Sentry

Application monitoring that automatically captures errors, performance issues, and user context from every layer of your stack. Sentry gives you full stack traces, breadcrumbs, session replay, and release-level regression tracking — so you spend less time reproducing bugs and more time fixing them.

What is Sentry?

Sentry is an open-source error monitoring and performance observability platform. Its SDK runs inside your application and automatically intercepts unhandled exceptions, Promise rejections, and crashed processes — capturing the full stack trace, request context, user info, and a trail of breadcrumbs showing what the user did before the error occurred.

Beyond errors, Sentry's performance module wraps your HTTP handlers, database queries, and async operations as spans, assembling them into distributed traces. You can find which endpoint is slow, which database query runs 500 times per request, and how a deployment correlated with a latency spike.

Key Features

• Error grouping — intelligent deduplication groups related stack traces, preventing notification floods
• Breadcrumbs — automatic trail of console logs, network requests, and navigation events leading up to the error
• Session Replay — DOM-mutation replay of user interactions at the moment an error occurred
• Performance tracing — distributed traces across frontend, API, and database layers
• Release tracking — tag errors with deployment releases; see exactly which release introduced a regression
• Source maps — automatically unminifies JavaScript stack traces for readable line-level context
• Alerts — configurable alert rules (error rate, new issue, regression) routing to Slack, PagerDuty, or email
• 100+ integrations — GitHub, GitLab, Jira, Slack, PagerDuty, AWS, Vercel, and more

SDK Initialization

// Sentry SDK initialization (Next.js / React)
import * as Sentry from '@sentry/nextjs';

Sentry.init({
  dsn: 'https://@o.ingest.sentry.io/',
  environment: process.env.NODE_ENV,
  release: process.env.NEXT_PUBLIC_VERCEL_GIT_COMMIT_SHA,
  tracesSampleRate: 1.0,      // 100% in dev; use 0.1–0.2 in prod
  profilesSampleRate: 1.0,    // Profiling (requires tracing enabled)
  replaysSessionSampleRate: 0.1,
  replaysOnErrorSampleRate: 1.0, // Always capture replays on error
  integrations: [
    Sentry.replayIntegration(),
    Sentry.browserTracingIntegration(),
  ],
});

Manual Capture & Context

// Manual error capture with context
try {
  await processOrder(orderId);
} catch (err) {
  Sentry.withScope((scope) => {
    scope.setTag('flow', 'checkout');
    scope.setUser({ id: user.id, email: user.email });
    scope.setExtra('orderId', orderId);
    scope.setLevel('error');
    Sentry.captureException(err);
  });
  throw err;
}

// Breadcrumbs for context trail
Sentry.addBreadcrumb({
  category: 'ui.click',
  message: 'User clicked checkout',
  level: 'info',
});

// Performance transaction
const transaction = Sentry.startTransaction({ name: 'process-payment' });
const span = transaction.startChild({ op: 'stripe.charge' });
await stripe.charges.create(chargeData);
span.finish();
transaction.finish();

SDK Installation (Common Platforms)

# Next.js
npx @sentry/wizard@latest -i nextjs

# Node.js / Express
npm install @sentry/node @sentry/profiling-node

# React
npm install @sentry/react

# Python (Django / FastAPI)
pip install sentry-sdk[fastapi]

# Go
go get github.com/getsentry/sentry-go

Sampling Strategy