Refine fanout timeline (#12507)

* chore(endpoints/hybrid-timeline): don't pack inside getFromDb

* chore(endpoints/hybrid-timeline): Redisから取得する部分のうちSTLに依存しなそうなところを別のServiceに切り出し

* chore(endpoints/local-timeline): FanoutTimelineEndpointServiceで再実装

* chore(endpoints/channels/timeline): FanoutTimelineEndpointServiceで再実装

* chore(endpoints/timeline): FanoutTimelineEndpointServiceで再実装

* chore(endpoints/user-list-timeline): FanoutTimelineEndpointServiceで再実装

* chore(endpoints/users/notes): FanoutTimelineEndpointServiceで再実装

* chore: add useDbFallback to FanoutTimelineEndpointService.timeline and always true for channel / user note list

* style: fix lint error

* chore: split logic to multiple functions

* chore: implement redis fallback

* chore: 成功率を上げる

* fix: db fallback not working

* feat: allowPartial

* chore(frontend): set allowPartial

* chore(backend): remove fallbackIfEmpty

HTL will never be purged so it's no longer required

* fix: missing allowPartial in channel timeline

* fix: type of timelineConfig in hybrid-timeline

---------

Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>

2 files changed, 129 insertions, 0 deletions

diff --git a/packages/backend/src/core/CoreModule.ts b/packages/backend/src/core/CoreModule.ts
index bf6f0ef879..bc6d24b951 100644
--- a/packages/backend/src/core/CoreModule.ts
+++ b/packages/backend/src/core/CoreModule.ts
@@ -4,6 +4,7 @@
  */
 
 import { Module } from '@nestjs/common';
+import { FanoutTimelineEndpointService } from '@/core/FanoutTimelineEndpointService.js';
 import { AccountMoveService } from './AccountMoveService.js';
 import { AccountUpdateService } from './AccountUpdateService.js';
 import { AiService } from './AiService.js';
@@ -195,6 +196,7 @@ const $SearchService: Provider = { provide: 'SearchService', useExisting: Search
 const $ClipService: Provider = { provide: 'ClipService', useExisting: ClipService };
 const $FeaturedService: Provider = { provide: 'FeaturedService', useExisting: FeaturedService };
 const $FanoutTimelineService: Provider = { provide: 'FanoutTimelineService', useExisting: FanoutTimelineService };
+const $FanoutTimelineEndpointService: Provider = { provide: 'FanoutTimelineEndpointService', useExisting: FanoutTimelineEndpointService };
 const $ChannelFollowingService: Provider = { provide: 'ChannelFollowingService', useExisting: ChannelFollowingService };
 const $RegistryApiService: Provider = { provide: 'RegistryApiService', useExisting: RegistryApiService };
 
