perf(backend): use mutex for nsfw model loading (#11109)

Co-authored-by: tamaina <tamaina@hotmail.co.jp>

1 files changed, 9 insertions, 1 deletions

diff --git a/packages/backend/src/core/AiService.ts b/packages/backend/src/core/AiService.ts
index 02501b832b..c0596446dd 100644
--- a/packages/backend/src/core/AiService.ts
+++ b/packages/backend/src/core/AiService.ts
@@ -4,6 +4,7 @@ import { dirname } from 'node:path';
 import { Inject, Injectable } from '@nestjs/common';
 import * as nsfw from 'nsfwjs';
 import si from 'systeminformation';
+import { Mutex } from 'async-mutex';
 import type { Config } from '@/config.js';
 import { DI } from '@/di-symbols.js';
 import { bindThis } from '@/decorators.js';
@@ -17,6 +18,7 @@ let isSupportedCpu: undefined | boolean = undefined;
 @Injectable()
 export class AiService {
 	private model: nsfw.NSFWJS;
+	private modelLoadMutex: Mutex = new Mutex();
 
 	constructor(
 		@Inject(DI.config)
@@ -39,7 +41,13 @@ export class AiService {
 
 			const tf = await import('@tensorflow/tfjs-node');
 
-			if (this.model == null) this.model = await nsfw.load(`file://${_dirname}/../../nsfw-model/`, { size: 299 });
+			if (this.model == null) {
+				await this.modelLoadMutex.runExclusive(async () => {
+					if (this.model == null) {
+						this.model = await nsfw.load(`file://${_dirname}/../../nsfw-model/`, { size: 299 });
+					}
+				});
+			}
 
 			const buffer = await fs.promises.readFile(path);
 			const image = await tf.node.decodeImage(buffer, 3) as any;