Merge pull request #5 from mitre/mutex-mount-unmount

Fix #3 use mutex to resolve race condition on non-atomic mount/unmoun…

src/thumbtack/__init__.py

@@ -1,5 +1,6 @@
 import logging
 import os
+import threading
 
 from pathlib import Path
 from pkg_resources import get_distribution, DistributionNotFound
@@ -52,6 +53,8 @@ def create_app(mount_dir=None, image_dir=None, database=None, base_url=None):
     elif os.environ.get("THUMBTACK_APPLICATION_ROOT"):
         app.config.update(APPLICATION_ROOT=os.environ.get("THUMBTACK_APPLICATION_ROOT"))
 
+    app.mnt_mutex = threading.Lock()
+
     # configure the rest
     configure(app, base_url)
     app.before_first_request(before_first_request)

src/thumbtack/resources.py

@@ -49,10 +49,12 @@ def put(self, image_path):
         """
         status = None
         try:
+            current_app.mnt_mutex.acquire()
             mounted_disk = mount_image(image_path)
 
             if mounted_disk and mounted_disk.mountpoint is not None:
                 current_app.logger.info(f"Image mounted successfully: {image_path}")
+                current_app.mnt_mutex.release()
                 return mounted_disk
 
         # TODO: refactor to not duplicate code in the mount_form in views.py
@@ -67,6 +69,7 @@ def put(self, image_path):
         except ImageNotInDatabaseError:
             status = f"Cannot mount {image_path}. Image is not in Thumbtack database."
 
+        current_app.mnt_mutex.release()
         current_app.logger.error(status)
         abort(400, message=str(status))
 
@@ -92,15 +95,17 @@ def get(self, image_path=None):
             abort(404, message=f"{image_path} not mounted")
         return mount_info
 
-    def delete(self, image_path):
+    def delete(self, image_path=None):
         """Unmounts an image file.
 
         Parameters
         ----------
         image_path : str
             Relative path to an image file to unmount.
         """
+        current_app.mnt_mutex.acquire()
         unmount_image(image_path)
+        current_app.mnt_mutex.release()
 
 
 class SupportedLibraries(Resource):