emit-io-next

Next.js bindings for emit-io-core — middleware logging and App Router route handler instrumentation.

Install

npm install emit-io-core emit-io-next

Quick Start

// lib/emit.ts
import { EmitIoStrategy, JSONTransport, LogLevelEnum } from 'emit-io-core'

export const emit = new EmitIoStrategy({
  transports: [new JSONTransport({ minLevel: LogLevelEnum.INFO })],
})

// middleware.ts
import { withLogger } from 'emit-io-next'
import { NextResponse } from 'next/server'
import { emit } from './lib/emit'

export default withLogger(
  async (req) => NextResponse.next(),
  { logger: emit, trackPageviews: true }
)

export const config = { matcher: ['/((?!_next|favicon).*)'] }

// app/api/orders/route.ts
import { instrumentRoute } from 'emit-io-next'
import { emit } from './lib/emit'

export const GET = instrumentRoute(
  async (req) => Response.json({ orders: [] }),
  { logger: emit, eventName: 'get-orders' }
)

API

withLogger(handler, options)

Wraps a Next.js middleware function. Adds:

• requestId from x-request-id header (or generates a UUID)
• ALS context with { requestId, path } for the duration of the request
• Auto-logs request start, completion, and errors via emit.info / emit.error
• Propagates x-request-id header in the response
• Optional pageview analytics event on GET requests

import { withLogger } from 'emit-io-next'
import type { MiddlewareOptions } from 'emit-io-next'

const options: MiddlewareOptions = {
  logger: emit,
  extractRequestId: (req) => req.headers.get('x-trace-id') ?? undefined,
  trackPageviews: true,   // default: true
}

export default withLogger(myHandler, options)

instrumentRoute(handler, options)

Wraps an App Router route handler (GET, POST, etc.). Adds:

• requestId + ALS context with { requestId, path, method }
• Logs completion with status and durationMs
• Catches errors and logs them before re-throwing

import { instrumentRoute } from 'emit-io-next'
import type { RouteHandlerOptions } from 'emit-io-next'

export const POST = instrumentRoute(
  async (req, ctx) => {
    const { id } = await ctx.params
    return Response.json({ id })
  },
  { logger: emit, eventName: 'create-order' }
)

ALS Context in Route Handlers

Both withLogger and instrumentRoute use runWithContext internally. Any log calls made within the handler automatically include requestId and other bound fields without manual threading.

// Inside a route wrapped with instrumentRoute:
emit.info('processing order', { orderId: '123' })
// → { msg: 'processing order', context: { requestId: 'uuid', path: '/api/orders', method: 'POST', orderId: '123' } }

Peer Dependencies

| Package | Version | |---|---| | emit-io-core | ^1.0.0 | | next | ^14.0.0 \|\| ^15.0.0 |

License

MIT