fix(desktop): never queue local proxy requests (#3421)

fluxer_desktop/src/main/DesktopOutboundHTTP.test.mjs

@@ -65,7 +65,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 				headers: null,
 				method: 'GET',
 				originTrust: DesktopOriginTrust.REGISTERED,
-				serviceName: 'test',
 				signal: null,
 				timeoutMs: 500,
 				url: 'https://media.internal/avatars/1.webp',
@@ -104,7 +103,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 				headers: null,
 				method: 'GET',
 				originTrust: DesktopOriginTrust.REGISTERED,
-				serviceName: 'test',
 				signal: null,
 				timeoutMs: 500,
 				url: 'https://media.internal/avatars/1.webp',
@@ -161,7 +159,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 				headers: null,
 				method: 'GET',
 				originTrust: DesktopOriginTrust.REGISTERED,
-				serviceName: 'test',
 				signal: null,
 				timeoutMs: 500,
 				url: 'https://media.mixed.example/avatars/1.webp',
@@ -193,44 +190,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 		outboundHTTP.cleanup();
 	});
 
-	test('a request that cannot be constructed releases its in-flight slot', async () => {
-		const {port, server} = await startServer({
-			'/ok': (_request, response) => sendImage(response, 'image/png', PNG_BYTES),
-		});
-		try {
-			const outboundHTTP = new DesktopOutboundHTTP({
-				resolveHostAddresses: stubResolver({'lan.example': ['127.0.0.1']}),
-			});
-			await outboundHTTP.registerAnchoredOrigins({
-				anchorOrigin: `http://lan.example:${port}`,
-				origins: [`http://lan.example:${port}`],
-			});
-			const send = (headers) =>
-				outboundHTTP.request({
-					body: null,
-					expectedOrigin: `http://lan.example:${port}`,
-					headers,
-					method: 'GET',
-					originTrust: DesktopOriginTrust.REGISTERED,
-					serviceName: 'slot-leak',
-					signal: null,
-					timeoutMs: 2000,
-					url: `http://lan.example:${port}/ok`,
-				});
-
-			for (let attempt = 0; attempt < 80; attempt += 1) {
-				await assert.rejects(send({'x-bad': 'a\u0001b'}));
-			}
-			const message = await send(null);
-
-			assert.equal(message.status, 200);
-			message.message.resume();
-			outboundHTTP.cleanup();
-		} finally {
-			server.close();
-		}
-	});
-
 	test('a request whose signal already aborted is refused instead of sent', async () => {
 		const seen = [];
 		const {port, server} = await startServer({
@@ -257,7 +216,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 					headers: null,
 					method: 'GET',
 					originTrust: DesktopOriginTrust.REGISTERED,
-					serviceName: 'aborted',
 					signal: controller.signal,
 					timeoutMs: 2000,
 					url: `http://lan.example:${port}/ok`,
@@ -289,7 +247,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 				headers: null,
 				method: 'GET',
 				originTrust: DesktopOriginTrust.REGISTERED,
-				serviceName: 'test',
 				signal: null,
 				timeoutMs: 2000,
 				url: `http://media.lan.example:${port}/media/ok`,
@@ -331,7 +288,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 					headers: {'content-type': 'application/json', 'x-fluxer-sudo-mode-jwt': 'previous'},
 					method,
 					originTrust: DesktopOriginTrust.REGISTERED,
-					serviceName: 'test',
 					signal: null,
 					timeoutMs: 2000,
 					url: `http://lan.example:${port}/api/v1/oauth2/applications/1`,
@@ -549,7 +505,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 			headers: null,
 			method: 'GET',
 			originTrust: DesktopOriginTrust.BOUND,
-			serviceName: 'test',
 			signal,
 			timeoutMs: 2000,
 			url: `https://home.example:${port}/ping`,
@@ -577,7 +532,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 			headers: null,
 			method: 'GET',
 			originTrust: DesktopOriginTrust.BOUND,
-			serviceName: 'test',
 			signal: null,
 			timeoutMs: 200,
 			url: 'http://blackhole.example:9/ping',
@@ -606,7 +560,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 				headers: null,
 				method: 'GET',
 				originTrust: DesktopOriginTrust.BOUND,
-				serviceName: 'test',
 				signal: null,
 				timeoutMs: 2000,
 				url: `http://mixed.example:${port}/ping`,
@@ -632,7 +585,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 					headers: null,
 					method: 'GET',
 					originTrust: DesktopOriginTrust.BOUND,
-					serviceName: 'test',
 					signal: null,
 					timeoutMs: 2000,
 					url: `http://127.0.0.1:${other.port}/steal`,
@@ -670,7 +622,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 					headers: null,
 					method: 'GET',
 					originTrust: DesktopOriginTrust.BOUND,
-					serviceName: 'test',
 					signal: null,
 					timeoutMs: 5000,
 					url: `http://127.0.0.1:${port}/ping`,
@@ -720,7 +671,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 					headers: {'content-type': 'text/plain'},
 					method: 'PUT',
 					originTrust: DesktopOriginTrust.BOUND,
-					serviceName: 'test',
 					signal: null,
 					timeoutMs: 5000,
 					url: `http://127.0.0.1:${port}/upload`,
@@ -775,7 +725,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 					headers: null,
 					method: 'GET',
 					originTrust: DesktopOriginTrust.REGISTERED,
-					serviceName: 'test',
 					signal: null,
 					timeoutMs: 2000,
 					url: 'https://unrouted.example/',
@@ -826,7 +775,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 				headers: null,
 				method: 'GET',
 				originTrust: DesktopOriginTrust.REGISTERED,
-				serviceName: 'test',
 				signal: null,
 				timeoutMs: 2000,
 				url: `http://dual.example:${port}/ping`,
@@ -857,7 +805,6 @@ describe('DesktopOutboundHTTP origin anchoring', () => {
 				headers: null,
 				method: 'GET',
 				originTrust: DesktopOriginTrust.REGISTERED,
-				serviceName: 'test',
 				signal: null,
 				timeoutMs: 3000,
 				url: `http://multi.example:${port}/ping`,
@@ -1007,7 +954,6 @@ describe('DesktopOutboundHTTP system proxy routes', () => {
 			headers: {Accept: 'image/png'},
 			method: 'GET',
 			originTrust: DesktopOriginTrust.REGISTERED,
-			serviceName: 'test',
 			signal: null,
 			timeoutMs: 500,
 			url: 'https://media.blocked.example/avatar.png',
@@ -1061,7 +1007,6 @@ describe('DesktopOutboundHTTP system proxy routes', () => {
 			headers: null,
 			method: 'GET',
 			originTrust,
-			serviceName: 'test',
 			signal: null,
 			timeoutMs: 500,
 			url,

