fix(backend): memory leak in memory caches (#14363)

* encapsulate `MemoryKVCache<T>`

* remove infinity caches

* encapsulate other caches

* add missing awaits to internally synchronize caches

* implement pull-through caching

* tune cache lifetimes

* optimize cache GC by stopping early

* summarize changes in CHANGELOG.md

* Fix timeout comments

Co-authored-by: かっこかり <67428053+kakkokari-gtyih@users.noreply.github.com>

* add comments about awaiting the redis write

---------

Co-authored-by: かっこかり <67428053+kakkokari-gtyih@users.noreply.github.com>

7 files changed, 19 insertions, 21 deletions

diff --git a/packages/backend/src/core/AvatarDecorationService.ts b/packages/backend/src/core/AvatarDecorationService.ts
index 8b54bbe012..4efd6122b1 100644
--- a/packages/backend/src/core/AvatarDecorationService.ts
+++ b/packages/backend/src/core/AvatarDecorationService.ts
@@ -29,7 +29,7 @@ export class AvatarDecorationService implements OnApplicationShutdown {
 		private moderationLogService: ModerationLogService,
 		private globalEventService: GlobalEventService,
 	) {
-		this.cache = new MemorySingleCache<MiAvatarDecoration[]>(1000 * 60 * 30);
+		this.cache = new MemorySingleCache<MiAvatarDecoration[]>(1000 * 60 * 30); // 30s
 
 		this.redisForSub.on('message', this.onMessage);
 	}
diff --git a/packages/backend/src/core/CacheService.ts b/packages/backend/src/core/CacheService.ts
index d008e7ec52..6725ebe75b 100644
--- a/packages/backend/src/core/CacheService.ts
+++ b/packages/backend/src/core/CacheService.ts
@@ -56,10 +56,10 @@ export class CacheService implements OnApplicationShutdown {
 	) {
 		//this.onMessage = this.onMessage.bind(this);
 
-		this.userByIdCache = new MemoryKVCache<MiUser>(Infinity);
-		this.localUserByNativeTokenCache = new MemoryKVCache<MiLocalUser | null>(Infinity);
-		this.localUserByIdCache = new MemoryKVCache<MiLocalUser>(Infinity);
-		this.uriPersonCache = new MemoryKVCache<MiUser | null>(Infinity);
+		this.userByIdCache = new MemoryKVCache<MiUser>(1000 * 60 * 5); // 5m
+		this.localUserByNativeTokenCache = new MemoryKVCache<MiLocalUser | null>(1000 * 60 * 5); // 5m
+		this.localUserByIdCache = new MemoryKVCache<MiLocalUser>(1000 * 60 * 5); // 5m
+		this.uriPersonCache = new MemoryKVCache<MiUser | null>(1000 * 60 * 5); // 5m
 
 		this.userProfileCache = new RedisKVCache<MiUserProfile>(this.redisClient, 'userProfile', {
 			lifetime: 1000 * 60 * 30, // 30m
@@ -135,14 +135,14 @@ export class CacheService implements OnApplicationShutdown {
 					if (user == null) {
 						this.userByIdCache.delete(body.id);
 						this.localUserByIdCache.delete(body.id);
-						for (const [k, v] of this.uriPersonCache.cache.entries()) {
+						for (const [k, v] of this.uriPersonCache.entries) {
 							if (v.value?.id === body.id) {
 								this.uriPersonCache.delete(k);
 							}
 						}
 					} else {
 						this.userByIdCache.set(user.id, user);
-						for (const [k, v] of this.uriPersonCache.cache.entries()) {
+						for (const [k, v] of this.uriPersonCache.entries) {
 							if (v.value?.id === user.id) {
 								this.uriPersonCache.set(k, user);
 							}
diff --git a/packages/backend/src/core/CustomEmojiService.ts b/packages/backend/src/core/CustomEmojiService.ts
index 7e11b9cdca..5db3c5b980 100644
--- a/packages/backend/src/core/CustomEmojiService.ts
+++ b/packages/backend/src/core/CustomEmojiService.ts
@@ -24,7 +24,7 @@ const parseEmojiStrRegexp = /^([-\w]+)(?:@([\w.-]+))?$/;
 
 @Injectable()
 export class CustomEmojiService implements OnApplicationShutdown {
-	private cache: MemoryKVCache<MiEmoji | null>;
+	private emojisCache: MemoryKVCache<MiEmoji | null>;
 	public localEmojisCache: RedisSingleCache<Map<string, MiEmoji>>;
 
 	constructor(
@@ -40,7 +40,7 @@ export class CustomEmojiService implements OnApplicationShutdown {
 		private moderationLogService: ModerationLogService,
 		private globalEventService: GlobalEventService,
 	) {
-		this.cache = new MemoryKVCache<MiEmoji | null>(1000 * 60 * 60 * 12);
+		this.emojisCache = new MemoryKVCache<MiEmoji | null>(1000 * 60 * 60 * 12); // 12h
 
 		this.localEmojisCache = new RedisSingleCache<Map<string, MiEmoji>>(this.redisClient, 'localEmojis', {
 			lifetime: 1000 * 60 * 30, // 30m
@@ -334,7 +334,7 @@ export class CustomEmojiService implements OnApplicationShutdown {
 			host,
 		})) ?? null;
 
