Nacos-config-demo

Introduction

Microservice, by design, should be stateless. What if we have certain configuration that has to be provided for the microservice to run? For example, a security token to access another service. Or, the url of the database to connect to. These information also changes with the deployment environment. Hence, a centralized server is critical in the architecture.
Nacos is a config server that serves micro services architecture. In this demo, we'll use a Spring Cloud application to access the config.

Pre-requisite

We need a Nacos server to run locally for the demo to work. Here are the steps:

git clone https://github.com/alibaba/nacos.git
cd nacos/
mvn -Prelease-nacos clean install -U  
ls -al distribution/target/

// change the $version to your actual path
cd distribution/target/nacos-server-$version/nacos/bin

sh startup.sh -m standalone

Replace the $version with the real version number.

Prep work

Once Nacos server is running, we should be able to access its dashbord at: http://localhost:8848/nacos/index.html.
The login/password is nacos/nacos.
Once logging, let's click on the + sign on the right side of the config table. At this point, we want to add a config:

Code example

We use Spring Cloud Alibaba framework for the demo. The code is pretty simple:

    @Value("${lesson.feedback:}")
    private String feedback;

    @RequestMapping(value = "/get")
    public String echo() {
        return feedback;
    }

We would create a REST api that prints out the query. The url is http://localhost:18083/get. And we would ask for the value of lesson.feedback that was created in the dashboard.
If we run the code, and then curl or use a browser to verify the result, we shall see the result great.

Under the hood

Many people might ask: How come we didn't specify the dataid and group that's used in the GUI? Well, that's because Spring Cloud is auto wiring the configuration to the application. The default rule are as follows:
Data id: spring.cloud.nacos.config.prefix
Group: spring.cloud.nacos.config.group
In our case, the data id is nacos-config-example.properties and group is DEFAULT_GROUP. Mystery solved!