Index: src/main/java/org/apache/jackrabbit/oak/plugins/index/lucene/OakDirectory.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/index/lucene/OakDirectory.java	(revision 1633283)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/index/lucene/OakDirectory.java	(working copy)
@@ -154,6 +154,8 @@
 
     private static class OakIndexFile {
 
+        private final boolean isReadOnly;
+
         private final String name;
 
         private final NodeBuilder file;
@@ -174,7 +176,10 @@
 
         private boolean blobModified = false;
 
-        public OakIndexFile(String name, NodeBuilder file) {
+        private volatile boolean isOpen = true;
+
+        public OakIndexFile(String name, NodeBuilder file, boolean isReadOnly) {
+            this.isReadOnly = isReadOnly;
             this.name = name;
             this.file = file;
             this.blobSize = determineBlobSize(file);
@@ -195,6 +200,7 @@
         }
 
         private OakIndexFile(OakIndexFile that) {
+            this.isReadOnly = that.isReadOnly;
             this.name = that.name;
             this.file = that.file;
             this.blobSize = that.blobSize;
@@ -225,6 +231,7 @@
 
         private void flushBlob() throws IOException {
             if (blobModified) {
+                checkState(!isReadOnly);
                 int n = (int) Math.min(blobSize, length - index * blobSize);
                 Blob b = file.createBlob(new ByteArrayInputStream(blob, 0, n));
                 if (index < data.size()) {
@@ -317,6 +324,16 @@
             }
         }
 
+        void close() throws IOException {
+            if (isOpen) {
+                if (!isReadOnly) {
+                    flush();
+                }
+                data.clear();
+                isOpen = false;
+            }
+        }
+
         @Override
         public String toString() {
             return name;
@@ -330,7 +347,7 @@
 
         public OakIndexInput(String name, NodeBuilder file) {
             super(name);
-            this.file = new OakIndexFile(name, file);
+            this.file = new OakIndexFile(name, file, true);
         }
 
         private OakIndexInput(OakIndexInput that) {
@@ -371,8 +388,8 @@
         }
 
         @Override
-        public void close() {
-            // do nothing
+        public void close() throws IOException {
+            file.close();
         }
 
     }
@@ -381,8 +398,8 @@
 
         private final OakIndexFile file;
 
-        public OakIndexOutput(String name, NodeBuilder file) throws IOException {
-            this.file = new OakIndexFile(name, file);
+        public OakIndexOutput(String name, NodeBuilder file) {
+            this.file = new OakIndexFile(name, file, false);
         }
 
         @Override
@@ -418,9 +435,8 @@
 
         @Override
         public void close() throws IOException {
-            flush();
+            file.close();
         }
-
     }
 
 }