enhance(backend): summalyの結果をキャッシュするように

packages/backend/src/misc/cache.ts

@@ -204,14 +204,12 @@ export class RedisSingleCache<T> {
 	}
 }
 
-// TODO: メモリ節約のためあまり参照されないキーを定期的に削除できるようにする？
-
 export class MemoryKVCache<T> {
-	private readonly cache = new Map<string, { date: number; value: T; }>();
+	protected readonly cache = new Map<string, { date: number; value: T; }>();
 	private readonly gcIntervalHandle = setInterval(() => this.gc(), 1000 * 60 * 3); // 3m
 
 	constructor(
-		private readonly lifetime: number,
+		protected readonly lifetime: number,
 	) {}
 
 	@bindThis
@@ -318,6 +316,34 @@ export class MemoryKVCache<T> {
 	}
 }
 
+export class MemoryLRUKVCache<T> extends MemoryKVCache<T> {
+	constructor(
+		lifetime: number,
+		private readonly limit: number,
+	) {
+		if (limit <= 0) {
+			throw new Error('Limit must be greater than 0');
+		}
+
+		super(lifetime);
+	}
+
+	@bindThis
+	public set(key: string, value: T): void {
+		while (this.cache.size >= this.limit) {
+			// 古い順から削除していく
+			const oldestKey = this.cache.keys().next().value;
+			if (oldestKey == null) {
+				throw new Error('Cache is empty but size exceeds the limit');
+			}
+			this.cache.delete(oldestKey);
+		}
+		// 挿入順を更新するために一度削除してから再挿入する
+		this.cache.delete(key);
+		super.set(key, value);
+	}
+}
+
 export class MemorySingleCache<T> {
 	private cachedAt: number | null = null;
 	private value: T | undefined;

packages/backend/src/server/web/UrlPreviewService.ts

@@ -3,22 +3,24 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import { Inject, Injectable } from '@nestjs/common';
+import { Inject, Injectable, OnApplicationShutdown } from '@nestjs/common';
 import type { SummalyResult } from '@misskey-dev/summaly';
 import { DI } from '@/di-symbols.js';
 import type { Config } from '@/config.js';
 import { HttpRequestService } from '@/core/HttpRequestService.js';
 import type Logger from '@/logger.js';
 import { query } from '@/misc/prelude/url.js';
+import { MemoryLRUKVCache } from '@/misc/cache.js';
 import { LoggerService } from '@/core/LoggerService.js';
 import { bindThis } from '@/decorators.js';
 import { ApiError } from '@/server/api/error.js';
 import { MiMeta } from '@/models/Meta.js';
 import type { FastifyRequest, FastifyReply } from 'fastify';
 
 @Injectable()
-export class UrlPreviewService {
+export class UrlPreviewService implements OnApplicationShutdown {
 	private logger: Logger;
+	private summaryCache: MemoryLRUKVCache<SummalyResult>;
 
 	constructor(
 		@Inject(DI.config)
@@ -31,6 +33,7 @@ export class UrlPreviewService {
 		private loggerService: LoggerService,
 	) {
 		this.logger = this.loggerService.getLogger('url-preview');
+		this.summaryCache = new MemoryLRUKVCache<SummalyResult>(1000 * 60 * 60, 100); // 1h, 100件
 	}
 
 	@bindThis
@@ -76,22 +79,29 @@ export class UrlPreviewService {
 			: `Getting preview of ${url}@${lang} ...`);
 
