mirror of
https://github.com/SickGear/SickGear.git
synced 2024-12-22 02:33:37 +00:00
431 lines
13 KiB
Python
431 lines
13 KiB
Python
"""Disk Cache Recipes
|
|
|
|
"""
|
|
|
|
import functools
|
|
import math
|
|
import os
|
|
import random
|
|
import threading
|
|
import time
|
|
|
|
from .core import ENOVAL, args_to_key, full_name
|
|
|
|
|
|
class Averager(object):
|
|
"""Recipe for calculating a running average.
|
|
|
|
Sometimes known as "online statistics," the running average maintains the
|
|
total and count. The average can then be calculated at any time.
|
|
|
|
>>> import diskcache
|
|
>>> cache = diskcache.FanoutCache()
|
|
>>> ave = Averager(cache, 'latency')
|
|
>>> ave.add(0.080)
|
|
>>> ave.add(0.120)
|
|
>>> ave.get()
|
|
0.1
|
|
>>> ave.add(0.160)
|
|
>>> ave.pop()
|
|
0.12
|
|
>>> print(ave.get())
|
|
None
|
|
|
|
"""
|
|
def __init__(self, cache, key, expire=None, tag=None):
|
|
self._cache = cache
|
|
self._key = key
|
|
self._expire = expire
|
|
self._tag = tag
|
|
|
|
def add(self, value):
|
|
"Add `value` to average."
|
|
with self._cache.transact(retry=True):
|
|
total, count = self._cache.get(self._key, default=(0.0, 0))
|
|
total += value
|
|
count += 1
|
|
self._cache.set(
|
|
self._key, (total, count), expire=self._expire, tag=self._tag,
|
|
)
|
|
|
|
def get(self):
|
|
"Get current average or return `None` if count equals zero."
|
|
total, count = self._cache.get(self._key, default=(0.0, 0), retry=True)
|
|
return None if count == 0 else total / count
|
|
|
|
def pop(self):
|
|
"Return current average and delete key."
|
|
total, count = self._cache.pop(self._key, default=(0.0, 0), retry=True)
|
|
return None if count == 0 else total / count
|
|
|
|
|
|
class Lock(object):
|
|
"""Recipe for cross-process and cross-thread lock.
|
|
|
|
>>> import diskcache
|
|
>>> cache = diskcache.Cache()
|
|
>>> lock = Lock(cache, 'report-123')
|
|
>>> lock.acquire()
|
|
>>> lock.release()
|
|
>>> with lock:
|
|
... pass
|
|
|
|
"""
|
|
def __init__(self, cache, key, expire=None, tag=None):
|
|
self._cache = cache
|
|
self._key = key
|
|
self._expire = expire
|
|
self._tag = tag
|
|
|
|
def acquire(self):
|
|
"Acquire lock using spin-lock algorithm."
|
|
while True:
|
|
added = self._cache.add(
|
|
self._key,
|
|
None,
|
|
expire=self._expire,
|
|
tag=self._tag,
|
|
retry=True,
|
|
)
|
|
if added:
|
|
break
|
|
time.sleep(0.001)
|
|
|
|
def release(self):
|
|
"Release lock by deleting key."
|
|
self._cache.delete(self._key, retry=True)
|
|
|
|
def locked(self):
|
|
"Return true if the lock is acquired."
|
|
return self._key in self._cache
|
|
|
|
def __enter__(self):
|
|
self.acquire()
|
|
|
|
def __exit__(self, *exc_info):
|
|
self.release()
|
|
|
|
|
|
class RLock(object):
|
|
"""Recipe for cross-process and cross-thread re-entrant lock.
|
|
|
|
>>> import diskcache
|
|
>>> cache = diskcache.Cache()
|
|
>>> rlock = RLock(cache, 'user-123')
|
|
>>> rlock.acquire()
|
|
>>> rlock.acquire()
|
|
>>> rlock.release()
|
|
>>> with rlock:
|
|
... pass
|
|
>>> rlock.release()
|
|
>>> rlock.release()
|
|
Traceback (most recent call last):
|
|
...
|
|
AssertionError: cannot release un-acquired lock
|
|
|
|
"""
|
|
def __init__(self, cache, key, expire=None, tag=None):
|
|
self._cache = cache
|
|
self._key = key
|
|
self._expire = expire
|
|
self._tag = tag
|
|
|
|
def acquire(self):
|
|
"Acquire lock by incrementing count using spin-lock algorithm."
|
|
pid = os.getpid()
|
|
tid = threading.get_ident()
|
|
pid_tid = '{}-{}'.format(pid, tid)
|
|
|
|
while True:
|
|
with self._cache.transact(retry=True):
|
|
value, count = self._cache.get(self._key, default=(None, 0))
|
|
if pid_tid == value or count == 0:
|
|
self._cache.set(
|
|
self._key, (pid_tid, count + 1),
|
|
expire=self._expire, tag=self._tag,
|
|
)
|
|
return
|
|
time.sleep(0.001)
|
|
|
|
def release(self):
|
|
"Release lock by decrementing count."
