diff --git a/packages/hydrooj/src/handler/judge.ts b/packages/hydrooj/src/handler/judge.ts
index 8fb44b3b8..6a5d35858 100644
--- a/packages/hydrooj/src/handler/judge.ts
+++ b/packages/hydrooj/src/handler/judge.ts
@@ -18,7 +18,7 @@ import task from '../model/task';
 import * as bus from '../service/bus';
 import { updateJudge } from '../service/monitor';
 import {
-    ConnectionHandler, Handler, post, Types,
+    ConnectionHandler, Handler, post, subscribe, Types,
 } from '../service/server';
 import { sleep } from '../utils';
 
@@ -180,15 +180,14 @@ class JudgeConnectionHandler extends ConnectionHandler {
 
     async prepare() {
         logger.info('Judge daemon connected from ', this.request.ip);
-        this.send({ language: setting.langs });
-        this.sendLanguageConfig = this.sendLanguageConfig.bind(this);
-        bus.on('system/setting', this.sendLanguageConfig);
+        this.sendLanguageConfig();
         // Ensure language sent
         await sleep(100);
         this.newTask();
     }
 
-    async sendLanguageConfig() {
+    @subscribe('system/setting')
+    sendLanguageConfig() {
         this.send({ language: setting.langs });
     }
 
@@ -226,7 +225,6 @@ class JudgeConnectionHandler extends ConnectionHandler {
 
     async cleanup() {
         logger.info('Judge daemon disconnected from ', this.request.ip);
-        bus.off('system/setting', this.sendLanguageConfig);
         if (this.processing) {
             await record.reset(this.processing.domainId, this.processing.rid, false);
             await task.add(this.processing);
diff --git a/packages/hydrooj/src/handler/manage.ts b/packages/hydrooj/src/handler/manage.ts
index 646bec10b..007a38983 100644
--- a/packages/hydrooj/src/handler/manage.ts
+++ b/packages/hydrooj/src/handler/manage.ts
@@ -14,7 +14,6 @@ import record from '../model/record';
 import * as setting from '../model/setting';
 import * as system from '../model/system';
 import user from '../model/user';
-import * as bus from '../service/bus';
 import {
     ConnectionHandler, Handler, param, requireSudo, Types,
 } from '../service/server';
@@ -176,7 +175,7 @@ class SystemSettingHandler extends SystemHandler {
             }
         }
         await Promise.all(tasks);
-        await bus.broadcast('system/setting', args);
+        this.ctx.broadcast('system/setting', args);
         this.back();
     }
 }
@@ -309,7 +308,7 @@ class SystemUserPrivHandler extends SystemHandler {
             const defaultPriv = system.get('default.priv');
             await user.coll.updateMany({ priv: defaultPriv }, { $set: { priv } });
             await system.set('default.priv', priv);
-            bus.broadcast('user/delcache', true);
+            this.ctx.broadcast('user/delcache', true);
         }
         this.back();
     }
diff --git a/packages/hydrooj/src/handler/record.ts b/packages/hydrooj/src/handler/record.ts
index 7440bf0c8..1c83334a3 100644
--- a/packages/hydrooj/src/handler/record.ts
+++ b/packages/hydrooj/src/handler/record.ts
@@ -15,8 +15,9 @@ import storage from '../model/storage';
 import * as system from '../model/system';
 import TaskModel from '../model/task';
 import user from '../model/user';
-import * as bus from '../service/bus';
-import { ConnectionHandler, param, Types } from '../service/server';
+import {
+    ConnectionHandler, param, subscribe, Types,
+} from '../service/server';
 import { buildProjection } from '../utils';
 import { ContestDetailBaseHandler } from './contest';
 import { postJudge } from './judge';
@@ -197,7 +198,7 @@ class RecordDetailHandler extends ContestDetailBaseHandler {
         const priority = await record.submissionPriority(this.user._id, -20);
         const isContest = this.rdoc.contest && this.rdoc.contest.toString() !== '000000000000000000000000';
         const rdoc = await record.reset(domainId, rid, true);
-        bus.broadcast('record/change', rdoc);
+        this.ctx.broadcast('record/change', rdoc);
         await record.judge(domainId, rid, priority, isContest ? { detail: false } : {});
         this.back();
     }
@@ -226,7 +227,6 @@ class RecordDetailHandler extends ContestDetailBaseHandler {
 }
 
 class RecordMainConnectionHandler extends ConnectionHandler {
-    cleanup: bus.Disposable = () => { };
     all = false;
     tid: string;
     uid: number;
@@ -273,7 +273,6 @@ class RecordMainConnectionHandler extends ConnectionHandler {
             this.checkPriv(PRIV.PRIV_MANAGE_ALL_DOMAIN);
             this.all = true;
         }
-        this.cleanup = bus.on('record/change', this.onRecordChange.bind(this));
     }
 
     async message(msg: { rids: string[] }) {
@@ -283,6 +282,7 @@ class RecordMainConnectionHandler extends ConnectionHandler {
         for (const rdoc of rdocs) this.onRecordChange(rdoc);
     }
 
