Issue #4824 - add configuration on RemoteEndpoint for maxOutgoingFrames

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-websocket/websocket-api/src/main/java/org/eclipse/jetty/websocket/api/RemoteEndpoint.java

@@ -141,6 +141,24 @@ public interface RemoteEndpoint
      */
     void setBatchMode(BatchMode mode);
 
+    /**
+     * Set the maximum number of frames which allowed to be waiting to be sent at any one time.
+     * The default value is -1, this indicates there is no limit on how many frames can be
+     * queued to be sent by the implementation.
+     *
+     * @param maxOutgoingFrames the max number of frames.
+     */
+    void setMaxOutgoingFrames(int maxOutgoingFrames);
+
+    /**
+     * Get the maximum number of frames which allowed to be waiting to be sent at any one time.
+     * The default value is -1, this indicates there is no limit on how many frames can be
+     * queued to be sent by the implementation.
+     *
+     * @return the max number of frames.
+     */
+    int getMaxOutgoingFrames();
+
     /**
      * Get the InetSocketAddress for the established connection.
      *

jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/WebSocketRemoteEndpoint.java

@@ -81,7 +81,9 @@ public class WebSocketRemoteEndpoint implements RemoteEndpoint
     private final OutgoingFrames outgoing;
     private final AtomicInteger msgState = new AtomicInteger();
     private final BlockingWriteCallback blocker = new BlockingWriteCallback();
+    private final AtomicInteger numOutgoingFrames = new AtomicInteger();
     private volatile BatchMode batchMode;
+    private int maxNumOutgoingFrames = -1;
 
     public WebSocketRemoteEndpoint(LogicalConnection connection, OutgoingFrames outgoing)
     {
@@ -303,6 +305,19 @@ public class WebSocketRemoteEndpoint implements RemoteEndpoint
         BatchMode batchMode = BatchMode.OFF;
         if (frame.isDataFrame())
             batchMode = getBatchMode();
+
+        if (maxNumOutgoingFrames > 0 && frame.isDataFrame())
+        {
+            // Increase the number of outgoing frames, will be decremented when callback is completed.
+            int outgoingFrames = numOutgoingFrames.incrementAndGet();
+            callback = from(callback, numOutgoingFrames::decrementAndGet);
+            if (outgoingFrames > maxNumOutgoingFrames)
+            {
+                callback.writeFailed(new IOException("Exceeded max outgoing frames: " + outgoingFrames + ">" + maxNumOutgoingFrames));
+                return;
+            }
+        }
+
         outgoing.outgoingFrame(frame, callback, batchMode);
     }
 
@@ -439,6 +454,18 @@ public class WebSocketRemoteEndpoint implements RemoteEndpoint
         this.batchMode = batchMode;
     }
 
+    @Override
+    public void setMaxOutgoingFrames(int maxOutgoingFrames)
+    {
+        this.maxNumOutgoingFrames = maxOutgoingFrames;
+    }
+
+    @Override
+    public int getMaxOutgoingFrames()
+    {
+        return maxNumOutgoingFrames;
+    }
+
     @Override
     public void flush() throws IOException
     {
@@ -459,4 +486,36 @@ public class WebSocketRemoteEndpoint implements RemoteEndpoint
     {
         return String.format("%s@%x[batching=%b]", getClass().getSimpleName(), hashCode(), getBatchMode());
     }
+
+    private static WriteCallback from(WriteCallback callback, Runnable completed)
+    {
+        return new WriteCallback()
+        {
+            @Override
+            public void writeFailed(Throwable x)
+            {
+                try
+                {
+                    callback.writeFailed(x);
+                }
+                finally
+                {
+                    completed.run();
+                }
+            }
+
+            @Override
+            public void writeSuccess()
+            {
+                try
+                {
+                    callback.writeSuccess();
+                }
+                finally
+                {
+                    completed.run();
+                }
+            }
+        };
+    }
 }