SpringCloud是如何动态更新配置的

# AutoConfiguration
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration,\
org.springframework.cloud.autoconfigure.LifecycleMvcEndpointAutoConfiguration,\
org.springframework.cloud.autoconfigure.RefreshAutoConfiguration,\
org.springframework.cloud.autoconfigure.RefreshEndpointAutoConfiguration,\
org.springframework.cloud.autoconfigure.WritableEnvironmentEndpointAutoConfiguration
# Application Listeners
org.springframework.context.ApplicationListener=\
org.springframework.cloud.bootstrap.BootstrapApplicationListener,\
org.springframework.cloud.bootstrap.LoggingSystemShutdownListener,\
org.springframework.cloud.context.restart.RestartListener
# Bootstrap components
org.springframework.cloud.bootstrap.BootstrapConfiguration=\
org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration,\
org.springframework.cloud.bootstrap.encrypt.EncryptionBootstrapConfiguration,\
org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration,\
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\
org.springframework.cloud.util.random.CachedRandomPropertySourceAutoConfiguration

@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
CompositePropertySource composite = new CompositePropertySource(
    BOOTSTRAP_PROPERTY_SOURCE_NAME);
AnnotationAwareOrderComparator.sort(this.propertySourceLocators);
boolean empty = true;
ConfigurableEnvironment environment = applicationContext.getEnvironment();
for (PropertySourceLocator locator : this.propertySourceLocators) {
  PropertySource<?> source = null;
  //回调所有实现PropertySourceLocator接口实例的locate方法，
  source = locator.locate(environment);
  if (source == null) {
    continue;
  }

  composite.addPropertySource(source);
  empty = false;
}
if (!empty) {
//从当前Enviroment中获取 propertySources
  MutablePropertySources propertySources = environment.getPropertySources();
  //省略...
  //将composite中的PropertySource添加到当前应用上下文的propertySources中
  insertPropertySources(propertySources, composite);
  //省略...
}

# Auto Configuration
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.consul.config.ConsulConfigAutoConfiguration
# Bootstrap Configuration
org.springframework.cloud.bootstrap.BootstrapConfiguration=\
org.springframework.cloud.consul.config.ConsulConfigBootstrapConfiguration

@Configuration(proxyBeanMethods = false)
@ConditionalOnConsulEnabled
public class ConsulConfigBootstrapConfiguration {

  @Configuration(proxyBeanMethods = false)
  @EnableConfigurationProperties
  @Import(ConsulAutoConfiguration.class)
  @ConditionalOnProperty(name = "spring.cloud.consul.config.enabled",
      matchIfMissing = true)
  protected static class ConsulPropertySourceConfiguration {

    @Autowired
    private ConsulClient consul;

    @Bean
    @ConditionalOnMissingBean
    public ConsulConfigProperties consulConfigProperties() {
      return new ConsulConfigProperties();
    }

    @Bean
    public ConsulPropertySourceLocator consulPropertySourceLocator(
        ConsulConfigProperties consulConfigProperties) {
      return new ConsulPropertySourceLocator(this.consul, consulConfigProperties);
    }

  }

}

@Override
@Retryable(interceptor = "consulRetryInterceptor")
public PropertySource<?> locate(Environment environment) {
  if (environment instanceof ConfigurableEnvironment) {
    ConfigurableEnvironment env = (ConfigurableEnvironment) environment;

    String appName = this.properties.getName();

    if (appName == null) {
      appName = env.getProperty("spring.application.name");
    }

    List<String> profiles = Arrays.asList(env.getActiveProfiles());

    String prefix = this.properties.getPrefix();

    List<String> suffixes = new ArrayList<>();
    // 不是文件类型的时候，后缀为 /，否则就是配置文件的后缀
    if (this.properties.getFormat() != FILES) {
      suffixes.add("/");
    } else {
      suffixes.add(".yml");
      suffixes.add(".yaml");
      suffixes.add(".properties");
    }

    // 路径
    String defaultContext = getContext(prefix, this.properties.getDefaultContext());

    for (String suffix : suffixes) {
      this.contexts.add(defaultContext + suffix);
    }
    // 追加环境及文件类型
    for (String suffix : suffixes) {
      addProfiles(this.contexts, defaultContext, profiles, suffix);
    }

    String baseContext = getContext(prefix, appName);

    // 应用名称前缀
    for (String suffix : suffixes) {
      this.contexts.add(baseContext + suffix);
    }
    for (String suffix : suffixes) {
      addProfiles(this.contexts, baseContext, profiles, suffix);
    }

    Collections.reverse(this.contexts);

