Learning and recording microservices (a brief introduction to spring cloud, Eureka introduction case)

Keywords: Programming Spring xml Java

1. Initialize Spring Cloud

1.1 what is microservice

Microservice is an architectural style that divides a single application into small service units

1.2 what is Spring Cloud

Spring Cloud is a collection of frameworks
Using the development convenience of Spring Boot, the development of distributed system is simplified

1.3 common modules of spring cloud

The main components of spring cloud include:
- Eureka: Service Registry for managing services
- Ribbon: load balancing (cluster)
- Hystix: fuse, which can prevent the avalanche effect of service.
- Zuul: service gateway, providing routing and forwarding, request filtering and other functions.
- Feign: service call to simplify the call of Http interface.

2. Registration center of erueka

2.1 overview

When developing large-scale projects, service providers and service callers will be very large, and the cost of managing services will increase exponentially.

Eureka will be responsible for service registration, discovery and status monitoring
- Registration: Eureka is responsible for managing and recording information of service providers
- Discovery: Service callers don't need to find their own services, but tell Eureka their own needs,
  
  Then Eureka will tell you the services that meet your needs
- Monitoring: the service provider and Eureka are monitored through the "heartbeat" mechanism. When a service provider has problems,
  
  Eureka will naturally remove it from the list of services

2.2 schematic diagram

Eureka: it is the service registry (it can be a cluster) that exposes its address externally
Provider: register your own information (address, what service to provide) with Eureka after startup
Consumer: subscribe to Eureka service, Eureka will send the address list of all providers of the corresponding service to consumers, and update it regularly
Heartbeat (renewal): the provider periodically refreshes its status to Eureka via http

3. Eureka introduction case

3.1 schematic diagram

3.2 configure parent project

Modify pom.xml to determine the version of spring cloud

<!-- 1 Determine spring boot Version-->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
    </parent>
    <!--2  Confirmed version-->
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
        <spring-cloud-release.version>Greenwich.RELEASE</spring-cloud-release.version>
    </properties>

    <!-- 3 locking sprig cloud Edition-->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud-release.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <!-- 4 Determine spring cloud Private warehouse-->
    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

3.3 configuration of Registration Center

Step 1: modify pom.xml file and add dependency

<dependencies>
    <!--web Start dependence-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- Eureka Server side -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
    </dependency>
</dependencies>

Step 2: modify the application.yml file configuration

# Port number
server:
  port: 10086
# Service name
spring:
  application:
    name: eureka_demo
# Configuration of eureka
eureka:
  client:
    service-url:
      defaultZone: http://localhost:${server.port}/eureka/
    register-with-eureka: false		#Do not register yourself with the registry
    fetch-registry: false			#Don't pull your own registration information from the registration center

Step 3: write the startup class and add comments

package com.czxy;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

/**
 * Created by Che on December 5, 2019
 */
@SpringBootApplication
@EnableEurekaServer		//Enable eureka service
public class EurekaApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaApplication.class,args);
    }
}

3.4 configuration service provider

Step 1: modify pom.xml file and add eureka client dependency

<dependencies>
        <!--web Start dependence-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- Eureka Client -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!--spring boot Monitor-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>

Step 2: create the yml file and determine the location of the eureka registry

#Port number
server:
  port: 8080
#Name
spring:
  application:
    name: service
#eureka configuration information
eureka:
  client:
    service-url:  #Registry location
      defaultZone: http://localhost:10086/eureka/
  instance: #Display effect in web page
    instance-id: ${spring.application.name}:${eureka.instance.prefer-ip-address}:${server.port}
    prefer-ip-address: true     #Show IP in registry

Step 3: add startup class annotation

package com.czxy;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

/**
 * Created by Che on December 5, 2019
 */
@SpringBootApplication
@EnableEurekaClient		//Start eureka client
public class ServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(ServiceApplication.class,args);
    }
}

Step 4: write test data (provide services)

Create TestController

package com.czxy.controller;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by Che on December 5, 2019
 */
@RestController
@RequestMapping("/test")
public class TestController {

    @GetMapping
    public ResponseEntity<String> testDemo01(){
        return ResponseEntity.ok("testDemo01");
    }
}

3.5 configure service users

Step 1: modify pom.xml file and add eureka client dependency

<dependencies>
        <!--web Start dependence-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- Eureka Client -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!--spring boot Monitor-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>