Implementing Service-to-Service Communication

RestClient client = RestClient.builder()
    .baseUrl("https://payments.internal")
    .defaultHeader("Authorization", "Bearer " + token)
    .requestFactory(new HttpComponentsClientHttpRequestFactory())
    .build();

Receipt r = client.post()
    .uri("/charges")
    .contentType(MediaType.APPLICATION_JSON)
    .body(new ChargeRequest(...))
    .retrieve()
    .body(Receipt.class);

public class OrderServiceImpl extends OrderServiceGrpc.OrderServiceImplBase {
    public void place(PlaceOrderRequest req, StreamObserver<OrderResponse> obs) {
        var o = service.place(toDomain(req));
        obs.onNext(toProto(o));
        obs.onCompleted();
    }
}

@CircuitBreaker(name = "fx", fallbackMethod = "stale")
@Retry(name = "fx")
@TimeLimiter(name = "fx")
public CompletableFuture<Rate> getRate(String pair) {
    return CompletableFuture.supplyAsync(() -> client.fetch(pair));
}
public CompletableFuture<Rate> stale(String pair, Throwable t) {
    return CompletableFuture.completedFuture(cache.get(pair));
}