RAHHH

backend/lib/python3.12/site-packages/twisted/_threads/_pool.py

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+# -*- test-case-name: twisted._threads.test -*-
+# Copyright (c) Twisted Matrix Laboratories.
+# See LICENSE for details.
+
+"""
+Top level thread pool interface, used to implement
+L{twisted.python.threadpool}.
+"""
+
+
+from queue import Queue
+from threading import Lock, Thread, local as LocalStorage
+from typing import Callable, Optional
+
+from typing_extensions import Protocol
+
+from twisted.python.log import err
+from ._ithreads import IWorker
+from ._team import Team
+from ._threadworker import LockWorker, ThreadWorker
+
+
+class _ThreadFactory(Protocol):
+    def __call__(self, *, target: Callable[..., object]) -> Thread:
+        ...
+
+
+def pool(
+    currentLimit: Callable[[], int], threadFactory: _ThreadFactory = Thread
+) -> Team:
+    """
+    Construct a L{Team} that spawns threads as a thread pool, with the given
+    limiting function.
+
+    @note: Future maintainers: while the public API for the eventual move to
+        twisted.threads should look I{something} like this, and while this
+        function is necessary to implement the API described by
+        L{twisted.python.threadpool}, I am starting to think the idea of a hard
+        upper limit on threadpool size is just bad (turning memory performance
+        issues into correctness issues well before we run into memory
+        pressure), and instead we should build something with reactor
+        integration for slowly releasing idle threads when they're not needed
+        and I{rate} limiting the creation of new threads rather than just
+        hard-capping it.
+
+    @param currentLimit: a callable that returns the current limit on the
+        number of workers that the returned L{Team} should create; if it
+        already has more workers than that value, no new workers will be
+        created.
+    @type currentLimit: 0-argument callable returning L{int}
+
+    @param threadFactory: Factory that, when given a C{target} keyword argument,
+        returns a L{threading.Thread} that will run that target.
+    @type threadFactory: callable returning a L{threading.Thread}
+
+    @return: a new L{Team}.
+    """
+
+    def startThread(target: Callable[..., object]) -> None:
+        return threadFactory(target=target).start()
+
+    def limitedWorkerCreator() -> Optional[IWorker]:
+        stats = team.statistics()
+        if stats.busyWorkerCount + stats.idleWorkerCount >= currentLimit():
+            return None
+        return ThreadWorker(startThread, Queue())
+
+    team = Team(
+        coordinator=LockWorker(Lock(), LocalStorage()),
+        createWorker=limitedWorkerCreator,
+        logException=err,
+    )
+    return team