gistfile1.js

var async_wrap = process.binding('async_wrap');
var uid = 0;

var kCallInitHook = 0;
var asyncHooksObject = {};

function asyncInit() {
  this._asyncQueue = { uid: ++uid };
  process._rawDebug('init    ' + this._asyncQueue.uid);
}

function asyncBefore() {
  process._rawDebug('before: ' + this._asyncQueue.uid);
}

function asyncAfter() {
  process._rawDebug('after:  ' + this._asyncQueue.uid);
}

async_wrap.setupHooks(asyncHooksObject, asyncInit, asyncBefore, asyncAfter);
asyncHooksObject[kCallInitHook] = 1;


var net = require('net');
var s = net.createServer();

s.on('connection', function onConnection(c) {
  c.end('Hello World\n');
});

s.listen(8000, function() {
  // Don't want to trace the req making the conntion. Only the received
  // req by the server.
  asyncHooksObject[kCallInitHook] = 0;

  // Create a connection for logging, then exit app.
  net.connect(8000, function() { });
});

Here's the annotated output

init    1
before: 1       # before hook called because child (2) was created
init    2
after:  1
before: 1            # actual before for event 1
after:  1
before: 2
after:  2
before: 2
after:  2