Add segments file info to Core admin status

The segments file name and size are useful information to know about
the current commit point.

Author: Shai Erera

solr/core/src/java/org/apache/solr/handler/admin/LukeRequestHandler.java

@@ -17,6 +17,10 @@
 
 package org.apache.solr.handler.admin;
 
+import static org.apache.lucene.index.IndexOptions.DOCS;
+import static org.apache.lucene.index.IndexOptions.DOCS_AND_FREQS;
+import static org.apache.lucene.index.IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS;
+
 import java.io.IOException;
 import java.lang.invoke.MethodHandles;
 import java.net.MalformedURLException;
@@ -41,6 +45,7 @@
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.DocValuesType;
 import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.IndexCommit;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexableField;
@@ -80,10 +85,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import static org.apache.lucene.index.IndexOptions.DOCS;
-import static org.apache.lucene.index.IndexOptions.DOCS_AND_FREQS;
-import static org.apache.lucene.index.IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS;
-
 /**
  * This handler exposes the internal lucene index.  It is inspired by and 
  * modeled on Luke, the Lucene Index Browser by Andrzej Bialecki.
@@ -586,8 +587,13 @@ public static SimpleOrderedMap<Object> getIndexInfo(DirectoryReader reader) thro
     indexInfo.add("current", reader.isCurrent() );
     indexInfo.add("hasDeletions", reader.hasDeletions() );
     indexInfo.add("directory", dir );
-    indexInfo.add("userData", reader.getIndexCommit().getUserData());
-    String s = reader.getIndexCommit().getUserData().get(SolrIndexWriter.COMMIT_TIME_MSEC_KEY);
+    IndexCommit indexCommit = reader.getIndexCommit();
+    String segmentsFileName = indexCommit.getSegmentsFileName();
+    indexInfo.add("segmentsFile", segmentsFileName);
+    indexInfo.add("segmentsFileSizeInBytes", indexCommit.getDirectory().fileLength(segmentsFileName));
+    Map<String,String> userData = indexCommit.getUserData();
+    indexInfo.add("userData", userData);
+    String s = userData.get(SolrIndexWriter.COMMIT_TIME_MSEC_KEY);
     if (s != null) {
       indexInfo.add("lastModified", new Date(Long.parseLong(s)));
     }