undici

An HTTP/1.1 client, written from scratch for Node.js.

Undici means eleven in Italian. 1.1 -> 11 -> Eleven -> Undici. It is also a Stranger Things reference.

Install

npm i undici

Benchmarks

Machine: 2.7 GHz Quad-Core Intel Core i7 Configuration: Node v14.2, HTTP/1.1 without TLS, 100 connections

http - keepalive - pipe x 5,120 ops/sec ±10.80% (65 runs sampled)
undici - pipeline - pipe x 6,227 ops/sec ±11.44% (71 runs sampled)
undici - request - pipe x 8,685 ops/sec ±8.96% (67 runs sampled)
undici - stream - pipe x 11,453 ops/sec ±3.69% (79 runs sampled)

The benchmark is a simple hello world example.

API

new undici.Client(url, opts)

A basic HTTP/1.1 client, mapped on top a single TCP/TLS connection. Keepalive is enabled by default, and it cannot be turned off.

The url will be used to extract the protocol and the domain/IP address. The path is discarded.

Options:

• timeout, the timeout after which a request will time out, in milliseconds. Default: 30e3 milliseconds (30s).

• maxAbortedPayload, the maximum number of bytes read after which an aborted response will close the connection. Closing the connection will error other inflight requests in the pipeline. Default: 1e6 bytes (1MiB).

• pipelining, the amount of concurrent requests to be sent over the single TCP/TLS connection according to RFC7230. Default: 1.

client.request(opts, callback(err, data))

Performs an HTTP request.

Options:

• path
• method
• body, it can be a String, a Buffer, Uint8Array or a stream.Readable.
• headers, an object with header-value pairs.
• idempotent, whether the requests can be safely retried or not. If false the request won't be sent until all preceeding requests in the pipeline has completed. Default: true if method is HEAD or GET.

Headers are represented by an object like this:

{
  'content-length': '123',
  'content-type': 'text/plain',
  connection: 'keep-alive',
  host: 'mysite.com',
  accept: '*/*'
}

Keys are lowercased. Values are not modified. If you don't specify a host header, it will be derived from the url of the client instance.

The data parameter in callback is defined as follow:

• statusCode
• headers
• body, a stream.Readable with the body to read. A user must either fully consume or destroy the body unless there is an error, or no further requests will be processed.

Returns a promise if no callback is provided.

Example:

const { Client } = require('undici')
const client = new Client(`http://localhost:3000`)

client.request({
  path: '/',
  method: 'GET'
}, function (err, data) {
  if (err) {
    // handle this in some way!
    return
  }
  const {
    statusCode,
    headers,
    body
  } = data


  console.log('response received', statusCode)
  console.log('headers', headers)

  body.setEncoding('utf8')
  body.on('data', console.log)

  client.close()
})

Abortion is supported by destroying the request or response body.

// Abort while sending request.
const body = new stream.Passthrough()
const promise = client.request({
  path: '/',
  method: 'POST',
  body
})
body.destroy()
const { statusCode, headers } = await promise

// Abort while reading response.
const { statusCode, headers, body } = await client.request({
  path: '/',
  method: 'GET'
})
body.destroy()

Promises and async await are supported as well!

const { statusCode, headers, body } = await client.request({
  path: '/',
  method: 'GET'
})

Non-idempotent requests will not be pipelined in order to avoid indirect failures.

Idempotent requests will be automatically retried if they fail due to indirect failure from the request at the head of the pipeline. This does not apply to idempotent requests with a stream request body.

client.stream(opts, factory(data), callback(err))

A faster version of request.

Unlike request this method expects factory to return a Writable which the response will be written to. This improves performance by avoiding creating an intermediate Readable when the user expects to directly pipe the response body to a Writable.

Options:

• ... same as request.
• opaque, passed as opaque to factory. Used to avoid creating a closure.

