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Add comprehensive metrics collection and rate limiting with middleware
Co-authored-by: jongalloway <[email protected]>
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9 files changed

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‎src/NLWebNet/Extensions/ApplicationBuilderExtensions.cs‎

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@@ -17,6 +17,8 @@ public static class ApplicationBuilderExtensions
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/// <returns>The application builder for chaining</returns>
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public static IApplicationBuilder UseNLWebNet(this IApplicationBuilder app)
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{
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app.UseMiddleware<RateLimitingMiddleware>();
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app.UseMiddleware<MetricsMiddleware>();
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app.UseMiddleware<NLWebMiddleware>();
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return app;
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} /// <summary>

‎src/NLWebNet/Extensions/ServiceCollectionExtensions.cs‎

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@@ -5,6 +5,7 @@
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using NLWebNet.MCP;
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using NLWebNet.Controllers;
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using NLWebNet.Health;
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using NLWebNet.RateLimiting;
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namespace NLWebNet;
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@@ -46,6 +47,12 @@ public static IServiceCollection AddNLWebNet(this IServiceCollection services, A
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.AddCheck<DataBackendHealthCheck>("data-backend")
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.AddCheck<AIServiceHealthCheck>("ai-service");
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// Add metrics
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services.AddMetrics();
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// Add rate limiting
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services.AddSingleton<IRateLimitingService, InMemoryRateLimitingService>();
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return services;
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}
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@@ -82,6 +89,12 @@ public static IServiceCollection AddNLWebNet<TDataBackend>(this IServiceCollecti
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.AddCheck<DataBackendHealthCheck>("data-backend")
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.AddCheck<AIServiceHealthCheck>("ai-service");
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// Add metrics
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services.AddMetrics();
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// Add rate limiting
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services.AddSingleton<IRateLimitingService, InMemoryRateLimitingService>();
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return services;
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}
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}

‎src/NLWebNet/Metrics/NLWebMetrics.cs‎

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using System.Diagnostics.Metrics;
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namespace NLWebNet.Metrics;
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/// <summary>
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/// Contains metric definitions and constants for NLWebNet monitoring
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/// </summary>
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public static class NLWebMetrics
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{
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/// <summary>
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/// The meter name for NLWebNet metrics
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/// </summary>
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public const string MeterName = "NLWebNet";
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/// <summary>
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/// The version for metrics tracking
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/// </summary>
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public const string Version = "1.0.0";
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/// <summary>
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/// Shared meter instance for all NLWebNet metrics
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/// </summary>
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public static readonly Meter Meter = new(MeterName, Version);
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// Request/Response Metrics
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public static readonly Counter<long> RequestCount = Meter.CreateCounter<long>(
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"nlweb.requests.total",
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description: "Total number of requests processed");
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public static readonly Histogram<double> RequestDuration = Meter.CreateHistogram<double>(
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"nlweb.request.duration",
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unit: "ms",
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description: "Duration of request processing in milliseconds");
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public static readonly Counter<long> RequestErrors = Meter.CreateCounter<long>(
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"nlweb.requests.errors",
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description: "Total number of request errors");
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// AI Service Metrics
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public static readonly Counter<long> AIServiceCalls = Meter.CreateCounter<long>(
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"nlweb.ai.calls.total",
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description: "Total number of AI service calls");
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public static readonly Histogram<double> AIServiceDuration = Meter.CreateHistogram<double>(
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"nlweb.ai.duration",
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unit: "ms",
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description: "Duration of AI service calls in milliseconds");
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public static readonly Counter<long> AIServiceErrors = Meter.CreateCounter<long>(
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"nlweb.ai.errors",
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description: "Total number of AI service errors");
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// Data Backend Metrics
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public static readonly Counter<long> DataBackendQueries = Meter.CreateCounter<long>(
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"nlweb.data.queries.total",
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description: "Total number of data backend queries");
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public static readonly Histogram<double> DataBackendDuration = Meter.CreateHistogram<double>(
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"nlweb.data.duration",
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unit: "ms",
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description: "Duration of data backend operations in milliseconds");
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public static readonly Counter<long> DataBackendErrors = Meter.CreateCounter<long>(
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"nlweb.data.errors",
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description: "Total number of data backend errors");
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// Health Check Metrics
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public static readonly Counter<long> HealthCheckExecutions = Meter.CreateCounter<long>(
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"nlweb.health.checks.total",
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description: "Total number of health check executions");
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public static readonly Counter<long> HealthCheckFailures = Meter.CreateCounter<long>(
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"nlweb.health.failures",
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description: "Total number of health check failures");
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// Business Metrics
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public static readonly Counter<long> QueryTypeCount = Meter.CreateCounter<long>(
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"nlweb.queries.by_type",
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description: "Count of queries by type (List, Summarize, Generate)");
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public static readonly Histogram<double> QueryComplexity = Meter.CreateHistogram<double>(
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"nlweb.queries.complexity",
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description: "Query complexity score based on length and structure");
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/// <summary>
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/// Common tag keys for consistent metric labeling
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/// </summary>
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public static class Tags
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{
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public const string Endpoint = "endpoint";
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public const string Method = "method";
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public const string StatusCode = "status_code";
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public const string QueryMode = "query_mode";
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public const string ErrorType = "error_type";
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public const string HealthCheckName = "health_check";
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public const string DataBackendType = "backend_type";
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public const string AIServiceType = "ai_service_type";
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}
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}

