Spring Cloud Config realizes unified management of configuration center: reduces error rate and improves maintainability

1. Introduction

1 Problems of traditional application configuration management

In traditional application development, it is often necessary to configure various parameters, such as database connection information, log levels, and so on. These configurations are scattered everywhere, making it difficult to manage and update in a unified manner, which increases maintenance costs.

2 Significance of Configuration Center

In order to solve the problem of traditional application configuration management, the configuration center came into being. The configuration center is a system for managing configuration information. The configuration is stored centrally for use by various applications to realize dynamic update and unified management of configuration. This greatly improves the maintainability and flexibility of the application.

3 Features of Spring Cloud Config

Spring Cloud Config is an open source project that provides external configuration support for distributed systems based on version control tools such as Git or Subversion. It can help architects and developers manage the configuration of all microservices, and provide a secure, scalable, and highly available distributed configuration center service. Key features and benefits of Spring Cloud Config include:

• Centralized management: gather all configuration information in one place for easy maintenance and management.
• Configuration version management: Automatically create a version for each configuration file and view historical versions.
• Security: configuration information is encrypted and stored, and HTTPS and other security protocols are used during remote transmission.
• Scalability: Multiple configuration center instances can be horizontally expanded and deployed to ensure high availability.
• Integrate multiple back-end storage: support multiple back-end storage methods (Git, SVN, local file system, etc.).

2. Spring Cloud Config architecture and implementation

1 The concept and principle of Spring Cloud Config Server

Spring Cloud Config Server is a distributed configuration center server provided by Spring Cloud, which is responsible for obtaining configuration information from back-end storage and exposing it to Config Client. Spring Cloud Config Server adopts the standard Spring Boot application as the basic framework, and can automatically integrate Eureka, Ribbon and other technologies to realize load balancing and service registration and discovery functions.

The workflow of Spring Cloud Config Server is as follows:

• When starting, read the relevant configuration of the back-end storage from the configuration file, such as version control tool information such as Git or Subversion.
• According to the client request, load the corresponding configuration information from the backend storage (such as Git).
• Return configuration information to the client.

2 Concept and usage of Spring Cloud Config Client

Spring Cloud Config Client is a configuration client provided by Spring Cloud, which is used to obtain configuration information from Spring Cloud Config Server. When the client starts, it will automatically obtain configuration information from the Config Server. If the configuration information changes, the client can also refresh the context to obtain the latest configuration again.

The basic steps of using Spring Cloud Config Client are as follows:

1. In the project configuration file (such as application.yml), specify the address of the Config Server and configuration file name and other related information.
2. In classes that need to use configuration information, use @Value annotations and ${} expressions to obtain corresponding configuration values.
   For example:

@Value("${database.url}")
private String dbUrl; 

3 Application of Spring Cloud Config in multi-environment and multi-project

In a distributed system there are usually multiple environments (such as development, test, production, etc.) and multiple projects. Spring Cloud Config can support the configuration information of different environments and different projects, as long as the corresponding profile is added after the configuration file name, and the configuration information of different environments or different projects can be specified.

For example, there is currently a configuration file named config-server.yml in the Git repository. You can create separate configuration files for different environments or different projects, such as config-server-dev.yml, config-server-prod.yml, and then in Specify the corresponding profile in Config Server and Config Client to realize multi-environment and multi-project configuration management.

3. The configuration file format and management method of Spring Cloud Config

1 Configuration file format

Spring Cloud Config supports two mainstream configuration file formats: Properties (Java property files) and YAML (data-centric format). In actual use, it depends on usage habits and teamwork.

Properties format configuration file example

# application.properties

server.port=8080
spring.datasource.url = jdbc:mysql://localhost:3306/test
spring.datasource.username=springuser
spring.datasource.password=ThePassword

Example of configuration file in YAML format

# application.yml

server:
    port: 8080
spring:
    datasource:
        url: jdbc:mysql://localhost:3306/test
        username: springuser
        password: ThePassword

2 Management methods of configuration files

Spring Cloud Config supports a variety of configuration file management methods, such as Git, SVN, and Native.

Among them, Git is the most commonly used method. Spring Cloud Config will periodically pull the configuration files in the Git repository to the local, and provide external access through the REST API.

Example of configuring a Git repository

Create a classpath:/config directory under the resources directory of the application, and create configuration files under this directory for different deployment environments (such as development, testing, and production) of the application.

For example, create a development environment configuration file application-dev.properties in the Git warehouse testconfig-repo, the content is as follows:

# application-dev.properties

server.port=8081
spring.datasource.url=jdbc:mysql://localhost:3306/devdb
spring.datasource.username=devuser
spring.datasource.password=dev-password

Specify the Git warehouse information in the configuration file application.yml of the Spring Cloud Config server instance:

# application.yml

server:
    port: 8888
spring:
    cloud:
        config:
            server:
                git:
                    uri: https://github.com/myusername/testconfig-repo.git
                    username: ${
    
    GIT_USERNAME}
                    password: ${
    
    GIT_PASSWORD}

3 Security of configuration files

Spring Cloud Config provides several ways to secure configuration files, the most common of which is using Spring Security to secure REST API endpoints.

The automatic configuration function of Spring Security can be enabled by introducing the spring-boot-starter-security dependency in the Spring Boot application.

4. Advanced features of Spring Cloud Config

1 Configuration file auto-refresh

Spring Cloud Config supports automatic refresh of configuration files to dynamically obtain the latest configuration information when the application is running.

