[REM3-338] Improve RemoteConnection handling of keep alive, by creati…

…ng the heart beat task less often

At RemoteConnection.send, replace heatKey removal by an update to expire time, and reschedule heart beat every time it runs

src/main/java/org/jboss/remoting3/remote/RemoteConnection.java

@@ -243,10 +243,11 @@ Connection getConnection() {
     final class RemoteWriteListener implements ChannelListener<ConduitStreamSinkChannel> {
 
         private final Queue<Pooled<ByteBuffer>> queue = new ArrayDeque<Pooled<ByteBuffer>>();
-        private XnioExecutor.Key heartKey;
+        private volatile XnioExecutor.Key heartKey;
         private boolean closed;
         private ByteBuffer headerBuffer = ByteBuffer.allocateDirect(4);
         private final ByteBuffer[] cachedArray = new ByteBuffer[] { headerBuffer, null };
+        private volatile long expireTime = -1;
 
         RemoteWriteListener() {
         }
@@ -312,7 +313,12 @@ public void handleEvent(final ConduitStreamSinkChannel channel) {
                             return;
                         } else {
                             if (heartbeatInterval != 0) {
-                                this.heartKey = channel.getWriteThread().executeAfter(heartbeatCommand, heartbeatInterval, TimeUnit.MILLISECONDS);
+                                this.expireTime = System.currentTimeMillis() + heartbeatInterval;
+                                 if (this.heartKey == null) {
+                                     final XnioExecutor executor = channel.getWriteThread();
+                                     final Runnable heartBeat = new HeartBeat(executor);
+                                     this.heartKey = executor.executeAfter(heartBeat, heartbeatInterval, TimeUnit.MILLISECONDS);
+                                 }
                             }
                         }
                         channel.suspendWrites();
@@ -356,8 +362,7 @@ public void shutdownWrites() {
         public void send(final Pooled<ByteBuffer> pooled, final boolean close) {
             connection.getIoThread().execute(() -> {
                 synchronized (queue) {
-                    XnioExecutor.Key heartKey1 = RemoteWriteListener.this.heartKey;
-                    if (heartKey1 != null) heartKey1.remove();
+                    this.expireTime = System.currentTimeMillis() + heartbeatInterval;
                     if (closed) { pooled.free(); return; }
                     if (close) { closed = true; }
                     boolean free = true;
@@ -390,9 +395,30 @@ public void send(final Pooled<ByteBuffer> pooled, final boolean close) {
                 }
             });
         }
+
+        private class HeartBeat implements Runnable {
+
+            private final XnioExecutor executor;
+
+            public HeartBeat(XnioExecutor executor) {
+                this.executor = executor;
+            }
+
+            public void run() {
+                long currentTime = System.currentTimeMillis();
+                if (currentTime >= expireTime) {
+                    sendAlive();
+                    heartKey = executor.executeAfter(this, heartbeatInterval, TimeUnit.MILLISECONDS);
+                } else {
+                    final long nextBeatInterval = expireTime - System.currentTimeMillis();
+                    // prevent negative intervals by scheduling to run immediately if nextBeatInterval happens to be negative
+                    heartKey = executor.executeAfter(this, nextBeatInterval < 0? 0: nextBeatInterval, TimeUnit.MILLISECONDS);
+                }
+
+            }
+        }
     }
 
-    private final Runnable heartbeatCommand = this::sendAlive;
 
     public String toString() {
         return String.format("Remoting connection %08x to %s of %s", Integer.valueOf(hashCode()), connection.getPeerAddress(), getRemoteConnectionProvider().getConnectionProviderContext().getEndpoint());