fluxer_desktop/src/main/DesktopOutboundHTTP.ts

@@ -28,8 +28,6 @@ const DESKTOP_OUTBOUND_HTTP_RESOLUTION_TIMEOUT_MS = 10_000;
 const DESKTOP_OUTBOUND_HTTP_MAX_TARGET_URL_BYTES = 16 * 1024;
 const DESKTOP_OUTBOUND_HTTP_MAX_REDIRECT_LOCATION_BYTES = 4096;
 const DESKTOP_OUTBOUND_HTTP_MAX_ORIGINS = 2048;
-const DESKTOP_OUTBOUND_HTTP_MAX_ORIGIN_REQUESTS_IN_FLIGHT = 128;
-const DESKTOP_OUTBOUND_HTTP_MAX_IN_FLIGHT_PER_SERVICE = 64;
 const DESKTOP_OUTBOUND_HTTP_MAX_PENDING_RESOLUTIONS = 64;
 const DESKTOP_OUTBOUND_HTTP_MAX_REQUEST_BODY_BYTES = 1024 * 1024;
 const DESKTOP_OUTBOUND_HTTP_STALE_SOCKET_ATTEMPTS = 1;
@@ -113,7 +111,6 @@ export interface DesktopOutboundHTTPRequest {
 	readonly maximumRequestBodyBytes?: number;
 	readonly method: string;
 	readonly originTrust: DesktopOriginTrust;
-	readonly serviceName: string;
 	readonly signal: AbortSignal | null;
 	readonly timeoutMs: number;
 	readonly url: string;
@@ -565,7 +562,7 @@ interface DesktopProxiedSend {
 	readonly body: Uint8Array | Readable | null;
 	readonly headers: Readonly<Record<string, string>>;
 	readonly method: string;
-	readonly release: () => void;
+	readonly release?: () => void;
 	readonly signal: AbortSignal | null;
 	readonly target: URL;
 	readonly timeout: () => Error;
@@ -578,20 +575,15 @@ export class DesktopOutboundHTTP {
 		maxSockets: DESKTOP_OUTBOUND_HTTP_MAX_SOCKETS,
 	});
 	private readonly httpsAgent: https.Agent;
-	private readonly originRequestHttpAgent = new HappyEyeballsHttpAgent({
-		keepAlive: true,
-		maxSockets: DESKTOP_OUTBOUND_HTTP_MAX_IN_FLIGHT_PER_SERVICE,
-	});
+	private readonly originRequestHttpAgent = new HappyEyeballsHttpAgent({keepAlive: true});
 	private readonly originRequestHttpsAgent: https.Agent;
 	private readonly bindings = new Map<string, DesktopOriginAddressBinding>();
 	private readonly pendingBindings = new Map<string, DesktopPendingOriginBinding>();
 	private readonly registeredRequirements = new Map<string, DesktopAddressRequirement>();
-	private readonly originRequestsInFlightByService = new Map<string, number>();
 	private readonly resolveHostAddresses: DesktopHostAddressResolver;
 	private readonly resolveProxy: DesktopProxyResolver;
 	private readonly sendThroughSession: DesktopSessionHTTPSender;
 	private inFlight = 0;
-	private originRequestsInFlight = 0;
 	private activeResolutions = 0;
 	private acceptingRequests = true;
 
