Comments, extraction, modifiers comments addressed.

community/kernel/src/main/java/org/neo4j/kernel/impl/spi/SimpleKernelContext.java

@@ -31,7 +31,7 @@ public class SimpleKernelContext implements KernelContext
 {
     private final FileSystemAbstraction fileSystem;
     private final File storeDir;
-    UsageDataKeys.OperationalMode operationalMode;
+    private final UsageDataKeys.OperationalMode operationalMode;
 
     public SimpleKernelContext( FileSystemAbstraction fileSystem, File storeDir, UsageDataKeys.OperationalMode operationalMode )
     {

community/lucene-index/src/main/java/org/neo4j/kernel/api/impl/index/LuceneIndexAccessor.java

@@ -132,16 +132,8 @@ public void close() throws IOException
         this.dir = dirFactory.open( indexFolder );
         if ( readOnly )
         {
-            try
-            {
-                this.writer = null;
-                searcherManager =
-                        new LuceneReferenceManager.Wrap<>( new SearcherManager( dir, new SearcherFactory() ) );
-            }
-            catch ( IndexNotFoundException e )
-            {
-                throw new IllegalStateException( "Index creation is not supported in read only mode.", e );
-            }
+            this.writer = null;
+            searcherManager = createReadOnlySearchManager();
         }
         else
         {
@@ -150,6 +142,18 @@ public void close() throws IOException
         }
     }
 
+    private LuceneReferenceManager.Wrap<IndexSearcher> createReadOnlySearchManager() throws IOException
+    {
+        try
+        {
+            return new LuceneReferenceManager.Wrap<>( new SearcherManager( dir, new SearcherFactory() ) );
+        }
+        catch ( IndexNotFoundException e )
+        {
+            throw new IllegalStateException( "Index creation is not supported in read only mode.", e );
+        }
+    }
+
     // test only
     LuceneIndexAccessor( LuceneDocumentStructure documentStructure, boolean readOnly, ReservingLuceneIndexWriter writer,
             LuceneReferenceManager<IndexSearcher> searcherManager,

community/lucene-index/src/main/java/org/neo4j/kernel/api/impl/index/LuceneLabelScanStore.java

@@ -263,6 +263,12 @@ public void init() throws IOException
             {
                 searcherManager = new SearcherManager( directory, new SearcherFactory() );
             }
+            catch ( IndexNotFoundException inf )
+            {
+                monitor.noIndex();
+                throw new IOException( "Label scan store not found while database was started in read only mode. " +
+                                       "To trigger a rebuild please restart database in writable mode.", inf );
+            }
             catch ( IOException e )
             {
                 monitor.corruptIndex( e );

community/lucene-index/src/test/java/org/neo4j/index/impl/lucene/CloseTrackingIndexReader.java

@@ -0,0 +1,177 @@
+/*
+ * Copyright (c) 2002-2016 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.index.impl.lucene;
+
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.FieldSelector;
+import org.apache.lucene.index.CorruptIndexException;
+import org.apache.lucene.index.FieldInfos;
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.index.TermDocs;
+import org.apache.lucene.index.TermEnum;
+import org.apache.lucene.index.TermFreqVector;
+import org.apache.lucene.index.TermPositions;
+import org.apache.lucene.index.TermVectorMapper;
+
+import java.io.IOException;
+import java.util.Map;
+
+class CloseTrackingIndexReader extends IndexReader
+{
+    private boolean closed = false;
+
+    @Override
+    public TermFreqVector[] getTermFreqVectors( int docNumber ) throws IOException
+    {
+        return new TermFreqVector[0];
+    }
+
+    @Override
+    public TermFreqVector getTermFreqVector( int docNumber, String field ) throws IOException
+    {
+        return null;
+    }
+
+    @Override
+    public void getTermFreqVector( int docNumber, String field, TermVectorMapper mapper ) throws IOException
+    {
+
+    }
+
+    @Override
+    public void getTermFreqVector( int docNumber, TermVectorMapper mapper ) throws IOException
+    {
+
+    }
+
+    @Override
+    public int numDocs()
+    {
+        return 0;
+    }
+
+    @Override
+    public int maxDoc()
+    {
+        return 0;
+    }
+
+    @Override
+    public Document document( int n, FieldSelector fieldSelector ) throws CorruptIndexException, IOException
+    {
+        return null;
+    }
+
+    @Override
+    public boolean isDeleted( int n )
+    {
+        return false;
+    }
+
+    @Override
+    public boolean hasDeletions()
+    {
+        return false;
+    }
+
+    @Override
+    public byte[] norms( String field ) throws IOException
+    {
+        return new byte[0];
+    }
+
+    @Override
+    public void norms( String field, byte[] bytes, int offset ) throws IOException
+    {
+
+    }
+
+    @Override
+    protected void doSetNorm( int doc, String field, byte value ) throws CorruptIndexException, IOException
+    {
+
+    }
+
+    @Override
+    public TermEnum terms() throws IOException
+    {
+        return null;
+    }
+
+    @Override
+    public TermEnum terms( Term t ) throws IOException
+    {
+        return null;
+    }
+
+    @Override
+    public int docFreq( Term t ) throws IOException
+    {
+        return 0;
+    }
+
+    @Override
+    public TermDocs termDocs() throws IOException
+    {
+        return null;
+    }
+
+    @Override
+    public TermPositions termPositions() throws IOException
+    {
+        return null;
+    }
+
+    @Override
+    protected void doDelete( int docNum ) throws CorruptIndexException, IOException
+    {
+
+    }
+
+    @Override
+    protected void doUndeleteAll() throws CorruptIndexException, IOException
+    {
+
+    }
+
+    @Override
+    protected void doCommit( Map<String,String> commitUserData ) throws IOException
+    {
+
+    }
+
+    @Override
+    protected void doClose() throws IOException
+    {
+        closed = true;
+    }
+
+    @Override
+    public FieldInfos getFieldInfos()
+    {
+        return null;
+    }
+
+    public boolean isClosed()
+    {
+        return closed;
+    }
+}