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spring cloud Config Server

Scenario

Problem: Distributed Microservices, Duplicate Configurations

In a microservices environment, each service often maintains its own configuration:

  • Database credentials (name, URL, username, password)
  • Environment properties
  • Common service URLs (e.g., Registry, Gateway)

Main Points

  • Configuration duplication across services
  • High maintenance effort — updating a property in multiple services
  • Risk of inconsistency in shared config values
  • Difficult to manage changes across environments (dev/test/prod)

Solution — Centralized Config Server

A Config Server stores all microservice configuration centrally and supplies it at runtime.

Benefits

  • Externalized configuration
  • Single source of truth
  • No duplication
  • Easy updates (change once → used by all services)

Microservice → Fetch config from Config Server on startup → Load config into memory

Config Server Architecture

Component Role
Config Server Serves configuration files to microservices
Git Repository Stores actual config files (application.properties / YAML)
Config Client Microservice that fetches config at startup

Implementing Spring Cloud Config Server

Supported Config Sources

  • GitHub / Git repo (recommended)
  • Local file system
  • Database (not common)

1. Add starter Dependency

 <!-- https://mvnrepository.com/artifact/org.springframework.cloud/spring-cloud-config-server -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-config-server</artifactId>
        <version>4.3.0</version>
    </dependency>

2. Enable Config Server :

Add annotation EnableConfigServer

@EnableConfigServer
@SpringBootApplication
public class ConfigServerApplication {

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

3. Accour an exception

Terminal :

If you are using the git profile, you need to set a Git URI in your configuration.
If you have set spring.cloud.config.server.bootstrap=true, you need to use a composite configuration.

4. Example Config File in GitHub

Create application.properties inside Git repo

    # Database Setup for PostgreSQL
    spring.datasource.url=jdbc:postgresql://localhost:5432/springdb
    spring.datasource.username=postgres
    spring.datasource.password=postgresql
    spring.datasource.driver-class-name=org.postgresql.Driver
    # Service Registry URL
    eureka.client.service-url.defaultzone=http://localhost:8761

5. Configure Config Server (application.properties)

spring.application.name=config-server
server.port=8090
server.servlet.context-path=/config

# Git Repo URL
spring.cloud.config.server.git.uri=https://github.com/alamgir-ahosain/Learn-Spring-Boot.git

6. Test Config Server

Access URL: http://localhost:8090/config/app/default

Sample JSON output 
{
  "name": "app",
  "profiles": ["default"],
  "propertySources": [
    {
      "source": {
        "spring.datasource.url": "jdbc:postgresql://localhost:5432/springdb",
        "spring.datasource.username": "postgres",
        "spring.datasource.password": "postgresql",
        "eureka.client.service-url.defaultzone": "http://localhost:8761"
      }
    }
  ]
}