perf: batch gateway submits and isolate callbacks

api/src/submit-outbox-worker.ts

@@ -0,0 +1,30 @@
+import 'reflect-metadata';
+import { NestFactory } from '@nestjs/core';
+import { createServer } from 'node:http';
+import { MetricsService } from './metrics/metrics.service';
+import { SendWorkerModule } from './send-worker.module';
+
+async function bootstrap() {
+  if (process.env.CMPP_PROCESS_ROLE !== 'outbox') {
+    throw new Error('submit-outbox-worker requires CMPP_PROCESS_ROLE=outbox');
+  }
+  const app = await NestFactory.createApplicationContext(SendWorkerModule);
+  app.enableShutdownHooks();
+  const metrics = app.get(MetricsService);
+  const host = process.env.API_OUTBOX_METRICS_HOST?.trim() || '127.0.0.1';
+  const port = Number(process.env.API_OUTBOX_METRICS_PORT ?? 9467);
+  const server = createServer((request, response) => {
+    if (request.method !== 'GET' || request.url !== '/metrics') {
+      response.writeHead(404).end();
+      return;
+    }
+    response.writeHead(200, { 'Content-Type': 'text/plain; version=0.0.4; charset=utf-8', 'Cache-Control': 'no-store' });
+    response.end(metrics.render());
+  });
+  await new Promise<void>((resolve, reject) => {
+    server.once('error', reject);
+    server.listen(port, host, resolve);
+  });
+}
+
+void bootstrap();