‎src/NLWebNet/Middleware/MetricsMiddleware.cs‎

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using Microsoft.AspNetCore.Http;
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using Microsoft.Extensions.Logging;
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using NLWebNet.Metrics;
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using System.Diagnostics;
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namespace NLWebNet.Middleware;
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/// <summary>
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/// Middleware for collecting metrics on HTTP requests
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/// </summary>
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public class MetricsMiddleware
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{
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private readonly RequestDelegate _next;
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private readonly ILogger<MetricsMiddleware> _logger;
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public MetricsMiddleware(RequestDelegate next, ILogger<MetricsMiddleware> logger)
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{
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_next = next ?? throw new ArgumentNullException(nameof(next));
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_logger = logger ?? throw new ArgumentNullException(nameof(logger));
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}
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public async Task InvokeAsync(HttpContext context)
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{
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var stopwatch = Stopwatch.StartNew();
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var path = context.Request.Path.Value ?? "unknown";
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var method = context.Request.Method;
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try
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{
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await _next(context);
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}
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catch (Exception ex)
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{
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// Record error metrics
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NLWebMetrics.RequestErrors.Add(1,
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.Endpoint, path),
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.Method, method),
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.ErrorType, ex.GetType().Name));
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_logger.LogError(ex, "Request failed for {Method} {Path}", method, path);
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throw;
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}
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finally
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{
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stopwatch.Stop();
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var duration = stopwatch.Elapsed.TotalMilliseconds;
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var statusCode = context.Response.StatusCode.ToString();
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// Record request metrics
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NLWebMetrics.RequestCount.Add(1,
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.Endpoint, path),
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.Method, method),
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.StatusCode, statusCode));
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NLWebMetrics.RequestDuration.Record(duration,
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.Endpoint, path),
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.Method, method),
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new KeyValuePair<string, object?>(NLWebMetrics.Tags.StatusCode, statusCode));
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_logger.LogDebug("Request {Method} {Path} completed in {Duration}ms with status {StatusCode}",
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method, path, duration, statusCode);
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}
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}
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}

