Improve performance of the folderSize function

patch by briareus; reviewed by Stefania for CASSANDRA-10677

CHANGES.txt

@@ -1,4 +1,5 @@
 3.2
+ * Improve performance of the folderSize function (CASSANDRA-10677)
  * Add support for type casting in selection clause (CASSANDRA-10310)
  * Added graphing option to cassandra-stress (CASSANDRA-7918)
  * Abort in-progress queries that time out (CASSANDRA-7392)

src/java/org/apache/cassandra/io/util/FileUtils.java

@@ -23,6 +23,7 @@ import java.nio.channels.FileChannel;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.*;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.text.DecimalFormat;
 import java.util.Arrays;
 import java.util.Collections;
@@ -518,25 +519,34 @@ public class FileUtils
                 break;
         }
     }
+
     /**
      * Get the size of a directory in bytes
-     * @param directory The directory for which we need size.
+     * @param folder The directory for which we need size.
      * @return The size of the directory
      */
-    public static long folderSize(File directory)
+    public static long folderSize(File folder)
     {
-        long length = 0;
-        for (File file : directory.listFiles())
+        final long [] sizeArr = {0L};
+        try
         {
-            if (file.isFile())
-                length += file.length();
-            else
-                length += folderSize(file);
+            Files.walkFileTree(folder.toPath(), new SimpleFileVisitor<Path>()
+            {
+                @Override
+                public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
+                {
+                    sizeArr[0] += attrs.size();
+                    return FileVisitResult.CONTINUE;
+                }
+            });
         }
-        return length;
+        catch (IOException e)
+        {
+            logger.error("Error while getting {} folder size. {}", folder, e);
+        }
+        return sizeArr[0];
     }
 
-
     public static void copyTo(DataInput in, OutputStream out, int length) throws IOException
     {
         byte[] buffer = new byte[64 * 1024];

test/unit/org/apache/cassandra/io/util/FileUtilsTest.java

@@ -20,11 +20,20 @@ package org.apache.cassandra.io.util;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.RandomAccessFile;
 import java.nio.charset.Charset;
 import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
 
 import org.junit.Test;
 
+import org.apache.cassandra.config.DatabaseDescriptor;
+import org.apache.cassandra.cql3.CQLTester;
+import org.apache.cassandra.schema.SchemaKeyspace;
+import org.apache.cassandra.utils.FBUtilities;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
@@ -52,4 +61,47 @@ public class FileUtilsTest
         assertEquals(0, b.length);
     }
 
+    @Test
+    public void testFolderSize() throws Exception
+    {
+        File folder = createFolder(Paths.get(DatabaseDescriptor.getAllDataFileLocations()[0], "testFolderSize"));
+        folder.deleteOnExit();
+
+        File childFolder = createFolder(Paths.get(folder.getPath(), "child"));
+
+        File[] files = {
+                       createFile(new File(folder, "001"), 10000),
+                       createFile(new File(folder, "002"), 1000),
+                       createFile(new File(folder, "003"), 100),
+                       createFile(new File(childFolder, "001"), 1000),
+                       createFile(new File(childFolder, "002"), 2000),
+        };
+
+        assertEquals(0, FileUtils.folderSize(new File(folder, "i_dont_exist")));
+        assertEquals(files[0].length(), FileUtils.folderSize(files[0]));
+
+        long size = FileUtils.folderSize(folder);
+        assertEquals(Arrays.stream(files).mapToLong(f -> f.length()).sum(), size);
+    }
+
+    private File createFolder(Path path)
+    {
+        File folder = path.toFile();
+        FileUtils.createDirectory(folder);
+        return folder;
+    }
+
+    private File createFile(File file, long size)
+    {
+        try
+        {
+            RandomAccessFile f = new RandomAccessFile(file, "rw");
+            f.setLength(size);
+        }
+        catch (Exception e)
+        {
+            System.err.println(e);
+        }
+        return file;
+    }
 }