diff --git a/packages/hydrooj/src/context.ts b/packages/hydrooj/src/context.ts
index 1c8a5faff..4c7346456 100644
--- a/packages/hydrooj/src/context.ts
+++ b/packages/hydrooj/src/context.ts
@@ -61,7 +61,9 @@ export class ApiMixin extends Service {
     setImmediate = T(setImmediate, clearImmediate);
     provideModule = T(provideModule);
     injectUI = T(inject);
-    broadcast = (event: keyof EventMap, ...payload) => this.ctx.emit('bus/broadcast', event, payload);
+    broadcast = (event: keyof EventMap, ...payload) =>
+        this.ctx.emit('bus/broadcast', event, payload, process.env.TRACE_BROADCAST ? new Error().stack : null);
+
     constructor(ctx) {
         super(ctx, '$api', true);
         ctx.mixin('$api', ['addScript', 'setImmediate', 'provideModule', 'injectUI', 'broadcast']);
diff --git a/packages/hydrooj/src/interface.ts b/packages/hydrooj/src/interface.ts
index 9be64681e..354c1da9e 100644
--- a/packages/hydrooj/src/interface.ts
+++ b/packages/hydrooj/src/interface.ts
@@ -639,6 +639,7 @@ export interface EventDoc {
     event: number | string;
     payload: string;
     expire: Date;
+    trace?: string;
 }
 
 export interface OpCountDoc {
diff --git a/packages/hydrooj/src/model/task.ts b/packages/hydrooj/src/model/task.ts
index e9bb19404..57831b991 100644
--- a/packages/hydrooj/src/model/task.ts
+++ b/packages/hydrooj/src/model/task.ts
@@ -144,12 +144,13 @@ const id = process.env.exec_mode === 'cluster_mode' ? hostname() : nanoid();
 
 export async function apply(ctx: Context) {
     ctx.on('domain/delete', (domainId) => coll.deleteMany({ domainId }));
-    ctx.on('bus/broadcast', (event, payload) => {
+    ctx.on('bus/broadcast', (event, payload, trace) => {
         collEvent.insertOne({
             ack: [id],
             event,
             payload: BSON.EJSON.stringify(payload),
             expire: new Date(Date.now() + 10000),
+            trace,
         });
     });
 
diff --git a/packages/hydrooj/src/service/bus.ts b/packages/hydrooj/src/service/bus.ts
index feeac7790..2b34f728d 100644
--- a/packages/hydrooj/src/service/bus.ts
+++ b/packages/hydrooj/src/service/bus.ts
@@ -38,7 +38,7 @@ export interface EventMap extends KnownHandlerEvents {
     'database/config': () => VoidReturn
 
     'system/setting': (args: Record<string, any>) => VoidReturn
-    'bus/broadcast': (event: keyof EventMap | keyof ServerEvents, payload: any) => VoidReturn
+    'bus/broadcast': (event: keyof EventMap | keyof ServerEvents, payload: any, trace?: string) => VoidReturn
     'monitor/update': (type: 'server' | 'judge', $set: any) => VoidReturn
     'monitor/collect': (info: any) => VoidReturn
     'api/update': () => void;