@@ -608,7 +600,6 @@ export class DesktopOutboundHTTP {
 		});
 		this.originRequestHttpsAgent = new HappyEyeballsHttpsAgent({
 			keepAlive: true,
-			maxSockets: DESKTOP_OUTBOUND_HTTP_MAX_IN_FLIGHT_PER_SERVICE,
 			...trust,
 		});
 	}
@@ -783,7 +774,6 @@ export class DesktopOutboundHTTP {
 		this.originRequestHttpsAgent.destroy();
 		this.bindings.clear();
 		this.registeredRequirements.clear();
-		this.originRequestsInFlightByService.clear();
 	}
 
 	private async routesDirect(url: URL): Promise<boolean> {
@@ -813,15 +803,6 @@ export class DesktopOutboundHTTP {
 		request: DesktopOutboundHTTPRequest,
 		target: URL,
 	): Promise<DesktopOutboundHTTPMessage> {
-		this.acquireSlot(request.serviceName);
-		let released = false;
-		const release = (): void => {
-			if (released) {
-				return;
-			}
-			released = true;
-			this.releaseSlot(request.serviceName);
-		};
 		return this.sendProxied({
 			body: this.proxiedRequestBody(request),
 			headers: requestHeaders(request.headers),
@@ -830,7 +811,6 @@ export class DesktopOutboundHTTP {
 			target,
 			timeout: () => new DesktopOutboundHTTPRequestTimeoutError(target.toString(), request.timeoutMs),
 			timeoutMs: request.timeoutMs,
-			release,
 		}).catch((error: unknown) => {
 			if (request.signal?.aborted === true) {
 				throw new DesktopOutboundHTTPRequestAbortedError(target.toString());
@@ -854,7 +834,7 @@ export class DesktopOutboundHTTP {
 		timer.unref();
 		const settle = (): void => {
 			clearTimeout(timer);
-			release();
+			release?.();
 		};
 		try {
 			const response = await this.sendThroughSession({
@@ -1083,42 +1063,11 @@ export class DesktopOutboundHTTP {
 		}
 	}
 
-	private acquireSlot(serviceName: string): void {
-		if (this.originRequestsInFlight >= DESKTOP_OUTBOUND_HTTP_MAX_ORIGIN_REQUESTS_IN_FLIGHT) {
-			throw new DesktopOutboundHTTPCapacityError('in-flight request');
-		}
-		const perService = this.originRequestsInFlightByService.get(serviceName) ?? 0;
-		if (perService >= DESKTOP_OUTBOUND_HTTP_MAX_IN_FLIGHT_PER_SERVICE) {
-			throw new DesktopOutboundHTTPCapacityError(`in-flight request for ${serviceName}`);
-		}
-		this.originRequestsInFlight += 1;
-		this.originRequestsInFlightByService.set(serviceName, perService + 1);
-	}
-
-	private releaseSlot(serviceName: string): void {
-		this.originRequestsInFlight -= 1;
-		const perService = (this.originRequestsInFlightByService.get(serviceName) ?? 1) - 1;
-		if (perService <= 0) {
-			this.originRequestsInFlightByService.delete(serviceName);
-		} else {
-			this.originRequestsInFlightByService.set(serviceName, perService);
-		}
-	}
-
 	private issueOriginRequest(
 		request: DesktopOutboundHTTPRequest,
 		target: URL,
 		binding: DesktopOriginAddressBinding,
 	): Promise<DesktopOutboundHTTPMessage> {
-		this.acquireSlot(request.serviceName);
-		let released = false;
-		const release = (): void => {
-			if (released) {
-				return;
-			}
-			released = true;
-			this.releaseSlot(request.serviceName);
-		};
 		return new Promise<DesktopOutboundHTTPMessage>((resolve, reject) => {
 			let attemptsRemaining = isReplayableRequest(request) ? DESKTOP_OUTBOUND_HTTP_STALE_SOCKET_ATTEMPTS : 0;
 			let active: http.ClientRequest | null = null;
@@ -1144,7 +1093,6 @@ export class DesktopOutboundHTTP {
 			const settle = (): void => {
 				clearTimeout(timeout);
 				request.signal?.removeEventListener('abort', onAbort);
-				release();
 			};
 			const destroyActive = (error: Error): void => {
 				active?.destroy(error);

fluxer_desktop/src/main/DesktopRuntimeSecurity.test.mjs

@@ -16,10 +16,12 @@ function createLogger() {
 
 function createSession() {
 	const session = {
+		requestFilter: null,
 		requestListener: null,
 		webRequest: {
-			onBeforeSendHeaders: (listener) => {
-				session.requestListener = listener;
+			onBeforeSendHeaders: (...args) => {
+				session.requestFilter = args.length > 1 ? args[0] : null;
+				session.requestListener = args.at(-1);
 			},
 		},
 	};
@@ -141,6 +143,12 @@ describe('DesktopRuntimeSecurity', () => {
 		);
 	});
 
+	test('only intercepts local app requests and the YouTube embed frame', () => {
+		const {session} = createInstalled();
+
+		assert.deepEqual(session.requestFilter, {urls: ['fluxer-app://*/*', 'https://www.youtube.com/embed/*']});
+	});
+
 	test('installs once per session and stops listening after cleanup', () => {
 		const {security, session} = createInstalled();
 		const firstRequestListener = session.requestListener;

fluxer_desktop/src/main/DesktopRuntimeSecurity.ts

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
-import {STABLE_APP_URL} from '@electron/common/Constants';
+import {DESKTOP_APP_SCHEME, STABLE_APP_URL} from '@electron/common/Constants';
 import {isPlainRecord} from '@electron/common/PlainRecord';
 
