Preserves the order of route definitions.

This preserves the order in which route definitions are composited together and likewise for routes this would ensure that route definitions from properties do not lose their relative ordering.

Fixes gh-1660

Author: ukayani

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/route/CompositeRouteDefinitionLocator.java

@@ -49,7 +49,8 @@ public CompositeRouteDefinitionLocator(Flux<RouteDefinitionLocator> delegates,
 
 	@Override
 	public Flux<RouteDefinition> getRouteDefinitions() {
-		return this.delegates.flatMap(RouteDefinitionLocator::getRouteDefinitions)
+		return this.delegates
+				.flatMapSequential(RouteDefinitionLocator::getRouteDefinitions)
 				.flatMap(routeDefinition -> {
 					if (routeDefinition.getId() == null) {
 						return randomId().map(id -> {

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/route/CompositeRouteLocator.java

@@ -31,7 +31,7 @@ public CompositeRouteLocator(Flux<RouteLocator> delegates) {
 
 	@Override
 	public Flux<Route> getRoutes() {
-		return this.delegates.flatMap(RouteLocator::getRoutes);
+		return this.delegates.flatMapSequential(RouteLocator::getRoutes);
 	}
 
 }