-side and server support for external configuration in the distributed systems. Through the config server, you can handle the external properties of the applications through all environments. With the help of Spring cloud-config, you can handle the configuration between different environments, because the application passes through different environments like a deployment pipeline to test-to -development. Features of Spring Cloud Config as follows:

  • Property values are encrypted and Decrypted.
  • It can be embedded easily in the spring Boot application.

9. Spring Cloud Netflix

It provides Integration of Netflix and OSS for the application of Spring Boot with the help of autoconfiguration. The features of Spring Cloud Netflix are as follows:

  • Service Discovery: The instances of Eureka are registered, and clients will find the instances through Spring-managed Beans.
  • Circuit Breaker: Hystrix dashboard is embedded through declaratory java configuration.
  • Filter and Router: Zuul filters are automatically registered.  

10. Spring Cloud Gateway

      It is used for developing API Gateway over Spring MVC. The main objective of Spring Cloud Gateway is to provide an efficient method to route towards API.

Features

  • It asserts, and filters are particular to routes.
  • On any requested attribute, it can match the routes.
  • It is developed on Spring Framework 5.
  • It integrates the Hystrix Circuit Breaker.

11) Spring Cloud DataFlow

   The Spring Cloud DataFlow gives resources to establish difficult topologies for batch data pipelines and streaming. Features of Dataflow are as follows:

  • To provide data pipelines, a spring cloud deployer is used by the spring cloud dataflow.
  • Task applications and Custom Stream are developed using Spring Boot Style Programming Model.
  • Dashboard Provides a graphical editor for developing collaborative data pipelines.

Eureka Naming Server

It is a rest-based server applied for AWS cloud services for load balancing.

Need For Naming Server

  • Eureka naming is used to diminish the gap between middle-tier Load balancer and Clients.
  • The naming server is used to decrease or increase the loads.
  • The Ribbon distributes the load to the current server through a naming server. 
  • It registers and provides instances to the microservice.

Setting up Naming Server

Following steps are necessary to set up a naming server.

  • First, we have to establish a component for the eureka naming server.
  • To connect to the Eureka Naming server, we have to update CurrencyCalculationService.
  • Eureka Naming Server is Connected to the CurrencyExchangeService.
  • Ribbon Should be Configured.

Connecting Spring Cloud Config Server to Local Git Repository

  • For connecting Local Git Repository to Spring Cloud Config Server, we have to discover the folder path.
  • We have to right-click the git-localconfig-repo-> properties-> we have to copy the label address of the location and paste the location inside the application properties file.

Virtualisation in Microservices

In Microservices, Virtualization is a method to copy the performance of particular components in cloud-based applications, API-driven applications. In microservice, we must have virtualisation, because these days cloud applications use several microservices for communicating with each other. In this environment, we will face some problems; they are:

  • The services present in the environment cannot be accessible at the moment.
  • Many services may not be accessible because of certain reasons.
  • Some common services are not easily accessible.

To solve these problems, we have a method called service virtualisation. Through this method, we can simulate or capture the services. Hoverfly is a recently developed tool which uses GO programming Language for service Virtualisation.

Conclusion

Spring Cloud is a section or a part of Spring. It is used to build cloud applications. As the demand for cloud applications is increasing, the demand for cloud applications is also increasing. Microservices use Spring cloud to create communication among the services. So, knowledge on spring cloud is essential to professionals who work on Cloud applications.