启动后分离一个 spawn 子进程

Question

我这样启动一个 spawn 子进程：

let process = spawn(apiPath, {
  detached: true
})

process.unref()

process.stdout.on('data', data => { /* do something */ })

当我启动进程时，我需要保持它的附加状态，因为我想读取它的输出。但是就在关闭我的节点进程（父进程）之前，我想分离所有未完成的子进程以将它们运行保留在后台，但是正如 the documentation 所说：

When using the detached option to start a long-running process, the process will not stay running in the background after the parent exits unless it is provided with a stdio configuration that is not connected to the parent.

但是使用选项 stdio: 'ignore' 我无法阅读 stdout，这是个问题。

我之前尝试过手动关闭管道来关闭父进程，但没有成功：

// Trigger just before the main process end
process.stdin.end()
process.stderr.unpipe()
process.stdout.unpipe()

Answer 1

经过多次测试，我至少找到了一种方法来解决这个问题：在离开主进程之前销毁所有管道。

一个棘手的问题是子进程必须正确处理管道破坏，否则它可能会出错并关闭。在这个例子中，节点子进程似乎没有问题，但它可能与其他场景不同。

main.js

const { spawn } = require('child_process')

console.log('Start Main')

let child = spawn('node', ['child.js'], { detached: true })
child.unref() // With this the main process end after fully disconnect the child

child.stdout.on('data', data => {
  console.log(`Got data : ${data}`)
})

// In real case should be triggered just before the end of the main process
setTimeout(() => {
  console.log('Disconnect the child')

  child.stderr.unpipe()
  child.stderr.destroy()
  child.stdout.unpipe()
  child.stdout.destroy()
  child.stdin.end()
  child.stdin.destroy()
}, 5000)

child.js

console.log('Start Child')

setInterval(function() {
   process.stdout.write('hello from child')
}, 1000)

产出

Start Main
Got data : Start Child

Got data : hello from child
Got data : hello from child
Got data : hello from child
Got data : hello from child
Disconnect the child

启动后分离一个 spawn 子进程

Detach a spawn child process after the start

node.js

multithreading

spawn

main.js

child.js

产出