socket._handle.fd invalid when domain is used

Version: 7.4
Platform: Linux DEV-PC 4.4.0-59-generic #80-Ubuntu SMP Fri Jan 6 17:47:47 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
Subsystem: http

This happens from node 4.x to 7.x as far as I've tested on MacOS and Ubuntu/Arch Linux with older/newer stack and software.

Example attached, shows that using domain name for HTTP request results in invalid socket _handle.fd

Usine createConnection directly gives a valid fd in both cases

I know that file descriptors in node are like black sheeps but is there something else that needs to be done to get a valid socket file descriptor or is this a genuine bug?

const http = require('http')
const net = require('net')

// this doesn't give valid fd handle
const r1 = http.get({ hostname: 'www.google.hr', port: 80 })

r1.on('socket', function(s)
{
    console.log("socket fd invalid", s._handle.fd)
})

// this does give valid fd handle, notice that ip is used instead of domain name
const r2 = http.get({ hostname: '213.202.89.187', port: 80 })

r2.on('socket', function(s)
{
    console.log("socket fd valid", s._handle.fd)
})

// this gives valid handle
const s1 = net.createConnection({ host: "www.google.com", port:80 }, function()
{
    console.log("socket fd valid:", s1._handle.fd)
})

// this gives valid handle
const s2 = net.createConnection({ host: "213.202.89.187", port:80 }, function()
{
    console.log("socket fd valid:", s2._handle.fd)
})

Not a bug - and it couldn't be, socket._handle.fd is internal and just for debugging.

What happens is that the DNS query is still in flight and the TCP connection hasn't been set up yet. Listen for the 'connect' event on the socket and only then inspect the .fd property.

in #8974 _handle.fd is presented as it is expected to be used even though it is internal

and this solution is a no go when one wants to set TCP_KEEPINTVL and TCP_KEEPCNT on that socket since it has to be set before connect so that connect is not hanging in specific cases (https://github.com/hertzg/node-net-keepalive)

I guess I can only resolve domain up front and then make a request as a workaround, yuck
Thanks nevertheless

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socket._handle.fd invalid when domain is used #10976

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socket._handle.fd invalid when domain is used #10976

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bnoordhuis commented on Jan 24, 2017

pkoretic commented on Jan 25, 2017

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