import asyncio
import time
from collections import Counter
from deprecated.sphinx import versionadded
import limits.typing
from limits.aio.storage.base import MovingWindowSupport, Storage
from limits.typing import Dict, List, Optional, Tuple, Type, Union
class LockableEntry(asyncio.Lock):
def __init__(self, expiry: int) -> None:
self.atime = time.time()
self.expiry = self.atime + expiry
super().__init__()
[docs]
@versionadded(version="2.1")
class MemoryStorage(Storage, MovingWindowSupport):
"""
rate limit storage using :class:`collections.Counter`
as an in memory storage for fixed and elastic window strategies,
and a simple list to implement moving window strategy.
"""
STORAGE_SCHEME = ["async+memory"]
"""
The storage scheme for in process memory storage for use in an
async context
"""
def __init__(
self, uri: Optional[str] = None, wrap_exceptions: bool = False, **_: str
) -> None:
self.storage: limits.typing.Counter[str] = Counter()
self.expirations: Dict[str, float] = {}
self.events: Dict[str, List[LockableEntry]] = {}
self.timer: Optional[asyncio.Task[None]] = None
super().__init__(uri, wrap_exceptions=wrap_exceptions, **_)
@property
def base_exceptions(
self,
) -> Union[Type[Exception], Tuple[Type[Exception], ...]]: # pragma: no cover
return ValueError
async def __expire_events(self) -> None:
for key in self.events.keys():
for event in list(self.events[key]):
async with event:
if event.expiry <= time.time() and event in self.events[key]:
self.events[key].remove(event)
for key in list(self.expirations.keys()):
if self.expirations[key] <= time.time():
self.storage.pop(key, None)
self.expirations.pop(key, None)
async def __schedule_expiry(self) -> None:
if not self.timer or self.timer.done():
self.timer = asyncio.create_task(self.__expire_events())
[docs]
async def incr(
self, key: str, expiry: int, elastic_expiry: bool = False, amount: int = 1
) -> int:
"""
increments the counter for a given rate limit key
:param key: the key to increment
:param expiry: amount in seconds for the key to expire in
:param elastic_expiry: whether to keep extending the rate limit
window every hit.
:param amount: the number to increment by
"""
await self.get(key)
await self.__schedule_expiry()
self.storage[key] += amount
if elastic_expiry or self.storage[key] == amount:
self.expirations[key] = time.time() + expiry
return self.storage.get(key, amount)
[docs]
async def get(self, key: str) -> int:
"""
:param key: the key to get the counter value for
"""
if self.expirations.get(key, 0) <= time.time():
self.storage.pop(key, None)
self.expirations.pop(key, None)
return self.storage.get(key, 0)
[docs]
async def clear(self, key: str) -> None:
"""
:param key: the key to clear rate limits for
"""
self.storage.pop(key, None)
self.expirations.pop(key, None)
self.events.pop(key, None)
[docs]
async def acquire_entry(
self, key: str, limit: int, expiry: int, amount: int = 1
) -> bool:
"""
:param key: rate limit key to acquire an entry in
:param limit: amount of entries allowed
:param expiry: expiry of the entry
:param amount: the number of entries to acquire
"""
if amount > limit:
return False
self.events.setdefault(key, [])
await self.__schedule_expiry()
timestamp = time.time()
try:
entry: Optional[LockableEntry] = self.events[key][limit - amount]
except IndexError:
entry = None
if entry and entry.atime >= timestamp - expiry:
return False
else:
self.events[key][:0] = [LockableEntry(expiry) for _ in range(amount)]
return True
[docs]
async def get_expiry(self, key: str) -> int:
"""
:param key: the key to get the expiry for
"""
return int(self.expirations.get(key, time.time()))
[docs]
async def get_num_acquired(self, key: str, expiry: int) -> int:
"""
returns the number of entries already acquired
:param key: rate limit key to acquire an entry in
:param expiry: expiry of the entry
"""
timestamp = time.time()
return (
len([k for k in self.events[key] if k.atime >= timestamp - expiry])
if self.events.get(key)
else 0
)
# FIXME: arg limit is not used
[docs]
async def get_moving_window(
self, key: str, limit: int, expiry: int
) -> Tuple[int, int]:
"""
returns the starting point and the number of entries in the moving
window
:param key: rate limit key
:param expiry: expiry of entry
:return: (start of window, number of acquired entries)
"""
timestamp = time.time()
acquired = await self.get_num_acquired(key, expiry)
for item in self.events.get(key, [])[::-1]:
if item.atime >= timestamp - expiry:
return int(item.atime), acquired
return int(timestamp), acquired
[docs]
async def check(self) -> bool:
"""
check if storage is healthy
"""
return True
[docs]
async def reset(self) -> Optional[int]:
num_items = max(len(self.storage), len(self.events))
self.storage.clear()
self.expirations.clear()
self.events.clear()
return num_items