fix(WebSocket): send STOMP heartbeats from the simple broker

src/main/java/org/wise/portal/spring/impl/WebSocketConfig.java

@@ -1,11 +1,15 @@
 package org.wise.portal.spring.impl;
 
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Lazy;
 import org.springframework.messaging.converter.MessageConverter;
 import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
 import org.springframework.messaging.handler.invocation.HandlerMethodReturnValueHandler;
 import org.springframework.messaging.simp.config.ChannelRegistration;
 import org.springframework.messaging.simp.config.MessageBrokerRegistry;
+import org.springframework.scheduling.TaskScheduler;
 import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
 import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
 import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;
@@ -17,9 +21,23 @@
 @EnableWebSocketMessageBroker
 public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
 
+  // Server heartbeats keep idle connections open through proxies. None are required from clients
+  // because browsers throttle timers in background tabs, which would get those sockets closed.
+  private static final long[] HEARTBEAT_MILLIS = { 20000, 0 };
+
+  private TaskScheduler messageBrokerTaskScheduler;
+
+  @Autowired
+  public void setMessageBrokerTaskScheduler(
+      @Lazy @Qualifier("messageBrokerTaskScheduler") TaskScheduler messageBrokerTaskScheduler) {
+    this.messageBrokerTaskScheduler = messageBrokerTaskScheduler;
+  }
+
   @Override
   public void configureMessageBroker(MessageBrokerRegistry config) {
-    config.enableSimpleBroker("/topic");
+    config.enableSimpleBroker("/topic")
+        .setHeartbeatValue(HEARTBEAT_MILLIS)
+        .setTaskScheduler(messageBrokerTaskScheduler);
     config.setApplicationDestinationPrefixes("/app");
   }
 

src/test/java/org/wise/portal/spring/impl/WebSocketConfigTest.java

@@ -0,0 +1,30 @@
+package org.wise.portal.spring.impl;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.ImportAutoConfiguration;
+import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
+import org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration;
+import org.springframework.messaging.simp.broker.SimpleBrokerMessageHandler;
+import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
+
+@SpringJUnitWebConfig(WebSocketConfig.class)
+@ImportAutoConfiguration({ JacksonAutoConfiguration.class, WebSocketMessagingAutoConfiguration.class })
+public class WebSocketConfigTest {
+
+  @Autowired
+  private SimpleBrokerMessageHandler simpleBroker;
+
+  @Test
+  public void simpleBroker_shouldSendHeartbeatsWithoutRequiringThemFromClients() {
+    assertArrayEquals(new long[] { 20000, 0 }, simpleBroker.getHeartbeatValue());
+  }
+
+  @Test
+  public void simpleBroker_shouldHaveATaskSchedulerForHeartbeats() {
+    assertNotNull(simpleBroker.getTaskScheduler());
+  }
+}