    CompositePropertySource composite = new CompositePropertySource("consul");

    for (String propertySourceContext : this.contexts) {
      try {
        ConsulPropertySource propertySource = null;
        if (this.properties.getFormat() == FILES) {
          // 获取值
          Response<GetValue> response = this.consul.getKVValue(propertySourceContext, this.properties.getAclToken());
          // 添加当前索引
          addIndex(propertySourceContext, response.getConsulIndex());
          // 如果值不为空，则更新值并初始化
          if (response.getValue() != null) {
            ConsulFilesPropertySource filesPropertySource = new ConsulFilesPropertySource(propertySourceContext, this.consul, this.properties);
            // 解析配置内容
            filesPropertySource.init(response.getValue());
            propertySource = filesPropertySource;
          }
        } else {
          propertySource = create(propertySourceContext, this.contextIndex);
        }
        if (propertySource != null) {
          composite.addPropertySource(propertySource);
        }
      } catch (Exception e) {
        if (this.properties.isFailFast()) {
          log.error("Fail fast is set and there was an error reading configuration from consul.");
          ReflectionUtils.rethrowRuntimeException(e);
        } else {
          log.warn("Unable to load consul config from " + propertySourceContext, e);
        }
      }
    }

    return composite;
  }
  return null;
}

public synchronized Set refresh() {

    Map<String, Object> before = extract(
            this.context.getEnvironment().getPropertySources());
    //1、加载最新的值，并替换Envrioment中旧值
    addConfigFilesToEnvironment();
    Set<String> keys = changes(before,
            extract(this.context.getEnvironment().getPropertySources())).keySet();
    this.context.publishEvent(new EnvironmentChangeEvent(context, keys));
    //2、将refresh scope中的Bean 缓存失效: 清空
    this.scope.refreshAll();
    return keys;
}

public class ConfigWatch implements ApplicationEventPublisherAware, SmartLifecycle {}

@Bean
@ConditionalOnProperty(name = "spring.cloud.consul.config.watch.enabled", matchIfMissing = true)
public ConfigWatch configWatch(ConsulConfigProperties properties,
                               ConsulPropertySourceLocator locator,
                               ConsulClient consul,
                               @Qualifier(CONFIG_WATCH_TASK_SCHEDULER_NAME) TaskScheduler taskScheduler) {
  return new ConfigWatch(properties, consul, locator.getContextIndexes(), taskScheduler);
}

@Override
public void start() {
  if (this.running.compareAndSet(false, true)) {
    this.watchFuture = this.taskScheduler.scheduleWithFixedDelay(
      this::watchConfigKeyValues, this.properties.getWatch().getDelay());
  }
}

// Timed 是 Prometheus 的监控
@Timed("consul.watch-config-keys")
public void watchConfigKeyValues() {
  if (this.running.get()) {
    // 遍历所有的配置的 key
    for (String context : this.consulIndexes.keySet()) {

      // turn the context into a Consul folder path (unless our config format
      // are FILES)
      if (this.properties.getFormat() != FILES && !context.endsWith("/")) {
        context = context + "/";
      }

      // 根据配置返回的 index 判断是否发生变化
      try {
        Long currentIndex = this.consulIndexes.get(context);
        if (currentIndex == null) {
          currentIndex = -1L;
        }

        log.trace("watching consul for context '" + context + "' with index " + currentIndex);

        // use the consul ACL token if found
        String aclToken = this.properties.getAclToken();
        if (StringUtils.isEmpty(aclToken)) {
          aclToken = null;
        }

        // 获取指定的 key
        Response<List<GetValue>> response = this.consul.getKVValues(context, aclToken, new QueryParams(this.properties.getWatch().getWaitTime(), currentIndex));

        // if response.value == null, response was a 404, otherwise it was a
        // 200
        // reducing churn if there wasn't anything
        if (response.getValue() != null && !response.getValue().isEmpty()) {
          Long newIndex = response.getConsulIndex();

          // 判断 key 的 index 是否相等，如果发生变化，则发出 RefreshEvent 事件
          if (newIndex != null && !newIndex.equals(currentIndex)) {
            // don't publish the same index again, don't publish the first
            // time (-1) so index can be primed
            // 没有发布过这个 index 的事件，且不是第一次发布
            if (!this.consulIndexes.containsValue(newIndex) && !currentIndex.equals(-1L)) {
              log.trace("Context " + context + " has new index " + newIndex);
              // 发送事件
              RefreshEventData data = new RefreshEventData(context, currentIndex, newIndex);
              this.publisher.publishEvent(new RefreshEvent(this, data, data.toString()));
            } else if (log.isTraceEnabled()) {
              log.trace("Event for index already published for context " + context);
            }
            this.consulIndexes.put(context, newIndex);
          } else if (log.isTraceEnabled()) {
            log.trace("Same index for context " + context);
          }
        } else if (log.isTraceEnabled()) {
          log.trace("No value for context " + context);
        }