+    @subscribe('record/change')
     async onRecordChange(rdoc: RecordDoc) {
         if (!this.all) {
             if (rdoc.domainId !== this.args.domainId) return;
@@ -318,7 +318,6 @@ class RecordMainConnectionHandler extends ConnectionHandler {
 }
 
 class RecordDetailConnectionHandler extends ConnectionHandler {
-    cleanup: bus.Disposable = () => { };
     pdoc: ProblemDoc;
     rid: string = '';
     disconnectTimeout: NodeJS.Timeout;
@@ -356,7 +355,6 @@ class RecordDetailConnectionHandler extends ConnectionHandler {
         this.pdoc = pdoc;
         this.throttleSend = throttle(this.sendUpdate, 1000, { trailing: true });
         this.rid = rid.toString();
-        this.cleanup = bus.on('record/change', this.onRecordChange.bind(this));
         this.onRecordChange(rdoc);
     }
 
@@ -367,6 +365,7 @@ class RecordDetailConnectionHandler extends ConnectionHandler {
         });
     }
 
+    @subscribe('record/change')
     // eslint-disable-next-line
     async onRecordChange(rdoc: RecordDoc, $set?: any, $push?: any) {
         if (rdoc._id.toString() !== this.rid) return;
diff --git a/packages/hydrooj/src/handler/training.ts b/packages/hydrooj/src/handler/training.ts
index b3c589d7d..c6553c0af 100644
--- a/packages/hydrooj/src/handler/training.ts
+++ b/packages/hydrooj/src/handler/training.ts
@@ -15,7 +15,6 @@ import storage from '../model/storage';
 import * as system from '../model/system';
 import * as training from '../model/training';
 import user from '../model/user';
-import * as bus from '../service/bus';
 import {
     Handler, param, post, Types,
 } from '../service/server';
@@ -64,7 +63,7 @@ class TrainingMainHandler extends Handler {
     @param('page', Types.PositiveInt, true)
     async get(domainId: string, page = 1) {
         const query: FilterQuery<TrainingDoc> = {};
-        await bus.parallel('training/list', query, this);
+        await this.ctx.parallel('training/list', query, this);
         const [tdocs, tpcount] = await paginate(
             training.getMulti(domainId),
             page,
@@ -102,7 +101,7 @@ class TrainingDetailHandler extends Handler {
     @param('uid', Types.PositiveInt, true)
     async get(domainId: string, tid: ObjectID, uid: number) {
         const tdoc = await training.get(domainId, tid);
-        await bus.parallel('training/get', tdoc, this);
+        await this.ctx.parallel('training/get', tdoc, this);
         let targetUser = this.user._id;
         let enrollUsers: number[] = [];
         let shouldCompare = false;
diff --git a/packages/hydrooj/src/service/decorators.ts b/packages/hydrooj/src/service/decorators.ts
index ff163e60b..ba8fb62db 100644
--- a/packages/hydrooj/src/service/decorators.ts
+++ b/packages/hydrooj/src/service/decorators.ts
@@ -4,7 +4,8 @@ import { Converter, Type, Validator } from '../lib/validator';
 import { EventMap } from './bus';
 import type { Handler } from './server';
 
-type MethodDecorator = (target: any, name: string, obj: any) => any;
+type MethodDecorator = (target: any, funcName: string, obj: any) => any;
+type ClassDecorator = <T extends new (...args: any[]) => any>(Class: T) => T extends new (...args: infer R) => infer S ? (...args: R) => S : never;
 export interface ParamOption<T> {
     name: string,
     source: 'all' | 'get' | 'post' | 'route',
@@ -82,10 +83,17 @@ export const post: DescriptorBuilder = (name, ...args) => _descriptor(_buildPara
 export const route: DescriptorBuilder = (name, ...args) => _descriptor(_buildParam(name, 'route', ...args));
 export const param: DescriptorBuilder = (name, ...args) => _descriptor(_buildParam(name, 'all', ...args));
 
-export const subscribe: (name: keyof EventMap) => MethodDecorator = (name) => (target, funcName, obj) => {
-    target.__subscribe ||= [];
-    target.__subscribe.push({ name, target: obj.value });
-    return obj;
+export const subscribe: (name: keyof EventMap) => MethodDecorator | ClassDecorator = (name) => (target, funcName, obj) => {
+    if (funcName) {
+        target.__subscribe ||= [];
+        target.__subscribe.push({ name, target: obj.value });
+        return obj;
+    }
+    return (...args) => {
+        const c = new target(...args); // eslint-disable-line new-cap
+        c.__subscribe = [{ name, target: c.send }];
+        return c;
+    };
 };
 
 export function requireSudo(target: any, funcName: string, obj: any) {