fastify plugin to forward the current http request to another server
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Latest commit 36a3153 Dec 18, 2018


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fastify plugin to forward the current http request to another server. HTTP2 to HTTP is supported too.


npm i fastify-reply-from


The following example set up two fastify servers and forward the request from one to the other.

'use strict'

const Fastify = require('fastify')

const target = Fastify({
  logger: true

target.get('/', (request, reply) => {
  reply.send('hello world')

const proxy = Fastify({
  logger: true

proxy.register(require('fastify-reply-from'), {
  base: 'http://localhost:3001/'

proxy.get('/', (request, reply) => {

target.listen(3001, (err) => {
  if (err) {
    throw err

  proxy.listen(3000, (err) => {
    if (err) {
      throw err


plugin options


Set the base URL for all the forwarded requests. Will be required if http2 is set to true Note that every path will be discarded.


Set to true if target server is http2 enabled.


Set to true to use undici instead of require('http'). Enabling this flag should guarantee 20-50% more throughput.

This flag could controls the settings of the undici client, like so:

proxy.register(require('fastify-reply-from'), {
  base: 'http://localhost:3001/',
  undici: {
    connections: 100,
    pipelining: 10


The number of parsed URLs that will be cached. Default: 100.


Defaults to 1 minute, passed down to http.Agent and https.Agent instances.


Defaults to 2048 sockets, passed down to http.Agent and https.Agent instances.


Defaults to true, passed down to https.Agent instances. This needs to be set to false to reply from https servers with self-signed certificates.

reply.from(source, [opts])

The plugin decores the Reply instance with a from method, which will reply to the original request from the desired source. The options allows to override any part of the request or response being sent or received to/from the source.


Called when an http response is received from the source. The default behavior is reply.send(res), which will be disabled if the option is specified.


Called to rewrite the headers of the response, before them being copied over to the outer response. It must return the new headers object.


Replaces the original querystring of the request with what is specified. This will get passed to querystring.stringify.


Replaces the original request body with what is specified. Unless [contentType][contentType] is specified, the content will be passed through JSON.stringify(). Setting this option will not verify if the http method allows for a body.


Override the 'Content-Type' header of the forwarded request, if we are already overriding the [body][body].


  • support overriding the body with a stream
  • forward the request id to the other peer might require some refacotring because we have to make the unique (see hyperid).
  • Support origin HTTP2 push
  • benchmarks