C#•2y ago

Attributes confusion

hey! I'm having trouble choosing an approach when using attributes.

I'm building a wrapper around

System.Threading.RateLimiting

System.Threading.RateLimiting

. I have an attribute

RateLimitAttribute

RateLimitAttribute

which is responsible for the basic logic and creation of

PartitionedRateLimiter

PartitionedRateLimiter

.

here’s the problem: I want to be able to create custom ignore policies (to have no limit in custom conditions) and pass them directly to the

RateLimitAttribute

RateLimitAttribute

, but I don’t know how to do this correctly and what approach to choose.

initially I wanted to make a base class

RateLimitPolicyAttribute

RateLimitPolicyAttribute

for all policies and later use it like this:

[RateLimit]
[IgnoreOwner, IgnoreAdmins, IgnorePremiumUsers]
public static void Foo() => throw NotImplementedException();

[RateLimit]
[IgnoreOwner, IgnoreAdmins, IgnorePremiumUsers]
public static void Foo() => throw NotImplementedException();

but the policies here can exist without the main

RateLimitAttribute

RateLimitAttribute

also, I thought about passing the policies directly to the main attribute, but this approach is not possible because the values in attribute parameters must be constant, so I can't just pass a list of policies. additionally, it'll be a very long line in length if I have many policies

how can I implement this most conveniently?

Zzobweyt hey! I'm having trouble choosing an approach when using attributes. I'm buildin...

PixxelKick•4/13/24, 6:06 AM

Option 1:
If these are user defined (not constants), then they have to pass in a list of Types most likely

Option 2:
If these are specific constants that you define and are an immutable list, I would just use a flagged Enum

PPixxelKick Option 1: If these are user defined (not constants), then they have to pass in a...

zobweytOP•4/13/24, 6:31 AM

these are user defined (not constants)

as for the list of types, how do you type them correctly? for example, just

Type[] policies

Type[] policies

? but how do you get the needed method to execute without hard-coding its name in a string? I was trying to find something like "generic type" so I could use it like that:

Type<BaseType>[] policies

Type<BaseType>[] policies

zobweytOP•4/13/24, 6:36 AM

or should I just do it like that:

if (type is not BaseType baseType)
    throw Exception();

baseType.MyMethod();

if (type is not BaseType baseType)
    throw Exception();

baseType.MyMethod();

Zzobweyt these are user defined (not constants) as for the list of types, how do you typ...

PixxelKick•4/13/24, 6:38 AM

You have to use reflection, it's why you'll notice many attributes take in Types as their params for basically this exact problem space

zobweytOP•4/13/24, 6:46 AM

thank you!! I'll look into it :)

canton7•4/13/24, 10:54 AM

Attributes can be generic these days. So you can do

[RateLimit<SomeCustomPolicy>]

[RateLimit<SomeCustomPolicy>]

, with associated generic type constraints

Ccanton7 Attributes can be generic these days. So you can do `[RateLimit<SomeCustomPolicy...

zobweytOP•4/13/24, 12:10 PM

I thought about this too, but what if you need multiple policies? also, you won't be able to use the

[RateLimit]

[RateLimit]

without the generic type

canton7•4/13/24, 12:11 PM

Yeah, you can apply it multiple times, or have multiple versions which take different numbers of types, but it gets a bit messy

canton7•4/13/24, 12:11 PM

You can have both

[RateLimit]

[RateLimit]

and

[RateLimit<Foo>]

[RateLimit<Foo>]

easily though

zobweytOP•4/13/24, 12:17 PM

if I allow to use multiple

[RateLimit]

[RateLimit]

attributes, then there will be multiple

PartitionedRateLimiter

PartitionedRateLimiter

instances, so the logic might be duplicated

zobweytOP•4/13/24, 12:19 PM

however, maybe I still need to rework the core attribute logic to make this possible

Ccanton7 Yeah, you can apply it multiple times, or have multiple versions which take diff...

zobweytOP•4/13/24, 12:20 PM

if there's no policy, then the rate limit should be applied to every request (which is the default policy)

zobweytOP•4/13/24, 12:21 PM

maybe I can do a

DefaultPolicy

DefaultPolicy

and use it like that

[RateLimit<DefaultPolicy>]

[RateLimit<DefaultPolicy>]

zobweytOP•4/13/24, 12:24 PM

well, it seems to be more customizable

Ccanton7 You can have both `[RateLimit]` and `[RateLimit<Foo>]` easily though

zobweytOP•4/13/24, 12:28 PM

speaking globally, what would you prefer as a user of it? pass policies into one attribute as the argument, thereby making the string infinitely long and unreadable, or make several such attributes that accept the policy as a generic argument creating a long chain of attributes on several lines?

canton7•4/13/24, 12:33 PM

Personally I don't like using attributes for that sort of stuff, as it's awkward to customise them. If I need to instantiate my policy with a particular parameter, say, that gets awkward. Particularly if that parameter is only known at runtime

zobweytOP•4/13/24, 12:36 PM

also, all of these attributes will always be executed before processing the request until there is a negative result or all attributes check the conditions (this is because of the framework's nature for which I am trying to implement it). because of this, there may be conflicts: for example, I have this method:

[RateLimit<AdminPolicy>]
[RateLimit<DefaultPolicy>]
public static void Foo() => throw NotImplementedException();

[RateLimit<AdminPolicy>]
[RateLimit<DefaultPolicy>]
public static void Foo() => throw NotImplementedException();

although

AdminPolicy

AdminPolicy

skips all requests, the following attribute is always executed after it, which will be valid for all requests

canton7•4/13/24, 12:36 PM

I mean, everything you're saying here isn't set in stone. It's up to you to define how the attributes interact

Ccanton7 Personally I don't like using attributes for that sort of stuff, as it's awkward...

zobweytOP•4/13/24, 12:40 PM

yeah, I'm of the same opinion, but the framework which I use decides the attributes interaction for me

zobweytOP•4/13/24, 12:41 PM

anyway, thank you so much for the suggestion! I'll try to implement something similar and compare it with other ideas :)