‎src/NLWebNet/Middleware/RateLimitingMiddleware.cs‎

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using Microsoft.AspNetCore.Http;
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using Microsoft.Extensions.Logging;
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using Microsoft.Extensions.Options;
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using NLWebNet.RateLimiting;
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using System.Text.Json;
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namespace NLWebNet.Middleware;
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/// <summary>
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/// Middleware for enforcing rate limits on requests
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/// </summary>
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public class RateLimitingMiddleware
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{
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private readonly RequestDelegate _next;
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private readonly IRateLimitingService _rateLimitingService;
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private readonly RateLimitingOptions _options;
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private readonly ILogger<RateLimitingMiddleware> _logger;
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public RateLimitingMiddleware(
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RequestDelegate next,
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IRateLimitingService rateLimitingService,
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IOptions<RateLimitingOptions> options,
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ILogger<RateLimitingMiddleware> logger)
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{
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_next = next ?? throw new ArgumentNullException(nameof(next));
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_rateLimitingService = rateLimitingService ?? throw new ArgumentNullException(nameof(rateLimitingService));
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_options = options.Value ?? throw new ArgumentNullException(nameof(options));
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_logger = logger ?? throw new ArgumentNullException(nameof(logger));
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}
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public async Task InvokeAsync(HttpContext context)
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{
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if (!_options.Enabled)
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{
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await _next(context);
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return;
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}
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var identifier = GetClientIdentifier(context);
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var isAllowed = await _rateLimitingService.IsRequestAllowedAsync(identifier);
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if (!isAllowed)
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{
44+
await HandleRateLimitExceeded(context, identifier);
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return;
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}
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// Add rate limit headers
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var status = await _rateLimitingService.GetRateLimitStatusAsync(identifier);
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context.Response.Headers.Append("X-RateLimit-Limit", _options.RequestsPerWindow.ToString());
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context.Response.Headers.Append("X-RateLimit-Remaining", status.RequestsRemaining.ToString());
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context.Response.Headers.Append("X-RateLimit-Reset", ((int)status.WindowResetTime.TotalSeconds).ToString());
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await _next(context);
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}
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private string GetClientIdentifier(HttpContext context)
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{
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// Try client ID header first if enabled
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if (_options.EnableClientBasedLimiting)
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{
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var clientId = context.Request.Headers[_options.ClientIdHeader].FirstOrDefault();
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if (!string.IsNullOrEmpty(clientId))
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{
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return $"client:{clientId}";
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}
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}
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// Fall back to IP-based limiting if enabled
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if (_options.EnableIPBasedLimiting)
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{
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var ip = context.Connection.RemoteIpAddress?.ToString() ?? "unknown";
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return $"ip:{ip}";
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}
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// Default fallback
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return "default";
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}
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private async Task HandleRateLimitExceeded(HttpContext context, string identifier)
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{
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var status = await _rateLimitingService.GetRateLimitStatusAsync(identifier);
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context.Response.StatusCode = 429; // Too Many Requests
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context.Response.Headers.Append("X-RateLimit-Limit", _options.RequestsPerWindow.ToString());
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context.Response.Headers.Append("X-RateLimit-Remaining", "0");
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context.Response.Headers.Append("X-RateLimit-Reset", ((int)status.WindowResetTime.TotalSeconds).ToString());
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context.Response.Headers.Append("Retry-After", ((int)status.WindowResetTime.TotalSeconds).ToString());
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var response = new
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{
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error = "rate_limit_exceeded",
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message = $"Rate limit exceeded. Maximum {_options.RequestsPerWindow} requests per {_options.WindowSizeInMinutes} minute(s).",
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retry_after_seconds = (int)status.WindowResetTime.TotalSeconds
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};
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context.Response.ContentType = "application/json";
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await context.Response.WriteAsync(JsonSerializer.Serialize(response));
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_logger.LogWarning("Rate limit exceeded for identifier {Identifier}. Requests: {Requests}/{Limit}",
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identifier, status.TotalRequests, _options.RequestsPerWindow);
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}
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}

‎src/NLWebNet/Models/NLWebOptions.cs‎

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using System.ComponentModel.DataAnnotations;
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using NLWebNet.RateLimiting;
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namespace NLWebNet.Models;
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@@ -65,4 +66,9 @@ public class NLWebOptions
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/// </summary>
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[Range(1, 1440)]
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public int CacheExpirationMinutes { get; set; } = 60;
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/// <summary>
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/// Rate limiting configuration
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/// </summary>
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public RateLimitingOptions RateLimiting { get; set; } = new();
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}

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