Distributed configuration using spring cloud config

What is spring cloud config

Spring cloud config helps application in externalising the configuration properties in a server/client model. Which means there is a config server where all client application connects and read the properties related to their application. Properties can be accessed basis on application name and configured profile.
It supports resource based configuration using GIT repository or local file system over HTTP. Properties are managed in form of key-value pair. Though it easily integrate with spring boot application but can be used by any application in other languages also as properties can be accessed through REST URLs also.

We are going to learn below things here.

1. GIT repository for configuration management
2. Cloud config server
3. Config client

GIT Repository

Here we are going to use GIT for configuration management which will be configured in config server. Setting up a GIT repository is very easy. We have to create the properties file using some naming pattern like <application_name>-<profile>.properties. Below is the structure of a GIT repository used for same purpose.

Config_repository

      microservice-app-DEV.properties

      microservice-app-PROD.properties

In above example "Config_repository" is our repository for configuration files where "microservice-app" is the application name and "DEV" or "PROD" is the profile name which details client application need to configure during connection to config server.
Below is the content of DEV properties file. Similarly PROD properties file will have details for production environment.

message=Welcome to Development!
world=Dev world

Cloud config server

We will create the config server using spring boot application. Below are the steps.

a. Create spring boot application
    You can either use spring initialiser (https://start.spring.io) or your favourite IDE to create the application.
b. Maven Dependencies
    Include below dependencies in your pom.xml.

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-config-server</artifactId>
        </dependency>

c. Java configuration
    Below is the spring boot main class with required configuration annotation @EnableConfigServer.

@SpringBootApplication
@EnableConfigServer
public class CloudConfigApplication {

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

d. Cloud application configuration (application.yml)
    I have used YML for application configuration but properties file also can be used. Below is the content of configuration file. Here I have configured my git project for demonstration purpose.

server.port : 8888
spring:
  cloud:
    config:
      server:
        git:
          uri : https://github.com/thetechnojournals/Config-repo/
          username: ${git_user}
          password: ${git_password}
          force-pull: true

spring.security.user.name: config_user
spring.security.user.password: Lwre15qlw@

User name and password configured here will be required by config client to connect with it.

After starting the cloud config server, you can verify the URL in browser as given below.
Syntax: http://<host:port>/<application_name>/<profile>
Example: http://localhost:8888/microservice-app/DEV

It will show you the similar result as given below.

{"name":"microservice-app","profiles":["DEV"],"label":null,"version":"2e7c382ac0bcd2c35892960487451b333847c844","state":null,"propertySources":[{"name":"https://github.com/ashokprajapati999/Config-repo//microservice-app-DEV.properties","source":{"message":"Welcome to Development!","world":"Dev world"}}]}

Cloud config client

Our config client application is created using spring boot application.

a. Create spring boot application
    You can either use spring initialiser (https://start.spring.io) or your favourite IDE to create the application.
b. Maven Dependencies
    Include below dependencies in your pom.xml.

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

c. bootstrap.yml
    A bootstrap configuration required to connect with cloud config server.

spring:
  profiles:
    active: PROD
  cloud:
    config:
      name: microservice-app
      uri: https://localhost:8888/
      username: config_user
      password: Lwre15qlw@

d. Properties usage
    Now our configuration is complete and we can use the properties in any of the spring managed class in the same way we do it in any regular spring application. See below example.

    @Value("${message}")
    private String message;

This concludes all the required components of spring cloud config server and client using GIT. Please let me know if you have any comment or suggestions.

If you are interested to know more about cloud configuration, like spring cloud bus using webhooks then please visit my another post.
config management using spring cloud bus