How to fix Error: Invalid trailer header (cannot use trailer with chunked encoding) in Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  // Declare which trailers will be sent after the body
  res.setHeader('Trailer', 'X-Checksum, X-Processing-Time');

  // Enable chunked encoding
  res.setHeader('Transfer-Encoding', 'chunked');
  res.setHeader('Content-Type', 'application/json');

  // Send the body
  res.write(JSON.stringify({ data: 'some data' }));
  res.write(JSON.stringify({ more: 'data' }));

  // Add trailers at the end, before calling end()
  res.addTrailers({
    'X-Checksum': 'abc123def456',
    'X-Processing-Time': '150ms'
  });

  res.end();
});

server.listen(3000);

const http = require('http');

const server = http.createServer((req, res) => {
  // REQUIRED: Set chunked encoding for trailers to work
  res.setHeader('Transfer-Encoding', 'chunked');

  // Declare trailers
  res.setHeader('Trailer', 'X-Signature');

  res.write('First chunk of data\n');
  res.write('Second chunk of data\n');

  // Add trailers before ending
  res.addTrailers({
    'X-Signature': 'signature-value'
  });

  res.end();
});

server.listen(3000);

const http = require('http');

const server = http.createServer((req, res) => {
  // Valid trailer names (custom or standard metadata headers)
  res.setHeader('Trailer', 'X-File-Checksum, X-Completion-Status');
  res.setHeader('Transfer-Encoding', 'chunked');

  res.write('Data chunk 1\n');
  res.write('Data chunk 2\n');

  // Valid trailers
  res.addTrailers({
    'X-File-Checksum': 'sha256:abc123',
    'X-Completion-Status': 'success'
  });

  res.end();
});

server.listen(3000);

const http = require('http');

const server = http.createServer((req, res) => {
  // Set trailers metadata
  res.setHeader('Trailer', 'X-Processing-Time, X-Records-Count');
  res.setHeader('Transfer-Encoding', 'chunked');
  res.setHeader('Content-Type', 'application/json');

  const data = [
    { id: 1, name: 'Record 1' },
    { id: 2, name: 'Record 2' }
  ];

  // Send body
  data.forEach(record => {
    res.write(JSON.stringify(record) + '\n');
  });

  // Add trailers BEFORE res.end()
  res.addTrailers({
    'X-Processing-Time': '42ms',
    'X-Records-Count': data.length.toString()
  });

  res.end();
});

server.listen(3000);

const http = require('http');

const server = http.createServer((req, res) => {
  // Check HTTP version
  console.log('HTTP version:', req.httpVersion);

  if (req.httpVersion < '1.1') {
    // HTTP/1.0: Don't use trailers
    res.setHeader('Content-Type', 'application/json');
    res.write(JSON.stringify({ message: 'HTTP/1.0 detected' }));
    res.end();
    return;
  }

  // HTTP/1.1 or higher: Safe to use trailers
  res.setHeader('Trailer', 'X-Version-Info');
  res.setHeader('Transfer-Encoding', 'chunked');

  res.write('Data for HTTP/1.1+');

  res.addTrailers({
    'X-Version-Info': 'HTTP/' + req.httpVersion
  });

  res.end();
});

server.listen(3000);

const http = require('http');

const options = {
  hostname: 'localhost',
  port: 3000,
  path: '/',
  method: 'GET'
};

const req = http.request(options, (res) => {
  console.log('Status:', res.statusCode);

  res.on('data', (chunk) => {
    console.log('Body chunk:', chunk.toString());
  });

  // Listen for trailers
  res.on('trailers', (trailers) => {
    console.log('Trailers received:', trailers);
    console.log('Checksum:', trailers['x-checksum']);
    console.log('Processing time:', trailers['x-processing-time']);
  });

  res.on('end', () => {
    console.log('Response complete');
  });
});

req.on('error', (e) => {
  console.error('Request error:', e);
});

req.end();