Spring Boot 4 Microservices & REST APIs · 강의

Ribbon을 사용한 클라이언트 측 부하 분산

여러 서비스 인스턴스에 클라이언트 측 부하 분산을 적용하도록 Ribbon을 통합합니다.

Ribbon을 사용한 클라이언트 측 부하 분산은(는) CoddyKit의 무료 Spring Boot 4 Microservices & REST APIs 강의입니다. 이것은 3개 중 2번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 Spring Boot 4 Microservices & REST APIs 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. Spring Boot 4 Microservices & REST APIs 강의에는 총 3개의 강의가 포함되어 있습니다.

이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.

What is Load Balancing?

In a microservices world, applications often have multiple copies (instances) of the same service running. This is for scalability and high availability.

Load balancing is the process of distributing incoming network traffic across these multiple instances. It ensures no single service instance gets overwhelmed.

Scalability: Handle more users by adding more instances.
High Availability: If one instance fails, others can take over.
Performance: Distribute work evenly to reduce response times.

Client-Side vs. Server-Side LB

There are two main types of load balancing:

Server-Side Load Balancing: A dedicated component (like Nginx or a hardware load balancer) sits in front of your services. Clients send requests to this component, and it forwards them to an appropriate service instance.
Client-Side Load Balancing: The client application itself is responsible for knowing about all available service instances and choosing one for each request. This is where tools like Ribbon come in!

Ribbon: Your Client-Side Helper

Ribbon is a client-side load balancer that integrates seamlessly with Spring Cloud applications. It helps your client service pick the right instance of a target service.

How does Ribbon know about service instances? It works hand-in-hand with a service discovery mechanism, like Eureka. Eureka tells Ribbon where services are, and Ribbon decides which one to call.

Adding Load Balancing Dependency

To enable client-side load balancing in your Spring Boot application, you typically include the Spring Cloud LoadBalancer dependency. While 'Ribbon' is in the lesson title, Spring Cloud LoadBalancer is its modern successor and works similarly.

Add this to your pom.xml:

<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

Load Balanced RestTemplate

The easiest way to use client-side load balancing is with Spring's RestTemplate. By simply adding the @LoadBalanced annotation to your RestTemplate bean, Spring configures it to use a load balancer.

When you make an HTTP call, you'll use the logical service name (e.g., my-service) instead of a specific IP address and port. The load balancer (Ribbon/Spring Cloud LoadBalancer) resolves this name to a real instance.

Client Calling a Service (Code)

Here's a simple Spring Boot client application that uses a load-balanced RestTemplate to call another service named my-service. For this to work, my-service must be registered with a service discovery server (like Eureka).

package com.coddykit;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@RestController
public class MyClientApplication {

    private final RestTemplate restTemplate;

    // Inject the load-balanced RestTemplate
    public MyClientApplication(@LoadBalanced RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    public static void main(String[] args) {
        SpringApplication.run(MyClientApplication.class, args);
    }

    // Define the load-balanced RestTemplate bean
    @Bean
    @LoadBalanced 
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

    // Endpoint to call 'my-service'
    @GetMapping("/call-my-service")
    public String callMyService() {
        // Use the logical service ID 'my-service'
        return restTemplate.getForObject("http://my-service/hello", String.class);
    }
}

Load Balancing Algorithms

Ribbon (and Spring Cloud LoadBalancer) can use different algorithms to decide which service instance to call. Some common ones include:

Round Robin: Distributes requests sequentially to each instance (e.g., instance 1, then 2, then 3, then 1 again).
Random: Picks a random instance for each request.
Availability Filtering: Ignores instances that are marked as down or unresponsive.
Weighted Response Time: Favors instances that have historically responded faster.

Configuring Load Balancing Rules

You can configure the load balancing rule for a specific service in your application.yml or application.properties. For example, to use a Round Robin rule for my-service (using older Ribbon config style):

my-service.ribbon.NFLoadBalancerRuleClassName=com.netflix.loadbalancer.RoundRobinRule

While this specific syntax is for older Ribbon, the concept of configuring rules per service is similar in Spring Cloud LoadBalancer, often done via custom configurations or properties.

Benefits of Client-Side LB

Client-side load balancing offers several advantages in a microservices architecture:

Simpler Infrastructure: No need for a separate hardware or software load balancer component.
Direct Communication: Clients communicate directly with service instances, potentially reducing latency.
Dynamic Scaling: Easily adapts to new service instances registering or deregistering with service discovery.
Granular Control: The client can implement custom load balancing logic or apply different rules per service.

Quick Check on Load Balancing

You've learned about client-side load balancing. Let's test your understanding.

Recap: Client-Side Load Balancing

Great job! You've explored client-side load balancing with Ribbon (and its successor, Spring Cloud LoadBalancer).

We learned that load balancing distributes traffic across service instances for scalability and availability.
Client-side load balancing means the client itself chooses which instance to call, often using a logical service name.
The @LoadBalanced annotation on a RestTemplate bean is key for enabling this feature in Spring Boot.
Various algorithms like Round Robin can be used to distribute requests.

This approach makes your microservices more robust and efficient!

자주 묻는 질문

“Ribbon을 사용한 클라이언트 측 부하 분산” 강의는 무료인가요?

네 — “Ribbon을 사용한 클라이언트 측 부하 분산” 전체 내용을 이 웹사이트에서 무료로 읽을 수 있습니다. 인터랙티브하게 실습하려면(내장 코드 에디터와 24/7 AI 튜터), CoddyKit PRO로 업그레이드하면 Spring Boot 4 Microservices & REST APIs 강의 전체를 잠금 해제할 수 있습니다. Spring Boot 4 Microservices & REST APIs 강의에는 총 3개의 강의가 포함되어 있습니다.

“Ribbon을 사용한 클라이언트 측 부하 분산”에서 뭘 배우나요?

여러 서비스 인스턴스에 클라이언트 측 부하 분산을 적용하도록 Ribbon을 통합합니다. 브라우저에서 직접 실행하는 실습 코드로 Spring Boot 4 Microservices & REST APIs을(를) 배우며, 24/7 AI 튜터가 강의를 진행하면서 질문에 답변해줍니다.

Spring Boot 4 Microservices & REST APIs을(를) 시작하는 데 경험이 필요한가요?

사전 경험은 필요하지 않습니다. CoddyKit의 Spring Boot 4 Microservices & REST APIs은(는) 초급자부터 고급 학습자까지를 위해 구성되어 있으므로, 여기서 시작하거나 처음부터 시작할 수 있으며 자신의 속도대로 진행할 수 있습니다. 이것은 3개 중 2번째 강의입니다.

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대부분의 CoddyKit 강의는 약 5~10분이 소요됩니다. 각 강의는 간결하고 인터랙티브하여 꾸준한 진행이 가능하며, 웹과 앱에서 중단한 부분부터 바로 시작할 수 있습니다.

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