Improve GRPC session error handling.

application/src/main/java/org/thingsboard/server/service/cluster/rpc/GrpcSession.java

@@ -95,15 +95,24 @@ public final class GrpcSession implements Closeable {
     }
 
     public void sendMsg(ClusterAPIProtos.ClusterMessage msg) {
-        outputStream.onNext(msg);
-    }
-
-    public void onError(Throwable t) {
-        outputStream.onError(t);
+        if (connected) {
+            try {
+                outputStream.onNext(msg);
+            } catch (Throwable t) {
+                try {
+                    outputStream.onError(t);
+                } catch (Throwable t2) {
+                }
+                listener.onError(GrpcSession.this, t);
+            }
+        } else {
+            log.warn("[{}] Failed to send message due to closed session!", sessionId);
+        }
     }
 
     @Override
     public void close() {
+        connected = false;
         try {
             outputStream.onCompleted();
         } catch (IllegalStateException e) {

pom.xml

@@ -61,10 +61,10 @@
         <mail.version>1.4.3</mail.version>
         <curator.version>4.2.0</curator.version>
         <protobuf.version>3.6.1</protobuf.version>
-        <grpc.version>1.16.1</grpc.version>
+        <grpc.version>1.19.0</grpc.version>
         <lombok.version>1.16.18</lombok.version>
         <paho.client.version>1.1.0</paho.client.version>
-        <netty.version>4.1.30.Final</netty.version>
+        <netty.version>4.1.34.Final</netty.version>
         <os-maven-plugin.version>1.5.0</os-maven-plugin.version>
         <rabbitmq.version>4.8.0</rabbitmq.version>
         <surfire.version>2.19.1</surfire.version>