data-for-logs

Structured HTTP request/response snapshots for server logging and observability.
Works with raw Node http, Express, and NestJS (Express adapter).

Captures everything useful from a request and its response — URL, query, params,
headers, body, IP, timing, status — with automatic redaction of secrets.

Installation

npm install data-for-logs

What you get in every log payload

{
  "timestamp": "2026-04-02T12:00:00.000Z",
  "event": "finish",
  "durationMs": 12.4,
  "request": {
    "method": "POST",
    "url": "/auth/login",
    "originalUrl": "/auth/login",
    "path": "/auth/login",
    "route": "/auth/login",
    "query": {},
    "params": {},
    "headers": {
      "content-type": "application/json",
      "authorization": "[REDACTED]"
    },
    "body": {
      "email": "[email protected]",
      "password": "[REDACTED]"
    },
    "ip": "203.0.113.10",
    "remoteAddress": "::ffff:127.0.0.1",
    "requestId": "x-request-id value (or correlation-id / traceparent)",
    "userAgent": "...",
    "contentType": "application/json"
  },
  "response": {
    "statusCode": 201,
    "statusMessage": "Created",
    "headers": { "content-type": "application/json" },
    "headersSent": true,
    "finished": true
  }
}

Usage in NestJS

1. Create the middleware file

// src/http-log.middleware.ts
import { Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';
import { createMiddleware } from 'data-for-logs';

const logMiddleware = createMiddleware(
  (_err, payload) => {
    console.log(JSON.stringify(payload)); // replace with your logger / Kafka producer
  },
  {
    includeBody: true,
    highResTime: () => performance.now(),
    redactBodyKeys: ['pin', 'otp', 'card_number'], // merged with built-in list
  },
);

@Injectable()
export class HttpLogMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    logMiddleware(req, res, next);
  }
}

2. Register it globally in AppModule

// src/app.module.ts
import { Module, NestModule, MiddlewareConsumer } from '@nestjs/common';
import { HttpLogMiddleware } from './http-log.middleware';

@Module({ /* ... */ })
export class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    consumer
      .apply(HttpLogMiddleware)
      .forRoutes('*'); // or specific controllers / paths
  }
}

3. Or register globally in main.ts (before routes)

// src/main.ts
import { createMiddleware } from 'data-for-logs';

const app = await NestFactory.create(AppModule);
app.use(createMiddleware((_err, payload) => logger.log(payload)));
await app.listen(3000);

API

createMiddleware(handler, options?)

Returns a ready-made (req, res, next) => void middleware function.
This is the recommended entry point for Nest / Express.

const mw = createMiddleware((_err, payload) => {
  kafkaProducer.send({
    topic: 'http-logs',
    messages: [{ value: JSON.stringify(payload) }],
  });
});

onResponseComplete(req, res, handler, options?)

Low-level hook. Fires handler exactly once when the response ends.
Returns a function you can call to force completion early (manual event).

const flush = onResponseComplete(req, res, (_err, payload) => {
  console.log(payload);
});
// flush(); // force early if needed

getRequestSnapshot(req, options?)

Returns the request snapshot immediately (no waiting for response).
Useful inside route handlers or interceptors.

const snap = getRequestSnapshot(req, { includeBody: true });

getResponseSnapshot(res)

Returns the response snapshot. Call after res.end() for complete data.

const snap = getResponseSnapshot(res);

Options

| Option | Type | Default | Description | |---|---|---|---| | includeBody | boolean | true | Include req.body in the snapshot | | includeRawBody | boolean | false | Include req.rawBody (if your middleware sets it) | | redactSensitiveHeaders | boolean | true | Redact authorization, cookie, set-cookie, x-api-key, proxy-authorization | | redactBodyKeys | string[] | null | Extra body keys to redact (merged with built-in list) | | maxBodyDepth | number | 8 | Max depth when cloning body | | maxBodyKeys | number | 200 | Max object keys per level | | maxArrayElements | number | 100 | Max array items to include | | maxStringLength | number | 10000 | Truncate strings longer than this | | highResTime | () => number | Date.now | Use performance.now() for sub-ms timing | | onHandlerError | (err) => void | — | Called if your handler throws |

Built-in redacted body keys

password, passwd, secret, token, access_token, refresh_token, authorization, credit_card, creditcard, cvv, ssn

Add more via redactBodyKeys option. All comparisons are case-insensitive.

event values

| Value | Meaning | |---|---| | finish | Response sent normally | | close | Client disconnected before response finished | | manual | You called the returned flush function early |

License

ISC