前言
DiscoveryClientRouteDefinitionLocator 用于从配置中心加载服务信息，并创建相应的路由。我这里使用的配置中心是nacos。
一、DiscoveryLocatorProperties
@ConfigurationProperties("spring.cloud.gateway.discovery.locator")
public class DiscoveryLocatorProperties {
//服务发现开关
private boolean enabled = false;
//路由id的前缀
private String routeIdPrefix;
//过滤服务
private String includeExpression = "true";
//gateway为每一个服务创建了一个router，这个router将以服务名开头的请求路径转发到对应的服务
private String urlExpression = "'lb://'+serviceId";
//将请求路径的服务名改为小写
private boolean lowerCaseServiceId = false;
//路由断言
private List<PredicateDefinition> predicates = new ArrayList<>();
//路由过滤器
private List<FilterDefinition> filters = new ArrayList<>();
}
在配置文件中打开服务发现的开关
spring.cloud.gateway.discovery.locator.enabled=true
spring.cloud.gateway.discovery.locator.lower-case-service-id=true
二、DiscoveryClientRouteDefinitionLocator
通过服务发现获取服务的路由信息
1、 bean的创建；
@Configuration(proxyBeanMethods = false)
@ConditionalOnProperty(value = "spring.cloud.discovery.reactive.enabled", matchIfMissing = true)
public static class ReactiveDiscoveryClientRouteDefinitionLocatorConfiguration {
@Bean
//打开了开关
@ConditionalOnProperty(name = "spring.cloud.gateway.discovery.locator.enabled")
public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(
ReactiveDiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) {
return new DiscoveryClientRouteDefinitionLocator(discoveryClient, properties);
}
}
2、 获取服务信息；
public DiscoveryClientRouteDefinitionLocator(ReactiveDiscoveryClient discoveryClient,
DiscoveryLocatorProperties properties) {
this(discoveryClient.getClass().getSimpleName(), properties);
//通过服务发现客户端从nacos服务端获取服务信息
serviceInstances = discoveryClient.getServices()
.flatMap(service -> discoveryClient.getInstances(service).collectList());
}
3、 获取nacos所有服务名；
1、discoveryClient.getServices( )
NacosReactiveDiscoveryClient.java
@Override
public Flux<String> getServices() {
return Flux.defer(() -> {
try {
return Flux.fromIterable(serviceDiscovery.getServices());
}
catch (Exception e) {
log.error("get services from nacos server fail,", e);
return Flux.empty();
}
}).subscribeOn(Schedulers.boundedElastic());
}
2、serviceDiscovery.getServices( )
NacosServiceDiscovery.java
public List<String> getServices() throws NacosException {
//组
String group = discoveryProperties.getGroup();
//从nacos获取所有注册的服务信息
ListView<String> services = namingService().getServicesOfServer(1,
Integer.MAX_VALUE, group);
return services.getData();
}
4、 从nacos服务端获取服务信息；
1、discoveryClient.getInstances(service)
@Override
public Flux<ServiceInstance> getInstances(String serviceId) {
return Mono.justOrEmpty(serviceId).flatMapMany(loadInstancesFromNacos())
.subscribeOn(Schedulers.boundedElastic());
}
2、loadInstancesFromNacos( )
private Function<String, Publisher<ServiceInstance>> loadInstancesFromNacos() {
return serviceId -> {
try {
return Flux.fromIterable(serviceDiscovery.getInstances(serviceId));
}
catch (NacosException e) {
log.error("get service instance[{}] from nacos error!", serviceId, e);
return Flux.empty();
}
};
}
3、
public List<ServiceInstance> getInstances(String serviceId) throws NacosException {
String group = discoveryProperties.getGroup();
//进入nacos服务发现流程
List<Instance> instances = namingService().selectInstances(serviceId, group,
true);
return hostToServiceInstanceList(instances, serviceId);
}
三、RefreshRoutesEvent
首先从NacosWatch开始分析
1、 NacosWatch实现了SmartLifecycle接口，在它的start()方法中会定时调度nacosServicesWatch()，默认间隔时30s；
this.watchFuture = this.taskScheduler.scheduleWithFixedDelay(
this::nacosServicesWatch, this.properties.getWatchDelay());
2、 nacosServicesWatch()；
public void nacosServicesWatch() {
//发布心跳事件 HeartbeatEvent
this.publisher.publishEvent(
new HeartbeatEvent(this, nacosWatchIndex.getAndIncrement()));
}
3、 RouteRefreshListener；
接收HeartbeatEvent，并发布刷新路由事件RefreshRoutesEvent
@Override
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) {
//处理心跳事件
HeartbeatEvent e = (HeartbeatEvent) event;
resetIfNeeded(e.getValue());
}
}
private void resetIfNeeded(Object value) {
if (this.monitor.update(value)) {
reset();
}
}
private void reset() {
//发布事件 RefreshRoutesEvent
this.publisher.publishEvent(new RefreshRoutesEvent(this));
}
4、 CachingRouteLocator；
接收RefreshRoutesEvent 事件，并发布路由刷新结果事件 RefreshRoutesResultEvent
通过fetch() 方法获取路由信息，分别从 PropertiesRouteDefinitionLocator 、InMemoryRouteDefinitionRepository 、DiscoveryClientRouteDefinitionLocator 获取路由信息。
@Override
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);
}, this::handleRefreshError), this::handleRefreshError);
}
catch (Throwable e) {
handleRefreshError(e);
}
}
5、 从DiscoveryClientRouteDefinitionLocator获取服务发现相关路由；
1、getRouteDefinitions( )
@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;
};
}
//从nacos服务端获取服务信息
return serviceInstances.filter(instances -> !instances.isEmpty()).map(instances -> instances.get(0))
.filter(includePredicate).map(instance -> {
//为每个服务构建RouteDefinition、PredicateDefinition、FilterDefinition
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;
});
}
总结
定时从nacos获取服务信息，为每个服务创建路由信息。
在用户请求时就将对应服务的请求转发到对应的服务上。