How to retry an external service when a call to an internal service fails using spring cloud gateway? - spring-boot

Question

I'm implementing a service that mocks another service available on the web.
I'm trying to configure the spring cloud gateway to reroute requests to the public service when a call to my implementation fails.
I tried using the Hystrix filter the following way:
spring:
cloud:
gateway:
routes:
- id: foo
uri: http://my-internal-service/
filters:
- name: Hystrix
args:
name: fallbackcmd
fallbackUri: https://the.public.service/
Unfortunately, like the documentation says:
Currently, only forward: schemed URIs are supported. If the fallback is called, the request will be forwarded to the controller matched by the URI.
Therefore, I can't use fallbackUri: https://....
Is there any plan to support this feature soon?
Otherwise, what are my options for this particular use case?

Answer 1

I ended up with a kind of hacky workaround that seems to work for my particular use case (i.e. a GET request):
Create my own fallback controller in the Gateway application
Configure the hystrix fallback to point to that controller
Use the WebClient to call my public service
This is what the end result looks like:
application.yml
spring:
cloud:
gateway:
default-filters:
- name: AddResponseHeader
args:
name: X-Data-Origin
value: My internal service
routes:
- id: foo
uri: http://my-internal-service/
filters:
- name: Hystrix
args:
name: local-service-fallback
fallbackUri: forward:/fallback/foo
FallbackController.java
#RestController
#RequestMapping(path = "/fallback")
public class FallbackController {
private static final String fallbackUri = "https://the.public.service";
WebClient webClient;
public FallbackController() {
webClient = WebClient.create(fallbackUri);
}
#GetMapping("/foo")
Mono<MyResponse> foo(ServerWebExchange failedExchange) {
failedExchange.getResponse().getHeaders().remove("X-Data-Origin");
failedExchange.getResponse().getHeaders().add("X-Data-Origin", "The public service");
// Now call the public service using the same GET request
UriComponents uriComponents = UriComponentsBuilder.newInstance()
.uri(URI.create(fallbackUri))
.path("/path/to/service")
.queryParams(failedExchange.getRequest().getQueryParams())
.build();
return WebClient.create(uriComponents.toUriString())
.get()
.accept(MediaType.TEXT_XML)
.exchange()
.doOnSuccess(clientResponse -> {
// Copy the headers from the public service's response back to our exchange's response
failedExchange.getResponse().getHeaders()
.addAll(clientResponse.headers().asHttpHeaders());
})
.flatMap(clientResponse -> {
log.info("Data origin: {}",
failedExchange.getResponse().getHeaders().get("X-Data-Origin"));
return clientResponse.bodyToMono(MyResponse.class);
});
}
}

Answer 2

I had similar problem to solve.
I added new route for fallback and it worked.
.route(p -> p .path("/fallback/foo").uri("https://example.com"))