Fail deleteFile silently in case file not present in composite directory (opensearch-project#18299)

Signed-off-by: Shreyansh Ray <rayshrey@amazon.com>

Author: rayshrey

server/src/main/java/org/opensearch/index/store/CompositeDirectory.java

@@ -143,7 +143,12 @@ public void deleteFile(String name) throws IOException {
         if (FileTypeUtils.isTempFile(name)) {
             localDirectory.deleteFile(name);
         } else if (Arrays.asList(listAll()).contains(name) == false) {
-            throw new NoSuchFileException("File " + name + " not found in directory");
+            /*
+             We can run into scenarios where stale files are evicted locally (zero refCount in FileCache) and
+             not present in remote as well (due to metadata refresh). In such scenarios listAll() of composite directory
+             will not show the file. Hence, we need to silently fail deleteFile operation for such files.
+             */
+            return;
         } else {
             List<String> blockFiles = listBlockFiles(name);
             if (blockFiles.isEmpty()) {

server/src/test/java/org/opensearch/index/store/CompositeDirectoryTests.java

@@ -80,8 +80,14 @@ public void testDeleteFile() throws IOException {
         compositeDirectory.deleteFile(FILE_PRESENT_LOCALLY);
         assertFalse(existsInCompositeDirectory(FILE_PRESENT_LOCALLY));
         assertFalse(existsInCompositeDirectory(BLOCK_FILE_PRESENT_LOCALLY));
-        // Reading deleted file from directory should result in NoSuchFileException
-        assertThrows(NoSuchFileException.class, () -> compositeDirectory.openInput(FILE_PRESENT_LOCALLY, IOContext.DEFAULT));
+        // Deletion of non-existent file should fail silently without throwing any error
+        Exception exception = null;
+        try {
+            compositeDirectory.deleteFile(NON_EXISTENT_FILE);
+        } catch (Exception e) {
+            exception = e;
+        }
+        assertNull(exception);
     }
 
     public void testFileLength() throws IOException {