 const SUB_FRAME_RESOURCE_TYPE = 'subFrame';
@@ -9,6 +9,10 @@ const REFERER_REQUEST_HEADER = 'Referer';
 const REFERER_HEADER_NAME_LOWERCASE = 'referer';
 const YOUTUBE_EMBED_FRAME_ORIGIN = 'https://www.youtube.com';
 const YOUTUBE_EMBED_FRAME_PATH_PREFIX = '/embed/';
+const DESKTOP_RUNTIME_SECURITY_REQUEST_URL_PATTERNS = [
+	`${DESKTOP_APP_SCHEME}://*/*`,
+	`${YOUTUBE_EMBED_FRAME_ORIGIN}${YOUTUBE_EMBED_FRAME_PATH_PREFIX}*`,
+];
 
 interface DesktopRuntimeSecurityLogger {
 	error: (...args: Array<unknown>) => void;
@@ -62,9 +66,12 @@ export class DesktopRuntimeSecurity {
 		}
 		this.installedSessions.add(session);
 		try {
-			session.webRequest.onBeforeSendHeaders((details: unknown, callback: unknown) => {
-				this.settleRequestHeaders(details, callback);
-			});
+			session.webRequest.onBeforeSendHeaders(
+				{urls: DESKTOP_RUNTIME_SECURITY_REQUEST_URL_PATTERNS},
+				(details: unknown, callback: unknown) => {
+					this.settleRequestHeaders(details, callback);
+				},
+			);
 		} catch (installationError) {
 			this.uninstall(session);
 			throw installationError;

fluxer_desktop/src/main/DesktopTrustedCertificates.test.mjs

@@ -41,7 +41,6 @@ async function fetchThrough(certificates, port) {
 			headers: null,
 			method: 'GET',
 			originTrust: DesktopOriginTrust.REGISTERED,
-			serviceName: 'test',
 			signal: null,
 			timeoutMs: 3000,
 			url: `https://ca.example:${port}/`,

fluxer_desktop/src/main/LocalAppProxyClient.ts

@@ -20,8 +20,6 @@ const LOCAL_APP_PROXY_REQUEST_BODY_MAX_BYTES = 100 * 1024 * 1024;
 export const LOCAL_APP_PROXY_ACCEPT_ENCODING = 'gzip, br';
 
 const LOCAL_APP_PROXY_RESOURCE_RESPONSE_HEADERS_DEADLINE_MS = 30_000;
-const LOCAL_APP_PROXY_MAX_CONCURRENT_REQUESTS = 32;
-const LOCAL_APP_PROXY_MAX_QUEUED_REQUESTS = 4096;
 const UPLOAD_PROGRESS_MIN_BYTES = 64 * 1024;
 const UPLOAD_PROGRESS_MIN_INTERVAL_MS = 100;
 const MINIMUM_RESPONSE_STATUS = 200;
@@ -42,101 +40,6 @@ class LocalAppProxyResponseHeadersDeadlineError extends Error {
 	}
 }
 
-class LocalAppProxyQueueOverflowError extends Error {
-	public constructor() {
-		super('Local app proxy has too many queued requests');
-		this.name = 'LocalAppProxyQueueOverflowError';
-	}
-}
-
-class LocalAppProxyConcurrencyPermit {
-	private releasePermit: (() => void) | null;
-
-	public constructor(releasePermit: () => void) {
-		this.releasePermit = releasePermit;
-	}
-
-	public release(): void {
-		const releasePermit = this.releasePermit;
-		if (releasePermit == null) {
-			return;
-		}
-		this.releasePermit = null;
-		releasePermit();
-	}
-}
-
-class LocalAppProxyResponseBodyLease {
-	public readonly reader: ReadableStreamDefaultReader<Uint8Array>;
-	private readonly permit: LocalAppProxyConcurrencyPermit;
-	private settled = false;
-
-	public constructor(body: ReadableStream<Uint8Array>, permit: LocalAppProxyConcurrencyPermit) {
-		this.reader = body.getReader();
-		this.permit = permit;
-	}
-
-	public release(): void {
-		if (this.settled) {
-			return;
-		}
-		this.settled = true;
-		try {
-			this.reader.releaseLock();
-		} finally {
-			this.permit.release();
-		}
-	}
-}
-
-class LocalAppProxyConcurrencyGate {
-	private active = 0;
-	private readonly waiting: Array<{readonly admit: () => void}> = [];
-	private readonly newestFirst: boolean;
-
-	public constructor(newestFirst: boolean) {
-		this.newestFirst = newestFirst;
-	}
-
-	public acquire(signal: AbortSignal): Promise<LocalAppProxyConcurrencyPermit> {
-		signal.throwIfAborted();
-		if (this.active < LOCAL_APP_PROXY_MAX_CONCURRENT_REQUESTS) {
-			this.active += 1;
-			return Promise.resolve(new LocalAppProxyConcurrencyPermit(() => this.release()));
-		}
-		if (this.waiting.length >= LOCAL_APP_PROXY_MAX_QUEUED_REQUESTS) {
-			throw new LocalAppProxyQueueOverflowError();
-		}
-		return new Promise<LocalAppProxyConcurrencyPermit>((resolve, reject) => {
-			let waiter: (typeof this.waiting)[number];
-			const onAbort = () => {
-				const index = this.waiting.indexOf(waiter);
-				if (index === -1) {
-					return;
-				}
-				this.waiting.splice(index, 1);
-				reject(signal.reason);
-			};
-			const admit = () => {
-				signal.removeEventListener('abort', onAbort);
-				resolve(new LocalAppProxyConcurrencyPermit(() => this.release()));
-			};
-			waiter = {admit};
-			this.waiting.push(waiter);
-			signal.addEventListener('abort', onAbort, {once: true});
-		});
-	}
-
-	private release(): void {
-		const next = this.newestFirst ? this.waiting.pop() : this.waiting.shift();
-		if (next != null) {
-			next.admit();
-			return;
-		}
-		this.active -= 1;
-	}
-}
-
 interface DesktopLocalAppProxyClientDependencies {
 	readonly outboundHTTP: DesktopOutboundHTTP;
 	readonly traffic: LocalAppProxyTraffic;
@@ -226,35 +129,20 @@ function emitLocalAppUploadProgress(progress: DesktopLocalAppUploadProgress): vo
 
