问题
Spring Cloud Gateway版本是2.2.9.RELEASE，原本项目中依赖服务自动发现来自动配置路由到微服务的，但是发现将spring.cloud.gateway.discovery.locator.enabled=false 启动之后Gateway依然会将所有微服务自动注册到路由中，百思不得其解，遂调试代码观察期启动过曾，记录此文以供参考，官方文档
可以看到此处明确表示，可以通过设置该值来讲微服务中服务自动添加到配置中。按照这个线索，找到了
org.springframework.cloud.gateway.discovery.DiscoveryClientRouteDefinitionLocator#getRouteDefinitions
这个类在之前的文章includeExpression中有提及过，在构造函数中对成员变量
public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {
private final DiscoveryLocatorProperties properties;
...
private Flux<List<ServiceInstance>> serviceInstances;
/**
* Kept for backwards compatibility. You should use the reactive discovery client.
* @param discoveryClient the blocking discovery client
* @param properties the configuration properties
* @deprecated kept for backwards compatibility
*/
@Deprecated
public DiscoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient,
DiscoveryLocatorProperties properties) {
this(discoveryClient.getClass().getSimpleName(), properties);
serviceInstances = Flux
.defer(() -> Flux.fromIterable(discoveryClient.getServices()))
.map(discoveryClient::getInstances)
.subscribeOn(Schedulers.boundedElastic());
}
public DiscoveryClientRouteDefinitionLocator(ReactiveDiscoveryClient discoveryClient,
DiscoveryLocatorProperties properties) {
this(discoveryClient.getClass().getSimpleName(), properties);
serviceInstances = discoveryClient.getServices()
.flatMap(service -> discoveryClient.getInstances(service).collectList());
}
...
这里会对serviceInstances进行初始化，从注册中心获取所有已注册的微服务实例进行填充，serviceInstance的获取结束了,在DiscoveryClientRouteDefinitionLocator还有一个重要的方法
#DiscoveryClientRouteDefinitionLocator
@Override
public Flux<RouteDefinition> getRouteDefinitions() {
SpelExpressionParser parser = new SpelExpressionParser();
Expression includeExpr = parser
.parseExpression(properties.getIncludeExpression());
Expression urlExpr = parser.parseExpression(properties.getUrlExpression());
Predicate<ServiceInstance> includePredicate;
if (properties.getIncludeExpression() == null
|| "true".equalsIgnoreCase(properties.getIncludeExpression())) {
includePredicate = instance -> true;
}
else {
includePredicate = instance -> {
Boolean include = includeExpr.getValue(evalCtxt, instance, Boolean.class);
if (include == null) {
return false;
}
return include;
};
}
return serviceInstances.filter(instances -> !instances.isEmpty())
.map(instances -> instances.get(0)).filter(includePredicate)
.map(instance -> {
RouteDefinition routeDefinition = buildRouteDefinition(urlExpr,
instance);
final ServiceInstance instanceForEval = new DelegatingServiceInstance(
instance, properties);
for (PredicateDefinition original : this.properties.getPredicates()) {
PredicateDefinition predicate = new PredicateDefinition();
predicate.setName(original.getName());
for (Map.Entry<String, String> entry : original.getArgs()
.entrySet()) {
String value = getValueFromExpr(evalCtxt, parser,
instanceForEval, entry);
predicate.addArg(entry.getKey(), value);
}
routeDefinition.getPredicates().add(predicate);
}
for (FilterDefinition original : this.properties.getFilters()) {
FilterDefinition filter = new FilterDefinition();
filter.setName(original.getName());
for (Map.Entry<String, String> entry : original.getArgs()
.entrySet()) {
String value = getValueFromExpr(evalCtxt, parser,
instanceForEval, entry);
filter.addArg(entry.getKey(), value);
}
routeDefinition.getFilters().add(filter);
}
return routeDefinition;
});
}
根据includeExpr 配置的sl表达式判断当前的serviceInstance是否服务转发要求。填充好predicate，filter之后返回routeDefinition，urlExpr的默认值是"lb://"+serverId，predicate匹配的path就等于serverId，有配置可以转换为小写spring.cloud.gateway.discovery.locator.lower-case-service-id=true因为eureka默认会uppercase serverId，filter中会StripPrefix=1，将路径中的serverId移除再转发给下游。路由定义的部分就这里了，他的刷新逻辑，依靠SpringRefreshContext 事件，具体的定义逻辑在org.springframework.cloud.gateway.config.GatewayAutoConfiguration
@Bean
@ConditionalOnClass(
name = "org.springframework.cloud.client.discovery.event.HeartbeatMonitor")
public RouteRefreshListener routeRefreshListener(
ApplicationEventPublisher publisher) {
return new RouteRefreshListener(publisher);
}
RouteRefreshListener 实现了ApplicationListener<ApplicationEvent>，监控以下几个事件，并按照条件进行逻辑执行
- ContextRefreshEvent 启动容器，或者beans重新加载
- RefreshScopeRefreshdEvent 是 Spring Cloud 中的一个事件，当 @RefreshScope 注解的 beans 被重新加载时发布。这个事件主要用于 Spring Cloud 的配置刷新机制，当配置中心的配置信息发生变化时，会触发该事件以刷新 beans。
- ParentHeartbeatEvent 是 Spring Cloud Bus 中的一个事件，用于在父上下文（通常是 Spring Cloud Config Server）发生心跳时发布。这个事件用于通知子上下文（如微服务）关于父上下文的健康状态。
- HeartbeatEvent 是 Spring Cloud Bus 中的另一个事件，用于在服务实例之间广播心跳消息，以检测和维持各个服务的健康状态。
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ContextRefreshedEvent) {
ContextRefreshedEvent refreshedEvent = (ContextRefreshedEvent) event;
if (!WebServerApplicationContext.hasServerNamespace(
refreshedEvent.getApplicationContext(), "management")) {
reset();
}
}
else if (event instanceof RefreshScopeRefreshedEvent
|| event instanceof InstanceRegisteredEvent) {
reset();
}
else if (event instanceof ParentHeartbeatEvent) {
ParentHeartbeatEvent e = (ParentHeartbeatEvent) event;
resetIfNeeded(e.getValue());
}
else if (event instanceof HeartbeatEvent) {
HeartbeatEvent e = (HeartbeatEvent) event;
resetIfNeeded(e.getValue());
}
}
容器启动完成之后，该监听器接收到ContextRefreshedEvent ，会执行reset方法，reset方法主要功能是发送一个RefreshRoutesEvent 事件，定义如下
public class RefreshRoutesEvent extends ApplicationEvent {
public RefreshRoutesEvent(Object source) {
super(source);
}
}
同样在AutoConfig中声明的CachingRouteLocator接收该参数，
tip:另外还有个
CachingRouteDefinitionLocator也生命监听 RefreshRoutesEvent事件，但是默认配置下并不会产生任何逻辑
@Bean
@Primary
@ConditionalOnMissingBean(name = "cachedCompositeRouteLocator")
// TODO: property to disable composite?
