logger

Produces structured request/response log entries with method, URL, client IP, request ID, status code, and duration. Sensitive headers are automatically redacted. Place first in the pipeline so every subsequent middleware has a request ID available.

Pipeline stage: Negotiation (first middleware)

Import

import {logger} from '@centralping/ergo';

Options

Option	Type	Default	Description
log	function	console.log	Log function for completed requests
error	function	console.error	Log function for errors
uuid	function	crypto.randomUUID	Fallback UUID generator
headerRequestIdName	string	'x-request-id'	Request ID header name. Normalized to lowercase at construction for req.headers lookup (Node lowercases incoming header keys). Non-string values throw TypeError.
headerRequestIpName	string	'x-real-ip'	Client IP header name. Normalized to lowercase at construction (same rationale as headerRequestIdName). Non-string values throw TypeError.
redactErrors	boolean	true	When true, error log entries use generic HTTP status text instead of err.message, and suppress stack and originalError. Set to false in development for full error details. Independent of handler()’s redactErrors option (which controls HTTP response bodies).
redactHeaders	Set<string>	See below	Headers replaced with '[REDACTED]'

Default Redacted Headers

authorization, proxy-authorization, cookie, set-cookie

Request ID Resolution Order

1. res.getHeader(headerRequestIdName) — set by ergo-router’s transport
2. req.headers[headerRequestIdName] — set by upstream proxy
3. uuid() — generated as fallback

Return Value

Returns a log entry stored on the domain accumulator at acc.log:

{
  requestId: '550e8400-e29b-41d4-a716-446655440000',
  timestamp: 1717041600000,
  ip: '127.0.0.1',
  method: 'GET',
  url: '/users',
  httpVersion: '1.1',
  host: {hostname, arch, platform, pid},
  request: {headers, encrypted, remoteAddress, remotePort}
}

On response finish, the log callback adds statusCode, duration, and response: {headers, statusMessage, writableFinished}.

Error Responses

None. Logger is observability-only.

Usage

Standalone

import {compose, logger} from '@centralping/ergo';

const pipeline = compose(
  logger({
    log: (info) => structuredLog.info(info),
    error: (info) => structuredLog.error(info),
  }),
);

ergo-router

const router = createRouter({
  defaults: {
    logger: {
      log: (info) => structuredLog.info(info),
    },
  },
});

RFC References

• RFC 9110 — HTTP Semantics

Related Recipes

• Structured Logging — Integrating pino or winston with the log callback and graceful() lifecycle logger

API Reference

See the auto-generated logger API docs.