doc: buffers are not sent over IPC with a socket

[timkuijsten]

Checklist

• documentation is changed or added
• the commit message follows commit guidelines

Affected core subsystem(s)

doc/child_process

Description of change

If a socket is sent to a child, any data that is buffered in the
socket will not be sent to the child. The child will only receive
data from the socket that is sent after the child has the socket.

[cjihrig]

This sentence seems incomplete. I would just stop after "will not be sent to the child." and remove the rest.

[cjihrig]

One comment, but LGTM.

[timkuijsten]

updated + added a new finding while trying to work around the issue myself.

[cjihrig]

Have you seen the keepOpen option to send()?

[timkuijsten]

No I had not, tnx! Updated the diff.

[addaleax]

LGTM, landing this…

[addaleax]

Landed in 5207526. Thank you!

[MylesBorins]

this is not landing cleanly, and I'm not 100% it applies to v4.x

Please backport if neccessary

[timkuijsten]

this is not landing cleanly, and I'm not 100% it applies to v4.x

It does apply to v4.x as well:

$ node --version
v4.4.7

$ cat m.js
const fork = require('child_process').fork
const net = require('net')

const cp = fork('./child.js')

net.createServer(c => {
  setTimeout(() => {
    cp.send({}, c)
  }, 500) // send the connection after a delay
}).listen(1234, () => {
  net.createConnection(1234, function() {
    var i = 0
    setInterval(() => {
      this.write(`${i++} `)
    }, 100) // start sending data before the connection is sent to the child
  })
})

$ cat child.js 
process.on('message', (m, c) => {
  console.log('child: got connection')
  c.pipe(process.stdout)
})

$ node m.js
child: got connection
4 5 6 7 8 ^C