Node 10.8.0 does not support `lookup` on `Agent`

[firasdib]

• Version: 10.8.0
• Platform: Linux
• Subsystem: CentOS

The docs state you can specify your own lookup function for DNS resolution when creating an Agent. See https://nodejs.org/dist/latest-v10.x/docs/api/net.html#net_socket_connect_options_connectlistener and https://nodejs.org/dist/latest-v10.x/docs/api/http.html#http_class_http_agent

However, this option is not respected in v10.8.0. After upgrading to v12, it worked as intended.

[ktrongnhan]

Custom lookup() DOES WORK as expected for me

• Version: 10.8.0
• Platform: Linux
• Subsystem: CentOS 7

Sample snippet

const http = require('http');

const agent = process.argv[2] === '--agent' ? new http.Agent({
  lookup: (hostname, opts, cb) => {
    cb && cb(new Error('unresolved hostname'), null, null);
  }
}) : null;

const requestOptions = {
  hostname: 'google.com',
  agent,
}

const req = http.request(requestOptions, (res) => {
  res.on('data', () => { });
  res.on('end', () => { console.log('request fulfilled'); });
}).end();

req.on('error', (e) => {
  console.error(`request error: ${e.message}`);
});

Results

$ node index.js 
request fulfilled
$ node index.js --agent
request error: unresolved hostname google.com:80
$ node --version
v10.8.0
$ uname -a
Linux localhost.localdomain 3.10.0-957.12.2.el7.x86_64 #1 SMP Tue May 14 21:24:32 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

[firasdib]

My issue was with using the global agent. I should have specified that.

[ktrongnhan]

@firasdib
Could you give me a snippet to look at? A single line of code can save thousand words :)

[firasdib]

@ktrongnhan I simply replaced the global agent like this:

const http = require('http');

http.globalAgent = new http.Agent({ lookup: customFunction });

[ktrongnhan]

@firasdib
#25170 has landed in v10.16.0-proposal. Seems like there will not be any change to the docs.

[bnoordhuis]

Closing, should be fixed by #25170.