From 94b95573419086e81452f06c9ec019fae80bb5b6 Mon Sep 17 00:00:00 2001
From: orebams <florencerasaq1@gmail.com>
Date: Sat, 26 Sep 2026 22:20:53 +0100
Subject: [PATCH] fix: configure status event listener limit

---
 .env.example                                  |  3 ++
 .../events/status-events.service.spec.ts      | 29 +++++++++++++++++++
 src/common/events/status-events.service.ts    | 12 ++++++--
 3 files changed, 41 insertions(+), 3 deletions(-)
 create mode 100644 src/common/events/status-events.service.spec.ts

diff --git a/.env.example b/.env.example
index 728ad0a..d2e8633 100644
--- a/.env.example
+++ b/.env.example
@@ -120,6 +120,9 @@ AVIATIONSTACK_API_KEY=    # optional — leave blank to use mock data
 # Port the API server listens on
 PORT=3001
 
+# Maximum listeners per policy status event emitter. Default: 1000.
+# STATUS_EVENTS_MAX_LISTENERS=1000
+
 # Environment: "development", "staging", or "production"
 NODE_ENV="development"
 
diff --git a/src/common/events/status-events.service.spec.ts b/src/common/events/status-events.service.spec.ts
new file mode 100644
index 0000000..7a3a1b1
--- /dev/null
+++ b/src/common/events/status-events.service.spec.ts
@@ -0,0 +1,29 @@
+import { StatusEventsService } from './status-events.service';
+import { ConfigService } from '@nestjs/config';
+import { EventEmitter } from 'events';
+
+describe('StatusEventsService', () => {
+  function build(configuredMaxListeners?: string) {
+    const config = {
+      get: jest.fn((key: string) => key === 'STATUS_EVENTS_MAX_LISTENERS' ? configuredMaxListeners : undefined),
+    };
+    const service = new StatusEventsService(undefined, undefined, config as unknown as ConfigService);
+
+    return { service, config };
+  }
+
+  it('uses the configured maximum listener count', () => {
+    const { service } = build('250');
+
+    expect((service as unknown as { emitter: EventEmitter }).emitter.getMaxListeners()).toBe(250);
+  });
+
+  it.each([undefined, '', '0', '-1', '1.5', 'not-a-number'])(
+    'uses the default maximum listener count for invalid configuration (%s)',
+    (configuredMaxListeners) => {
+      const { service } = build(configuredMaxListeners);
+
+      expect((service as unknown as { emitter: EventEmitter }).emitter.getMaxListeners()).toBe(1000);
+    },
+  );
+});
\ No newline at end of file
diff --git a/src/common/events/status-events.service.ts b/src/common/events/status-events.service.ts
index d53df00..4485871 100644
--- a/src/common/events/status-events.service.ts
+++ b/src/common/events/status-events.service.ts
@@ -9,6 +9,7 @@ import {
 } from '@nestjs/common';
 import { EventEmitter } from 'events';
 import * as crypto from 'crypto';
+import { ConfigService } from '@nestjs/config';
 import type Redis from 'ioredis';
 import { PrismaService } from '../../prisma/prisma.service';
 
@@ -19,6 +20,7 @@ export interface PolicyStatusEvent {
 }
 
 const STATUS_EVENTS_CHANNEL = 'policy:status:events';
+const DEFAULT_MAX_LISTENERS = 1000;
 
 /**
  * StatusEventsService — pub/sub for policy status changes (#349).
@@ -42,10 +44,14 @@ export class StatusEventsService implements OnModuleInit, OnModuleDestroy {
     private readonly redis?: Redis,
     @Optional()
     private readonly prisma?: PrismaService,
+    @Optional()
+    private readonly config?: ConfigService,
   ) {
-    // Default is 10 — a popular policy with many open SSE connections
-    // shouldn't trigger Node's "possible memory leak" warning.
-    this.emitter.setMaxListeners(1000);
+    const configuredMaxListeners = Number(this.config?.get<string>('STATUS_EVENTS_MAX_LISTENERS'));
+    const maxListeners = Number.isSafeInteger(configuredMaxListeners) && configuredMaxListeners > 0
+      ? configuredMaxListeners
+      : DEFAULT_MAX_LISTENERS;
+    this.emitter.setMaxListeners(maxListeners);
   }
 
   setPolicyOwner(policyId: string, owner: string): void {