feat: queue message payloads

Add sent payloads to message
queue and resend if no response
to message inside MaxMessageSuspendTimeout

fixes #20507

flow-client/src/main/java/com/vaadin/client/communication/MessageHandler.java

@@ -295,10 +295,10 @@ protected void handleJSON(final ValueMap valueMap) {
         }
 
         /**
-         * Should only prepare resync after the if (locked ||
+         * Should only prepare resync after the (locked ||
          * !isNextExpectedMessage(serverId)) {...} since
          * stateTree.repareForResync() will remove the nodes, and if locked is
-         * true, it will return without handling the message, thus won't adding
+         * true, it will return without handling the message, thus won't add
          * nodes back.
          *
          * This is related to https://github.com/vaadin/flow/issues/8699 It

flow-client/src/main/java/com/vaadin/client/communication/MessageSender.java

@@ -15,7 +15,11 @@
  */
 package com.vaadin.client.communication;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import com.google.gwt.core.client.GWT;
+import com.google.gwt.user.client.Timer;
 
 import com.vaadin.client.ConnectionIndicator;
 import com.vaadin.client.Console;
@@ -67,6 +71,10 @@ public enum ResynchronizationState {
 
     private JsonObject pushPendingMessage;
 
+    private List<JsonObject> messageQueue = new ArrayList<>();
+
+    private Timer resendMessageTimer;
+
     /**
      * Creates a new instance connected to the given registry.
      *
@@ -166,7 +174,6 @@ protected void send(final JsonArray reqInvocations,
             final JsonObject extraJson) {
         registry.getRequestResponseTracker().startRequest();
         send(preparePayload(reqInvocations, extraJson));
-
     }
 
     private JsonObject preparePayload(final JsonArray reqInvocations,
@@ -192,12 +199,33 @@ private JsonObject preparePayload(final JsonArray reqInvocations,
 
     /**
      * Sends an asynchronous or synchronous UIDL request to the server using the
-     * given URI.
+     * given URI. Adds message to message queue and postpones sending if queue
+     * not empty.
      *
      * @param payload
      *            The contents of the request to send
      */
     public void send(final JsonObject payload) {
+        if (!registry.getRequestResponseTracker().hasActiveRequest()) {
+            // Someone called send directly as request not set active.
+            // If queue empty add message and wait to send.
+            if (!messageQueue.isEmpty()) {
+                messageQueue.add(payload);
+                return;
+            }
+        }
+        messageQueue.add(payload);
+        sendPayload(payload);
+    }
+
+    /**
+     * Sends an asynchronous or synchronous UIDL request to the server using the
+     * given URI.
+     *
+     * @param payload
+     *            The contents of the request to send
+     */
+    private void sendPayload(final JsonObject payload) {
         if (push != null && push.isBidirectional()) {
             // When using bidirectional transport, the payload is not resent
             // to the server during reconnection attempts.
@@ -211,6 +239,17 @@ public void send(final JsonObject payload) {
         } else {
             Console.debug("send XHR");
             registry.getXhrConnection().send(payload);
+
+            // resend last payload if response hasn't come in.
+            resendMessageTimer = new Timer() {
+                @Override
+                public void run() {
+                    resendMessageTimer = null;
+                    registry.getXhrConnection().send(payload);
+                }
+            };
+            resendMessageTimer.schedule(registry.getApplicationConfiguration()
+                    .getMaxMessageSuspendTimeout());
         }
     }
 
@@ -311,12 +350,35 @@ public void setClientToServerMessageId(int nextExpectedId, boolean force) {
                             ApplicationConstants.CLIENT_TO_SERVER_ID) < nextExpectedId) {
                 pushPendingMessage = null;
             }
+            if (!messageQueue.isEmpty()) {
+                synchronized (messageQueue) {
+                    // If queued message is the expected one. remove from queue
+                    // and sen next message if any.
+                    if (messageQueue.get(0)
+                            .getNumber(ApplicationConstants.CLIENT_TO_SERVER_ID)
+                            + 1 == nextExpectedId) {
+                        if (resendMessageTimer != null) {
+                            resendMessageTimer.cancel();
+                            resendMessageTimer = null;
+                        }
+                        messageQueue.remove(0);
+                        if (!messageQueue.isEmpty()) {
+                            sendPayload(messageQueue.get(0));
+                        }
+                    }
+                }
+            }
             return;
         }
         if (force) {
             Console.debug(
                     "Forced update of clientId to " + clientToServerMessageId);
             clientToServerMessageId = nextExpectedId;
+            messageQueue.clear();
+            if (resendMessageTimer != null) {
+                resendMessageTimer.cancel();
+                resendMessageTimer = null;
+            }
             return;
         }