Redis list with expiring entries?

Question

I'm looking for a way to store a list of items for a user, that will expire within 24 hours. Is there a way to accomplish this using Redis? I was thinking of just using the list and setting an expiration for each individual item, is there a better way?

Answer 1

As noted in the accepted answer, expiration in Redis is only performed at key-level - nested elements cannot be expired.

To implement a list with expiring elements, you can use the Sorted Set data structure. Every member's score should be the current epoch, so you'll retain the order of insertion. If the values (members) aren't unique, make them so by concatenating the epoch, e.g.:

ZADD user1:items 1514822755 1514822755:value
ZADD user1:items 1514822758 1514822758:value

To "expire" items, call ZREMRANGEBYSCORE from -inf and the current epoch minus 24 hours.

Answer 2

NO, you CANNOT set expiration for each item in a LIST. You can only set an expiration for the entire LIST.

In order to achieve what you want, you need to have a key for each item:

SET user1:item1 value EX 86400
SET uesr1:iter2 value EX 86400
SET user2:item1 value EX 86400

To get all items of a specified user, you can use the SCAN command with a pattern (or use the Keyspace Notification to achieve better performance, but with more complex work):

SCAN 0 MATCH user1:*