-		const emoji = await this.cache.fetch(`${name} ${host}`, queryOrNull);
+		const emoji = await this.emojisCache.fetch(`${name} ${host}`, queryOrNull);
 
 		if (emoji == null) return null;
 		return emoji.publicUrl || emoji.originalUrl; // || emoji.originalUrl してるのは後方互換性のため（publicUrlはstringなので??はだめ）
@@ -361,7 +361,7 @@ export class CustomEmojiService implements OnApplicationShutdown {
 	 */
 	@bindThis
 	public async prefetchEmojis(emojis: { name: string; host: string | null; }[]): Promise<void> {
-		const notCachedEmojis = emojis.filter(emoji => this.cache.get(`${emoji.name} ${emoji.host}`) == null);
+		const notCachedEmojis = emojis.filter(emoji => this.emojisCache.get(`${emoji.name} ${emoji.host}`) == null);
 		const emojisQuery: any[] = [];
 		const hosts = new Set(notCachedEmojis.map(e => e.host));
 		for (const host of hosts) {
@@ -376,7 +376,7 @@ export class CustomEmojiService implements OnApplicationShutdown {
 			select: ['name', 'host', 'originalUrl', 'publicUrl'],
 		}) : [];
 		for (const emoji of _emojis) {
-			this.cache.set(`${emoji.name} ${emoji.host}`, emoji);
+			this.emojisCache.set(`${emoji.name} ${emoji.host}`, emoji);
 		}
 	}
 
@@ -401,7 +401,7 @@ export class CustomEmojiService implements OnApplicationShutdown {
 
 	@bindThis
 	public dispose(): void {
-		this.cache.dispose();
+		this.emojisCache.dispose();
 	}
 
 	@bindThis
diff --git a/packages/backend/src/core/RelayService.ts b/packages/backend/src/core/RelayService.ts
index 8dd3d64f5b..db32114346 100644
--- a/packages/backend/src/core/RelayService.ts
+++ b/packages/backend/src/core/RelayService.ts
@@ -35,7 +35,7 @@ export class RelayService {
 		private createSystemUserService: CreateSystemUserService,
 		private apRendererService: ApRendererService,
 	) {
-		this.relaysCache = new MemorySingleCache<MiRelay[]>(1000 * 60 * 10);
+		this.relaysCache = new MemorySingleCache<MiRelay[]>(1000 * 60 * 10); // 10m
 	}
 
 	@bindThis
diff --git a/packages/backend/src/core/RoleService.ts b/packages/backend/src/core/RoleService.ts
index 7966774673..0210012a03 100644
--- a/packages/backend/src/core/RoleService.ts
+++ b/packages/backend/src/core/RoleService.ts
@@ -127,10 +127,8 @@ export class RoleService implements OnApplicationShutdown, OnModuleInit {
 		private moderationLogService: ModerationLogService,
 		private fanoutTimelineService: FanoutTimelineService,
 	) {
-		//this.onMessage = this.onMessage.bind(this);
-
-		this.rolesCache = new MemorySingleCache<MiRole[]>(1000 * 60 * 60 * 1);
-		this.roleAssignmentByUserIdCache = new MemoryKVCache<MiRoleAssignment[]>(1000 * 60 * 60 * 1);
+		this.rolesCache = new MemorySingleCache<MiRole[]>(1000 * 60 * 60); // 1h
+		this.roleAssignmentByUserIdCache = new MemoryKVCache<MiRoleAssignment[]>(1000 * 60 * 5); // 5m
 
 		this.redisForSub.on('message', this.onMessage);
 	}
diff --git a/packages/backend/src/core/UserKeypairService.ts b/packages/backend/src/core/UserKeypairService.ts
index 51ac99179a..92d61cd103 100644
--- a/packages/backend/src/core/UserKeypairService.ts
+++ b/packages/backend/src/core/UserKeypairService.ts
@@ -25,7 +25,7 @@ export class UserKeypairService implements OnApplicationShutdown {
 	) {
 		this.cache = new RedisKVCache<MiUserKeypair>(this.redisClient, 'userKeypair', {
 			lifetime: 1000 * 60 * 60 * 24, // 24h
-			memoryCacheLifetime: Infinity,
+			memoryCacheLifetime: 1000 * 60 * 60, // 1h
 			fetcher: (key) => this.userKeypairsRepository.findOneByOrFail({ userId: key }),
 			toRedisConverter: (value) => JSON.stringify(value),
 			fromRedisConverter: (value) => JSON.parse(value),
diff --git a/packages/backend/src/core/activitypub/ApDbResolverService.ts b/packages/backend/src/core/activitypub/ApDbResolverService.ts
index f6b70ead44..4192e8659a 100644
--- a/packages/backend/src/core/activitypub/ApDbResolverService.ts
+++ b/packages/backend/src/core/activitypub/ApDbResolverService.ts
@@ -54,8 +54,8 @@ export class ApDbResolverService implements OnApplicationShutdown {
 		private cacheService: CacheService,
 		private apPersonService: ApPersonService,
 	) {
-		this.publicKeyCache = new MemoryKVCache<MiUserPublickey | null>(Infinity);
-		this.publicKeyByUserIdCache = new MemoryKVCache<MiUserPublickey | null>(Infinity);
+		this.publicKeyCache = new MemoryKVCache<MiUserPublickey | null>(1000 * 60 * 60 * 12); // 12h
+		this.publicKeyByUserIdCache = new MemoryKVCache<MiUserPublickey | null>(1000 * 60 * 60 * 12); // 12h
 	}
 
 	@bindThis