Use a ThreadPoolExecutor to concurrently store files during import (#1427)

* Use a `ThreadPoolExecutor` to concurrently store files during import

CTFd/utils/exports/__init__.py

@@ -8,6 +8,7 @@ import zipfile
 import dataset
 import six
 from alembic.util import CommandError
+from concurrent import futures
 from flask import current_app as app
 from flask_migrate import upgrade as migration_upgrade
 from sqlalchemy.exc import OperationalError, ProgrammingError
@@ -311,17 +312,25 @@ def import_ctf(backup, erase=True):
     # Extracting files
     files = [f for f in backup.namelist() if f.startswith("uploads/")]
     uploader = get_uploader()
-    for f in files:
-        filename = f.split(os.sep, 1)
 
-        if (
-            len(filename) < 2 or os.path.basename(filename[1]) == ""
-        ):  # just an empty uploads directory (e.g. uploads/) or any directory
-            continue
+    awaitables = []
+    with futures.ThreadPoolExecutor() as executor:
+        for f in files:
+            filename = f.split(os.sep, 1)
 
-        filename = filename[1]  # Get the second entry in the list (the actual filename)
-        source = backup.open(f)
-        uploader.store(fileobj=source, filename=filename)
+            # just an empty uploads directory (e.g. uploads/) or any directory
+            if len(filename) < 2 or os.path.basename(filename[1]) == "":
+                continue
+
+            # Get the second entry in the list (the actual filename)
+            filename = filename[1]
+            source = backup.open(f)
+
+            # Parallelize the storage requests
+            awaitables.append(executor.submit(uploader.store, source, filename))
+
+        # Await the storage requests
+        futures.wait(awaitables, return_when=futures.FIRST_EXCEPTION)
 
     # Alembic sqlite support is lacking so we should just create_all anyway
     try: