fix: only create multiproc dir when prometheus and celery metrics are enabled

Author: adinhodovic

src/django_o11y/__init__.py

@@ -18,14 +18,45 @@
 except PackageNotFoundError:
     __version__ = "unknown"
 
-# Create the multiproc dir before model imports trigger prometheus_client writes.
-# Falls back to PROMETHEUS_MULTIPROC_DIR for operators who set it directly.
-_multiproc_dir = os.environ.get(
-    "DJANGO_O11Y_METRICS_MULTIPROC_BASE_DIR"
-) or os.environ.get("PROMETHEUS_MULTIPROC_DIR")
-if _multiproc_dir:
-    os.environ.setdefault("PROMETHEUS_MULTIPROC_DIR", _multiproc_dir)
-    pathlib.Path(_multiproc_dir).mkdir(parents=True, exist_ok=True)
+
+def _is_celery_worker() -> bool:
+    import sys
+
+    argv = sys.argv
+    return bool(argv) and os.path.basename(argv[0]) == "celery" and "worker" in argv
+
+
+def _is_prefork_web_server() -> bool:
+    import sys
+
+    return "gunicorn" in sys.modules or "uwsgi" in sys.modules
+
+
+def _bool_env(key: str, default: bool) -> bool:
+    raw = os.environ.get(key)
+    if raw is None:
+        return default
+    return raw.lower() not in ("false", "0", "no", "off")
+
+
+# Only create the multiproc dir when it will actually be used:
+# - Gunicorn/uWSGI with prometheus enabled
+# - Celery worker with both prometheus and celery metrics enabled
+_need_multiproc = (
+    _is_prefork_web_server()
+    and _bool_env("DJANGO_O11Y_METRICS_PROMETHEUS_ENABLED", True)
+) or (
+    _is_celery_worker()
+    and _bool_env("DJANGO_O11Y_METRICS_PROMETHEUS_ENABLED", True)
+    and _bool_env("DJANGO_O11Y_CELERY_METRICS_ENABLED", True)
+)
+if _need_multiproc:
+    _multiproc_dir = os.environ.get(
+        "DJANGO_O11Y_METRICS_MULTIPROC_BASE_DIR"
+    ) or os.environ.get("PROMETHEUS_MULTIPROC_DIR")
+    if _multiproc_dir:
+        os.environ.setdefault("PROMETHEUS_MULTIPROC_DIR", _multiproc_dir)
+        pathlib.Path(_multiproc_dir).mkdir(parents=True, exist_ok=True)
 
 default_app_config = "django_o11y.apps.DjangoO11yConfig"