Load simulation module

order/order-worker/src/main/java/demo/OrderWorker.java

@@ -3,8 +3,10 @@ package demo;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
+import org.springframework.context.annotation.Bean;
 import org.springframework.hateoas.config.EnableHypermediaSupport;
 import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
+import org.springframework.web.client.RestTemplate;
 
 @SpringBootApplication
 @EnableDiscoveryClient
@@ -13,4 +15,9 @@ public class OrderWorker {
     public static void main(String[] args) {
         SpringApplication.run(OrderWorker.class, args);
     }
+
+    @Bean
+    public RestTemplate restTemplate() {
+        return new RestTemplate();
+    }
 }

order/order-worker/src/main/java/demo/order/StateFactory.java

@@ -6,6 +6,8 @@ import demo.order.event.OrderEvent;
 import demo.order.event.OrderEventType;
 import demo.order.event.OrderEvents;
 import org.apache.log4j.Logger;
+import org.springframework.cloud.client.ServiceInstance;
+import org.springframework.cloud.client.discovery.DiscoveryClient;
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.client.Traverson;
@@ -14,31 +16,57 @@ import org.springframework.messaging.support.MessageBuilder;
 import org.springframework.statemachine.StateMachine;
 import org.springframework.stereotype.Service;
 import org.springframework.util.Assert;
+import org.springframework.web.client.RestTemplate;
 
 import java.net.URI;
-import java.util.HashMap;
-import java.util.Map;
+import java.util.*;
 
 @Service
 public class StateFactory {
 
     final private Logger log = Logger.getLogger(StateFactory.class);
     final private StateService stateService;
+    final private RestTemplate restTemplate;
+    final private DiscoveryClient discoveryClient;
 
-    public StateFactory(StateService stateService) {
+    public StateFactory(StateService stateService, RestTemplate restTemplate, DiscoveryClient discoveryClient) {
         this.stateService = stateService;
+        this.restTemplate = restTemplate;
+        this.discoveryClient = discoveryClient;
     }
 
     public Order apply(OrderEvent orderEvent) {
         Assert.notNull(orderEvent, "Cannot apply a null event");
         Assert.notNull(orderEvent.getId(), "The event payload's identity link was not found");
 
+        List<ServiceInstance> serviceInstances = discoveryClient.getInstances("order-web");
+        Assert.notEmpty(serviceInstances, "No instances available for order-web");
+        Integer instanceNum = new Random().nextInt(serviceInstances.size());
+        ServiceInstance orderService = serviceInstances.get(instanceNum);
+
+        URI orderHref = getLoadBalanceUri(orderService, URI.create(orderEvent.getLink("order").getHref()));
+        URI selfHref = getLoadBalanceUri(orderService, URI.create(orderEvent.getLink("self").getHref()));
+
+        orderEvent.getLinks()
+                .replaceAll(a -> Objects.equals(a.getRel(), "order") ? new Link(orderHref
+                        .toString(), "order") : a);
+
+        orderEvent.getLinks()
+                .replaceAll(a -> Objects.equals(a.getRel(), "self") ? new Link(selfHref
+                        .toString(), "self") : a);
+
         StateMachine<OrderStatus, OrderEventType> stateMachine = getStateMachine(orderEvent);
         stateMachine.stop();
 
         return stateMachine.getExtendedState().get("order", Order.class);
     }
 
+    private URI getLoadBalanceUri(ServiceInstance serviceInstance, URI uri) {
+        return URI.create(uri.toString()
+                .replace(uri.getHost(), serviceInstance.getHost())
+                .replace(":" + uri.getPort(), ":" + String.valueOf(serviceInstance.getPort())));
+    }
+
     private StateMachine<OrderStatus, OrderEventType> getStateMachine(OrderEvent orderEvent) {
         Link eventId = orderEvent.getId();
         log.info(String.format("Order event received: %s", eventId));
@@ -67,13 +95,18 @@ public class StateFactory {
     }
 
     private OrderEvents getEventLog(OrderEvent event) {
+
+        // Replace the host and port of the link with an available instance
+        URI orderHref = URI.create(event.getLink("order")
+                .getHref());
+
         // Follow the hypermedia link to fetch the attached order
-        Traverson traverson = new Traverson(
-                URI.create(event.getLink("order")
-                        .getHref()),
+        Traverson traverson = new Traverson(orderHref,
                 MediaTypes.HAL_JSON
         );
 
+        traverson.setRestOperations(restTemplate);
+
         // Get the event log for the attached order resource
         return traverson.follow("events")
                 .toEntity(OrderEvents.class)

order/order-worker/src/main/java/demo/order/event/OrderEvent.java

@@ -1,6 +1,8 @@
 package demo.order.event;
 
+import com.fasterxml.jackson.annotation.JsonIgnore;
 import demo.domain.AbstractEntity;
+import org.springframework.hateoas.Link;
 
 public class OrderEvent extends AbstractEntity {
 
@@ -21,6 +23,12 @@ public class OrderEvent extends AbstractEntity {
         this.type = type;
     }
 
+    @JsonIgnore
+    @Override
+    public Link getId() {
+        return super.getId();
+    }
+
     @Override
     public String toString() {
         return "OrderEvent{" +