feat: Use X-Accel-Redirect to improve file download speed

Instead of making FastAPI handle file download, which has serious
performance issues on big files [1], this change uses nginx's `X-Accel`
feature to delegate single-file downloads to nginx.

Partial fix for #1079, as it solves the CPU usage issue for single-file
downloads.

[1] https://github.com/fastapi/fastapi/discussions/6050

backend/config/__init__.py

@@ -13,7 +13,8 @@ GUNICORN_WORKERS: Final = int(os.environ.get("GUNICORN_WORKERS", 2))
 
 # PATHS
 ROMM_BASE_PATH: Final = os.environ.get("ROMM_BASE_PATH", "/romm")
-LIBRARY_BASE_PATH: Final = f"{ROMM_BASE_PATH}/library"
+LIBRARY_PATH_SUFFIX: Final = "/library"
+LIBRARY_BASE_PATH: Final = f"{ROMM_BASE_PATH}{LIBRARY_PATH_SUFFIX}"
 RESOURCES_BASE_PATH: Final = f"{ROMM_BASE_PATH}/resources"
 ASSETS_BASE_PATH: Final = f"{ROMM_BASE_PATH}/assets"
 FRONTEND_RESOURCES_PATH: Final = "/assets/romm/resources"

backend/endpoints/rom.py

@@ -9,6 +9,7 @@ from anyio import Path, open_file
 from config import (
     DISABLE_DOWNLOAD_ENDPOINT_AUTH,
     LIBRARY_BASE_PATH,
+    LIBRARY_PATH_SUFFIX,
     RESOURCES_BASE_PATH,
 )
 from decorators.auth import protected_route
@@ -22,7 +23,7 @@ from endpoints.responses.rom import (
 )
 from exceptions.endpoint_exceptions import RomNotFoundInDatabaseException
 from exceptions.fs_exceptions import RomAlreadyExistsException
-from fastapi import File, HTTPException, Query, Request, UploadFile, status
+from fastapi import File, HTTPException, Query, Request, Response, UploadFile, status
 from fastapi.responses import FileResponse
 from handler.database import db_platform_handler, db_rom_handler
 from handler.filesystem import fs_resource_handler, fs_rom_handler
@@ -210,17 +211,28 @@ async def get_rom_content(
     if not rom:
         raise RomNotFoundInDatabaseException(id)
 
-    rom_path = f"{LIBRARY_BASE_PATH}/{rom.full_path}"
     files_to_download = files or [r["filename"] for r in rom.files]
 
     if not rom.multi:
-        return FileResponse(path=rom_path, filename=rom.file_name)
+        return Response(
+            headers={
+                "Content-Disposition": f'attachment; filename="{quote(rom.file_name)}"',
+                "Content-Type": "application/octet-stream",
+                "X-Accel-Redirect": f"{LIBRARY_PATH_SUFFIX}/{rom.full_path}",
+            },
+        )
 
     if len(files_to_download) == 1:
-        return FileResponse(
-            path=f"{rom_path}/{files_to_download[0]}", filename=files_to_download[0]
+        return Response(
+            headers={
+                "Content-Disposition": f'attachment; filename="{quote(files_to_download[0])}"',
+                "Content-Type": "application/octet-stream",
+                "X-Accel-Redirect": f"{LIBRARY_PATH_SUFFIX}/{rom.full_path}/{files_to_download[0]}",
+            },
         )
 
+    rom_path = f"{LIBRARY_BASE_PATH}/{rom.full_path}"
+
     # Builds a generator of tuples for each member file
     async def local_files() -> AsyncIterator[AsyncMemberFile]:
         async def contents(filename: str) -> AsyncIterator[bytes]:

docker/nginx/default.conf

@@ -87,5 +87,11 @@ http {
                 proxy_set_header Upgrade $http_upgrade;
                 proxy_set_header Connection "upgrade";
             }
+
+            # Library files
+            location /library {
+                internal;
+                alias /romm/library;
+            }
         }
 }