Enable mypy on nova/utils.py

As a follow up for a review comment in [1] this patch enables mypy for
nova/utils, fixes the existing mypy findings, and adds some trivial type
annotations where make sense.

[1]https://review.opendev.org/c/openstack/nova/+/956089/comment/caec94ed_4fdb16bf/

Change-Id: I29ca69bd1e583adc1b1f408bd45de183649986d2
Signed-off-by: Balazs Gibizer <gibi@redhat.com>

nova/utils.py

@@ -28,6 +28,7 @@ import re
 import shutil
 import tempfile
 import time
+import typing as ty
 
 from eventlet import tpool
 import futurist
@@ -75,11 +76,16 @@ SM_SKIP_KEYS = (
     'img_mappings', 'img_block_device_mapping',
 )
 
-_FILE_CACHE = {}
+_FILE_CACHE: dict[str, dict] = {}
 
 _SERVICE_TYPES = service_types.ServiceTypes()
 
-DEFAULT_EXECUTOR = None
+# NOTE(gibi): futurist does not expose the common based class.
+# NOTE(gibi): we can simplify this when eventlet is removed.
+Executor: ty.TypeAlias = (
+    futurist.GreenThreadPoolExecutor | futurist.ThreadPoolExecutor)
+
+DEFAULT_EXECUTOR: Executor | None = None
 
 
 def cooperative_yield():
@@ -105,7 +111,7 @@ def destroy_default_executor():
     DEFAULT_EXECUTOR = None
 
 
-def create_executor(max_workers):
+def create_executor(max_workers) -> Executor:
     if concurrency_mode_threading():
         executor = futurist.ThreadPoolExecutor(max_workers)
     else:
@@ -113,7 +119,7 @@ def create_executor(max_workers):
     return executor
 
 
-def _get_default_executor():
+def _get_default_executor() -> Executor:
     global DEFAULT_EXECUTOR
 
     if not DEFAULT_EXECUTOR:
@@ -563,7 +569,9 @@ def _serialize_profile_info():
     return trace_info
 
 
-def spawn(func, *args, **kwargs) -> futurist.Future:
+def spawn(
+    func: ty.Callable[..., ty.Any], *args: ty.Any, **kwargs: ty.Any
+) -> futurist.Future:
     """Passthrough method for eventlet.spawn.
 
     This utility exists so that it can be stubbed for testing without
@@ -577,7 +585,11 @@ def spawn(func, *args, **kwargs) -> futurist.Future:
     return spawn_on(_get_default_executor(), func, *args, **kwargs)
 
 
-def spawn_after(seconds, func, *args, **kwargs) -> futurist.Future:
+def spawn_after(
+    seconds: float,
+    func: ty.Callable[..., ty.Any],
+    *args: ty.Any, **kwargs: ty.Any
+) -> futurist.Future:
     """Executing the function asynchronously after the given time."""
 
     def delayed(*args, **kwargs):
@@ -587,7 +599,7 @@ def spawn_after(seconds, func, *args, **kwargs) -> futurist.Future:
     return spawn(delayed, *args, **kwargs)
 
 
-def _executor_is_full(executor):
+def _executor_is_full(executor: Executor) -> bool:
     if concurrency_mode_threading():
         # TODO(gibi): Move this whole logic to futurist ThreadPoolExecutor
         # so that we can avoid accessing the internals of the executor
@@ -599,7 +611,11 @@ def _executor_is_full(executor):
     return False
 
 
-def spawn_on(executor, func, *args, **kwargs) -> futurist.Future:
+def spawn_on(
+    executor: Executor,
+    func: ty.Callable[..., ty.Any],
+    *args: ty.Any, **kwargs: ty.Any,
+) -> futurist.Future:
     """Passthrough method to run func on a thread in a given executor.
 
     It will also grab the context from the threadlocal store and add it to
@@ -1089,6 +1105,7 @@ def run_once(message, logger, cleanup=None):
     logger and cleanup function will be propagated to the caller.
     """
     def outer_wrapper(func):
+        @ty.no_type_check
         @functools.wraps(func)
         def wrapper(*args, **kwargs):
             if not wrapper.called:
@@ -1138,6 +1155,7 @@ def latch_error_on_raise(retryable=(_SentinelException,)):
     """
 
     def outer_wrapper(func):
+        @ty.no_type_check
         @functools.wraps(func)
         def wrapper(*args, **kwargs):
             if wrapper.error:
@@ -1272,10 +1290,10 @@ def concurrency_mode_threading():
     return not monkey_patch.is_patched()
 
 
-SCATTER_GATHER_EXECUTOR = None
+SCATTER_GATHER_EXECUTOR: Executor | None = None
 
 
-def get_scatter_gather_executor():
+def get_scatter_gather_executor() -> Executor:
     """Returns the executor used for scatter/gather operations."""
     global SCATTER_GATHER_EXECUTOR
 
@@ -1313,10 +1331,10 @@ def destroy_scatter_gather_executor():
     SCATTER_GATHER_EXECUTOR = None
 
 
-CACHE_IMAGES_EXECUTOR = None
+CACHE_IMAGES_EXECUTOR: Executor | None = None
 
 
-def get_cache_images_executor():
+def get_cache_images_executor() -> Executor:
     """Returns the executor used for cache images operations."""
     global CACHE_IMAGES_EXECUTOR
 
@@ -1350,7 +1368,7 @@ def destroy_cache_images_executor():
     CACHE_IMAGES_EXECUTOR = None
 
 
-def _log_executor_stats(executor):
+def _log_executor_stats(executor: Executor) -> None:
     if CONF.thread_pool_statistic_period < 0:
         return
 

pyproject.toml

@@ -137,6 +137,7 @@ files = [
     "nova/scheduler/client/report.py",
     "nova/scheduler/request_filter.py",
     "nova/scheduler/utils.py",
+    "nova/utils.py",
     "nova/virt/driver.py",
     "nova/virt/hardware.py",
     "nova/virt/libvirt/machine_type_utils.py",