Node.js Error Monitoring

Your server crashed.
Process exited: code 1.
100% of requests failed.

Node.js doesn't crash gracefully — it crashes completely. Every endpoint, every user, gone. DeepTracer catches unhandled exceptions and promise rejections before your server goes dark, investigates the root cause with AI, and tells you the fix.

Start monitoring free See how it works

Production server — 3:47am

What happened on your server

$ node server.js

Server listening on port 3000

[req] GET /api/users → 200 8ms

[req] GET /api/dashboard → 200 14ms

[req] POST /api/orders → 200 31ms

UnhandledPromiseRejection: TypeError

Cannot read properties of undefined

(reading 'price')

at processOrder (/app/orders.js:47)

at async handler (/app/routes/api.js:23)

✗ Process exited with code 1 All requests failing · Server unreachable · 3:47:22am

DeepTracer — already on it

Server crash detected — orders.js:47

Process exited · 3:47am · Investigation started automatically

AI Investigation TypeError: Cannot read 'price'

Root Cause

processOrder() in orders.js:47 calls order.items.reduce() without checking if order.items exists. A POST /api/orders request with a malformed body (items: null) triggered the crash.

Suggested Fix

Add a null check before reduce() Validate order.items at the handler level, not inside the reducer. Return a 400 response for malformed requests instead of letting them crash the process.

Express & Fastify

Next.js API routes

Background workers

Free tier — 5 lines of code

Node.js in production

3 ways Node.js kills
your server silently

React crashes one component. Node.js crashes everything — every route, every user, every request in flight. And it usually happens at 3am.

async function processOrder(orderId) {

const order = await db.find(orderId)

// 💀 order could be null — nobody checks

return order.items.map(i => i.price)

}

// No try/catch. Rejection floats up... nowhere.

UnhandledPromiseRejection — TypeError: Cannot read properties of null (reading 'map'). No handler caught this. Node.js terminates the process.

01 / 03

The async trap

async/await looks safe but any unhandled rejection crashes the process. One missing try/catch — or a null from the database — and your server is gone.

Heap usage over time 1.5 GB limit

7pm

256 MB

9pm

560 MB

11pm

950 MB

1am

1.28 GB

3am

1.5 GB

OOM KILLED — process terminated by OS. Server gone.

02 / 03

Memory leak → OOM kill

Unbounded caches, event listeners never removed, closures holding references — heap grows for hours until the OS kills your process. No warning. No stack trace. Just gone.

cors()

↓

rateLimit()

↓

auth()

↓

parseBody()

✗

router()

↓

response

All routes dead. One middleware throws synchronously — Express can't recover, process exits.

03 / 03

Uncaught throw in middleware

A synchronous throw anywhere in your Express middleware chain kills the entire process. Every active request, every endpoint, every user — all cut off instantly.

Setup in 5 minutes

Three steps.
Your server is protected.

No agents to install, no YAML config, no infrastructure changes. Just npm install and 5 lines of code.

Init at the top of your entry file

Must be first — before any imports — so it catches everything.

server.js

// ← first line of your entry file

import DeepTracer from '@deeptracer/node'

DeepTracer.init({

apiKey: process.env.DEEPTRACER_KEY,

environment: 'production',

})

// now import the rest of your app

import './app.js'

$ npm i @deeptracer/node

Automatically catches:

unhandledRejection uncaughtException SIGTERM

Add the error middleware

One line at the end of your Express app catches every thrown error.

app.js

import express from 'express'

import { errorHandler } from '@deeptracer/node'

const app = express()

// ... your routes ...

// ← add this after all routes

app.use(errorHandler())

Also works with:

Fastify Hono Next.js API Workers

Your agent starts watching

DeepTracer monitors your process 24/7 — errors, memory, uptime.

Agent active — production ↑ 4d 12h

GET /api/users 200 8ms

Heap 312 MB / 1.5 GB healthy

UnhandledRejection — orders.js:47

AI investigation started automatically

Root cause found · fix ready

"Add a null check before calling .map() — order.items was undefined from a malformed POST body."

Pricing

Node.js monitoring
that's actually free.

No credit card. No 14-day trial. No "free" plan that emails you to upgrade every day. A real free tier that covers most side projects — forever.

Free

Reactive Mode

$0 / month

Forever free. No card required.

Start free — no card

Unlike Sentry, our free tier catches unhandled rejections and uncaught exceptions with AI root cause — not just error counts.

1 Node.js project

25,000 events / month

Unhandled rejection capture

Uncaught exception capture

3 AI investigations / month

10 AI chat messages / month

1-day log retention

24/7 ambient monitoring

Slack / email alerts

Common questions

Does it work with Express, Fastify, Hono, and other Node.js frameworks?

Yes. The DeepTracer.init() call hooks into Node.js process events directly — it's framework-agnostic. The optional errorHandler() middleware is Express-compatible (Fastify, Hono, and Koa have their own one-line integrations). If you're running background workers or CLI scripts with no HTTP framework, init() alone is enough.

What if the process crashes before the error data is sent?

DeepTracer flushes synchronously on uncaughtException and unhandledRejection before the process exits — so error data is captured even if the server goes down immediately after. The SDK uses a fast, synchronous HTTP write for crash events specifically to handle this. Memory OOM kills are the exception — in that case, we capture the trend data leading up to the kill, so you can see the leak in the timeline.

Does it catch errors in async functions that don't have try/catch?

Yes — that's the whole point. Node.js emits an unhandledRejection event for any promise that rejects without a .catch() or try/catch. DeepTracer listens to this event at the process level, captures the full stack trace with context, and starts an AI investigation. You don't need to wrap every async function — we catch what falls through.

How does this compare to Sentry for Node.js?

Sentry captures errors and groups them by fingerprint — then it's up to you to investigate. DeepTracer goes further: it captures the error, runs an AI investigation to find the root cause, and tells you the fix. It also monitors LLM usage (OpenAI, Anthropic), memory trends, and process health — things Sentry doesn't touch. And it's $19/mo vs Sentry's $26/mo, with a real free tier that doesn't require a credit card.

Will it slow down my Node.js server?

No measurable impact. The SDK is event-driven — it only runs when something happens (a request, an error, a metric tick). Normal request handling is zero-touch. Error capture and reporting happens asynchronously off the critical path, except for crash events which use a fast synchronous flush. The SDK adds under 50ms of startup time to your process.

Will DeepTracer capture sensitive data from my error traces?

DeepTracer captures stack traces, error messages, request metadata (method, route, status code), and environment context. It does not capture request bodies or response bodies by default — you control what gets sent. We automatically scrub common patterns like authorization headers, passwords, and tokens from captured data. You can add custom scrub rules in your project settings.

Free tier — no card required

Your next unhandled rejection
is already written.

Somewhere in your codebase, there's an async function without a try/catch. A null from the database that nobody checks. A memory leak that's been growing since Tuesday. DeepTracer catches it before your users do.

Start monitoring free

Get started in 30 seconds ~5 min setup

$ npm i @deeptracer/node

import DeepTracer from '@deeptracer/node'

DeepTracer.init({ apiKey: process.env.DEEPTRACER_KEY })

// That's it. Your server is now watched.

Next.js monitoring · React monitoring · vs Sentry · vs Datadog

Your server crashed. Process exited: code 1. 100% of requests failed.

3 ways Node.js killsyour server silently

Three steps.Your server is protected.

Node.js monitoringthat's actually free.