@@ -331,6 +333,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		ClipService,
 		FeaturedService,
 		FanoutTimelineService,
+		FanoutTimelineEndpointService,
 		ChannelFollowingService,
 		RegistryApiService,
 		ChartLoggerService,
@@ -460,6 +463,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$ClipService,
 		$FeaturedService,
 		$FanoutTimelineService,
+		$FanoutTimelineEndpointService,
 		$ChannelFollowingService,
 		$RegistryApiService,
 		$ChartLoggerService,
@@ -590,6 +594,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		ClipService,
 		FeaturedService,
 		FanoutTimelineService,
+		FanoutTimelineEndpointService,
 		ChannelFollowingService,
 		RegistryApiService,
 		FederationChart,
@@ -718,6 +723,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$ClipService,
 		$FeaturedService,
 		$FanoutTimelineService,
+		$FanoutTimelineEndpointService,
 		$ChannelFollowingService,
 		$RegistryApiService,
 		$FederationChart,
diff --git a/packages/backend/src/core/FanoutTimelineEndpointService.ts b/packages/backend/src/core/FanoutTimelineEndpointService.ts
new file mode 100644
index 0000000000..157fcbe877
--- /dev/null
+++ b/packages/backend/src/core/FanoutTimelineEndpointService.ts
@@ -0,0 +1,123 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { DI } from '@/di-symbols.js';
+import { bindThis } from '@/decorators.js';
+import type { MiUser } from '@/models/User.js';
+import type { MiNote } from '@/models/Note.js';
+import { Packed } from '@/misc/json-schema.js';
+import type { NotesRepository } from '@/models/_.js';
+import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
+import { FanoutTimelineService } from '@/core/FanoutTimelineService.js';
+
+@Injectable()
+export class FanoutTimelineEndpointService {
+	constructor(
+		@Inject(DI.notesRepository)
+		private notesRepository: NotesRepository,
+
+		private noteEntityService: NoteEntityService,
+		private fanoutTimelineService: FanoutTimelineService,
+	) {
+	}
+
+	@bindThis
+	async timeline(ps: {
+		untilId: string | null,
+		sinceId: string | null,
+		limit: number,
+		allowPartial: boolean,
+		me?: { id: MiUser['id'] } | undefined | null,
+		useDbFallback: boolean,
+		redisTimelines: string[],
+		noteFilter: (note: MiNote) => boolean,
+		dbFallback: (untilId: string | null, sinceId: string | null, limit: number) => Promise<MiNote[]>,
+	}): Promise<Packed<'Note'>[]> {
+		return await this.noteEntityService.packMany(await this.getMiNotes(ps), ps.me);
+	}
+
+	@bindThis
+	private async getMiNotes(ps: {
+		untilId: string | null,
+		sinceId: string | null,
+		limit: number,
+		allowPartial: boolean,
+		me?: { id: MiUser['id'] } | undefined | null,
+		useDbFallback: boolean,
+		redisTimelines: string[],
+		noteFilter: (note: MiNote) => boolean,
+		dbFallback: (untilId: string | null, sinceId: string | null, limit: number) => Promise<MiNote[]>,
+	}): Promise<MiNote[]> {
+		let noteIds: string[];
+		let shouldFallbackToDb = false;
+
+		// 呼び出し元と以下の処理をシンプルにするためにdbFallbackを置き換える
+		if (!ps.useDbFallback) ps.dbFallback = () => Promise.resolve([]);
+
+		const redisResult = await this.fanoutTimelineService.getMulti(ps.redisTimelines, ps.untilId, ps.sinceId);
+
+		const redisResultIds = Array.from(new Set(redisResult.flat(1)));
+
+		redisResultIds.sort((a, b) => a > b ? -1 : 1);
+		noteIds = redisResultIds.slice(0, ps.limit);
+
+		shouldFallbackToDb = shouldFallbackToDb || (noteIds.length === 0);
+
+		if (!shouldFallbackToDb) {
+			const redisTimeline: MiNote[] = [];
+			let readFromRedis = 0;
+			let lastSuccessfulRate = 1; // rateをキャッシュする？
+			let trialCount = 1;
+
+			while ((redisResultIds.length - readFromRedis) !== 0) {
+				const remainingToRead = ps.limit - redisTimeline.length;
+
+				// DBからの取り直しを減らす初回と同じ割合以上で成功すると仮定するが、クエリの長さを考えて三倍まで
+				const countToGet = remainingToRead * Math.ceil(Math.min(1.1 / lastSuccessfulRate, 3));
+				noteIds = redisResultIds.slice(readFromRedis, readFromRedis + countToGet);
+
+				readFromRedis += noteIds.length;
+
+				const gotFromDb = await this.getAndFilterFromDb(noteIds, ps.noteFilter);
+				redisTimeline.push(...gotFromDb);
+				lastSuccessfulRate = gotFromDb.length / noteIds.length;
+
+				console.log(`fanoutTimelineTrial#${trialCount++}: req: ${ps.limit}, tried: ${noteIds.length}, got: ${gotFromDb.length}, rate: ${lastSuccessfulRate}, total: ${redisTimeline.length}, fromRedis: ${redisResultIds.length}`);
+
+				if (ps.allowPartial ? redisTimeline.length !== 0 : redisTimeline.length >= ps.limit) {
+					// 十分Redisからとれた
+					return redisTimeline.slice(0, ps.limit);
+				}
+			}
+
+			// まだ足りない分はDBにフォールバック
+			const remainingToRead = ps.limit - redisTimeline.length;
+			const gotFromDb = await ps.dbFallback(noteIds[noteIds.length - 1], ps.sinceId, remainingToRead);
+			redisTimeline.push(...gotFromDb);
+			console.log(`fanoutTimelineTrial#db: req: ${ps.limit}, tried: ${remainingToRead}, got: ${gotFromDb.length}, since: ${noteIds[noteIds.length - 1]}, until: ${ps.untilId}, total: ${redisTimeline.length}`);
+			return redisTimeline;
+		}
+
+		return await ps.dbFallback(ps.untilId, ps.sinceId, ps.limit);
+	}
+
+	private async getAndFilterFromDb(noteIds: string[], noteFilter: (note: MiNote) => boolean): Promise<MiNote[]> {
+		const query = this.notesRepository.createQueryBuilder('note')
+			.where('note.id IN (:...noteIds)', { noteIds: noteIds })
+			.innerJoinAndSelect('note.user', 'user')
+			.leftJoinAndSelect('note.reply', 'reply')
+			.leftJoinAndSelect('note.renote', 'renote')
+			.leftJoinAndSelect('reply.user', 'replyUser')
+			.leftJoinAndSelect('renote.user', 'renoteUser')
+			.leftJoinAndSelect('note.channel', 'channel');
+
+		const notes = (await query.getMany()).filter(noteFilter);
+
+		notes.sort((a, b) => a.id > b.id ? -1 : 1);
+
+		return notes;
+	}
+}