utilityProcess

utilityProcess creates a child process with Node.js and Message ports enabled. It provides the equivalent of child_process.fork API from Node.js but instead uses Services API from Chromium to launch the child process.

Process: Main

Methods

utilityProcess.fork(modulePath[, args][, options])

• modulePath string - Path to the script that should run as entrypoint in the child process.
• args string[] (optional) - List of string arguments that will be available as process.argv in the child process.
• options Object (optional)
  • env Object (optional) - Environment key-value pairs. Default is process.env.
  • execArgv string[] (optional) - List of string arguments passed to the executable.
  • cwd string (optional) - Current working directory of the child process.
  • session Session (optional) - Sets the session used by the process for network requests. By default, network requests from the utility process will use the system network context which does not have HTTP cache support. Setting a session enables HTTP caching and other session-specific network features. See session for more information.
  • partition string (optional) - Sets the session used by the process according to the session's partition string. If partition starts with persist:, the process will use a persistent session available to all pages in the app with the same partition. If there is no persist: prefix, the process will use an in-memory session. By assigning the same partition, multiple processes can share the same session. If the session option is set, this option is ignored.
  • stdio (string[] | string) (optional) - Allows configuring the mode for stdout and stderr of the child process. Default is inherit. String value can be one of pipe, ignore, inherit, for more details on these values you can refer to stdio documentation from Node.js. Currently this option only supports configuring stdout and stderr to either pipe, inherit or ignore. Configuring stdin to any property other than ignore is not supported and will result in an error. For example, the supported values will be processed as following:
    • pipe: equivalent to ['ignore', 'pipe', 'pipe']
    • ignore: equivalent to ['ignore', 'ignore', 'ignore']
    • inherit: equivalent to ['ignore', 'inherit', 'inherit'] (the default)
  • serviceName string (optional) - Name of the process that will appear in name property of ProcessMetric returned by app.getAppMetrics and child-process-gone event of app. Default is Node Utility Process.
  • allowLoadingUnsignedLibraries boolean (optional) macOS - With this flag, the utility process will be launched via the Electron Helper (Plugin).app helper executable on macOS, which can be codesigned with com.apple.security.cs.disable-library-validation and com.apple.security.cs.allow-unsigned-executable-memory entitlements. This will allow the utility process to load unsigned libraries. Unless you specifically need this capability, it is best to leave this disabled. Default is false.
  • disclaim boolean (optional) macOS - With this flag, the utility process will disclaim responsibility for the child process. This causes the operating system to consider the child process as a separate entity for purposes of security policies like Transparency, Consent, and Control (TCC). When responsibility is disclaimed, the parent process will not be attributed for any TCC requests initiated by the child process. This is useful when launching processes that run third-party or otherwise untrusted code. Default is false.
  • respondToAuthRequestsFromMainProcess boolean (optional) - With this flag, all HTTP 401 and 407 network requests created via the net module will allow responding to them via the login event on the UtilityProcess instance when a session is provided, or via the app#login event in the main process when using the default system network context. Without this flag, auth challenges are handled by the default login event on the ClientRequest object. Default is false.

Returns UtilityProcess

[!NOTE] utilityProcess.fork can only be called after the ready event has been emitted on App.

Class: UtilityProcess

Instances of the UtilityProcess represent the Chromium spawned child process with Node.js integration.

UtilityProcess is an EventEmitter.

Instance Methods

child.postMessage(message, [transfer])

• message any
• transfer MessagePortMain[] (optional)

Send a message to the child process, optionally transferring ownership of zero or more MessagePortMain objects.

For example:

// Main process
const { port1, port2 } = new MessageChannelMain()
const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
child.postMessage({ message: 'hello' }, [port1])

// Child process
process.parentPort.once('message', (e) => {
  const [port] = e.ports
  // ...
})

child.kill()

Returns boolean

Terminates the process gracefully. On POSIX, it uses SIGTERM but will ensure the process is reaped on exit. This function returns true if the kill is successful, and false otherwise.

Instance Properties

child.pid

A Integer | undefined representing the process identifier (PID) of the child process. Until the child process has spawned successfully, the value is undefined. When the child process exits, then the value is undefined after the exit event is emitted.

const child = utilityProcess.fork(path.join(__dirname, 'test.js'))

console.log(child.pid) // undefined

child.on('spawn', () => {
  console.log(child.pid) // Integer
})

child.on('exit', () => {
  console.log(child.pid) // undefined
})

[!NOTE] You can use the pid to determine if the process is currently running.

child.stdout

A NodeJS.ReadableStream | null that represents the child process's stdout. If the child was spawned with options.stdio[1] set to anything other than 'pipe', then this will be null. When the child process exits, then the value is null after the exit event is emitted.

// Main process
const { port1, port2 } = new MessageChannelMain()
const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
child.stdout.on('data', (data) => {
  console.log(`Received chunk ${data}`)
})

child.stderr

A NodeJS.ReadableStream | null that represents the child process's stderr. If the child was spawned with options.stdio[2] set to anything other than 'pipe', then this will be null. When the child process exits, then the value is null after the exit event is emitted.

Instance Events

Event: 'spawn'

Emitted once the child process has spawned successfully.

Event: 'error' Experimental

Returns:

• type string - Type of error. One of the following values:
  • FatalError
• location string - Source location from where the error originated.
• report string - Node.js diagnostic report.

Emitted when the child process needs to terminate due to non continuable error from V8.

No matter if you listen to the error event, the exit event will be emitted after the child process terminates.

Event: 'exit'

Returns:

• code number - Contains the exit code for the process obtained from waitpid on POSIX, or GetExitCodeProcess on Windows.

Emitted after the child process ends.

Event: 'message'

Returns:

• message any

Emitted when the child process sends a message using process.parentPort.postMessage().

Event: 'login'

Returns:

• authenticationResponseDetails Object
  • url URL
  • pid number
• authInfo Object
  • isProxy boolean
  • scheme string
  • host string
  • port Integer
  • realm string
• callback Function
  • username string (optional)
  • password string (optional)

Emitted when the utility process encounters an HTTP 401 or 407 authentication challenge, if the process was created with both respondToAuthRequestsFromMainProcess: true and a session option. The callback should be called with credentials to respond to the challenge. Calling callback without arguments will cancel the request.

This behaves the same as the login event on app but is scoped to the individual utility process instance.

const { session, utilityProcess } = require('electron')

const ses = session.defaultSession
const child = utilityProcess.fork('./worker.js', [], {
  session: ses,
  respondToAuthRequestsFromMainProcess: true
})

child.on('login', (authenticationResponseDetails, authInfo, callback) => {
  callback('username', 'password')
})