diff --git a/lucene/core/src/java/org/apache/lucene/index/SegmentInfos.java b/lucene/core/src/java/org/apache/lucene/index/SegmentInfos.java
index 40f03e8601d..3b95f25d90d 100644
--- a/lucene/core/src/java/org/apache/lucene/index/SegmentInfos.java
+++ b/lucene/core/src/java/org/apache/lucene/index/SegmentInfos.java
@@ -485,7 +485,7 @@ public final class SegmentInfos implements Cloneable, Iterable<SegmentCommitInfo
     out.writeVInt(Version.LATEST.major);
     out.writeVInt(Version.LATEST.minor);
     out.writeVInt(Version.LATEST.bugfix);
-    System.out.println(Thread.currentThread().getName() + ": now write " + out.getName() + " with version=" + version);
+    //System.out.println(Thread.currentThread().getName() + ": now write " + out.getName() + " with version=" + version);
 
     out.writeLong(version); 
     out.writeInt(counter); // write counter
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyJob.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyJob.java
index 217c2c0500e..1e63d1fedb9 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyJob.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyJob.java
@@ -30,8 +30,9 @@ import org.apache.lucene.index.CorruptIndexException;
 import org.apache.lucene.util.IOUtils;
 
 /** Handles copying one set of files, e.g. all files for a new NRT point, or files for pre-copying a merged segment.
- *  This notifies the caller via OnceDone when the job finishes or failed. */
-
+ *  This notifies the caller via OnceDone when the job finishes or failed.
+ *
+ * @lucene.experimental */
 public abstract class CopyJob implements Comparable<CopyJob> {
   private final static AtomicLong counter = new AtomicLong();
   protected final ReplicaNode dest;
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyState.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyState.java
index c19fabc1e33..630c3a96c6c 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyState.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/CopyState.java
@@ -24,7 +24,9 @@ import java.util.Set;
 import org.apache.lucene.index.SegmentInfos;
 import org.apache.lucene.store.Directory;
 
-/** Holds incRef'd file level details for one point-in-time segment infos on the primary node. */
+/** Holds incRef'd file level details for one point-in-time segment infos on the primary node.
+ *
+ * @lucene.experimental */
 public class CopyState {
 
   public final Map<String,FileMetaData> files;
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/FileMetaData.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/FileMetaData.java
index aca408c60d6..427b1d1a39e 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/FileMetaData.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/FileMetaData.java
@@ -17,7 +17,9 @@ package org.apache.lucene.replicator.nrt;
  * limitations under the License.
  */
 
-/** Holds metadata details about a single file that we use to confirm two files (one remote, one local) are in fact "identical". */
+/** Holds metadata details about a single file that we use to confirm two files (one remote, one local) are in fact "identical".
+ *
+ * @lucene.experimental */
 
 class FileMetaData {
 
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/Node.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/Node.java
index 742b19fdd29..34175723758 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/Node.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/Node.java
@@ -44,7 +44,9 @@ import org.apache.lucene.store.IndexInput;
 import org.apache.lucene.store.RAMOutputStream;
 import org.apache.lucene.util.StringHelper;
 
-/** Common base class for {@link PrimaryNode} and {@link ReplicaNode}. */
+/** Common base class for {@link PrimaryNode} and {@link ReplicaNode}.
+ *
+ * @lucene.experimental */
 
 abstract class Node implements Closeable {
 
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/NodeCommunicationException.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/NodeCommunicationException.java
index 67a9d0a1fb5..d286f3dc0f0 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/NodeCommunicationException.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/NodeCommunicationException.java
@@ -17,6 +17,12 @@ package org.apache.lucene.replicator.nrt;
  * limitations under the License.
  */
 
+/**
+ * Should be thrown by subclasses of {@link PrimaryNode} and {@link ReplicaNode} if a non-fatal exception
+ * occurred while communicating between nodes.
+ *
+ * @lucene.experimental
+ */
 public class NodeCommunicationException extends RuntimeException {
   public NodeCommunicationException(String when, Throwable cause) {
     super(when);
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/PrimaryNode.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/PrimaryNode.java
index 3cff95e90dd..7343b69e634 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/PrimaryNode.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/PrimaryNode.java
@@ -46,7 +46,10 @@ import org.apache.lucene.util.ThreadInterruptedException;
  * replicas since step 2) could otherwise be done concurrently with replicas copying files over.
  */
 
-/** Node that holds an IndexWriter, indexing documents into its local index. */
+/** Node that holds an IndexWriter, indexing documents into its local index.
+ *
+ * @lucene.experimental */
+
 public abstract class PrimaryNode extends Node {
 
   // Current NRT segment infos, incRef'd with IndexWriter.deleter:
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaFileDeleter.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaFileDeleter.java
index 652b3af4e5e..41e0a6f6a42 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaFileDeleter.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaFileDeleter.java
@@ -34,8 +34,6 @@ import org.apache.lucene.store.IOContext;
 
