@phylum/process-task v3.1.0

Process Task

Create tasks that run child processes.

Installation

npm i @phylum/process-task

Usage

createProcessTask(spawn[, options])

Create a task that spawns a process and waits for it to exit.

const cp = require('child_process')
const {createProcessTask} = require('@phylum/process-task')

const task = createProcessTask(ctx => cp.exec('echo Hello World!'))

• spawn <function> - A function to spawn the process. + ctx <Context> - The task context is passed with the first argument. + return <ChildProcess> - A child process (or any object that exposes the same api)
• options <object> - Optional. An object with the following options: + expect <number> | <string> - The exit code or signal to expect. If the process exits with another code or signal, the task will reject. Default is 0 + killOnDispose <boolean> - True to kill the process when the task is disposed and the process is still running. If your process will run forever, you should set this to true. Default is false.

ProcessTaskState

The ProcessTaskState class manages a single child process that can be spawned and killed manually. It is killed automatically when the task is disposed.

const {ProcessTaskState} = require('@phylum/process-task')

new ProcessTaskState(ctx, spawn)

const cp = require('child_process')

async function example(ctx) {
	const state = new ProcessTaskState(ctx, () => {
		return cp.fork('foo.js')
	})

	state.spawn()
}

• ctx <Pipeline.Context> - The pipeline context to attach to.
• spawn <function> - A function to spawn a child process. The context is passed with the first argument and the function must return the new child process.

state.ctx

Get the <Pipeline.Context> the state was bound to.

state.ctx === ctx

state.process

Get the current <ChildProcess>. If the process has been killed using state.kill(..) or the process emitted an exit event, this property will be set to null

if (state.process) {
	state.process.send('Hello World!')
}

state.spawn()

Spawn the process if not alive.

if (state.spawn()) {
	// A new process has been spawned.
} else {
	// The process is alive.
}

• returns <ChildProcess> | false - The new child process if created or false otherwise.

state.respawn()

Kill the current process if alive and spawn a new one.

const proc = state.respawn()

• returns <ChildProcess> - The new child process.

state.kill([signal])

Kill the current process if alive. Only use this function if you are expecting the process to exit after receiving the signal. Otherwise use state.process.kill(..)

state.kill()
state.process === null

Note that state.process will be set to null after calling this function.

Event: 'spawn'

The spawn event is emitted when a new process has been spawned using state.spawn(..) or state.respawn(..). The child process is passed with the first argument. This can be useful for listening to process related events like ipc messages.

state.on('spawn', process => {
	process.on('message', msg => {
		console.log('Message from child process:', msg)
	})
})