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Class: Client

Extends: undici.Dispatcher

A basic HTTP/1.1 client, mapped on top a single TCP/TLS connection. Pipelining is disabled by default.

Requests are not guaranteed to be dispatched in order of invocation.

new Client(url[, options])

Arguments:

  • url URL | string - Should only include the protocol, hostname, and port.
  • options ClientOptions (optional)

Returns: Client

Parameter: ClientOptions

  • bodyTimeout number | null (optional) - Default: 300e3 - The timeout after which a request will time out, in milliseconds. Monitors time between receiving body data. Use 0 to disable it entirely. Defaults to 300 seconds.
  • headersTimeout number | null (optional) - Default: 300e3 - The amount of time the parser will wait to receive the complete HTTP headers while not sending the request. Defaults to 300 seconds.
  • keepAliveMaxTimeout number | null (optional) - Default: 600e3 - The maximum allowed keepAliveTimeout when overridden by keep-alive hints from the server. Defaults to 10 minutes.
  • keepAliveTimeout number | null (optional) - Default: 4e3 - The timeout after which a socket without active requests will time out. Monitors time between activity on a connected socket. This value may be overridden by keep-alive hints from the server. See MDN: HTTP - Headers - Keep-Alive directives for more details. Defaults to 4 seconds.
  • keepAliveTimeoutThreshold number | null (optional) - Default: 1e3 - A number subtracted from server keep-alive hints when overriding keepAliveTimeout to account for timing inaccuracies caused by e.g. transport latency. Defaults to 1 second.
  • maxHeaderSize number | null (optional) - Default: 16384 - The maximum length of request headers in bytes. Defaults to 16KiB.
  • maxResponseSize number | null (optional) - Default: -1 - The maximum length of response body in bytes. Set to -1 to disable.
  • pipelining number | null (optional) - Default: 1 - The amount of concurrent requests to be sent over the single TCP/TLS connection according to RFC7230. Carefully consider your workload and environment before enabling concurrent requests as pipelining may reduce performance if used incorrectly. Pipelining is sensitive to network stack settings as well as head of line blocking caused by e.g. long running requests. Set to 0 to disable keep-alive connections.
  • connect ConnectOptions | Function | null (optional) - Default: null.
  • strictContentLength Boolean (optional) - Default: true - Whether to treat request content length mismatches as errors. If true, an error is thrown when the request content-length header doesn't match the length of the request body.
  • interceptors { Client: DispatchInterceptor[] } - Default: [RedirectInterceptor] - A list of interceptors that are applied to the dispatch method. Additional logic can be applied (such as, but not limited to: 302 status code handling, authentication, cookies, compression and caching). Note that the behavior of interceptors is Experimental and might change at any given time.
  • autoSelectFamily: boolean (optional) - Default: depends on local Node version, on Node 18.13.0 and above is false. Enables a family autodetection algorithm that loosely implements section 5 of RFC 8305. See here for more details. This option is ignored if not supported by the current Node version.
  • autoSelectFamilyAttemptTimeout: number - Default: depends on local Node version, on Node 18.13.0 and above is 250. The amount of time in milliseconds to wait for a connection attempt to finish before trying the next address when using the autoSelectFamily option. See here for more details.

Parameter: ConnectOptions

Every Tls option, see here. Furthermore, the following options can be passed:

  • socketPath string | null (optional) - Default: null - An IPC endpoint, either Unix domain socket or Windows named pipe.
  • maxCachedSessions number | null (optional) - Default: 100 - Maximum number of TLS cached sessions. Use 0 to disable TLS session caching. Default: 100.
  • timeout number | null (optional) - Default 10e3
  • servername string | null (optional)
  • keepAlive boolean | null (optional) - Default: true - TCP keep-alive enabled
  • keepAliveInitialDelay number | null (optional) - Default: 60000 - TCP keep-alive interval for the socket in milliseconds

Example - Basic Client instantiation

This will instantiate the undici Client, but it will not connect to the origin until something is queued. Consider using client.connect to prematurely connect to the origin, or just call client.request.

