Uvicorn: use --uds instead of --fd 0 to enable multi-worker support

cvat/settings/base.py

@@ -15,7 +15,9 @@
 https://docs.djangoproject.com/en/2.0/ref/settings/
 """
 
+import fcntl
 import os
+import stat
 import sys
 import tempfile
 import urllib
@@ -452,9 +454,49 @@ class REDIS_INMEM_DATABASES(IntEnum):
 
 EVENTS_LOCAL_DB_ROOT = BASE_DIR / "events"
 EVENTS_LOCAL_DB_ROOT.mkdir(parents=True, exist_ok=True)
+_events_local_db_slot_lock_fd = None
+
+
+def _resolve_events_local_db_filename(template: str) -> str:
+    global _events_local_db_slot_lock_fd
+
+    pid = os.getpid()
+    worker = pid
+
+    if "{worker" in template:
+        try:
+            workers = max(1, int(os.getenv("NUMPROCS", "1")))
+        except ValueError:
+            workers = 1
+
+        slot_locks_root = EVENTS_LOCAL_DB_ROOT / ".slots"
+        slot_locks_root.mkdir(parents=True, exist_ok=True)
+
+        for slot in range(workers):
+            lock_file = slot_locks_root / f"worker_{slot:03d}.lock"
+            fd = os.open(lock_file, os.O_RDWR | os.O_CREAT, stat.S_IRUSR | stat.S_IWUSR)
+            try:
+                fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
+            except BlockingIOError:
+                os.close(fd)
+                continue
+
+            _events_local_db_slot_lock_fd = fd
+            worker = slot
+            break
+
+    try:
+        return template.format(worker=worker)
+    except (KeyError, ValueError, IndexError):
+        return template
+
+
+events_local_db_filename = _resolve_events_local_db_filename(
+    os.getenv("CVAT_EVENTS_LOCAL_DB_FILENAME", "events.db")
+)
 EVENTS_LOCAL_DB_FILE = Path(
     EVENTS_LOCAL_DB_ROOT,
-    os.getenv("CVAT_EVENTS_LOCAL_DB_FILENAME", "events.db"),
+    events_local_db_filename,
 )
 EVENTS_LOCAL_DB_FILE.touch(exist_ok=True)
 

supervisord/server.conf

@@ -9,14 +9,14 @@ startretries=5
 numprocs=1
 process_name=%(program_name)s-%(process_num)d
 
-[fcgi-program:uvicorn]
-socket=unix:///tmp/uvicorn.sock
+[program:uvicorn]
 command=%(ENV_HOME)s/wait_for_deps.sh
     python3 -m uvicorn
-        --fd 0
+        --uds /tmp/uvicorn.sock
         --forwarded-allow-ips='*'
+        --workers %(ENV_NUMPROCS)s
         cvat.asgi:application
 autorestart=true
-environment=CVAT_EVENTS_LOCAL_DB_FILENAME="events_%(process_num)03d.db"
-numprocs=%(ENV_NUMPROCS)s
+environment=CVAT_EVENTS_LOCAL_DB_FILENAME="events_{worker:03d}.db"
+numprocs=1
 process_name=%(program_name)s-%(process_num)d