[backend/federation] Add short-lived cache for non-specific federation requests

Iceshrimp.Backend/Controllers/Federation/ActivityPubController.cs

@@ -12,6 +12,7 @@ using Iceshrimp.Backend.Core.Middleware;
 using Iceshrimp.Backend.Core.Queues;
 using Iceshrimp.Backend.Core.Services;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.OutputCaching;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Options;
 using Newtonsoft.Json.Linq;
@@ -108,6 +109,7 @@ public class ActivityPubController(
 
 	[HttpGet("/users/{id}")]
 	[AuthorizedFetch]
+	[OutputCache(PolicyName = "federation")]
 	[MediaTypeRouteFilter("application/activity+json", "application/ld+json")]
 	[OverrideResultType<ASActor>]
 	[ProducesResults(HttpStatusCode.OK, HttpStatusCode.MovedPermanently)]
@@ -129,6 +131,7 @@ public class ActivityPubController(
 
 	[HttpGet("/users/{id}/collections/featured")]
 	[AuthorizedFetch]
+	[OutputCache(PolicyName = "federation")]
 	[OverrideResultType<ASOrderedCollection>]
 	[ProducesResults(HttpStatusCode.OK)]
 	[ProducesErrors(HttpStatusCode.NotFound)]
@@ -159,6 +162,7 @@ public class ActivityPubController(
 
 	[HttpGet("/@{acct}")]
 	[AuthorizedFetch]
+	[OutputCache(PolicyName = "federation")]
 	[MediaTypeRouteFilter("application/activity+json", "application/ld+json")]
 	[OverrideResultType<ASActor>]
 	[ProducesResults(HttpStatusCode.OK, HttpStatusCode.MovedPermanently)]
@@ -212,6 +216,7 @@ public class ActivityPubController(
 
 	[HttpGet("/emoji/{name}")]
 	[AuthorizedFetch]
+	[OutputCache(PolicyName = "federation")]
 	[MediaTypeRouteFilter("application/activity+json", "application/ld+json")]
 	[OverrideResultType<ASEmoji>]
 	[ProducesResults(HttpStatusCode.OK)]

Iceshrimp.Backend/Controllers/Federation/WellKnownController.cs

@@ -9,6 +9,7 @@ using Iceshrimp.Backend.Core.Federation.WebFinger;
 using Iceshrimp.Backend.Core.Middleware;
 using Microsoft.AspNetCore.Cors;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.OutputCaching;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Options;
 
@@ -17,6 +18,7 @@ namespace Iceshrimp.Backend.Controllers.Federation;
 [FederationApiController]
 [Route("/.well-known")]
 [EnableCors("well-known")]
+[OutputCache(PolicyName = "federation")]
 public class WellKnownController(IOptions<Config.InstanceSection> config, DatabaseContext db) : ControllerBase
 {
 	[HttpGet("webfinger")]

Iceshrimp.Backend/Core/Extensions/ServiceExtensions.cs

@@ -374,10 +374,22 @@ public static class ServiceExtensions
 			options.AddScheme<IAuthenticationHandler>("StubAuthenticationHandler", null);
 		});
 	}
+
+	public static void AddOutputCacheWithOptions(this IServiceCollection services)
+	{
+		services.AddOutputCache(options =>
+		{
+			options.AddPolicy("conditional", o => o.With(ctx => ctx.HttpContext.ShouldCacheOutput()));
+			options.AddPolicy("federation", o => o.SetVaryByHeader("Accept").Expire(TimeSpan.FromSeconds(60)));
+			options.DefaultExpirationTimeSpan = TimeSpan.FromDays(365);
+		});
+	}
 }
 
 public static partial class HttpContextExtensions
 {
+	private const string CacheKey = "shouldCache";
+
 	public static string GetRateLimitPartition(this HttpContext ctx, bool includeRoute) =>
 		(includeRoute ? ctx.Request.Path.ToString() + "#" : "") + (GetRateLimitPartitionInternal(ctx) ?? "");
 
@@ -385,6 +397,11 @@ public static partial class HttpContextExtensions
 		ctx.GetUser()?.Id ??
 		ctx.Request.Headers["X-Forwarded-For"].FirstOrDefault() ??
 		ctx.Connection.RemoteIpAddress?.ToString();
+
+	public static void CacheOutput(this HttpContext ctx) => ctx.Items[CacheKey] = true;
+
+	public static bool ShouldCacheOutput(this HttpContext ctx) =>
+		ctx.Items.TryGetValue(CacheKey, out var s) && s is true;
 }
 
 #region AsyncDataProtection handlers

Iceshrimp.Backend/Startup.cs

@@ -24,6 +24,7 @@ builder.Services
        .AddPlugins(PluginLoader.Assemblies);
 
 builder.Services.AddSwaggerGenWithOptions();
+builder.Services.AddOutputCacheWithOptions();
 builder.Services.AddLogging(logging => logging.AddCustomConsoleFormatter());
 builder.Services.AddDatabaseContext(builder.Configuration);
 builder.Services.AddSlidingWindowRateLimiter();
@@ -38,6 +39,7 @@ builder.Services.AddAntiforgery(o => o.Cookie.Name = "CSRF-Token");
 
 builder.Services.AddServices(builder.Configuration);
 builder.Services.ConfigureServices(builder.Configuration);
+
 builder.WebHost.ConfigureKestrel(builder.Configuration);
 builder.WebHost.UseStaticWebAssets();
 
@@ -64,6 +66,7 @@ app.UseAuthorization();
 app.UseWebSockets(new WebSocketOptions { KeepAliveInterval = TimeSpan.FromSeconds(30) });
 app.UseCustomMiddleware();
 app.UseAntiforgery();
+app.UseOutputCache();
 
 app.MapStaticAssetsWithTransparentDecompression();
 app.MapControllers();