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RateLimiterExtensions provides a single AddCustomRateLimiter extension method on IServiceCollection that consolidates every service registration the application needs: the Redis connection, the RedisRateLimiter singleton, four built-in ASP.NET Core rate-limiting policies, health checks with a Redis probe and a UI, and Swagger. Calling this one method in Program.cs replaces a large block of repetitive setup code and keeps the startup entry point concise.

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Namespace

namespace Dotnet_RateLimiter.Extensions;

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Method: AddCustomRateLimiter

public static IServiceCollection AddCustomRateLimiter(
    this IServiceCollection services,
    IConfiguration configuration)
Returns: IServiceCollection — the same services instance, enabling fluent chaining.
​
services
IServiceCollection
required
The service collection to register all dependencies into. Passed implicitly as the extension target (i.e. builder.Services).
​
configuration
IConfiguration
required
The application configuration object. The method reads the Redis connection string from the key Redis:ConnectionString. If the key is absent it falls back to "localhost:6379".

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What It Registers

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Full Source

public static IServiceCollection AddCustomRateLimiter(this IServiceCollection services,
    IConfiguration configuration)
{
    var redisConnectionString = configuration.GetSection("Redis:ConnectionString").Value
                                ?? "localhost:6379";

    var redis = ConnectionMultiplexer.Connect(redisConnectionString);
    services.AddSingleton<IConnectionMultiplexer>(redis);
    services.AddHealthChecks()
        .AddRedis(
            redisConnectionString: configuration.GetSection("Redis:ConnectionString").Value!,
            name: "Redis Server",
            tags: ["db", "cache", "redis"]
        );

    services.AddHealthChecksUI(settings =>
    {
        settings.AddHealthCheckEndpoint("Main App", "http://localhost:8080/health");
        settings.SetEvaluationTimeInSeconds(5);
    }).AddInMemoryStorage();

    services.AddSingleton<RedisRateLimiter>();
    services.AddControllers();
    services.AddEndpointsApiExplorer();
    services.AddSwaggerGen();
    services.AddRateLimiter(options =>
    {
        options.AddFixedWindowLimiter("FixedWindowPolicy", opt =>
        {
            opt.Window = TimeSpan.FromSeconds(5);
            opt.PermitLimit = 5;
            opt.QueueLimit = 10;
            //LIFO approach : Last in First out
            opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
        }).RejectionStatusCode = 429;

        options.AddSlidingWindowLimiter("SlidingWindowPolicy", opt =>
        {
            opt.Window = TimeSpan.FromSeconds(10);
            opt.PermitLimit = 5;
            opt.QueueLimit = 10;
            //LIFO approach : Last in First out
            opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
            opt.SegmentsPerWindow = 4;
        }).RejectionStatusCode = 429;

        options.AddConcurrencyLimiter("ConcurrencyPolicy", opt =>
        {
            opt.PermitLimit = 7;
            opt.QueueLimit = 3;
            //LIFO approach : Last in First out
            opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
        }).RejectionStatusCode = 429;

        options.AddTokenBucketLimiter("BucketPolicy", opt =>
        {
            opt.TokenLimit = 5;
            opt.QueueLimit = 2;
            //LIFO approach : Last in First out
            opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
            opt.ReplenishmentPeriod = TimeSpan.FromSeconds(5);
            opt.AutoReplenishment = true;
            opt.TokensPerPeriod = 3;
        }).RejectionStatusCode = 429;
    });
    return services;
}

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Registration Breakdown

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1. IConnectionMultiplexer — Redis Connection

var redisConnectionString = configuration.GetSection("Redis:ConnectionString").Value
                            ?? "localhost:6379";

var redis = ConnectionMultiplexer.Connect(redisConnectionString);
services.AddSingleton<IConnectionMultiplexer>(redis);
Creates and registers a StackExchange.Redis ConnectionMultiplexer as a singleton using the connection string from configuration. Falls back to localhost:6379 if the config key is not present. Required appsettings.json key: 
{
  "Redis": {
    "ConnectionString": "localhost:6379"
  }
}

