TTL and EXPIRE functions?

[cohawk]

Looking through the docs and codebase I do not see a way to return a key's current TTL - only set it. Unless I am missing it somewhere? (https://redis.io/commands/ttl)

Also along those lines it would be nice to have a Redis like EXPIRE function (https://redis.io/commands/expire) to refresh a key's TTL (get and set) or return 0/false if the key does not exist (or already expired).

[cabol]

@cohawk I agree, it would be helpful to have these functions (especially the ttl to retrieve the remaining TTL for a specific key). But, I'm not sure to add them to the current cache interface. So my idea is:

1. For the TTL which is more related to the Nebulex.Object module, I've added a function there in order to retrieve the remaining TTL. For Example:

MyCache.set("foo", "bar", ttl: 10)
:timer.sleep(5000)

remaining_ttl =
  "foo"
  |> MyCache.get(return: :object)
  |> Nebulex.Object.ttl()

2. For the EXPIRE funtion, I think it is very easy to implement it using the current cache interface For example, using the update function we can implement something vey similar:

MyCache.update("foo", nil, &(&1), ttl: 5)

• If the key doesn't exist, the update will return nil and nothing is stored in the cache (this is because we are passing as initial value nil).
• If the key exists, the current value is kept and the other properties of the object like the ttl are updated (the function &(&1) is ensuring the same value)

Example:

remaining_ttl =
  "foo"
  |> MyCache.update(nil, &(&1), ttl: 5, return: :object) # this acts as EXPIRE function
  |> Nebulex.Object.ttl()

Let me know your thoughts!

[cohawk]

@cabol, simple and beautiful. Passing the &(&1) function is much better than the get_and_update method that I was looking into.

I think I would still create wrapper functions with documentation (at least in my code) using your above examples and explanations, since I could see myself looking back at the Expire code block and not remembering exactly what it was doing.

But either way both functions are now possible. Thanks for your great work on the library!

[cabol]

@cohawk thanks :) !!