fix(connect): serialize nginx reload requests

api/src/unraid-api/nginx/nginx.service.spec.ts

@@ -0,0 +1,36 @@
+import { execa } from 'execa';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { NginxService } from '@app/unraid-api/nginx/nginx.service.js';
+
+vi.mock('execa', () => ({
+    execa: vi.fn(),
+}));
+
+describe('NginxService', () => {
+    const mockExeca = vi.mocked(execa);
+
+    beforeEach(() => {
+        vi.clearAllMocks();
+    });
+
+    it('coalesces concurrent reload requests', async () => {
+        const firstService = new NginxService();
+        const secondService = new NginxService();
+
+        const results = await Promise.all([firstService.reload(), secondService.reload()]);
+
+        expect(results).toEqual([true, true]);
+        expect(mockExeca).toHaveBeenCalledTimes(1);
+        expect(mockExeca).toHaveBeenCalledWith('/etc/rc.d/rc.nginx', ['reload']);
+    });
+
+    it('allows a new reload after the previous one completes', async () => {
+        const service = new NginxService();
+
+        await service.reload();
+        await service.reload();
+
+        expect(mockExeca).toHaveBeenCalledTimes(2);
+    });
+});

api/src/unraid-api/nginx/nginx.service.ts

@@ -2,12 +2,30 @@ import { Injectable, Logger } from '@nestjs/common';
 
 import { execa } from 'execa';
 
+let activeReload: Promise<boolean> | undefined;
+
 @Injectable()
 export class NginxService {
     private readonly logger = new Logger(NginxService.name);
 
     /** reloads nginx via its rc script */
-    async reload() {
+    async reload(): Promise<boolean> {
+        if (activeReload) {
+            this.logger.debug('Nginx reload already in progress; waiting for it to complete');
+            return activeReload;
+        }
+
+        const reload = this.executeReload();
+        activeReload = reload;
+
+        try {
+            return await reload;
+        } finally {
+            activeReload = undefined;
+        }
+    }
+
+    private async executeReload(): Promise<boolean> {
         try {
             await execa('/etc/rc.d/rc.nginx', ['reload']);
             this.logger.log('Nginx reloaded');