      } catch (Exception e) {
        // only fail fast on the initial query, otherwise just log the error
        if (this.firstTime && this.properties.isFailFast()) {
          log.error("Fail fast is set and there was an error reading configuration from consul.");
          ReflectionUtils.rethrowRuntimeException(e);
        } else if (log.isTraceEnabled()) {
          log.trace("Error querying consul Key/Values for context '" + context + "'", e);
        } else if (log.isWarnEnabled()) {
          // simplified one line log message in the event of an agent
          // failure
          log.warn("Error querying consul Key/Values for context '" + context + "'. Message: " + e.getMessage());
        }
      }
    }
  }
  this.firstTime = false;
}

@Override
public void onApplicationEvent(ApplicationEvent event) {
  if (event instanceof ApplicationReadyEvent) {
    handle((ApplicationReadyEvent) event);
  }
  else if (event instanceof RefreshEvent) {
    handle((RefreshEvent) event);
  }
}

else if (event instanceof RefreshEvent) {
  handle((RefreshEvent) event);
}

public void handle(RefreshEvent event) {
  if (this.ready.get()) { // don't handle events before app is ready
    log.debug("Event received " + event.getEventDesc());
    Set<String> keys = this.refresh.refresh();
    log.info("Refresh keys changed: " + keys);
  }
}

public synchronized Set<String> refresh() {
  Set<String> keys = refreshEnvironment();
  this.scope.refreshAll();
  return keys;
}

public synchronized Set<String> refreshEnvironment() {
  Map<String, Object> before = extract(
      this.context.getEnvironment().getPropertySources());
  addConfigFilesToEnvironment();
  Set<String> keys = changes(before,
      extract(this.context.getEnvironment().getPropertySources())).keySet();
  this.context.publishEvent(new EnvironmentChangeEvent(this.context, keys));
  return keys;
}

/* For testing. */ ConfigurableApplicationContext addConfigFilesToEnvironment() {
  ConfigurableApplicationContext capture = null;
  try {
    StandardEnvironment environment = copyEnvironment(
        this.context.getEnvironment());
    SpringApplicationBuilder builder = new SpringApplicationBuilder(Empty.class)
        .bannerMode(Mode.OFF).web(WebApplicationType.NONE)
        .environment(environment);
    // Just the listeners that affect the environment (e.g. excluding logging
    // listener because it has side effects)
    builder.application()
        .setListeners(Arrays.asList(new BootstrapApplicationListener(),
            new ConfigFileApplicationListener()));
    capture = builder.run();
    if (environment.getPropertySources().contains(REFRESH_ARGS_PROPERTY_SOURCE)) {
      environment.getPropertySources().remove(REFRESH_ARGS_PROPERTY_SOURCE);
    }
    MutablePropertySources target = this.context.getEnvironment()
        .getPropertySources();
    String targetName = null;
    for (PropertySource<?> source : environment.getPropertySources()) {
      String name = source.getName();
      if (target.contains(name)) {
        targetName = name;
      }
      if (!this.standardSources.contains(name)) {
        if (target.contains(name)) {
          target.replace(name, source);
        }
        else {
          if (targetName != null) {
            target.addAfter(targetName, source);
            // update targetName to preserve ordering
            targetName = name;
          }
          else {
            // targetName was null so we are at the start of the list
            target.addFirst(source);
            targetName = name;
          }
        }
      }
    }
  }
    ......
|

this.scope.refreshAll();

@EventListener(classes = RefreshScopeRefreshedEvent.class)
public void updateChange(RefreshScopeRefreshedEvent event) {
  //这里获取到的新的值
  String pwd = redisProperties.getPassword();
  System.out.print("new pwd: " + pwd);
}

@EventListener(classes = EnvironmentChangeEvent.class)
public void updateChange(EnvironmentChangeEvent event) {
  Set<String> updatedKeys = event.getKeys();
  System.out.print(updatedKeys);
  for (String key : updatedKeys) {
    if (key.equals("redis.password")) {
      System.out.print("new password: " + context.getEnvironment().getProperty(key));
      //    do something
    }
  }
  //这里获取到的还是旧的值
  String pwd = redisProperties.getPassword();
  System.out.print("old pwd: " + pwd);
}