Nacos hand to hand teaching [i] dynamic configuration of Nacos

1、 Preface

When we use a technology, we must first understand why we use it , What problems can it help us solve .

In the single architecture, we write the configuration in the configuration file , But one disadvantage is that every time you modify the configuration, you need to restart the service to take effect . It can also be maintained when there are few application instances , If it is a micro service architecture, there are dozens of hundreds of instances , Restart all instances every time you modify the configuration , It not only increases the instability of the system , It also greatly increases the maintenance cost .

nacos Configuration center , It can standardize the configuration 、 Unified format , When the configuration information changes , Changes take effect in real time , There is no need to restart the server , Can automatically perceive the corresponding changes , And send the new changes to the corresponding procedures , Respond quickly to change .

This article is based on Cloud Alibaba 2021.0.1.0 + Springboot 2.6.3

2、 Practice

nacos I won't talk about the download and installation of .nacos-server The default is to start in cluster mode , Here we use stand-alone mode .

startup.cmd -m standalone

After new project Add dependency first

        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
            <version>2021.0.1.0</version>
        </dependency>
       <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
            <version>3.1.2</version>
        </dependency>

  Here we need to pay attention to , This version is no longer loaded by default bootstrap file , If you need to load bootstrap Files need to be manually added with dependencies .

Then we go to nacos Create a new namespace on the console

So get a namespace id, Then go to the configuration file in the project to fill .

spring:
  cloud:
    nacos:
      config:
        server-addr:  service ip:8848
        file-extension: yaml
        namespace: 434e7801-0b5d-4fd2-b96a-acbac849fd84
  application:
    name: nacos-demo
  profiles:
    active: dev

  Go again nacos Console , In the configuration list, select the namespace we just created , Point rightmost + Number

  Write a test interface , Start project , So let's test that out

@RefreshScope
@RestController
public class ConfigController {

    @Value("${user.name}")
    private String name;

    @GetMapping("/test")
    public String test(){
        return name;
    }
}

First of all, we found that the project is based on 8082 Port boot

After calling the interface

We noticed that there is a @RefreshScope This annotation can help realize configuration hot loading .

After we modify the configuration file , Do not restart the project , Call the interface again

3、 analysis

There must be many questions after practice , At this point, let's analyze ：

Data Id: Its value is Prefix - Environmental Science - Extension

${spring.cloud.nacos.config.prefix}-${spring.profiles.active}.${spring.cloud.nacos.config.file-extension}

• prefix： Prefix , The default is spring.application.name Value . The priority of value taking is first spring.cloud.nacos.config.prefix, Retake spring.cloud.nacos.config.name, Finally take spring.application.name, Just get a value .
• active： Configure the operating environment , That is, the current environment corresponds to profile. When spring.profiles.active It's empty time , Corresponding connector ”-“ There will be no ,dataId The splicing format of becomes ${prefix}.${file-extension}
• file-exetension： The type of configuration file , The default is properties, You can also configure items through spring.cloud.nacos.config.file-extension To configure the , At present, the supported types are TEXT、JSON、XML、YAML、HTML、Properties

NameSpace: In fact, we can also see from the examples , Nacos Introduce namespace Namespace To manage and isolate multiple environment configurations and services . for example , You may have a local development environment dev、 Test environment test、 Production environment prod Three different environments , Then you can create three different Namespace Distinguish between different environments .

Group: Compare fine-grained isolation , For example, user microservices are grouped separately USER_GROUP