Order
This article mainly studies how spring cloud gateway integrates hystrix.
maven
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>Add spring-cloud-starter-netflix-hystrix dependency and turn on hy strix.
Configuration instance
hystrix.command.fallbackcmd.execution.isolation.thread.timeoutInMilliseconds: 5000
spring:
cloud:
gateway:
discovery:
locator:
enabled: true
routes:
- id: employee-service
uri: lb://employee-service
predicates:
- Path=/employee/**
filters:
- RewritePath=/employee/(?<path>.*), /$\{path}
- name: Hystrix
args:
name: fallbackcmd
fallbackUri: forward:/fallback- First of all, a filter with a name of Hystrix is configured in the filter, which actually corresponds to HystrixGatewayFilterFactory.
- Then specify the name of the hystrix command and the fallbackUri, noting that the fallbackUri starts with forward.
- Finally, the timeout period of the command is specified by hy strix.command.fallackcmd.execution.isolation.thread.timeoutinmilliseconds.
Fallback instance
@RestController
@RequestMapping("/fallback")
public class FallbackController {
@RequestMapping("")
public String fallback(){
return "error";
}
}Source code analysis
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 {
@Bean
public HystrixGatewayFilterFactory hystrixGatewayFilterFactory(DispatcherHandler dispatcherHandler) {
return new HystrixGatewayFilterFactory(dispatcherHandler);
}
}
//......
}With the introduction of Spring-Cloud-Starter-Netflix-Hystrix class library, there will be HystrixObservableContext.class, RxReactive Streams.class, and HystrixConfiguration will be opened.
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 status
setResponseStatus(exchange, HttpStatus.GATEWAY_TIMEOUT);
return exchange.getResponse().setComplete();
}
}
return Mono.error(throwable);
}).then();
};
}
//......
}RouteHystrixCommand is created here, converted to Mono, and then it is judged at the time of onErrorResume that if the failureType of HystrixRuntimeException is FailureType.TIMEOUT type, the Gateway _ Timeout (504, “Gateway Timeout”) status code is returned.
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));
}
}- The construct method, rxreactive streams.to Observable (this.chain.filter (exchange)), is rewritten here to convert reactor’s Mono to rxjava’s observable.
- The resumeWithFallback method is rewritten here to reroute to the address of the fallbackUri in case of a fallbackUri.
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;
}
}You can see that Config has verified the fallbackUri. if it is not null, it must start with forward.
Summary
Spring cloud gateway integrates hystrix into the following steps:
- Add spring-cloud-starter-netflix-hy strix dependency
- Add a filter with name Hystrix to the filter corresponding to route, and specify the name of hystrix command and its fallbackUri (
Optional) - Specify the timeout period for the hystrix command, etc.