Background and Motivation
In #44140 issue, one of The dream scenario for a better ASP.NET Core rate limiter middleware as @maartenba says, would be able Have a feature on the current HttpContext that gives access to the current rate limit context, so these details can also be returned on successful requests, or added to telemetry.. This API proposal addresses this concern.
Proposed API
Below API supposes, that we have RateLimiterMiddleware in our app, which responsibility is to create IRateLimiterContextFeature for each request:
var app = builder.Build();
app.UseRateLimiter();
Now we can access to this interface in any custom middleware or controller:
namespace Microsoft.AspNetCore.RateLimiting.Features;
public interface IRateLimiterContextFeature
{
HttpContext HttpContext { get; set; }
RateLimitLease Lease { get; set; }
PartitionedRateLimiter<HttpContext>? GlobalLimiter { get; set; }
PartitionedRateLimiter<HttpContext> EndpointLimiter { get; set; }
}Usage Examples
Scenario 1: get statistics from limiters in custom telemetry middleware:
public Task Invoke(HttpContext context)
{
var rlContext = context.Features.Get<IRateLimiterContextFeature>();
var globalStatistics = rlContext.GlobalLimiter.GetStatistics(context);
var endpointStatistics = rlContext.EndpointLimiter.GetStatistics(context);
_someTelemetryService.PushStatisticsToPrometheus(globalStatistics);
_someTelemetryService.PushStatisticsToPrometheus(endpointStatistics);
}Scenario 2: Get metadata from successful RateLimiterLease for this request
public Task Invoke(HttpContext context)
{
var rlContext = context.Features.Get<IRateLimiterContextFeature>();
if (rlContext.Lease.TryGetMetadata("SOME_METADATA", out var metadata)
{
// Do some additional stuff, depends on metadata
}
}Alternative Design - 1
As @Tratcher said, there is a risk, that RateLimitLease would be disposed early. To prevent that, we can introduce facade-like class to wrap Lease with undisposable entity:
public interface IRateLimiterContextFeature
{
HttpContext HttpContext { get; }
RateLimitLeaseInfo LeaseInfo { get; }
PartitionedRateLimiter<HttpContext>? GlobalLimiter { get; }
PartitionedRateLimiter<HttpContext> EndpointLimiter { get; }
}
public abstract class RateLimitLeaseInfo
{
// Same props as RateLimitLease, but without Dispose()
}Alternative Design - 2
Also, Instead of using HttpContext Features, we can use HttpContext.Items and Extension methods, like its done in Microsoft.AspNetCore.Authentication extention methods (HttpContext.SingIn, HttpContext.ChallangeAsync, etc).
So, we use the Alternative Design - 1 approach with Facade-like api, but implemented with extension methods
// very simple example of implementation (for only 1 method) just to show the API
public static class HttpContextRateLimiterExtentions
{
public static RateLimiterStatistics GetRateLimiterStatistics(this HttpContext context)
{
// just for example - the code is not correct
var limiter = (PartitionedRateLimiter<HttpContext>)context.Items["SomeGlobalLimiter"];
var stats = limiter?.GetStatistics(context);
return stats;
}
}
// and then in some middleware:
var statistics = HttpContext.GetRateLimiterStatistics();Risks
In Design 1:
- would anyone use this to dispose of the lease early? Would that have any strange side-effects, especially if it got double-disposed by the middleware later?
Background and Motivation
In #44140 issue, one of The dream scenario for a better ASP.NET Core rate limiter middleware as @maartenba says, would be able Have a feature on the current HttpContext that gives access to the current rate limit context, so these details can also be returned on successful requests, or added to telemetry.. This API proposal addresses this concern.
Proposed API
Below API supposes, that we have
RateLimiterMiddlewarein our app, which responsibility is to createIRateLimiterContextFeaturefor each request:Now we can access to this interface in any custom middleware or controller:
Usage Examples
Scenario 1: get statistics from limiters in custom telemetry middleware:
Scenario 2: Get metadata from successful RateLimiterLease for this request
Alternative Design - 1
As @Tratcher said, there is a risk, that
RateLimitLeasewould be disposed early. To prevent that, we can introduce facade-like class to wrap Lease with undisposable entity:Alternative Design - 2
Also, Instead of using
HttpContextFeatures, we can useHttpContext.Itemsand Extension methods, like its done inMicrosoft.AspNetCore.Authenticationextention methods (HttpContext.SingIn,HttpContext.ChallangeAsync, etc).So, we use the Alternative Design - 1 approach with Facade-like api, but implemented with extension methods
Risks
In Design 1: