TEZ-4455: Add LoggingHandler in ShuffleHandler pipeline for better de…

…buggability. (apache#249) (Dmitriy Fingerman reviewed by Laszlo Bodor)

(cherry picked from commit 65f9ee3)
(cherry picked from commit 2c2be57)

tez-plugins/tez-aux-services/src/main/java/org/apache/tez/auxservices/ShuffleHandler.java

@@ -32,6 +32,8 @@
 import static io.netty.handler.codec.http.HttpResponseStatus.OK;
 import static io.netty.handler.codec.http.HttpResponseStatus.UNAUTHORIZED;
 import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
+import io.netty.handler.logging.LogLevel;
+import io.netty.handler.logging.LoggingHandler;
 
 import java.io.File;
 import java.io.FileNotFoundException;
@@ -598,6 +600,9 @@ public void initChannel(NioSocketChannel ch) throws Exception {
         if (sslFactory != null) {
           pipeline.addLast("ssl", new SslHandler(sslFactory.createSSLEngine()));
         }
+        if (LOG.isDebugEnabled()) {
+          pipeline.addLast("loggingHandler", new LoggingHandler(LogLevel.DEBUG));
+        }
         pipeline.addLast("decoder", new HttpRequestDecoder());
         pipeline.addLast("aggregator", new HttpObjectAggregator(1 << 16));
         pipeline.addLast("encoder", new HttpResponseEncoder());