khushalps
b53ef86ef8
git-subtree-dir: utils_v2 git-subtree-split: 7f273565196085feb05ee3328aa2e80d3d721fc3
160 lines
6.9 KiB
Python
160 lines
6.9 KiB
Python
"""
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AUTHOR:
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Khushal P Soonderji
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DATE:
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Saturday, 7th Jun., 2025
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OBJECTIVE:
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To have a mechanism where multiple instances of a cron script can be running and can have a mechanism to call
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dibs on the right to execute a particular activity by announcing their availability.
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REFERENCES:
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N/A
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DOWNLOADS:
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N/A
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"""
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# *****************************************************************************************************************
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# ***** ****
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# *** IMPORT ***
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# ***** ****
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# *****************************************************************************************************************
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# My utils:
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from utils_v2.cache.async_redis_cache_v2 import AsyncRedisCache
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# To make a decorator:
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from functools import wraps
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# For hashing and shortening the hash:
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import hashlib
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import base64
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# for random values:
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import random
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# For asynchronous activities:
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import asyncio
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# To work with datatypes:
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from typing import Callable
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# *****************************************************************************************************************
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# ***** ****
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# *** MACROS / ONE-TIME INIT ***
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# ***** ****
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# *****************************************************************************************************************
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# --- Nothing Yet
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# *****************************************************************************************************************
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# ***** ****
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# *** VARIABLES ***
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# ***** ****
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# *****************************************************************************************************************
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# --- Nothing Yet
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# *****************************************************************************************************************
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# ***** ****
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# *** CLASSES ***
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# ***** ****
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# *****************************************************************************************************************
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# --- Nothing Yet
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# *****************************************************************************************************************
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# ***** ****
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# *** FUNCTIONS ***
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# ***** ****
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# *****************************************************************************************************************
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def call_dibs_through_redis(
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cache: AsyncRedisCache | Callable,
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max_dibs: int = 1,
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min_random_delay: float = 0.0,
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max_random_delay: float = 0.0,
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expiry: float = 5.0
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):
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"""
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This decorator factory will be used to decorate functions in cron scripts such that each instance can claim dibs
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over the execution of the function. In case other instance(s) have already claimed dibs, this instance's claim will
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be rejected.
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:param cache: The instance of 'AsyncRedisCache'.
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:param max_dibs: The maximum number of instances that should be allowed to execute the wrapped function.
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:param min_random_delay: The minimum delay in seconds to sleep before claiming dibs.
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:param max_random_delay: The maximum delay in seconds to sleep before claiming dibs.
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:param expiry: The time in seconds after which the cached data must be cleared.
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:return: The decorator that automatically caches your data.
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"""
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def decorator(func):
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@wraps(func)
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async def wrapper(*args, **kwargs):
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# Fetch the cache from a callable if needed:
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_cache = cache() if isinstance(cache, Callable) else cache
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if not isinstance(_cache, AsyncRedisCache): return None
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# In case a random delay has been requested:
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if max_random_delay > 0.0:
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await asyncio.sleep(min_random_delay + (random.random() * (max_random_delay - min_random_delay)))
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# We first use the name of the function and the inputs given to it to generate a key for Redis with the
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# simple hashing and shortening by way of base64 strings:
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inputs_given = "cron_dibs_" + func.__name__ + str([_ for _ in args]) + str(kwargs)
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sha256_hash = hashlib.sha256()
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sha256_hash.update(inputs_given.encode("utf-8"))
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hashed_key = sha256_hash.digest()
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base64_key = base64.b64encode(hashed_key).decode("utf-8")
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# We increment a counter in Redis to check what our claim no. is:
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claim_no = await _cache.count(key = base64_key, value = 1, expiry = expiry, raise_exception = False)
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# If the claim no. is within the limit defined by max. dibs,
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# We execute the wrapped function:
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if claim_no <= max_dibs: response = await func(*args, **kwargs)
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# Otherwise, we don't execute the function:
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else: response = f"Other instances claimed the dibs. Claim No: {claim_no}"
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# Return the response from the wrapped function.
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return response
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return wrapper
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return decorator
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# *****************************************************************************************************************
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# ***** ****
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# *** MAIN PROGRAM ***
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# ***** ****
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# *****************************************************************************************************************
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if __name__ == "__main__":
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pass
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