 export class DesktopLocalAppProxyClient {
 	private readonly outboundHTTP: DesktopOutboundHTTP;
-	private readonly traffic: LocalAppProxyTraffic;
-	private readonly concurrency: LocalAppProxyConcurrencyGate;
 	private readonly responseHeadersDeadlineMs: number | null;
 
 	public constructor(dependencies: DesktopLocalAppProxyClientDependencies) {
 		this.outboundHTTP = dependencies.outboundHTTP;
-		this.traffic = dependencies.traffic;
-		const remoteResource = dependencies.traffic === LocalAppProxyTraffic.REMOTE_RESOURCE;
-		this.concurrency = new LocalAppProxyConcurrencyGate(remoteResource);
-		this.responseHeadersDeadlineMs = remoteResource ? LOCAL_APP_PROXY_RESOURCE_RESPONSE_HEADERS_DEADLINE_MS : null;
+		this.responseHeadersDeadlineMs =
+			dependencies.traffic === LocalAppProxyTraffic.REMOTE_RESOURCE
+				? LOCAL_APP_PROXY_RESOURCE_RESPONSE_HEADERS_DEADLINE_MS
+				: null;
 	}
 
 	public async fetch(request: LocalAppProxyFetchRequest): Promise<Response> {
-		const permit = await this.concurrency.acquire(request.signal);
-		try {
-			return await this.runFetchWithinHeadersDeadline(request, permit);
-		} catch (error) {
-			permit.release();
-			throw error;
-		}
-	}
-
-	private async runFetchWithinHeadersDeadline(
-		request: LocalAppProxyFetchRequest,
-		permit: LocalAppProxyConcurrencyPermit,
-	): Promise<Response> {
 		const deadlineMs = this.responseHeadersDeadlineMs;
 		if (deadlineMs == null || requestHasBody(request.method)) {
-			return await this.runFetch(request, permit);
+			return await this.runFetch(request);
 		}
 		const deadline = new AbortController();
 		const timer = setTimeout(
@@ -263,16 +151,13 @@ export class DesktopLocalAppProxyClient {
 		);
 		timer.unref();
 		try {
-			return await this.runFetch({...request, signal: AbortSignal.any([request.signal, deadline.signal])}, permit);
+			return await this.runFetch({...request, signal: AbortSignal.any([request.signal, deadline.signal])});
 		} finally {
 			clearTimeout(timer);
 		}
 	}
 
-	private async runFetch(
-		request: LocalAppProxyFetchRequest,
-		permit: LocalAppProxyConcurrencyPermit,
-	): Promise<Response> {
+	private async runFetch(request: LocalAppProxyFetchRequest): Promise<Response> {
 		const target = new URL(request.targetURL);
 		const body = requestHasBody(request.method) ? request.body : null;
 		const outboundRequest: DesktopOutboundHTTPRequest = {
@@ -282,12 +167,11 @@ export class DesktopLocalAppProxyClient {
 			maximumRequestBodyBytes: LOCAL_APP_PROXY_REQUEST_BODY_MAX_BYTES,
 			method: request.method,
 			originTrust: DesktopOriginTrust.REGISTERED,
-			serviceName: this.traffic,
 			signal: request.signal,
 			timeoutMs: LOCAL_APP_PROXY_DEADLINE_MS,
 			url: target.href,
 		};
-		return buildProxyResponse(await this.outboundHTTP.request(outboundRequest), request.method, permit);
+		return buildProxyResponse(await this.outboundHTTP.request(outboundRequest), request.method);
 	}
 
 	public async settleFailure({
@@ -368,11 +252,7 @@ function instrumentedRequestBody(
 	);
 }
 
-function buildProxyResponse(
-	message: DesktopOutboundHTTPMessage,
-	method: string,
-	permit: LocalAppProxyConcurrencyPermit,
-): Response {
+function buildProxyResponse(message: DesktopOutboundHTTPMessage, method: string): Response {
 	try {
 		const status = message.status;
 		if (status < MINIMUM_RESPONSE_STATUS || status > MAXIMUM_RESPONSE_STATUS) {
@@ -381,59 +261,20 @@ function buildProxyResponse(
 		const headers = responseHeaders(message.headers);
 		if (method === LOCAL_APP_PROXY_HEAD_METHOD || NULL_BODY_STATUSES.has(status)) {
 			message.message.resume();
-			permit.release();
 			return new Response(null, {status, statusText: message.statusText, headers});
 		}
 		const decoded = decodedMessageStream(message.message, contentEncoding(message.headers));
-		const body = holdPermitForResponseBody(Readable.toWeb(decoded) as ReadableStream<Uint8Array>, permit);
-		return new Response(body, {
+		return new Response(Readable.toWeb(decoded) as ReadableStream<Uint8Array>, {
 			status,
 			statusText: message.statusText,
 			headers,
 		});
 	} catch (error) {
 		message.message.destroy();
-		permit.release();
 		throw error;
 	}
 }
 
