108 lines
3.4 KiB
Python
108 lines
3.4 KiB
Python
# Copyright 2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from typing import Generic, Hashable, List, Set, TypeVar
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import attr
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logger = logging.getLogger(__name__)
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T = TypeVar("T", bound=Hashable)
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@attr.s(slots=True, frozen=True, auto_attribs=True)
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class _Entry(Generic[T]):
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end_key: int
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elements: Set[T] = attr.Factory(set)
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class WheelTimer(Generic[T]):
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"""Stores arbitrary objects that will be returned after their timers have
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expired.
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"""
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def __init__(self, bucket_size: int = 5000) -> None:
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"""
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Args:
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bucket_size: Size of buckets in ms. Corresponds roughly to the
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accuracy of the timer.
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"""
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self.bucket_size: int = bucket_size
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self.entries: List[_Entry[T]] = []
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self.current_tick: int = 0
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def insert(self, now: int, obj: T, then: int) -> None:
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"""Inserts object into timer.
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Args:
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now: Current time in msec
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obj: Object to be inserted
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then: When to return the object strictly after.
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"""
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then_key = int(then / self.bucket_size) + 1
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now_key = int(now / self.bucket_size)
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if self.entries:
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min_key = self.entries[0].end_key
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max_key = self.entries[-1].end_key
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if min_key < now_key - 10:
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# If we have ten buckets that are due and still nothing has
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# called `fetch()` then we likely have a bug that is causing a
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# memory leak.
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logger.warning(
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"Inserting into a wheel timer that hasn't been read from recently. Item: %s",
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obj,
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)
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if then_key <= max_key:
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# The max here is to protect against inserts for times in the past
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self.entries[max(min_key, then_key) - min_key].elements.add(obj)
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return
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next_key = now_key + 1
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if self.entries:
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last_key = self.entries[-1].end_key
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else:
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last_key = next_key
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# Handle the case when `then` is in the past and `entries` is empty.
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then_key = max(last_key, then_key)
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# Add empty entries between the end of the current list and when we want
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# to insert. This ensures there are no gaps.
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self.entries.extend(_Entry(key) for key in range(last_key, then_key + 1))
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self.entries[-1].elements.add(obj)
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def fetch(self, now: int) -> List[T]:
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"""Fetch any objects that have timed out
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Args:
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now: Current time in msec
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Returns:
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List of objects that have timed out
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"""
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now_key = int(now / self.bucket_size)
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ret: List[T] = []
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while self.entries and self.entries[0].end_key <= now_key:
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ret.extend(self.entries.pop(0).elements)
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return ret
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def __len__(self) -> int:
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return sum(len(entry.elements) for entry in self.entries)
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