 // TODO: can we factor/share with IFD: this is doing exactly the same thing, but on the replica side
 
-// TODO: once LUCENE-6835 is in, this class becomes a lot simpler?
-
 class ReplicaFileDeleter {
   private final Map<String,Integer> refCounts = new HashMap<String,Integer>();
   private final Directory dir;
@@ -50,7 +48,7 @@ class ReplicaFileDeleter {
    *  (can be opened), false if it cannot be opened, and
    *  (unlike Java's File.exists) throws IOException if
    *  there's some unexpected error. */
-  static boolean slowFileExists(Directory dir, String fileName) throws IOException {
+  private static boolean slowFileExists(Directory dir, String fileName) throws IOException {
     try {
       dir.openInput(fileName, IOContext.DEFAULT).close();
       return true;
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaNode.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaNode.java
index 62827e857ec..4caf5cfa639 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaNode.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/ReplicaNode.java
@@ -50,7 +50,9 @@ import org.apache.lucene.store.IndexOutput;
 import org.apache.lucene.store.Lock;
 import org.apache.lucene.util.IOUtils;
 
-/** Replica node, that pulls index changes from the primary node by copying newly flushed or merged index files */
+/** Replica node, that pulls index changes from the primary node by copying newly flushed or merged index files.
+ * 
+ *  @lucene.experimental */
 
 abstract class ReplicaNode extends Node {
 
diff --git a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/SegmentInfosSearcherManager.java b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/SegmentInfosSearcherManager.java
index 72ed9213d3c..bae260615fe 100644
--- a/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/SegmentInfosSearcherManager.java
+++ b/lucene/replicator/src/java/org/apache/lucene/replicator/nrt/SegmentInfosSearcherManager.java
@@ -36,7 +36,9 @@ import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.ThreadInterruptedException;
 
 /** A SearcherManager that refreshes via an externally provided (NRT) SegmentInfos, either from {@link IndexWriter} or via
- *  nrt replication to another index. */
+ *  nrt replication to another index.
+ *
+ * @lucene.experimental */
 class SegmentInfosSearcherManager extends ReferenceManager<IndexSearcher> {
   private volatile SegmentInfos currentInfos;
   private final Directory dir;
diff --git a/lucene/replicator/src/test/org/apache/lucene/replicator/nrt/TestStressNRTReplication.java b/lucene/replicator/src/test/org/apache/lucene/replicator/nrt/TestStressNRTReplication.java
index fff59fa68d1..d9222c0330c 100644
--- a/lucene/replicator/src/test/org/apache/lucene/replicator/nrt/TestStressNRTReplication.java
+++ b/lucene/replicator/src/test/org/apache/lucene/replicator/nrt/TestStressNRTReplication.java
@@ -58,10 +58,6 @@ import org.apache.lucene.util.ThreadInterruptedException;
 
 import com.carrotsearch.randomizedtesting.SeedUtils;
 
-// nocommit why so many "hit SocketException during commit with R0"?
-
-// nocommit why all these NodeCommunicationExcs?
-
 /*
   TODO
     - fangs
@@ -1145,7 +1141,9 @@ public class TestStressNRTReplication extends LuceneTestCase {
             }
           } catch (IOException se) {
             // Assume primary crashed
-            message("top: indexer lost connection to primary");
+            if (c != null) {
+              message("top: indexer lost connection to primary");
+            }
             try {
               c.close();
             } catch (Throwable t) {
diff --git a/lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java b/lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java
index aa892096a92..ef4397f40af 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java
@@ -432,7 +432,7 @@ public class MockDirectoryWrapper extends BaseDirectoryWrapper {
         throw new AssertionError();
       }
 
-      if (true || LuceneTestCase.VERBOSE) {
+      if (LuceneTestCase.VERBOSE) {
         System.out.println("MockDirectoryWrapper: " + action + " unsynced file: " + name);
       }
     }
diff --git a/solr/core/src/java/org/apache/solr/core/StandardIndexReaderFactory.java b/solr/core/src/java/org/apache/solr/core/StandardIndexReaderFactory.java
index 71cb012ae97..9ad40034e96 100644
--- a/solr/core/src/java/org/apache/solr/core/StandardIndexReaderFactory.java
+++ b/solr/core/src/java/org/apache/solr/core/StandardIndexReaderFactory.java
@@ -26,7 +26,6 @@ import org.apache.lucene.store.Directory;
  * {@link DirectoryReader}.
  * 
  * @see DirectoryReader#open(Directory)
- * @see DirectoryReader#open(IndexWriter, boolean)
  */
 public class StandardIndexReaderFactory extends IndexReaderFactory {