diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index e40b933d468..83b52fdf281 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -88,6 +88,9 @@ Trunk (unreleased changes)
     HADOOP-8523. test-patch.sh doesn't validate patches before building
     (Jack Dintruff via jeagles)
 
+    HADOOP-8642. ProtobufRpcEngine should log all RPCs if TRACE logging is
+    enabled (todd)
+
   BUG FIXES
 
     HADOOP-8177. MBeans shouldn't try to register when it fails to create MBeanName.
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
index a923186511a..b0f5c93f757 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
@@ -1399,5 +1399,10 @@ public class Client {
       result = PRIME * result + ((ticket == null) ? 0 : ticket.hashCode());
       return result;
     }
+    
+    @Override
+    public String toString() {
+      return serverPrincipal + "@" + address;
+    }
   }  
 }
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java
index 1bf6e4c55fb..96ca97817ab 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java
@@ -51,13 +51,14 @@ import com.google.protobuf.BlockingService;
 import com.google.protobuf.Descriptors.MethodDescriptor;
 import com.google.protobuf.Message;
 import com.google.protobuf.ServiceException;
+import com.google.protobuf.TextFormat;
 
 /**
  * RPC Engine for for protobuf based RPCs.
  */
 @InterfaceStability.Evolving
 public class ProtobufRpcEngine implements RpcEngine {
-  private static final Log LOG = LogFactory.getLog(ProtobufRpcEngine.class);
+  public static final Log LOG = LogFactory.getLog(ProtobufRpcEngine.class);
   
   static { // Register the rpcRequest deserializer for WritableRpcEngine 
     org.apache.hadoop.ipc.Server.registerProtocolEngine(
@@ -191,16 +192,29 @@ public class ProtobufRpcEngine implements RpcEngine {
 
       HadoopRpcRequestProto rpcRequest = constructRpcRequest(method, args);
       RpcResponseWritable val = null;
+      
+      if (LOG.isTraceEnabled()) {
+        LOG.trace(Thread.currentThread().getId() + ": Call -> " +
+            remoteId + ": " + method.getName() +
+            " {" + TextFormat.shortDebugString((Message) args[1]) + "}");
+      }
       try {
         val = (RpcResponseWritable) client.call(RPC.RpcKind.RPC_PROTOCOL_BUFFER,
             new RpcRequestWritable(rpcRequest), remoteId);
+
       } catch (Throwable e) {
+        if (LOG.isTraceEnabled()) {
+          LOG.trace(Thread.currentThread().getId() + ": Exception <- " +
+              remoteId + ": " + method.getName() +
+                " {" + e + "}");
+        }
+
         throw new ServiceException(e);
       }
 
       if (LOG.isDebugEnabled()) {
         long callTime = Time.now() - startTime;
-        LOG.debug("Call: " + method.getName() + " " + callTime);
+        LOG.debug("Call: " + method.getName() + " took " + callTime + "ms");
       }
       
       Message prototype = null;
@@ -213,6 +227,13 @@ public class ProtobufRpcEngine implements RpcEngine {
       try {
         returnMessage = prototype.newBuilderForType()
             .mergeFrom(val.responseMessage).build();
+
+        if (LOG.isTraceEnabled()) {
+          LOG.trace(Thread.currentThread().getId() + ": Response <- " +
+              remoteId + ": " + method.getName() +
+                " {" + TextFormat.shortDebugString(returnMessage) + "}");
+        }
+
       } catch (Throwable e) {
         throw new ServiceException(e);
       }