-function holdPermitForResponseBody(
-	body: ReadableStream<Uint8Array>,
-	permit: LocalAppProxyConcurrencyPermit,
-): ReadableStream<Uint8Array> {
-	const lease = new LocalAppProxyResponseBodyLease(body, permit);
-	return new ReadableStream<Uint8Array>({
-		async pull(controller) {
-			try {
-				const chunk = await lease.reader.read();
-				if (chunk.done) {
-					try {
-						controller.close();
-					} finally {
-						lease.release();
-					}
-					return;
-				}
-				controller.enqueue(chunk.value);
-			} catch (error) {
-				try {
-					controller.error(error);
-				} finally {
-					lease.release();
-				}
-			}
-		},
-		async cancel(reason) {
-			try {
-				await lease.reader.cancel(reason);
-			} finally {
-				lease.release();
-			}
-		},
-	});
-}
-
 function responseHeaders(incoming: http.IncomingHttpHeaders): Headers {
 	const headers = new Headers();
 	for (const [name, value] of Object.entries(incoming)) {

fluxer_desktop/src/main/LocalAppProxyConcurrency.test.mjs

@@ -2,7 +2,7 @@
 
 import assert from 'node:assert/strict';
 import {Buffer} from 'node:buffer';
-import {Readable} from 'node:stream';
+import {PassThrough, Readable} from 'node:stream';
 import {describe, mock, test} from 'node:test';
 import {installElectronStub} from './LocalAppTestSupport.test.mjs';
 
@@ -10,17 +10,9 @@ installElectronStub();
 
 const {DesktopLocalAppProxyClient, LocalAppProxyTraffic} = await import('./LocalAppProxyClient.ts');
 
-const PROXY_MAX_CONCURRENT_REQUESTS = 32;
-const PROXY_MAX_QUEUED_REQUESTS = 4096;
-const OUTBOUND_MAX_IN_FLIGHT_PER_SERVICE = 64;
 const RENDERED_AVATAR_COUNT = 120;
-
-class DesktopOutboundHTTPCapacityError extends Error {
-	constructor(limit) {
-		super(`Desktop outbound HTTP exceeded its ${limit} limit`);
-		this.name = 'DesktopOutboundHTTPCapacityError';
-	}
-}
+const PARKED_MEDIA_BODY_COUNT = 200;
+const RESOURCE_HEADERS_DEADLINE_MS = 30_000;
 
 function tick() {
 	return new Promise((resolve) => {
@@ -28,33 +20,6 @@ function tick() {
 	});
 }
 
-function createOutboundHTTP() {
-	const state = {inFlight: 0, peakInFlight: 0, started: 0, pending: []};
-	const outboundHTTP = {
-		request: (request) => {
-			if (state.inFlight >= OUTBOUND_MAX_IN_FLIGHT_PER_SERVICE) {
-				throw new DesktopOutboundHTTPCapacityError(`in-flight request for ${request.serviceName}`);
-			}
-			state.inFlight += 1;
-			state.started += 1;
-			state.peakInFlight = Math.max(state.peakInFlight, state.inFlight);
-			return new Promise((resolve) => {
-				state.pending.push(() => {
-					state.inFlight -= 1;
-					resolve({
-						headers: {'content-type': 'image/webp'},
-						message: Readable.from([Buffer.from('avatar-bytes')]),
-						status: 200,
-						statusText: 'OK',
-						url: new URL(request.url),
-					});
-				});
-			});
-		},
-	};
-	return {outboundHTTP, state};
-}
-
 function avatarRequest(index, signal) {
 	return {
 		targetURL: `https://media.fluxer.app/avatars/${index}.webp`,
@@ -68,131 +33,17 @@ function avatarRequest(index, signal) {
 	};
 }
 