​
2. Health Checks — Redis Probe

services.AddHealthChecks()
    .AddRedis(
        redisConnectionString: configuration.GetSection("Redis:ConnectionString").Value!,
        name: "Redis Server",
        tags: ["db", "cache", "redis"]
    );
Adds the AspNetCore.HealthChecks.Redis probe. The health check endpoint is mapped in Program.cs at /health using UIResponseWriter.WriteHealthCheckUIResponse.
PropertyValue
NameRedis Server
Tagsdb, cache, redis
Endpoint (Program.cs)/health

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3. Health Checks UI — InMemory Storage

services.AddHealthChecksUI(settings =>
{
    settings.AddHealthCheckEndpoint("Main App", "http://localhost:8080/health");
    settings.SetEvaluationTimeInSeconds(5);
}).AddInMemoryStorage();
Registers the HealthChecks UI dashboard with in-memory storage. The UI polls the /health endpoint every 5 seconds.
PropertyValue
Monitored endpointhttp://localhost:8080/health
Poll interval5 seconds
StorageIn-memory
UI path (Program.cs)/health-ui

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4. RedisRateLimiter Singleton

services.AddSingleton<RedisRateLimiter>();
Registers the core distributed rate-limiter service. See RedisRateLimiter for full details.

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5. Controllers, API Explorer, and SwaggerGen

services.AddControllers();
services.AddEndpointsApiExplorer();
services.AddSwaggerGen();
Standard registrations for MVC controllers and the Swagger/OpenAPI document generator. UseSwagger() and UseSwaggerUI() are called in Program.cs in the development environment.

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6. Rate Limiting Policies

Four named policies are registered via services.AddRateLimiter(...). All four use QueueProcessingOrder.OldestFirst and return 429 on rejection.
FixedWindowPolicy
options.AddFixedWindowLimiter("FixedWindowPolicy", opt =>
{
    opt.Window = TimeSpan.FromSeconds(5);
    opt.PermitLimit = 5;
    opt.QueueLimit = 10;
    opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
}).RejectionStatusCode = 429;
PropertyValue
Window5 seconds
PermitLimit5 requests
QueueLimit10 requests
QueueProcessingOrderOldestFirst
Rejection status429
SlidingWindowPolicy
options.AddSlidingWindowLimiter("SlidingWindowPolicy", opt =>
{
    opt.Window = TimeSpan.FromSeconds(10);
    opt.PermitLimit = 5;
    opt.QueueLimit = 10;
    opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
    opt.SegmentsPerWindow = 4;
}).RejectionStatusCode = 429;
PropertyValue
Window10 seconds
PermitLimit5 requests
QueueLimit10 requests
SegmentsPerWindow4
QueueProcessingOrderOldestFirst
Rejection status429
ConcurrencyPolicy
options.AddConcurrencyLimiter("ConcurrencyPolicy", opt =>
{
    opt.PermitLimit = 7;
    opt.QueueLimit = 3;
    opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
}).RejectionStatusCode = 429;
PropertyValue
PermitLimit7 concurrent requests
QueueLimit3 requests
QueueProcessingOrderOldestFirst
Rejection status429
BucketPolicy
options.AddTokenBucketLimiter("BucketPolicy", opt =>
{
    opt.TokenLimit = 5;
    opt.QueueLimit = 2;
    opt.QueueProcessingOrder = QueueProcessingOrder.OldestFirst;
    opt.ReplenishmentPeriod = TimeSpan.FromSeconds(5);
    opt.AutoReplenishment = true;
    opt.TokensPerPeriod = 3;
}).RejectionStatusCode = 429;
PropertyValue
TokenLimit5 tokens (bucket capacity)
QueueLimit2 requests
ReplenishmentPeriod5 seconds
TokensPerPeriod3 tokens added per period
AutoReplenishmenttrue
QueueProcessingOrderOldestFirst
Rejection status429

​
Usage

// Program.cs
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddCustomRateLimiter(builder.Configuration);

var app = builder.Build();
Because the method returns IServiceCollection you can chain additional registrations: 
builder.Services
    .AddCustomRateLimiter(builder.Configuration)
    .AddSingleton<IMyService, MyService>();

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