To enable this feature, you need to configure the client application and add Actuator dependencies. Then trigger an automatic refresh of the configuration file by accessing the refresh endpoint in Actuator.

2 Configuration file encryption and decryption

In order to protect sensitive information in Spring Cloud Config from being leaked, Spring Cloud provides a way to encrypt configuration files.

Sensitive information is encrypted and stored in Git repositories using JCE keys. Decryption can be performed by introducing the corresponding dependency library in the client application.

3 Configuration update based on Spring Cloud Bus

Spring Cloud Config supports configuration updates based on Spring Cloud Bus. When the application needs to receive the configuration file update notification, it can quickly obtain the latest configuration information.

The easiest way to use Spring Cloud Bus is to configure RabbitMQ or Kafka and then pass notification messages through the message bus to all application instances that need to update the configuration.

5. Precautions for using Spring Cloud Config

1 Fault tolerance and high availability of Spring Cloud Config Server

• Spring Cloud Config Server uses Git and other version control tools as the way to store configuration files at the back end, which ensures data persistence, but when the Git warehouse is unavailable, the application may not be able to start normally. The fault tolerance and high availability of Spring Cloud Config Server can be increased by:
  • Configure multiple Config Server instances and distribute requests through a load balancer
  • Cache configuration files locally to reduce dependence on remote Git repositories. When Git repositories are unavailable, they can still be read from the local cache

2 Security issues when adding sensitive information to the configuration center

• When adding sensitive information to the configuration center, you need to pay attention to security issues. For example, sensitive information such as database connection information and passwords should be encrypted before uploading.
  Spring Cloud Config Server supports decrypting encrypted configuration files, which can be used after decryption before the application obtains the configuration files.
• In Spring Cloud Config, you can choose to use the symmetric encryption AES encryption algorithm or the asymmetric encryption RSA encryption algorithm for configuration file encryption.

3 Version control and rollback mechanism of Spring Cloud Config

• Spring Cloud Config Server uses Git warehouse as the way to store configuration files at the back end, so it has the characteristics of code version control and rollback mechanism.
• In Git, you can use mechanisms such as branches and tags for version control. When you find a problem with the configuration file, you can roll back to the previous version to solve the problem.

6. Application practice and case introduction of Spring Cloud Config

1 Application of Spring Cloud Config in microservice architecture

• In the microservice architecture, there are a large number of services and complex configuration dependencies between services. Using Spring Cloud Config can achieve centralized management and configuration, reducing duplicate code and configuration files, and facilitating maintenance and upgrades.
• Spring Cloud Config and Spring Cloud Bus can automatically refresh the configuration file. When the configuration file is modified, the configuration file information can be sent to all services that have subscribed to the event for update through the message bus.

2 Application practice of Spring Cloud Config in cloud computing, container and other scenarios

• Due to the rapid changes in the creation and destruction of containers in a containerized deployment environment, efficient management of configuration files is required. Using Spring Cloud Config can realize the persistent storage of configuration management, and can choose different back-end storage solutions according to business needs, such as Git, SVN, JDBC, etc.
• As an independent service, Spring Cloud Config can be integrated with container management systems such as Kubernetes and Mesos to achieve flexible and automatic management of configuration information in cloud computing environments.

3 Successful cases of Spring Cloud Config in enterprises

• When financial institutions use Spring Cloud Config for configuration management, they have successfully realized centralized configuration management under the microservice architecture, and can choose different back-end storage solutions according to actual needs, such as Git. By using Spring Cloud Bus to automatically refresh configuration information, the productivity of configuration management is improved, and the security of configuration information is guaranteed.
• The e-commerce enterprise successfully achieved rapid configuration deployment and update when using Spring Cloud Config for centralized configuration management, thereby improving the maintainability and stability of the application. At the same time, Spring Cloud Config also realizes the sharing and reusability of public configurations for enterprises, saving unnecessary development costs and time.

7. Summary and review

1 Advantages and disadvantages of Spring Cloud Config

advantage

• Centralized management of configuration files for easy maintenance and updates.
• Supports parsing of multiple configuration file formats, such as JSON, YAML, and Properties.
• Customized configurations can be made for different environments and different applications.
• Use HTTP API to integrate into the application program, easy to use.
• Supports multiple storage backends, such as Git, local file system, JDBC, etc.

shortcoming

• Once the configuration service fails, it will affect all applications using the configuration service.
• There is a delay in reading the configuration, which can cause longer application startup times.

2 The status and role of Spring Cloud Config in the microservice architecture

Spring Cloud Config is an important part of the microservice architecture, and its role is mainly reflected in the following three aspects:

1. Centralized management and maintenance of various configurations required in the entire microservice architecture, avoiding the tedious and error-prone manual modification of configuration files.
2. Support dynamic refresh configuration, update the configuration of the application program in real time, ensuring the up-to-dateness of the application.
3. By cooperating with components such as Spring Cloud Eureka and Spring Cloud Bus, the system can be made more flexible, scalable and reliable, and the maintainability and security of the system are improved.

// 代码示例：从Spring Cloud Config中获取配置
@SpringBootApplication
@RestController
@RefreshScope //注解表示能够动态刷新配置
public class ConfigClientApplication {
    
    
  
  @Value("${foo.bar}")
  String fooBar;

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

  @RequestMapping("/foo")
  public String hi() {
    
    
    return fooBar; // 返回配置值
  }
}

The above code demonstrates how to integrate Spring Cloud Config into the application and obtain foo.barthe configuration values. Due to the use of @RefreshScopeannotations, when the configuration file changes, the application will automatically refresh the configuration.