fix: prometheus multproc dir permissions error

src/common/core/constants.py

@@ -1 +1 @@
-DEFAULT_PROMETHEUS_MULTIPROC_DIR = "/tmp/flagsmith-prometheus"
+DEFAULT_PROMETHEUS_MULTIPROC_DIR_NAME = "flagsmith-prometheus"

src/common/core/main.py

@@ -1,7 +1,6 @@
 import contextlib
 import logging
 import os
-import shutil
 import sys
 import typing
 
@@ -10,7 +9,7 @@
 )
 
 from common.core.cli import healthcheck
-from common.core.constants import DEFAULT_PROMETHEUS_MULTIPROC_DIR
+from common.prometheus.multiprocessing import prepare_prom_multiproc_dir
 
 logger = logging.getLogger(__name__)
 
@@ -35,6 +34,9 @@ def ensure_cli_env() -> typing.Generator[None, None, None]:
 
     # TODO @khvn26 Move logging setup to here
 
+    # Prometheus multiproc support
+    prepare_prom_multiproc_dir()
+
     # Currently we don't install Flagsmith modules as a package, so we need to add
     # $CWD to the Python path to be able to import them
     sys.path.append(os.getcwd())
@@ -43,18 +45,6 @@ def ensure_cli_env() -> typing.Generator[None, None, None]:
     # without resorting to it being set outside of the application
     os.environ.setdefault("DJANGO_SETTINGS_MODULE", "settings.dev")
 
-    # Set up Prometheus' multiprocess mode
-    prometheus_multiproc_dir_name = os.environ.setdefault(
-        "PROMETHEUS_MULTIPROC_DIR",
-        DEFAULT_PROMETHEUS_MULTIPROC_DIR,
-    )
-    shutil.rmtree(prometheus_multiproc_dir_name, ignore_errors=True)
-    os.makedirs(prometheus_multiproc_dir_name, exist_ok=True)
-    logger.info(
-        "Re-created %s for Prometheus multi-process mode",
-        prometheus_multiproc_dir_name,
-    )
-
     if "docgen" in sys.argv:
         os.environ["DOCGEN_MODE"] = "true"
 

src/common/prometheus/__init__.py

@@ -1,3 +1,16 @@
-from common.prometheus.utils import Histogram
+from typing import Any
 
-__all__ = ("Histogram",)
+_utils = ("Histogram",)
+
+
+def __getattr__(name: str) -> Any:
+    """
+    Since utils imports django.conf.settings, we lazy load any objects that
+    we want to import to prevent django.core.exceptions.ImproperlyConfigured
+    due to settings not being configured.
+    """
+    if name in _utils:
+        from common.prometheus import utils
+
+        return getattr(utils, name)
+    raise AttributeError(name)

src/common/prometheus/multiprocessing.py

@@ -0,0 +1,36 @@
+import os
+import pathlib
+import shutil
+from tempfile import gettempdir
+
+from common.core.constants import DEFAULT_PROMETHEUS_MULTIPROC_DIR_NAME
+
+
+def prepare_prom_multiproc_dir() -> None:
+    prom_dir = pathlib.Path(
+        os.environ.setdefault(
+            "PROMETHEUS_MULTIPROC_DIR",
+            os.path.join(gettempdir(), DEFAULT_PROMETHEUS_MULTIPROC_DIR_NAME),
+        )
+    )
+
+    if prom_dir.exists():
+        for p in prom_dir.rglob("*"):
+            try:
+                # Ensure that the cleanup doesn't silently fail on
+                # files and subdirs created by other users.
+                p.chmod(0o777)
+            except Exception:  # pragma: no cover
+                pass
+
+        shutil.rmtree(prom_dir, ignore_errors=True)
+
+    prom_dir.mkdir(parents=True, exist_ok=True)
+
+    # While `mkdir` sets mode=0o777 by default, this can be affected by umask resulting in
+    # lesser permissions for other users. This step ensures the directory is writable for
+    # all users.
+    try:
+        prom_dir.chmod(0o777)
+    except PermissionError:
+        pass

src/task_processor/processor.py

@@ -194,7 +194,7 @@ def _run_task(
         "result": result.lower(),
     }
 
-    timer.labels(**labels)  # type: ignore[no-untyped-call]
+    timer.labels(**labels)
     ctx.close()
 
     metrics.flagsmith_task_processor_finished_tasks_total.labels(**labels).inc()