Fastify Logging Integration

LogTide’s Fastify SDK provides a native plugin that hooks into Fastify’s lifecycle for automatic request logging, per-request scoping, and distributed tracing.

Why use LogTide with Fastify?

• Native plugin architecture: Follows Fastify plugin conventions
• Lifecycle hooks: Automatic instrumentation via onRequest, onResponse, onError
• Per-request scoping: Isolated context per request through decorators
• Auto-shutdown: Flushes logs on server close via onClose hook
• Zero overhead: Asynchronous batching keeps Fastify fast

Prerequisites

• Node.js 18+
• Fastify 4.x or 5.x
• LogTide instance with a DSN

Installation

npm install @logtide/fastify

Quick Start

import Fastify from 'fastify';
import { hub } from '@logtide/core';
import { logtide } from '@logtide/fastify';

const fastify = Fastify();

// Register the plugin (initializes LogTide automatically)
await fastify.register(logtide, {
  dsn: process.env.LOGTIDE_DSN,
  service: 'api-server',
  environment: process.env.NODE_ENV,
});

fastify.get('/users/:id', async (request) => {
  request.logtideScope.setTag('userId', request.params.id);

  hub.captureLog('info', 'Fetching user', {
    userId: request.params.id,
  });

  return { id: request.params.id };
});

await fastify.listen({ port: 3000 });

Plugin Options

await fastify.register(logtide, {
  dsn: process.env.LOGTIDE_DSN,
  service: 'api-server',
  environment: process.env.NODE_ENV,
  release: '1.0.0',
  tracesSampleRate: 1.0,
});

Request Scoping

Each request gets an isolated scope:

fastify.addHook('onRequest', async (request) => {
  request.logtideScope.setExtra('userId', request.user?.id);
  request.logtideScope.setTag('tenant', request.headers['x-tenant-id']);
});

Lifecycle Integration

The plugin hooks into Fastify’s lifecycle automatically:

Hook	Behavior
onRequest	Creates scope, extracts traceparent, starts span
onResponse	Logs completion with duration and status
onError	Captures errors with request context
onClose	Flushes pending events on shutdown

Error Handling

fastify.setErrorHandler((error, request, reply) => {
  // Error already captured by LogTide plugin
  reply.status(error.statusCode || 500).send({
    error: error.message,
    traceId: request.logtideTraceId,
  });
});

Next Steps

• JavaScript SDK - Core SDK reference
• Fastify SDK Reference - Full API documentation
• Docker Integration - Container deployments