Revert "Delete unused utils.py"

This reverts commit f2eb15d.

Author: denschub

server/server/utils.py

@@ -0,0 +1,84 @@
+import sys
+from contextlib import suppress
+from logging import getLogger
+from time import sleep, time
+from uuid import uuid4
+
+from redis.exceptions import WatchError
+
+if sys.version_info[:2] < (3, 12):
+    from collections.abc import Iterable, Iterator
+    from itertools import islice
+    from typing import TypeVar
+
+LOG = getLogger("webcompatmanager.utils")
+
+
+class RedisLock:
+    """Simple Redis mutex lock.
+
+    based on: https://redislabs.com/ebook/part-2-core-concepts \
+              /chapter-6-application-components-in-redis/6-2-distributed-locking \
+              /6-2-3-building-a-lock-in-redis/
+
+    Not using RedLock because it isn't passable as a celery argument, so we can't
+    release the lock in an async chain.
+    """
+
+    def __init__(self, conn, name, unique_id=None):
+        self.conn = conn
+        self.name = name
+        if unique_id is None:
+            self.unique_id = str(uuid4())
+        else:
+            self.unique_id = unique_id
+
+    def acquire(self, acquire_timeout=10, lock_expiry=None):
+        end = time() + acquire_timeout
+        while time() < end:
+            if self.conn.set(self.name, self.unique_id, ex=lock_expiry, nx=True):
+                LOG.debug("Acquired lock: %s(%s)", self.name, self.unique_id)
+                return self.unique_id
+
+            sleep(0.05)
+
+        LOG.debug("Failed to acquire lock: %s(%s)", self.name, self.unique_id)
+        return None
+
+    def release(self):
+        with self.conn.pipeline() as pipe:
+            while True:
+                with suppress(WatchError):
+                    pipe.watch(self.name)
+                    existing = pipe.get(self.name)
+                    if not isinstance(existing, str):
+                        existing = existing.decode("ascii")
+
+                    if existing == self.unique_id:
+                        pipe.multi()
+                        pipe.delete(self.name)
+                        pipe.execute()
+                        LOG.debug("Released lock: %s(%s)", self.name, self.unique_id)
+                        return True
+
+                    pipe.unwatch()
+                    break
+
+        LOG.debug(
+            "Failed to release lock: %s(%s) != %s", self.name, self.unique_id, existing
+        )
+        return False
+
+
+if sys.version_info[:2] < (3, 12):
+    # generic type for `batched` below
+    _T = TypeVar("_T")
+
+    # added to itertools in 3.12
+    def batched(iterable: Iterable[_T], n: int) -> Iterator[tuple[_T, ...]]:
+        # batched('ABCDEFG', 3) → ABC DEF G
+        if n < 1:
+            raise ValueError("n must be at least one")
+        iterator = iter(iterable)
+        while batch := tuple(islice(iterator, n)):
+            yield batch