diff --git a/examples/mnist/estimator/mnist_pipeline.py b/examples/mnist/estimator/mnist_pipeline.py
index 0939df1f..87a2c256 100644
--- a/examples/mnist/estimator/mnist_pipeline.py
+++ b/examples/mnist/estimator/mnist_pipeline.py
@@ -181,6 +181,7 @@ def parse(ln):
     model = TFModel(args) \
         .setInputMapping({'image': 'features'}) \
         .setOutputMapping({'logits': 'prediction'}) \
+        .setSignatureDefKey('serving_default') \
         .setExportDir(args.export_dir) \
         .setBatchSize(args.batch_size)
 
diff --git a/examples/mnist/keras/mnist_pipeline.py b/examples/mnist/keras/mnist_pipeline.py
index 00365070..f20dd50f 100644
--- a/examples/mnist/keras/mnist_pipeline.py
+++ b/examples/mnist/keras/mnist_pipeline.py
@@ -134,6 +134,7 @@ def parse(ln):
     model = TFModel(args) \
         .setInputMapping({'image': 'conv2d_input'}) \
         .setOutputMapping({'dense_1': 'prediction'}) \
+        .setSignatureDefKey('serving_default') \
         .setExportDir(args.export_dir) \
         .setBatchSize(args.batch_size)
 
diff --git a/tensorflowonspark/TFNode.py b/tensorflowonspark/TFNode.py
index 85a3f812..6bbed0bb 100644
--- a/tensorflowonspark/TFNode.py
+++ b/tensorflowonspark/TFNode.py
@@ -231,6 +231,9 @@ def __init__(self, mgr, train_mode=True, qname_in='input', qname_out='output', i
     self.done_feeding = False
     self.input_tensors = [tensor for col, tensor in sorted(input_mapping.items())] if input_mapping is not None else None
 
+    self.queue_in = mgr.get_queue(qname_in)
+    self.queue_out = mgr.get_queue(qname_out)
+
   def next_batch(self, batch_size):
     """Gets a batch of items from the input RDD.
 
@@ -249,34 +252,33 @@ def next_batch(self, batch_size):
     Returns:
       A batch of items or a dictionary of tensors.
     """
-    logger.debug("next_batch() invoked")
-    queue = self.mgr.get_queue(self.qname_in)
     tensors = [] if self.input_tensors is None else {tensor: [] for tensor in self.input_tensors}
     count = 0
+    queue_in = self.queue_in
+    no_input_tensors = self.input_tensors is None
     while count < batch_size:
-      item = queue.get(block=True)
+      item = queue_in.get(block=True)
       if item is None:
         # End of Feed
         logger.info("next_batch() got None")
-        queue.task_done()
+        queue_in.task_done()
         self.done_feeding = True
         break
       elif type(item) is marker.EndPartition:
         # End of Partition
         logger.info("next_batch() got EndPartition")
-        queue.task_done()
+        queue_in.task_done()
         if not self.train_mode and count > 0:
           break
       else:
         # Normal item
-        if self.input_tensors is None:
+        if no_input_tensors:
           tensors.append(item)
         else:
           for i in range(len(self.input_tensors)):
             tensors[self.input_tensors[i]].append(item[i])
         count += 1
-        queue.task_done()
-    logger.debug("next_batch() returning {0} items".format(count))
+        queue_in.task_done()
     return tensors
 
   def should_stop(self):
@@ -292,11 +294,9 @@ def batch_results(self, results):
     Args:
       :results: array of output data for the equivalent batch of input data.
     """
-    logger.debug("batch_results() invoked")
-    queue = self.mgr.get_queue(self.qname_out)
+    queue = self.queue_out
     for item in results:
       queue.put(item, block=True)
-    logger.debug("batch_results() returning data")
 
   def terminate(self):
     """Terminate data feeding early.