The data parameter in factory is defined as follow:

• statusCode
• headers
• opaque

Returns a promise if no callback is provided.

const { Client } = require('undici')
const client = new Client(`http://localhost:3000`)
const fs = require('fs')

client.stream({
  path: '/',
  method: 'GET',
  opaque: filename
}, ({ statusCode, headers, opaque: filename }) => {
  console.log('response received', statusCode)
  console.log('headers', headers)
  return fs.createWriteStream(filename)
}, (err) => {
  if (err) {
    console.error('failure', err)
  } else {
    console.log('success')
  }
})

opaque makes it possible to avoid creating a closure for the factory method:

function (req, res) {
   return client.stream({ ...opts, opaque: res }, proxy)
}

Instead of:

function (req, res) {
   return client.stream(opts, (data) => {
     // Creates closure to capture `res`.
     proxy({ ...data, opaque: res })
   }
}

client.pipeline(opts, handler(data))

For easy use with stream.pipeline.

Options:

• ... same as request.

The data parameter in handler is defined as follow:

• statusCode
• headers
• body, a stream.Readable with the body to read. A user must either fully consume or destroy the body unless there is an error, or no further requests will be processed.

Unlike request this method expects handler to return a Writable which the response will be written to. Usually it should just return the body argument unless some kind of transformation needs to be performed based on e.g. headers or statusCode.

The handler should validate the response and save any required state. If there is an error it should be thrown.

const { Client } = require('undici')
const client = new Client(`http://localhost:3000`)
const fs = require('fs')
const stream = require('stream')

stream.pipeline(
  fs.createReadStream('source.raw'),
  client.pipeline({
    path: '/',
    method: 'PUT',
  }, ({ statusCode, headers, body }) => {
    if (statusCode !== 201) {
      throw new Error('invalid response')
    }

    if (isZipped(headers)) {
      return pipeline(body, unzip(), () => {})
    }

    return body
  }),
  fs.createReadStream('response.raw'),
  (err) => {
    if (err) {
      console.error('failed')
    } else {
      console.log('succeeded')
    }
  }
)

client.close([callback])

Closes the client and gracefully waits fo enqueued requests to complete before invoking the callback.

Returns a promise if no callback is provided.

client.destroy([err][, callback])

Destroy the client abruptly with the given err. All the current and enqueued requests will be aborted and error. Waits until socket is closed before invoking the callback.

Returns a promise if no callback is provided.

client.pipelining

Property to get and set the pipelining factor.

client.pending

Number of queued requests.

client.running

Number of inflight requests.

client.size

Number of queued and inflight requests.

client.connected

True if the client has an active connection. The client will lazily create a connection when it receives a request and will destroy it if there is no activity for the duration of the timeout value.

client.full

True if client.size is greater than the client.pipelining factor. Keeping a client full ensures that once a inflight requests finishes the the pipeline will schedule new one and keep the pipeline saturated.

client.closed

True after client.close() has been called.

client.destroyed

True after client.destroyed() has been called or client.close() has been called and the client shutdown has completed.

Events

• 'drain', emitted when client.size decreases to 0 and the client is not closed or destroyed.

• 'connect', emitted when a socket has been created and connected. The client will connect once client.size > 0.

• 'reconnect', emitted when socket has disconnected. The client will reconnect if or once client.size > 0.

new undici.Pool(url, opts)

A pool of Client connected to the same upstream target. A pool creates a fixed number of Client

Options:

• ... same as new Client.
• connections, the number of clients to create. Default 100.

pool.request(req, callback)

Calls client.request(req, callback) on one of the clients.

pool.stream(req, factory, callback)

Calls client.stream(req, factory, callback) on one of the clients.

pool.pipeline(req, handler)

Calls client.pipeline(req, handler) on one of the clients.

pool.close([callback])

Calls client.close(callback) on all the clients.

pool.destroy([err][, callback])

Calls client.destroy(err, callback) on all the clients.

undici.errors

Undici exposes a variety of error objects that you can use to enhance your error handling. You can find all the error objects inside the errors key.

const { errors } = require('undici')

Error	Error Codes	Description
InvalidArgumentError	UND_ERR_INVALID_ARG	Generated when in case of a bad configuration.
TimeoutError	UND_ERR_TIMEOUT	Generated when a request exceeds the timeout option.
RequestAbortedError	UND_ERR_ABORTED	Generated if the request has been aborted by the user
ClientDestroyedError	UND_ERR_DESTROYED	Generated when trying to use a destroyed client.
ClientClosedError	UND_ERR_CLOSED	Generated when trying to use a closed client.
SocketError	UND_ERR_SOCKET	Generated if there is an error with the socket.

License

MIT