Spring Cloud Config 流程源码详解

2018-08-30 本文已影响0人黄大海

Server

如何加载

核心接口是EnvironmentRepository，提供配置的读取

public interface EnvironmentRepository {
      Environment findOne(String application, String profile, String label);
  }

EnvironmentRepository有多种实现，基于JDBC、SVN、GIT等等
默认情况下，使用的是 MultipleJGitEnvironmentRepository(可以配置多个地址的GIT数据源)
ConfigServerAutoConfiguration -> EnvironmentRepositoryConfiguration -> DefaultRepositoryConfiguration

@Configuration
  @ConditionalOnMissingBean(value = EnvironmentRepository.class)
  class DefaultRepositoryConfiguration {
      ...
      @Bean
      public MultipleJGitEnvironmentRepository defaultEnvironmentRepository(...) throws Exception {
          return gitEnvironmentRepositoryFactory.build(environmentProperties);
      }
  }

MultipleJGitEnvironmentRepository 代理遍历每个 JGitEnvironmentRepository， JGitEnvironmentRepository 下使用 NativeEnvironmentRepository 代理读取本地文件。
AbstractScmEnvironmentRepository#findOne

public synchronized Environment findOne(String application, String profile, String label) {
      NativeEnvironmentRepository delegate = new NativeEnvironmentRepository(getEnvironment(),
              new NativeEnvironmentProperties());
      Locations locations = getLocations(application, profile, label);
      delegate.setSearchLocations(locations.getLocations());
      Environment result = delegate.findOne(application, profile, "");
      ...
              getUri());
  }

其中getLocations这部会从GIT远程仓库同步到本地
JGitEnvironmentRepository#getLocations -> JGitEnvironmentRepository.refresh

public String refresh(String label) {
       Git git = createGitClient();
       ...
       checkout(git, label);
       ...
       merge(git, label);
       ...
       resetHard(...)
       ...
}

配置文件加载优先级顺序（上面的覆盖下面的）

模式	应用
{spring.application.name}-{profile}.properties/yml	应用-环境-配置
{spring.application.name}.properties/yml	应用-全局-配置
application-{profile}.properties/yml	公众-环境-配置
application.properties/yml	公众-全局-配置

具体的逻辑参考NativeEnvironmentRepository和ConfigFileApplicationListener

如何注入

ConfigServer本身也可以注入自己的读取的配置，使得其他服务可以和ConfigServer配置在一起，比如Eureka
Config的自身注入在BootStrap阶段
ConfigServerBootstrapConfiguration#LocalPropertySourceLocatorConfiguration

 @Configuration
  @ConditionalOnProperty("spring.cloud.config.server.bootstrap")
  public class ConfigServerBootstrapConfiguration {
      @Bean
      public EnvironmentRepositoryPropertySourceLocator environmentRepositoryPropertySourceLocator() {
          return new EnvironmentRepositoryPropertySourceLocator(this.repository, this.client.getName(),
                  this.client.getProfile(), getDefaultLabel());
      }
  }

EnvironmentRepositoryPropertySourceLocator会调用EnvironmentRepository获取配置

public class EnvironmentRepositoryPropertySourceLocator implements PropertySourceLocator{
      @Override
      public PropertySource<?> locate(Environment environment) {
          CompositePropertySource composite = new CompositePropertySource("configService");
          for (PropertySource source : environmentRepository.findOne(name, profiles, label)
                  .getPropertySources()) {
              composite.addPropertySource(...);
          }
          return composite;
      }
}

PropertySourceBootstrapConfiguration#init负责所有BootStrap配置的加载，所有实现PropertySourceLocator接口的服务都会被调用

CompositePropertySource composite = new CompositePropertySource(
              BOOTSTRAP_PROPERTY_SOURCE_NAME);
  for (PropertySourceLocator locator : this.propertySourceLocators) {
      PropertySource<?> source = locator.locate(environment);
      composite.addPropertySource(source);
  }

Client

2种高可用方式， Spring-Cloud-Config-Client配置存在两种策略
1. 通过ConfigServer获取注册中心地址和其他配置
2. 通过注册中心获取ConfigServer地址，然后获得其他配置
参考国内比较成熟的分布式集中配置，比如百度Disconf，携程Apollo等基本都是第1种策略，好处是唯一需要本地写死的是配置中心的参数.
但是Spring Cloud 1.X 并不支持ConfigServer集群的高可用配置。需要单独将spring-cloud-starter-config升级到2.x（可以和其他1.x组件混用）
升级后就可以配多个地址了，如下：

spring:
  application:
    name: user
  cloud:
    config:
      fail-fast: true
      profile: dev
      label: master
      uri: http://localhost:8761/config, http://localhost:8762/config, http://localhost:8763/config

但是网上更多介绍的是第二种方案，这里也贴出来。配置项更多了，需要同时指定configserver和eureka

spring:
  application:
    name: user
  cloud:
    config:
      fail-fast: true
      profile: dev
      label: master
      discovery:
        enabled: true
        serviceId: dashboard
      
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/,http://localhost2:8762/eureka,http://localhost3:8763/eureka

启动过程和ConfigServer注入过程类似
ConfigServiceBootstrapConfiguration -> ConfigServicePropertySourceLocator -> locate

public PropertySource<?> locate(Environment environment) {
    CompositePropertySource composite = new CompositePropertySource("configService");
    ...
    RestTemplate restTemplate = getSecureRestTemplate(properties);
    ...
    Environment result = getRemoteEnvironment(restTemplate...);
    ...
    for (PropertySource source : result.getPropertySources()) {
        ...
        composite.addPropertySource(source);
    }
    ...
}

该服务实现了PropertySourceLocator接口，在PropertySourceBootstrapConfiguration#init中会被注入到bootStrap的context中
方案2比方案1多一个环节，configServer 的 uri 是由注册中心获取的
DiscoveryClientConfigServiceBootstrapConfiguration#refresh

@ConditionalOnProperty(value = "spring.cloud.config.discovery.enabled", matchIfMissing = false)
@Configuration
@EnableDiscoveryClient
public class DiscoveryClientConfigServiceBootstrapConfiguration {
    void refresh() {
        String serviceId = this.config.getDiscovery().getServiceId();
        List<ServiceInstance> serviceInstances = this.instanceProvider
                    .getConfigServerInstances(serviceId);
        for (int i = 0; i < serviceInstances.size(); i++) {
                ServiceInstance server = serviceInstances.get(i);
                String url = getHomePage(server);
                listOfUrls.add(url);
        }
        ...
        configClientProperties.setUri(listOfUrls);
    }
}

Spring Cloud Config 流程源码详解

Server

Client

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