Throttling actions in .Net Core 2.1 using AttributeFilter

I have previously written about Throttling in the pre-core times, and this is sort of the update to that post – with a bit of fixes and tweaks.

Lets get to it;

A few changes:

In my last post I did things a bit differently, for instance; I used to throw a custom exception type and handle that as a response, I have learned that this is an anti-pattern and is strongly discouraged (at least by David Fowler).
Anyway now we return a class, which is basically just my old ApiException type, just without the inherited bits of Exception. – this is both cheaper and cleaner.
Also since we are using .NET Core, we are using IMemoryCache instead of HttpRuntime.Cache – which is also nice.


On to the attribute:

There isn’t a lot to it to be honest.

  1. Check for existence of cache entry
  2. If none, create one and set allowExecute = true
  3. If allowExecute != true, return throttle response and short-circuit the pipeline.

Do note that this throttle uses IP as it’s target, but could easily be username or similar.


[IPThrottling("GetItems", 300)]
public ActionResult<IEnumerable<string>> Get()
    return new string[] { "value1", "value2" };

The above throttles for 300 seconds for the GetItems key, so you can group together functionality as well, if you really need to.

Ill talk about the custom response in a different blogpost

Easy, simple HttpRuntime.Cache

A simple to use caching function that both gets and/or sets the key depending on results.

This is a post for my future self. – Hi future self! (wave).
The following is an easy to use caching function.

The function gets or updates based on results.
The wrapper helps create different cacheExpirations based on needs.

Documenting roles with swashbuckle

How to document attribute usage with swagger

You could basically document any attribute you have decorated your actions with, but this will focus mainly on documenting the role part of the Authorize attribute.
When using roles based authentication I like to document the roles in my swagger spec, this gives a nice indication, to the consumer, of which roles are required for different endpoints.
Here I have a basic Authorize attribute with a required role of “Admin”.

As with most other things swashbuckle related, we need to create an IOperationFilter

And that is it, you have now auto documented every role required across your API.
The swagger docs will look like the following.