|
|
pid = os.getpid()
|
|
tid = threading.get_ident()
|
|
pid_tid = '{}-{}'.format(pid, tid)
|
|
|
|
with self._cache.transact(retry=True):
|
|
value, count = self._cache.get(self._key, default=(None, 0))
|
|
is_owned = pid_tid == value and count > 0
|
|
assert is_owned, 'cannot release un-acquired lock'
|
|
self._cache.set(
|
|
self._key, (value, count - 1),
|
|
expire=self._expire, tag=self._tag,
|
|
)
|
|
|
|
def __enter__(self):
|
|
self.acquire()
|
|
|
|
def __exit__(self, *exc_info):
|
|
self.release()
|
|
|
|
|
|
class BoundedSemaphore(object):
|
|
"""Recipe for cross-process and cross-thread bounded semaphore.
|
|
|
|
>>> import diskcache
|
|
>>> cache = diskcache.Cache()
|
|
>>> semaphore = BoundedSemaphore(cache, 'max-cons', value=2)
|
|
>>> semaphore.acquire()
|
|
>>> semaphore.acquire()
|
|
>>> semaphore.release()
|
|
>>> with semaphore:
|
|
... pass
|
|
>>> semaphore.release()
|
|
>>> semaphore.release()
|
|
Traceback (most recent call last):
|
|
...
|
|
AssertionError: cannot release un-acquired semaphore
|
|
|
|
"""
|
|
def __init__(self, cache, key, value=1, expire=None, tag=None):
|
|
self._cache = cache
|
|
self._key = key
|
|
self._value = value
|
|
self._expire = expire
|
|
self._tag = tag
|
|
|
|
def acquire(self):
|
|
"Acquire semaphore by decrementing value using spin-lock algorithm."
|
|
while True:
|
|
with self._cache.transact(retry=True):
|
|
value = self._cache.get(self._key, default=self._value)
|
|
if value > 0:
|
|
self._cache.set(
|
|
self._key, value - 1,
|
|
expire=self._expire, tag=self._tag,
|
|
)
|
|
return
|
|
time.sleep(0.001)
|
|
|
|
def release(self):
|
|
"Release semaphore by incrementing value."
|
|
with self._cache.transact(retry=True):
|
|
value = self._cache.get(self._key, default=self._value)
|
|
assert self._value > value, 'cannot release un-acquired semaphore'
|
|
value += 1
|
|
self._cache.set(
|
|
self._key, value, expire=self._expire, tag=self._tag,
|
|
)
|
|
|
|
def __enter__(self):
|
|
self.acquire()
|
|
|
|
def __exit__(self, *exc_info):
|
|
self.release()
|
|
|
|
|
|
def throttle(cache, count, seconds, name=None, expire=None, tag=None,
|
|
time_func=time.time, sleep_func=time.sleep):
|
|
"""Decorator to throttle calls to function.
|
|
|
|
>>> import diskcache, time
|
|
>>> cache = diskcache.Cache()
|
|
>>> count = 0
|
|
>>> @throttle(cache, 2, 1) # 2 calls per 1 second
|
|
... def increment():
|
|
... global count
|
|
... count += 1
|
|
>>> start = time.time()
|
|
>>> while (time.time() - start) <= 2:
|
|
... increment()
|
|
>>> count in (6, 7) # 6 or 7 calls depending on CPU load
|
|
True
|
|
|
|
"""
|
|
def decorator(func):
|
|
rate = count / float(seconds)
|
|
key = full_name(func) if name is None else name
|
|
now = time_func()
|
|
cache.set(key, (now, count), expire=expire, tag=tag, retry=True)
|
|
|
|
@functools.wraps(func)
|
|
def wrapper(*args, **kwargs):
|
|
while True:
|
|
with cache.transact(retry=True):
|
|
last, tally = cache.get(key)
|
|
now = time_func()
|
|
tally += (now - last) * rate
|
|
delay = 0
|
|
|
|
if tally > count:
|
|
cache.set(key, (now, count - 1), expire)
|
|
elif tally >= 1:
|
|
cache.set(key, (now, tally - 1), expire)
|
|
else:
|
|
delay = (1 - tally) / rate
|
|
|
|
if delay:
|
|
sleep_func(delay)
|
|
else:
|
|
break
|
|
|
|
return func(*args, **kwargs)
|
|
|
|
return wrapper
|
|
|
|
return decorator
|
|
|
|
|
|
def barrier(cache, lock_factory, name=None, expire=None, tag=None):
|
|
"""Barrier to calling decorated function.
|
|
|
|
Supports different kinds of locks: Lock, RLock, BoundedSemaphore.
