zmoog
commented
2 weeks ago I can probably add cache expiration to avoid a stale region list:
import threading
import time
from functools import wraps
from typing import Any, Callable
def cache_for(seconds: int) -> Callable:
"""
Caches the result of a function for a specified number of seconds."""
def decorator(func: Callable) -> Callable:
lock = threading.Lock()
cache = {}
hits = misses = 0
@wraps(func)
def wrapper(*args: Any, **kwargs: Any) -> Any:
nonlocal hits, misses
with lock:
key = str(args) + str(kwargs)
current_time = time.time()
if key in cache:
result, timestamp = cache[key]
if current_time - timestamp < seconds:
hits += 1
return result
misses += 1
result = func(*args, **kwargs)
cache[key] = (result, current_time)
return result
def cache_stats() -> dict:
"""
Returns the cache statistics.
:return: A dictionary containing the cache statistics"""
with lock:
return {'hits': hits, 'misses': misses}
wrapper.cache_stats = cache_stats
return wrapper
return decorator
@cache_for(seconds=60)
def describe_regions(all_regions: bool = True) -> Any:
"""
Fetches all regions from AWS and returns the response.
:return: The response from the describe_regions method
"""
return get_ec2_client().describe_regions(AllRegions=all_regions)
# Example usage with AWS regions
import boto3
def get_ec2_client():
return boto3.client('ec2')
# Example usage to access cache statistics
if __name__ == "__main__":
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 0, 'misses': 1}
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 1, 'misses': 1}
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 2, 'misses': 1}
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 3, 'misses': 1}
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 4, 'misses': 1}
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 5, 'misses': 1}
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 6, 'misses': 1}
describe_regions(all_regions=False)
print(describe_regions.cache_stats()) # {'hits': 7, 'misses': 1}I get the following output:
{'hits': 0, 'misses': 1}
{'hits': 1, 'misses': 1}
{'hits': 2, 'misses': 1}
{'hits': 3, 'misses': 1}
{'hits': 4, 'misses': 1}
{'hits': 5, 'misses': 1}
{'hits': 6, 'misses': 1}
{'hits': 7, 'misses': 1}
constanca-m
What does this PR do?
Caches EC2:DescribeRegion API calls response.
Why is it important?
On high-volume deployments, ESF can hit the EC2:DescribeRegions API requests limit, causing throttling errors like the following:
ESF needs the list of existing regions to parse incoming events from the
cloudwatch-logsinput. Since new AWS region additions do not happen frequently, picking up and caching the list of existing regions at function startup seems adequate.The list of existing AWS regions is available at https://aws.amazon.com/about-aws/global-infrastructure/regions_az/
Checklist
CHANGELOG.md