'use strict'
import { Client } from 'undici'

const client = new Client('http://localhost:3000')

Example - Custom connector

This will allow you to perform some additional check on the socket that will be used for the next request.

'use strict'
import { Client, buildConnector } from 'undici'

const connector = buildConnector({ rejectUnauthorized: false })
const client = new Client('https://localhost:3000', {
  connect (opts, cb) {
    connector(opts, (err, socket) => {
      if (err) {
        cb(err)
      } else if (/* assertion */) {
        socket.destroy()
        cb(new Error('kaboom'))
      } else {
        cb(null, socket)
      }
    })
  }
})

Instance Methods

Client.close([callback])

Implements Dispatcher.close([callback]).

Client.destroy([error, callback])

Implements Dispatcher.destroy([error, callback]).

Waits until socket is closed before invoking the callback (or returning a promise if no callback is provided).

Client.connect(options[, callback])

See Dispatcher.connect(options[, callback]).

Client.dispatch(options, handlers)

Implements Dispatcher.dispatch(options, handlers).

Client.pipeline(options, handler)

See Dispatcher.pipeline(options, handler).

Client.request(options[, callback])

See Dispatcher.request(options [, callback]).

Client.stream(options, factory[, callback])

See Dispatcher.stream(options, factory[, callback]).

Client.upgrade(options[, callback])

See Dispatcher.upgrade(options[, callback]).

Instance Properties

Client.closed

  • boolean

true after client.close() has been called.

Client.destroyed

  • boolean

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

Client.pipelining

  • number

Property to get and set the pipelining factor.

Instance Events

Event: 'connect'

See Dispatcher Event: 'connect'.

Parameters:

  • origin URL
  • targets Array<Dispatcher>

Emitted when a socket has been created and connected. The client will connect once client.size > 0.

Example - Client connect event

import { createServer } from 'http'
import { Client } from 'undici'
import { once } from 'events'

const server = createServer((request, response) => {
  response.end('Hello, World!')
}).listen()

await once(server, 'listening')

const client = new Client(`http://localhost:${server.address().port}`)

client.on('connect', (origin) => {
  console.log(`Connected to ${origin}`) // should print before the request body statement
})

try {
  const { body } = await client.request({
    path: '/',
    method: 'GET'
  })
  body.setEncoding('utf-8')
  body.on('data', console.log)
  client.close()
  server.close()
} catch (error) {
  console.error(error)
  client.close()
  server.close()
}

Event: 'disconnect'

See Dispatcher Event: 'disconnect'.

Parameters:

  • origin URL
  • targets Array<Dispatcher>
  • error Error

Emitted when socket has disconnected. The error argument of the event is the error which caused the socket to disconnect. The client will reconnect if or once client.size > 0.

Example - Client disconnect event

import { createServer } from 'http'
import { Client } from 'undici'
import { once } from 'events'

const server = createServer((request, response) => {
  response.destroy()
}).listen()

await once(server, 'listening')

const client = new Client(`http://localhost:${server.address().port}`)

client.on('disconnect', (origin) => {
  console.log(`Disconnected from ${origin}`)
})

try {
  await client.request({
    path: '/',
    method: 'GET'
  })
} catch (error) {
  console.error(error.message)
  client.close()
  server.close()
}

Event: 'drain'

Emitted when pipeline is no longer busy.

See Dispatcher Event: 'drain'.

Example - Client drain event

import { createServer } from 'http'
import { Client } from 'undici'
import { once } from 'events'

const server = createServer((request, response) => {
  response.end('Hello, World!')
}).listen()

await once(server, 'listening')

const client = new Client(`http://localhost:${server.address().port}`)

client.on('drain', () => {
  console.log('drain event')
  client.close()
  server.close()
})

const requests = [
  client.request({ path: '/', method: 'GET' }),
  client.request({ path: '/', method: 'GET' }),
  client.request({ path: '/', method: 'GET' })
]

await Promise.all(requests)

console.log('requests completed')

Event: 'error'

Invoked for users errors such as throwing in the onError handler.