-async function pump(state, work) {
-	let finished = false;
-	const result = work.finally(() => {
-		finished = true;
-	});
-	result.catch(() => {});
-	while (!finished) {
-		for (const settle of state.pending.splice(0)) {
-			settle();
-		}
-		await tick();
-	}
-	return await result;
-}
-
-function readAvatar(client, index, signal) {
-	return client.fetch(avatarRequest(index, signal)).then(async (response) => ({
-		status: response.status,
-		text: await response.text(),
-	}));
-}
-
-describe('the local app proxy bounds its own concurrency instead of overrunning outbound HTTP', () => {
-	test('every avatar of a fully rendered chat resolves rather than tripping the outbound capacity cap', async () => {
-		const {outboundHTTP, state} = createOutboundHTTP();
-		const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
-		const controller = new AbortController();
-
-		const fetches = [];
-		for (let index = 0; index < RENDERED_AVATAR_COUNT; index += 1) {
-			fetches.push(readAvatar(client, index, controller.signal));
-		}
-		const responses = await pump(state, Promise.all(fetches));
-
-		assert.equal(responses.length, RENDERED_AVATAR_COUNT);
-		assert.deepEqual(new Set(responses.map((response) => response.status)), new Set([200]));
-		assert.equal(state.started, RENDERED_AVATAR_COUNT);
-		assert.deepEqual(
-			responses.map((response) => response.text),
-			new Array(RENDERED_AVATAR_COUNT).fill('avatar-bytes'),
-		);
-	});
-
-	test('no more requests are in flight at any instant than the proxy concurrency limit', async () => {
-		const {outboundHTTP, state} = createOutboundHTTP();
-		const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
-		const controller = new AbortController();
-
-		const fetches = [];
-		for (let index = 0; index < RENDERED_AVATAR_COUNT; index += 1) {
-			fetches.push(readAvatar(client, index, controller.signal));
-		}
-		await tick();
-		const peakBeforeAnyCompletion = state.peakInFlight;
-		await pump(state, Promise.all(fetches));
-
-		assert.equal(peakBeforeAnyCompletion, PROXY_MAX_CONCURRENT_REQUESTS);
-		assert.equal(state.peakInFlight, PROXY_MAX_CONCURRENT_REQUESTS);
-	});
-
-	test('an aborted waiter rejects with the abort reason and leaves its queue slot to the next waiter', async () => {
-		const {outboundHTTP, state} = createOutboundHTTP();
-		const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
-		const held = new AbortController();
-
-		const holding = [];
-		for (let index = 0; index < PROXY_MAX_CONCURRENT_REQUESTS; index += 1) {
-			holding.push(readAvatar(client, index, held.signal));
-		}
-		await tick();
-		assert.equal(state.started, PROXY_MAX_CONCURRENT_REQUESTS);
-
-		const abandoned = new AbortController();
-		const abandonedFetch = client.fetch(avatarRequest(998, abandoned.signal));
-		const survivor = readAvatar(client, 999, held.signal);
-		const reason = new Error('the renderer navigated away');
-		abandoned.abort(reason);
-
-		await assert.rejects(abandonedFetch, (error) => error === reason);
-		assert.equal(state.started, PROXY_MAX_CONCURRENT_REQUESTS);
-
-		state.pending.shift()();
-		await tick();
-		await tick();
-		assert.equal(state.started, PROXY_MAX_CONCURRENT_REQUESTS + 1);
-
-		const settled = await pump(state, Promise.all([survivor, ...holding]));
-		assert.equal(settled[0].status, 200);
-		assert.equal(settled.length, PROXY_MAX_CONCURRENT_REQUESTS + 1);
-	});
-
-	test('the queue refuses a request past its bound rather than growing without limit', async () => {
-		const {outboundHTTP, state} = createOutboundHTTP();
-		const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
-		const controller = new AbortController();
-
-		const accepted = [];
-		for (let index = 0; index < PROXY_MAX_CONCURRENT_REQUESTS + PROXY_MAX_QUEUED_REQUESTS; index += 1) {
-			accepted.push(readAvatar(client, index, controller.signal));
-		}
-
-		await assert.rejects(
-			client.fetch(avatarRequest(Number.MAX_SAFE_INTEGER, controller.signal)),
-			(error) => error.name === 'LocalAppProxyQueueOverflowError',
-		);
-
-		const settled = await pump(state, Promise.all(accepted));
-		assert.equal(settled.length, PROXY_MAX_CONCURRENT_REQUESTS + PROXY_MAX_QUEUED_REQUESTS);
-	});
-});
-
-const RESOURCE_HEADERS_DEADLINE_MS = 30_000;
-
-function createSilentUpstream() {
+function createUpstream({streamBodies}) {
 	const state = {started: [], aborted: 0};
 	const outboundHTTP = {
 		request: (request) =>
 			new Promise((resolve, reject) => {
 				const entry = {
 					url: request.url,
-					serviceName: request.serviceName,
 					answer: () =>
 						resolve({
 							headers: {'content-type': 'image/webp'},
-							message: Readable.from([Buffer.from('avatar-bytes')]),
+							message: streamBodies ? new PassThrough() : Readable.from([Buffer.from('avatar-bytes')]),
 							status: 200,
 							statusText: 'OK',
 							url: new URL(request.url),
@@ -212,80 +63,64 @@ function createSilentUpstream() {
 	return {outboundHTTP, state};
 }
 
-function apiRequest(signal) {
-	return {...avatarRequest(0, signal), targetURL: 'https://api.fluxer.app/v1/users/@me'};
-}
+describe('the local app proxy never queues a request behind another', () => {
+	test('every avatar of a fully rendered chat starts at once', async () => {
+		const {outboundHTTP, state} = createUpstream({streamBodies: false});
+		const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
+		const renderer = new AbortController();
 
