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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依赖，开启hystrix
配置实例
hystrix.command.fallbackcmd.execution.isolation.thread.timeoutInMilliseconds: 5000spring: cloud: gateway: discovery: locator: enabled: true routes: - id: employee-service uri: lb://employee-service predicates: - Path=/employeepublic 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 status setResponseStatus(exchange, HttpStatus.GATEWAY_TIMEOUT); return exchange.getResponse().setComplete(); } } return Mono.error(throwable); }).then(); }; } //......}这里创建了RouteHystrixCommand，将其转换为Mono，然后在onErrorResume的时候判断如果HystrixRuntimeException的failureType是FailureType.TIMEOUT类型的话，则返回GATEWAY_TIMEOUT(504, "Gateway Timeout")状态码。
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; } @Override protected Observable<Void> construct() { return RxReactiveStreams.toObservable(this.chain.filter(exchange)); } @Override protected 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)); } }这里重写了construct方法，RxReactiveStreams.toObservable(this.chain.filter(exchange))，将reactor的Mono转换为rxjava的Observable
这里重写了resumeWithFallback方法，针对有fallbackUri的情况，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校验了fallbackUri，如果不为null，则必须以forward开头
小结
spring cloud gateway集成hystrix，分为如下几步：
添加spring-cloud-starter-netflix-hystrix依赖
在对应route的filter添加name为Hystrix的filter，同时指定hystrix command的名称，及其fallbackUri(可选)
指定该hystrix command的超时时间等。
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