server: refactor meta caching

This removes the "caching" that re-fetches the instance meta information
from the database every 10 seconds.

packages/backend/src/misc/fetch-meta.ts

@@ -1,44 +1,44 @@
+import push from 'web-push';
 import { db } from '@/db/postgre.js';
 import { Meta } from '@/models/entities/meta.js';
+import { getFetchInstanceMetadataLock } from '@/misc/app-lock.js';
 
 let cache: Meta;
 
-export async function fetchMeta(noCache = false): Promise<Meta> {
-	if (!noCache && cache) return cache;
+/**
+ * Performs the primitive database operation to set the server configuration
+ */
+export async function setMeta(meta: Meta): Promise<void> {
+	const unlock = await getFetchInstanceMetadataLock('localhost');
 
-	return await db.transaction(async transactionalEntityManager => {
-		// 過去のバグでレコードが複数出来てしまっている可能性があるので新しいIDを優先する
-		const metas = await transactionalEntityManager.find(Meta, {
+	// try to mitigate older bugs where multiple meta entries may have been created
+	db.manager.clear(Meta);
+	db.manager.insert(Meta, meta);
+
+	unlock();
+}
+
+/**
+ * Performs the primitive database operation to fetch server configuration.
+ * Writes to `cache` instead of returning.
+ */
+async function getMeta(): Promise<void> {
+	const unlock = await getFetchInstanceMetadataLock('localhost');
+
+	// new IDs are prioritised because multiple records may have been created due to past bugs
+	cache = db.manager.findOne(Meta, {
 		order: {
 			id: 'DESC',
 		},
 	});
 
-		const meta = metas[0];
-
-		if (meta) {
-			cache = meta;
-			return meta;
-		} else {
-			// metaが空のときfetchMetaが同時に呼ばれるとここが同時に呼ばれてしまうことがあるのでフェイルセーフなupsertを使う
-			const saved = await transactionalEntityManager
-				.upsert(
-					Meta,
-					{
-						id: 'x',
-					},
-					['id'],
-				)
-				.then((x) => transactionalEntityManager.findOneByOrFail(Meta, x.identifiers[0]));
-
-			cache = saved;
-			return saved;
-		}
-	});
+	unlock();
 }
 
-setInterval(() => {
-	fetchMeta(true).then(meta => {
-		cache = meta;
-	});
-}, 1000 * 10);
+export async function fetchMeta(noCache = false): Promise<Meta> {
+	if (!noCache && cache) return cache;
+
+	await getMeta();
+
+	return cache;
+}

packages/backend/src/server/api/endpoints/admin/update-meta.ts

@@ -1,6 +1,5 @@
-import { Meta } from '@/models/entities/meta.js';
 import { insertModerationLog } from '@/services/insert-moderation-log.js';
-import { db } from '@/db/postgre.js';
+import { fetchMeta, setMeta } from '@/misc/fetch-meta.js';
 import define from '../../define.js';
 
 export const meta = {
@@ -375,20 +374,10 @@ export default define(meta, paramDef, async (ps, me) => {
 		set.deeplIsPro = ps.deeplIsPro;
 	}
 
-	await db.transaction(async transactionalEntityManager => {
-		const metas = await transactionalEntityManager.find(Meta, {
-			order: {
-				id: 'DESC',
-			},
-		});
-
-		const meta = metas[0];
-
-		if (meta) {
-			await transactionalEntityManager.update(Meta, meta.id, set);
-		} else {
-			await transactionalEntityManager.save(Meta, set);
-		}
+	const meta = await fetchMeta();
+	await setMeta({
+		...meta,
+		...set,
 	});
 
 	insertModerationLog(me, 'updateMeta');