Cache WorkerState host property (#9044)

Author: fjetter

distributed/scheduler.py

@@ -32,7 +32,16 @@
 )
 from contextlib import suppress
 from functools import partial
-from typing import TYPE_CHECKING, Any, ClassVar, Literal, NamedTuple, cast, overload
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    ClassVar,
+    Final,
+    Literal,
+    NamedTuple,
+    cast,
+    overload,
+)
 
 import psutil
 import tornado.web
@@ -413,7 +422,7 @@ class WorkerState:
 
     #: This worker's unique key. This can be its connected address
     #: (such as ``"tcp://127.0.0.1:8891"``) or an alias (such as ``"alice"``).
-    address: str
+    address: Final[str]
 
     pid: int
     name: Hashable
@@ -513,6 +522,9 @@ class WorkerState:
     #: on the worker.
     needs_what: dict[TaskState, int]
 
+    #: The hostname / IP address identifying the machine this worker is on.
+    host: Final[str]
+
     __slots__ = tuple(__annotations__)
 
     def __init__(
@@ -564,6 +576,7 @@ def __init__(
         self.needs_what = {}
         self._network_occ = 0
         self._occupancy_cache = None
+        self.host = get_address_host(self.address)
 
     def __hash__(self) -> int:
         return self._hash
@@ -584,10 +597,6 @@ def has_what(self) -> Set[TaskState]:
         """
         return self._has_what.keys()
 
-    @property
-    def host(self) -> str:
-        return get_address_host(self.address)
-
     @property
     def memory(self) -> MemoryState:
         """Polished memory metrics for the worker.