 		try {
-			const summary = this.meta.urlPreviewSummaryProxyUrl
-				? await this.fetchSummaryFromProxy(url, this.meta, lang)
-				: await this.fetchSummary(url, this.meta, lang);
-
-			this.logger.succ(`Got preview of ${url}: ${summary.title}`);
-
-			if (!(summary.url.startsWith('http://') || summary.url.startsWith('https://'))) {
-				throw new Error('unsupported schema included');
+			const summary = await this.summaryCache.fetchMaybe(
+				`${url}@${lang ?? '_DEFAULT_'}`,
+				async () => {
+					const result = await (this.meta.urlPreviewSummaryProxyUrl ? this.fetchSummaryFromProxy(url, lang) : this.fetchSummary(url, lang));
+					if (!result.url.startsWith('http://') && !result.url.startsWith('https://')) {
+						return undefined;
+					}
+					if (result.player.url && !result.player.url.startsWith('http://') && !result.player.url.startsWith('https://')) {
+						return undefined;
+					}
+
+					result.icon = this.wrap(result.icon);
+					result.thumbnail = this.wrap(result.thumbnail);
+
+					return result;
+				},
+			);
+
+			if (summary == null) {
+				throw new Error('Invalid summary');
 			}
 
-			if (summary.player.url && !(summary.player.url.startsWith('http://') || summary.player.url.startsWith('https://'))) {
-				throw new Error('unsupported schema included');
-			}
-
-			summary.icon = this.wrap(summary.icon);
-			summary.thumbnail = this.wrap(summary.thumbnail);
+			this.logger.succ(`Got preview of ${url}: ${summary.title}`);
 
 			// Cache 1day
 			reply.header('Cache-Control', 'max-age=86400, immutable');
@@ -112,7 +122,7 @@ export class UrlPreviewService {
 		}
 	}
 
-	private async fetchSummary(url: string, meta: MiMeta, lang?: string): Promise<SummalyResult> {
+	private async fetchSummary(url: string, lang?: string): Promise<SummalyResult> {
 		const agent = this.config.proxy
 			? {
 				http: this.httpRequestService.httpAgent,
@@ -126,25 +136,35 @@ export class UrlPreviewService {
 			followRedirects: this.meta.urlPreviewAllowRedirect,
 			lang: lang ?? 'ja-JP',
 			agent: agent,
-			userAgent: meta.urlPreviewUserAgent ?? undefined,
-			operationTimeout: meta.urlPreviewTimeout,
-			contentLengthLimit: meta.urlPreviewMaximumContentLength,
-			contentLengthRequired: meta.urlPreviewRequireContentLength,
+			userAgent: this.meta.urlPreviewUserAgent ?? undefined,
+			operationTimeout: this.meta.urlPreviewTimeout,
+			contentLengthLimit: this.meta.urlPreviewMaximumContentLength,
+			contentLengthRequired: this.meta.urlPreviewRequireContentLength,
 		});
 	}
 
-	private fetchSummaryFromProxy(url: string, meta: MiMeta, lang?: string): Promise<SummalyResult> {
-		const proxy = meta.urlPreviewSummaryProxyUrl!;
+	private fetchSummaryFromProxy(url: string, lang?: string): Promise<SummalyResult> {
+		const proxy = this.meta.urlPreviewSummaryProxyUrl!;
 		const queryStr = query({
 			url: url,
 			lang: lang ?? 'ja-JP',
 			followRedirects: this.meta.urlPreviewAllowRedirect,
-			userAgent: meta.urlPreviewUserAgent ?? undefined,
-			operationTimeout: meta.urlPreviewTimeout,
-			contentLengthLimit: meta.urlPreviewMaximumContentLength,
-			contentLengthRequired: meta.urlPreviewRequireContentLength,
+			userAgent: this.meta.urlPreviewUserAgent ?? undefined,
+			operationTimeout: this.meta.urlPreviewTimeout,
+			contentLengthLimit: this.meta.urlPreviewMaximumContentLength,
+			contentLengthRequired: this.meta.urlPreviewRequireContentLength,
 		});
 
 		return this.httpRequestService.getJson<SummalyResult>(`${proxy}?${queryStr}`, 'application/json, */*', undefined, true);
 	}
+
+	@bindThis
+	public dispose(): void {
+		this.summaryCache.dispose();
+	}
+
+	@bindThis
+	public onApplicationShutdown(): void {
+		this.dispose();
+	}
 }