-describe('media that a slow or silent self-host never answers cannot wedge the local app proxy', () => {
-	test('avatars dropped while their upstream sends no headers free their permits at the headers deadline', async () => {
+		const fetches = [];
+		for (let index = 0; index < RENDERED_AVATAR_COUNT; index += 1) {
+			fetches.push(client.fetch(avatarRequest(index, renderer.signal)));
+		}
+		await tick();
+		assert.equal(state.started.length, RENDERED_AVATAR_COUNT);
+
+		for (const entry of state.started) {
+			entry.answer();
+		}
+		const texts = await Promise.all(fetches.map(async (fetch) => await (await fetch).text()));
+		assert.deepEqual(texts, new Array(RENDERED_AVATAR_COUNT).fill('avatar-bytes'));
+	});
+
+	test('a media request starts at once while earlier response bodies sit unread', async () => {
+		const {outboundHTTP, state} = createUpstream({streamBodies: true});
+		const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
+		const renderer = new AbortController();
+
+		for (let index = 0; index < PARKED_MEDIA_BODY_COUNT; index += 1) {
+			const fetch = client.fetch(avatarRequest(index, renderer.signal));
+			await tick();
+			state.started.at(-1).answer();
+			assert.equal((await fetch).status, 200);
+		}
+
+		const next = client.fetch(avatarRequest(PARKED_MEDIA_BODY_COUNT, renderer.signal));
+		await tick();
+		assert.equal(state.started.length, PARKED_MEDIA_BODY_COUNT + 1);
+		state.started.at(-1).answer();
+		assert.equal((await next).status, 200);
+		renderer.abort();
+	});
+});
+
+describe('media that a slow or silent self-host never answers is cut off', () => {
+	test('a silent upstream is aborted at the headers deadline', async () => {
 		mock.timers.enable({apis: ['setTimeout']});
 		try {
-			const {outboundHTTP, state} = createSilentUpstream();
+			const {outboundHTTP, state} = createUpstream({streamBodies: false});
 			const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
 			const renderer = new AbortController();
-			const dropped = [];
-			for (let index = 0; index < PROXY_MAX_CONCURRENT_REQUESTS; index += 1) {
-				const fetch = client.fetch(avatarRequest(index, renderer.signal));
-				fetch.catch(() => {});
-				dropped.push(fetch);
-			}
+			const silent = client.fetch(avatarRequest(0, renderer.signal));
+			silent.catch(() => {});
 			await tick();
-			const fresh = client.fetch(avatarRequest(1000, renderer.signal));
-			await tick();
-			assert.equal(state.started.length, PROXY_MAX_CONCURRENT_REQUESTS);
 
 			mock.timers.tick(RESOURCE_HEADERS_DEADLINE_MS);
-			await Promise.allSettled(dropped);
-			await tick();
 
-			assert.equal(state.aborted, PROXY_MAX_CONCURRENT_REQUESTS);
-			assert.equal(state.started.length, PROXY_MAX_CONCURRENT_REQUESTS + 1);
-			state.started.at(-1).answer();
-			const response = await fresh;
-			assert.equal(response.status, 200);
-			assert.equal(await response.text(), 'avatar-bytes');
+			await assert.rejects(silent, (error) => error.name === 'LocalAppProxyResponseHeadersDeadlineError');
+			assert.equal(state.aborted, 1);
 		} finally {
 			mock.timers.reset();
 		}
 	});
-
-	test('API requests keep flowing while every media permit is held by a silent upstream', async () => {
-		const {outboundHTTP, state} = createSilentUpstream();
-		const media = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
-		const api = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.API});
-		const renderer = new AbortController();
-		for (let index = 0; index < PROXY_MAX_CONCURRENT_REQUESTS * 2; index += 1) {
-			media.fetch(avatarRequest(index, renderer.signal)).catch(() => {});
-		}
-		await tick();
-		const apiCall = api.fetch(apiRequest(renderer.signal));
-		await tick();
-		const started = state.started.at(-1);
-		assert.equal(started.url, 'https://api.fluxer.app/v1/users/@me');
-		assert.equal(started.serviceName, LocalAppProxyTraffic.API);
-		started.answer();
-		assert.equal((await apiCall).status, 200);
-		renderer.abort();
-	});
-
-	test('the newest queued media request is admitted first so what is on screen loads before what scrolled away', async () => {
-		const {outboundHTTP, state} = createSilentUpstream();
-		const client = new DesktopLocalAppProxyClient({outboundHTTP, traffic: LocalAppProxyTraffic.REMOTE_RESOURCE});
-		const renderer = new AbortController();
-		const fetches = [];
-		for (let index = 0; index < PROXY_MAX_CONCURRENT_REQUESTS + 3; index += 1) {
-			const fetch = client.fetch(avatarRequest(index, renderer.signal));
-			fetch.catch(() => {});
-			fetches.push(fetch);
-		}
-		await tick();
-		state.started[0].answer();
-		await (await fetches[0]).text();
-		await tick();
-		assert.equal(
-			state.started.at(-1).url,
-			`https://media.fluxer.app/avatars/${PROXY_MAX_CONCURRENT_REQUESTS + 2}.webp`,
-		);
-		renderer.abort();
-	});
 });

fluxer_desktop/src/main/SelectedInstanceFetch.ts

@@ -15,7 +15,6 @@ const INSTANCE_RESPONSE_MAX_BYTES = 1024 * 1024;
 const INSTANCE_RESPONSE_MAX_CHUNKS = 1024;
 const INSTANCE_FETCH_TIMEOUT_MS = 15_000;
 
-const SELECTED_INSTANCE_SERVICE_NAME = 'desktop_selected_instance';
 const INSTANCE_RESPONSE_DESCRIPTION = 'Instance response';
 const RESET_CONTENT_STATUS = 205;
 
@@ -80,7 +79,6 @@ export class DesktopSelectedInstanceClient {
 			headers: request.headers ?? null,
 			method,
 			originTrust: DesktopOriginTrust.BOUND,
-			serviceName: SELECTED_INSTANCE_SERVICE_NAME,
 			signal: request.signal ?? null,
 			timeoutMs,
 			url: request.url,