C#C
C#•2y ago
zobweyt

Implementing rate limiting for discord bot interactions with absolute expiration of items

I’m trying to create a simple and customizable RateLimitAttribute for interactions in Discord.Net using their preconditions.

I'm too confused about all the possibilities. So, how would you implement this? What decisions would you make and what data structures would you use?

Expected usage


[RateLimit(max: 2, period: TimeSpan.FromMinutes(1), ignore: Ignore.Owner | Ignore.DMs)]
[SlashCommand("ping", "Pings the bot.")]
public async Task PingAsync() => await RespondAsync("Pong!");


Expected behavior


/ping
— Pong! (count is now 1)

/ping
— Pong! (count is now 2)

/ping
— Wait 60 seconds for limit to expire!

/ping (30 seconds later)
— Wait 30 seconds for limit to expire!

… (30 seconds later)
— Remove rate limit from store in background.

/ping (any time later)
— Pong! (count is now 1)

Wanted features:


  • Users can define custom ignore policies: for instance, if you have a database with different roles like admins and regular users, you might want to apply rate limiting to all users but exclude admins.
  • Users can access the store of rate limits: for example, EPIC RPG’s /cd command shows the cooldowns for each command per user.
### Problems I’ve met

  • Attributes require constant values: TimeSpan cannot be used directly. Instead, people use parameters specifying periods in seconds. Alternatively, a converter could be used with double period and enum TimeMeasure.
  • Caching with absolute expiration: IMemoryCache's AbsoluteExpiration simplifies caching implementation because it removes the rate limits right when they expire, but the keys there are strings and not generic types. Using System.Threading.RateLimiting, it’s hard to display the exact remaining time until the limit expires.
Was this page helpful?