spring cloud gateway集成hystrix

本文主要研究一下spring cloud gateway如何集成hystrix

maven

<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-hystrix</artifactId></dependency>

添加spring-cloud-starter-netflix-hystrix依賴，開啟hystrix

配置實例

hystrix.command.fallbackcmd.execution.isolation.thread.timeoutInMilliseconds: 5000spring: cloud: gateway: discovery:locator: enabled: true routes: - id: employee-serviceuri: lb://employee-servicepredicates:- Path=/employee/**filters:- RewritePath=/employee/(?<path>.*), /${path}- name: Hystrix args: name: fallbackcmd fallbackUri: forward:/fallback 首先filter里頭配置了name為Hystrix的filter，實際是對應HystrixGatewayFilterFactory 然后指定了hystrix command的名稱，及fallbackUri，注意fallbackUri要以forward開頭 最后通過hystrix.command.fallbackcmd.execution.isolation.thread.timeoutInMilliseconds指定該command的超時時間fallback實例

@RestController@RequestMapping('/fallback')public class FallbackController { @RequestMapping('') public String fallback(){return 'error'; }}源碼解析

GatewayAutoConfiguration

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@Configuration@ConditionalOnProperty(name = 'spring.cloud.gateway.enabled', matchIfMissing = true)@EnableConfigurationProperties@AutoConfigureBefore(HttpHandlerAutoConfiguration.class)@AutoConfigureAfter({GatewayLoadBalancerClientAutoConfiguration.class, GatewayClassPathWarningAutoConfiguration.class})@ConditionalOnClass(DispatcherHandler.class)public class GatewayAutoConfiguration { //...... @Configuration @ConditionalOnClass({HystrixObservableCommand.class, RxReactiveStreams.class}) protected static class HystrixConfiguration {@Beanpublic HystrixGatewayFilterFactory hystrixGatewayFilterFactory(DispatcherHandler dispatcherHandler) { return new HystrixGatewayFilterFactory(dispatcherHandler);} } //......}

引入spring-cloud-starter-netflix-hystrix類庫，就有HystrixObservableCommand.class, RxReactiveStreams.class，便開啟HystrixConfiguration

HystrixGatewayFilterFactory

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/HystrixGatewayFilterFactory.java

/** * Depends on `spring-cloud-starter-netflix-hystrix`, {@see http://cloud.spring.io/spring-cloud-netflix/} * @author Spencer Gibb */public class HystrixGatewayFilterFactory extends AbstractGatewayFilterFactory<HystrixGatewayFilterFactory.Config> { public static final String FALLBACK_URI = 'fallbackUri'; private final DispatcherHandler dispatcherHandler; public HystrixGatewayFilterFactory(DispatcherHandler dispatcherHandler) {super(Config.class);this.dispatcherHandler = dispatcherHandler; } @Override public List<String> shortcutFieldOrder() {return Arrays.asList(NAME_KEY); } public GatewayFilter apply(String routeId, Consumer<Config> consumer) {Config config = newConfig();consumer.accept(config);if (StringUtils.isEmpty(config.getName()) && !StringUtils.isEmpty(routeId)) { config.setName(routeId);}return apply(config); } @Override public GatewayFilter apply(Config config) {//TODO: if no name is supplied, generate one from command id (useful for default filter)if (config.setter == null) { Assert.notNull(config.name, 'A name must be supplied for the Hystrix Command Key'); HystrixCommandGroupKey groupKey = HystrixCommandGroupKey.Factory.asKey(getClass().getSimpleName()); HystrixCommandKey commandKey = HystrixCommandKey.Factory.asKey(config.name); config.setter = Setter.withGroupKey(groupKey) .andCommandKey(commandKey);}return (exchange, chain) -> { RouteHystrixCommand command = new RouteHystrixCommand(config.setter, config.fallbackUri, exchange, chain); return Mono.create(s -> {Subscription sub = command.toObservable().subscribe(s::success, s::error, s::success);s.onCancel(sub::unsubscribe); }).onErrorResume((Function<Throwable, Mono<Void>>) throwable -> {if (throwable instanceof HystrixRuntimeException) { HystrixRuntimeException e = (HystrixRuntimeException) throwable; if (e.getFailureType() == TIMEOUT) { //TODO: optionally set statussetResponseStatus(exchange, HttpStatus.GATEWAY_TIMEOUT);return exchange.getResponse().setComplete(); }}return Mono.error(throwable); }).then();}; } //......}

這里創建了RouteHystrixCommand，將其轉換為Mono，然后在onErrorResume的時候判斷如果HystrixRuntimeException的failureType是FailureType.TIMEOUT類型的話，則返回GATEWAY_TIMEOUT(504, 'Gateway Timeout')狀態碼。

RouteHystrixCommand

//TODO: replace with HystrixMonoCommand that we write private class RouteHystrixCommand extends HystrixObservableCommand<Void> {private final URI fallbackUri;private final ServerWebExchange exchange;private final GatewayFilterChain chain;RouteHystrixCommand(Setter setter, URI fallbackUri, ServerWebExchange exchange, GatewayFilterChain chain) { super(setter); this.fallbackUri = fallbackUri; this.exchange = exchange; this.chain = chain;}@Overrideprotected Observable<Void> construct() { return RxReactiveStreams.toObservable(this.chain.filter(exchange));}@Overrideprotected Observable<Void> resumeWithFallback() { if (this.fallbackUri == null) {return super.resumeWithFallback(); } //TODO: copied from RouteToRequestUrlFilter URI uri = exchange.getRequest().getURI(); //TODO: assume always? boolean encoded = containsEncodedParts(uri); URI requestUrl = UriComponentsBuilder.fromUri(uri) .host(null) .port(null) .uri(this.fallbackUri) .build(encoded) .toUri(); exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl); ServerHttpRequest request = this.exchange.getRequest().mutate().uri(requestUrl).build(); ServerWebExchange mutated = exchange.mutate().request(request).build(); return RxReactiveStreams.toObservable(HystrixGatewayFilterFactory.this.dispatcherHandler.handle(mutated));} } 這里重寫了construct方法，RxReactiveStreams.toObservable(this.chain.filter(exchange))，將reactor的Mono轉換為rxjava的Observable 這里重寫了resumeWithFallback方法，針對有fallbackUri的情況，重新路由到fallbackUri的地址Config

public static class Config {private String name;private Setter setter;private URI fallbackUri;public String getName() { return name;}public Config setName(String name) { this.name = name; return this;}public Config setFallbackUri(String fallbackUri) { if (fallbackUri != null) {setFallbackUri(URI.create(fallbackUri)); } return this;}public URI getFallbackUri() { return fallbackUri;}public void setFallbackUri(URI fallbackUri) { if (fallbackUri != null && !'forward'.equals(fallbackUri.getScheme())) {throw new IllegalArgumentException('Hystrix Filter currently only supports ’forward’ URIs, found ' + fallbackUri); } this.fallbackUri = fallbackUri;}public Config setSetter(Setter setter) { this.setter = setter; return this;} }

可以看到Config校驗了fallbackUri，如果不為null，則必須以forward開頭

小結

spring cloud gateway集成hystrix，分為如下幾步：

添加spring-cloud-starter-netflix-hystrix依賴 在對應route的filter添加name為Hystrix的filter，同時指定hystrix command的名稱，及其fallbackUri(可選) 指定該hystrix command的超時時間等。

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