Add script to efficiently delete a large number of nested empty folders in an HNS bucket. (#13497)

* Add script to efficiently delete a large number of nested empty folders.

---------

Co-authored-by: mabsaleh <[email protected]>

Author: mabsaleh

storage/hierarchical-namespace/README.md

@@ -0,0 +1,37 @@
+# GCS HNS Folder Management Scripts
+
+This directory contains scripts for managing folders in Google Cloud Storage
+(GCS) Hierarchical Namespace (HNS) enabled buckets.
+
+## Scripts
+
+### `delete_empty_folders.py`
+
+This script recursively deletes empty folders within a specified GCS bucket and
+(optional) prefix.
+
+**Features:**
+
+*   **Recursive Deletion:** Traverses and deletes nested empty folders.
+*   **Depth-First Deletion:** Deletes the deepest folders first to ensure parent
+    folders are empty before deletion attempts.
+*   **Parallel Execution:** Uses a thread pool to delete folders concurrently
+    for improved performance.
+*   **Configurable:** Allows setting the target bucket, folder prefix, and
+    number of workers.
+*   **Error Handling:** Retries on transient errors and logs failures.
+*   **Progress Reporting:** Periodically logs deletion statistics.
+
+**Usage:**
+
+1.  **Authenticate:** `bash gcloud auth application-default login`
+2.  **Configure:** Update the variables at the top of the script:
+    *   `BUCKET_NAME`: The name of your GCS HNS bucket.
+    *   `FOLDER_PREFIX`: (Optional) The prefix to limit deletion scope (e.g.,
+        `archive/`). Leave empty to scan the whole bucket. Must end with `/` if
+        specified.
+    *   `MAX_WORKERS`: Number of concurrent deletion threads.
+3.  **Run:** `bash python3 delete_empty_folders.py`
+
+**Note:** This script *only* deletes folders. Folders containing any objects
+will not be deleted, and a "Failed Precondition" warning will be logged.