public RouteLocator cachedCompositeRouteLocator(List<RouteLocator> routeLocators) {
return new CachingRouteLocator(
new CompositeRouteLocator(Flux.fromIterable(routeLocators)));
}
event invoke方法如下
public void onApplicationEvent(RefreshRoutesEvent event) {
try {
fetch().collect(Collectors.toList()).subscribe(list -> Flux.fromIterable(list)
.materialize().collect(Collectors.toList()).subscribe(signals -> {
applicationEventPublisher
.publishEvent(new RefreshRoutesResultEvent(this));
cache.put(CACHE_KEY, signals);
}, throwable -> handleRefreshError(throwable)));
}
catch (Throwable e) {
handleRefreshError(e);
}
}
CompositeRouteLocator的目的是混合 多个来源的Routers定义比如配置文件，接口，注册中心，通过@Bean形式定义的路由。可以理解成mixed route locator。
fetch方法就是获取所有RouteLocator的路由定义
private Flux<Route> fetch() { return this.delegate.getRoutes().sort(AnnotationAwareOrderComparator.INSTANCE); }
这里其实就是指定，之前org.springframework.cloud.gateway.discovery.DiscoveryClientRouteDefinitionLocator#getRouteDefinitions的方法也就是获取具体的路由定义，获取成功之后放入缓存，Fire RefreshRoutesResultEvent事件就解决了，开发人员可以通过 监听RefreshRoutesResultEvent 主动感知当前的路由变化。路由加载流程到此结束，
后语
我的问题是通过设置spring.cloud.gateway.discovery.locator.enabled依然没有办法让微服务注册失效，在整个流程中并没有看到使用该数值的地方，难道这是一个bug？转念一想DiscoveryClientRouteDefinitionLocator只需要阻止该Bean的注册即可取消掉从eureka获取服务实例的能力，通过引用关系可知
org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration.ReactiveDiscoveryClientRouteDefinitionLocatorConfigurationorg.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration.BlockingDiscoveryClientRouteDefinitionLocatorConfiguration
这里两处找到了其定义，一个是为reactive非阻塞io准备的，一个是为阻塞io准备的，根据源代码可知,具体执行提供那个Locator取决于spring.cloud.discovery.reactive.enabled，我的项目中是通过VM Options参数的形式传入的-Dspring.cloud.config.discovery.enabled=true，所以我在这两个方法处都打了断点。
@Configuration(proxyBeanMethods = false)
@ConditionalOnProperty(value = "spring.cloud.discovery.reactive.enabled",
matchIfMissing = true)
public static class ReactiveDiscoveryClientRouteDefinitionLocatorConfiguration {
@Bean
@ConditionalOnProperty(name = "spring.cloud.gateway.discovery.locator.enabled")
public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(
ReactiveDiscoveryClient discoveryClient,
DiscoveryLocatorProperties properties) {
return new DiscoveryClientRouteDefinitionLocator(discoveryClient, properties);
}
}
@Configuration(proxyBeanMethods = false)
@Deprecated
@ConditionalOnProperty(value = "spring.cloud.discovery.reactive.enabled",
havingValue = "false")
public static class BlockingDiscoveryClientRouteDefinitionLocatorConfiguration {
@Bean
@ConditionalOnProperty(name = "spring.cloud.gateway.discovery.locator.enabled")
public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(
DiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) {
return new DiscoveryClientRouteDefinitionLocator(discoveryClient, properties);
}
}
当我准备要执行调试模式想看看具体是哪个Bean被初始化的时候，恍然大悟看到了DiscoveryClientRouteDefinitionLocator的依赖，我自己在GatewayApplication 中手动注册了Bean
@Bean
public DiscoveryClientRouteDefinitionLocator discoveryClientRouteLocator(ReactiveDiscoveryClient discoveryClient,
DiscoveryLocatorProperties discoveryLocatorProperties) {
return new DiscoveryClientRouteDefinitionLocator(discoveryClient, discoveryLocatorProperties);
}
真的是笑死，出这个问题的原因是因为最开始的代码使用的出c4o老师生成的，一开始并不明确该代码的作用，后面查看文档才知道用于微服务发现。已经不在关注这里了。
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