|
|
|
|
>>> import diskcache, time
|
|
>>> cache = diskcache.Cache()
|
|
>>> @barrier(cache, Lock)
|
|
... def work(num):
|
|
... print('worker started')
|
|
... time.sleep(1)
|
|
... print('worker finished')
|
|
>>> import multiprocessing.pool
|
|
>>> pool = multiprocessing.pool.ThreadPool(2)
|
|
>>> _ = pool.map(work, range(2))
|
|
worker started
|
|
worker finished
|
|
worker started
|
|
worker finished
|
|
>>> pool.terminate()
|
|
|
|
"""
|
|
def decorator(func):
|
|
key = full_name(func) if name is None else name
|
|
lock = lock_factory(cache, key, expire=expire, tag=tag)
|
|
|
|
@functools.wraps(func)
|
|
def wrapper(*args, **kwargs):
|
|
with lock:
|
|
return func(*args, **kwargs)
|
|
|
|
return wrapper
|
|
|
|
return decorator
|
|
|
|
|
|
def memoize_stampede(cache, expire, name=None, typed=False, tag=None, beta=1):
|
|
"""Memoizing cache decorator with cache stampede protection.
|
|
|
|
Cache stampedes are a type of system overload that can occur when parallel
|
|
computing systems using memoization come under heavy load. This behaviour
|
|
is sometimes also called dog-piling, cache miss storm, cache choking, or
|
|
the thundering herd problem.
|
|
|
|
The memoization decorator implements cache stampede protection through
|
|
early recomputation. Early recomputation of function results will occur
|
|
probabilistically before expiration in a background thread of
|
|
execution. Early probabilistic recomputation is based on research by
|
|
Vattani, A.; Chierichetti, F.; Lowenstein, K. (2015), Optimal Probabilistic
|
|
Cache Stampede Prevention, VLDB, pp. 886-897, ISSN 2150-8097
|
|
|
|
If name is set to None (default), the callable name will be determined
|
|
automatically.
|
|
|
|
If typed is set to True, function arguments of different types will be
|
|
cached separately. For example, f(3) and f(3.0) will be treated as distinct
|
|
calls with distinct results.
|
|
|
|
The original underlying function is accessible through the `__wrapped__`
|
|
attribute. This is useful for introspection, for bypassing the cache, or
|
|
for rewrapping the function with a different cache.
|
|
|
|
>>> from diskcache import Cache
|
|
>>> cache = Cache()
|
|
>>> @memoize_stampede(cache, expire=1)
|
|
... def fib(number):
|
|
... if number == 0:
|
|
... return 0
|
|
... elif number == 1:
|
|
... return 1
|
|
... else:
|
|
... return fib(number - 1) + fib(number - 2)
|
|
>>> print(fib(100))
|
|
354224848179261915075
|
|
|
|
An additional `__cache_key__` attribute can be used to generate the cache
|
|
key used for the given arguments.
|
|
|
|
>>> key = fib.__cache_key__(100)
|
|
>>> del cache[key]
|
|
|
|
Remember to call memoize when decorating a callable. If you forget, then a
|
|
TypeError will occur.
|
|
|
|
:param cache: cache to store callable arguments and return values
|
|
:param float expire: seconds until arguments expire
|
|
:param str name: name given for callable (default None, automatic)
|
|
:param bool typed: cache different types separately (default False)
|
|
:param str tag: text to associate with arguments (default None)
|
|
:return: callable decorator
|
|
|
|
"""
|
|
# Caution: Nearly identical code exists in Cache.memoize
|
|
def decorator(func):
|
|
"Decorator created by memoize call for callable."
|
|
base = (full_name(func),) if name is None else (name,)
|
|
|
|
def timer(*args, **kwargs):
|
|
"Time execution of `func` and return result and time delta."
|
|
start = time.time()
|
|
result = func(*args, **kwargs)
|
|
delta = time.time() - start
|
|
return result, delta
|
|
|
|
@functools.wraps(func)
|
|
def wrapper(*args, **kwargs):
|
|
"Wrapper for callable to cache arguments and return values."
|
|
key = wrapper.__cache_key__(*args, **kwargs)
|
|
pair, expire_time = cache.get(
|
|
key, default=ENOVAL, expire_time=True, retry=True,
|
|
)
|
|
|
|
if pair is not ENOVAL:
|
|
result, delta = pair
|
|
now = time.time()
|
|
ttl = expire_time - now
|
|
|
|
if (-delta * beta * math.log(random.random())) < ttl:
|
|
return result # Cache hit.
|
|
|
|
# Check whether a thread has started for early recomputation.
|
|
|
|
thread_key = key + (ENOVAL,)
|
|
thread_added = cache.add(
|
|
thread_key, None, expire=delta, retry=True,
|
|
)
|
|
|
|
if thread_added:
|
|
# Start thread for early recomputation.
|
|
def recompute():
|
|
with cache:
|
|
pair = timer(*args, **kwargs)
|
|
cache.set(
|
|
key, pair, expire=expire, tag=tag, retry=True,
|
|
)
|
|
thread = threading.Thread(target=recompute)
|
|
thread.daemon = True
|
|
thread.start()
|
|
|
|
return result
|
|
|
|
pair = timer(*args, **kwargs)
|
|
cache.set(key, pair, expire=expire, tag=tag, retry=True)
|
|
return pair[0]
|
|
|
|
def __cache_key__(*args, **kwargs):
|
|
"Make key for cache given function arguments."
|
|
return args_to_key(base, args, kwargs, typed)
|
|
|
|
wrapper.__cache_key__ = __cache_key__
|
|
return wrapper
|
|
|
|
return decorator
|