CNDB-16175: CNDB-15990: Avoid varargs allocations in atomicMoveWithFallback (#2124)

riptano/cndb#15990

- What: Eliminates unnecessary array allocations in
PathUtils.atomicMoveWithFallback() by pre-allocating CopyOption[] arrays
as static constants.

- Why: JFR profiling showed this method was a memory allocation hotspot
during RemoteFileCache preloading. Each call to Files.move() with
varargs parameters created new arrays, causing excessive GC pressure.

Author: lesnik2u

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

@@ -99,9 +99,31 @@ public final class PathUtils
     private static final Logger logger = LoggerFactory.getLogger(PathUtils.class);
     private static final NoSpamLogger nospam1m = NoSpamLogger.getLogger(logger, 1, TimeUnit.MINUTES);
 
-    private static Consumer<Path> onDeletion = path -> {};
     private static final boolean USE_NIX_RECURSIVE_DELETE = CassandraRelevantProperties.USE_NIX_RECURSIVE_DELETE.getBoolean();
 
+    private static volatile boolean DAEMON_SETUP_COMPLETED = false;
+
+    private static final CopyOption[] ATOMIC_MOVE_OPTIONS = {
+        StandardCopyOption.REPLACE_EXISTING,
+        StandardCopyOption.ATOMIC_MOVE
+    };
+
+    private static final CopyOption[] REPLACE_EXISTING_OPTIONS = {
+        StandardCopyOption.REPLACE_EXISTING
+    };
+
+    private static Consumer<Path> onDeletion = path -> {
+        if (DAEMON_SETUP_COMPLETED)
+            setDeletionListener(ignore -> {});
+        else if (logger.isTraceEnabled())
+            logger.trace("Deleting file during startup: {}", path);
+    };
+
+    public static void daemonSetupCompleted()
+    {
+        DAEMON_SETUP_COMPLETED = true;
+    }
+
     public static FileChannel newReadChannel(Path path) throws NoSuchFileException
     {
         return newFileChannel(path, READ_OPTIONS);
@@ -556,12 +578,12 @@ private static void atomicMoveWithFallback(Path from, Path to) throws IOExceptio
     {
         try
         {
-            Files.move(from, to, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.ATOMIC_MOVE);
+            Files.move(from, to, ATOMIC_MOVE_OPTIONS);
         }
         catch (AtomicMoveNotSupportedException e)
         {
             logger.trace("Could not do an atomic move", e);
-            Files.move(from, to, StandardCopyOption.REPLACE_EXISTING);
+            Files.move(from, to, REPLACE_EXISTING_OPTIONS);
         }
     }