Is it posible to hook redis before key expired

Question

I have set an expiration value to a key in redis, and want to get the opportunity to run a piece of code before the key will be deleted by redis. Is it possible, and if so how...? Thanks

Answer 1

My solution was to create a new key, with the same name as the one I wanted to hook, only I added a prefix for it indicating it's a key for timeouts usage ("TO") - something like:

set key1 data1
set TO_key1 ""
expire TO_key1 20

In the example above, as soon as "TO_key1" will expire, it will notify my program and I'll get the opportunity to run my code before I will manually delete "key1".

• I found this link very useful for creating the listener for redis: Redis Key expire notification with Jedis

Answer 2

This isn't possible with standard OS Redis... yet. There is a way, however, to do something similar without too much hassle. If you stop using Redis' expiry (at least for those keys that you're interesting in "hooking") and manage expiry "manually" in your code, you can do anything you want before/during/after the expiry event.

Since Redis offers key-level expiry out of the box, people are usually content with it. In some cases, i.e.g. expiring members in a Set, the only way to go is the manual approach but that approach is still valid for regular keys when you need finer control.