[NO ISSUE][OTH] Introduce Whispered Messages

- user model changes: no
- storage format changes: no
- interface changes: yes

Details:
- Add whispered flag to IMessage API.
- Log whispered messages as trace rather than info level
  to avoid filling the info log with high frequency messages.

Change-Id: I5c24205f5c25bf9f6aa245e8f1200b046390a915
Reviewed-on: https://asterix-gerrit.ics.uci.edu/3220
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/asterixdb/asterix-active/src/main/java/org/apache/asterix/active/message/ActiveStatsResponse.java b/asterixdb/asterix-active/src/main/java/org/apache/asterix/active/message/ActiveStatsResponse.java
index 8738a06..63f68a7 100644
--- a/asterixdb/asterix-active/src/main/java/org/apache/asterix/active/message/ActiveStatsResponse.java
+++ b/asterixdb/asterix-active/src/main/java/org/apache/asterix/active/message/ActiveStatsResponse.java
@@ -74,4 +74,8 @@
         broker.respond(reqId, this);
     }
 
+    @Override
+    public boolean isWhispered() {
+        return true;
+    }
 }
diff --git a/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/CCMessageBroker.java b/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/CCMessageBroker.java
index 5f42d7a..623a0be 100644
--- a/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/CCMessageBroker.java
+++ b/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/CCMessageBroker.java
@@ -40,6 +40,7 @@
 import org.apache.hyracks.control.cc.ClusterControllerService;
 import org.apache.hyracks.control.cc.NodeControllerState;
 import org.apache.hyracks.control.cc.cluster.INodeManager;
+import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
@@ -59,9 +60,7 @@
     @Override
     public void receivedMessage(IMessage message, String nodeId) throws Exception {
         ICcAddressedMessage msg = (ICcAddressedMessage) message;
-        if (LOGGER.isInfoEnabled()) {
-            LOGGER.info("Received message: " + msg);
-        }
+        IMessage.logMessage(LOGGER, message);
         ICcApplicationContext appCtx = (ICcApplicationContext) ccs.getApplicationContext();
         msg.handle(appCtx);
     }
diff --git a/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/NCMessageBroker.java b/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/NCMessageBroker.java
index e4fe4f3..26f6524 100644
--- a/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/NCMessageBroker.java
+++ b/asterixdb/asterix-app/src/main/java/org/apache/asterix/messaging/NCMessageBroker.java
@@ -92,9 +92,7 @@
     @Override
     public void receivedMessage(IMessage message, String nodeId) throws Exception {
         INcAddressedMessage absMessage = (INcAddressedMessage) message;
-        if (LOGGER.isInfoEnabled()) {
-            LOGGER.info("Received message: " + absMessage);
-        }
+        IMessage.logMessage(LOGGER, message);
         ncs.getExecutor().submit(() -> {
             try {
                 absMessage.handle(appContext);
diff --git a/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessage.java b/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessage.java
index 2f5a873..94e08d7 100644
--- a/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessage.java
+++ b/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessage.java
@@ -20,6 +20,22 @@
 
 import java.io.Serializable;
 
+import org.apache.logging.log4j.Level;
+import org.apache.logging.log4j.Logger;
+
 public interface IMessage extends Serializable {
 
+    /**
+     * @return true if the message is whispered, otherwise false.
+     */
+    default boolean isWhispered() {
+        return false;
+    }
+
+    static void logMessage(Logger logger, IMessage msg) {
+        final Level logLevel = msg.isWhispered() ? Level.TRACE : Level.INFO;
+        if (logger.isEnabled(logLevel)) {
+            logger.info("Received message: {}", msg);
+        }
+    }
 }
diff --git a/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessageBroker.java b/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessageBroker.java
index 8aaa563..2de734f 100644
--- a/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessageBroker.java
+++ b/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/messages/IMessageBroker.java
@@ -20,6 +20,5 @@
 
 public interface IMessageBroker {
 
-    public void receivedMessage(IMessage message, String nodeId) throws Exception;
-
+    void receivedMessage(IMessage message, String nodeId) throws Exception;
 }