Runtime Ops Basics

mkdir prod-api && cd prod-api
npm init -y
npm pkg set type=module
npm install express@5 pg
npm install -D typescript@5.6 @types/node

console.log(JSON.stringify({
  event: "boot",
  node: process.version,
  env: process.env.NODE_ENV,
  pid: process.pid,
}));

app.get("/health", (_req, res) => res.json({ status: "ok" }));
app.get("/ready", async (_req, res) => {
  const ok = await pool.query("SELECT 1");
  res.status(ok ? 200 : 503).json({ status: ok ? "ready" : "not_ready" });
});

process.on("uncaughtException", (err) => {
  console.error(JSON.stringify({ event: "uncaughtException", message: err.message, stack: err.stack }));
  // Policy A: exit and let supervisor restart (recommended for APIs)
  process.exit(1);
});

process.on("unhandledRejection", (reason) => {
  console.error(JSON.stringify({ event: "unhandledRejection", reason: String(reason) }));
  process.exit(1);
});

app.get("/metrics/memory", (_req, res) => {
  const m = process.memoryUsage();
  res.json({
    rss: m.rss,
    heapUsed: m.heapUsed,
    heapTotal: m.heapTotal,
    external: m.external,
  });
});

NODE_OPTIONS="--max-old-space-size=384"

const server = app.listen(port, "0.0.0.0");
 
function shutdown(signal: string) {
  console.log(JSON.stringify({ event: "shutdown", signal }));
  server.close(async () => {
    await pool.end();
    process.exit(0);
  });
  setTimeout(() => process.exit(1), 30_000).unref();
}
 
process.on("SIGTERM", () => shutdown("SIGTERM"));
process.on("SIGINT", () => shutdown("SIGINT"));

// ecosystem.config.cjs
module.exports = {
  apps: [{
    name: "api",
    script: "dist/main.js",
    instances: 2,
    exec_mode: "cluster",
    max_memory_restart: "512M",
    kill_timeout: 30_000,
    listen_timeout: 10_000,
  }],
};

pm2 start ecosystem.config.cjs
pm2 save