Redis 缓存过期比设置的过期时间快很多

Question

When trying to read from the cache using the python Redis package, it shows as expired. This happens within 5 seconds of setting the cache. Any reads within the 5 seconds work though.

But the key is set to expire in 180 seconds or 3 minutes. Is this even remotely possible. Also the redis key is not written to / invalidated anytime after the first write.

import redis
time_to_expire_s=180
client = redis.StrictRedis(host=self.host, port=self.port, password=self.password)
client.set(key, zlib.compress(value.encode('utf-8')), ex=time_to_expire_s)

Is this weird behavior. Setting to a longer cache like 3600 (1hr) solves my issue, but wanted to know why a 3-minute cache would expire in 5 seconds...

Thank you

Answer 1

I'd definitely point to the Redis server you are running, it might be misconfigured, I'm giving you a fully working example below, which uses docker and keeps the cache for 3 minutes (or whatever time you want):

Firstly, assuming you have docker installed:

docker pull redis

Secondly run your container and exposes the port 6379

docker run -d -p 6379:6379 redis:latest

And here it goes the Python code which works perfectly by keeping the cache for 180 seconds:

from redis.client import Redis
import random
import zlib

class Cache:
   def __init__(self):
      self.time_to_expire_s=180
      self.client = Redis(host="localhost", port=6379)
   def set_key(self, key, value):
      self.client.set(key, zlib.compress(value.encode('utf-8')), ex=self.time_to_expire_s)
   def get_key(self, key):
      return self.client.get(key)

if __name__ == "__main__":
   cache = Cache()
   rnd = random.Random()
   rnd_num=  rnd.randint(1,100)
   print(f"rdn {rnd_num}")
   if cache.get_key("MyCacheKey") is None:
      cache.set_key("MyCacheKey", "Myvalue"+str(rnd_num))
   else:
      print(zlib.decompress(cache.get_key("MyCacheKey")))