domains.js

var d = createDomain(
  // The `onyield` function is guaranteed to run always exactly once.
  // The only exception is when a parent domain of this domain dies.
  // The `onyield` function is ran in the parent domain, e.g. the domain
  // that was active at the time the domain was created.
  function onyield(err, some, result) {
    if (err) return console.log("shit! something fucked up");
    console.log("The domain had no errors! It's results were " 
                + some + " and " + result);
  }
);

// Run some code in the domain
// d.run() must be called from the parent domain.
d.run(function() {
  fs.stat('/foo/bar', function(err, stats) {
    // Throwing will make the domain die.
    if (err) throw err;
    
    var s = fs.createWriteStream("out.bar", "w");
    s.write(JSON.stringify(stats), function() {
      s.end("the end");
    });
    
    s.on('end', function() {
      // domain is a global that always points to the current domain
      domain.setResult(null, "it", "worked");
    });
  });
});


var d2 = createDomain(function onyield2(err) {
  if (err) console.log(err);
  console.log("the end");
});

// Domains will yield after after the number of io handles / nextTicks / 
// timers within it drops to zero, but not before at least one piece of code 
// has been run in the domain.
d2.run(function() {});

// Because the domain already yielded, this run() call will be ignored.
d2.run(something);


// Streams (and maybe some other classes) have an associated domain. All 
// callbacks must be attached from in that domain, and the callbacks will
// also run inside that domain. `createDomain` takes an optional first 
// parameter to import a socket into that domain. The socket cannot have
// any callbacks attached at that point.
net.createServer(
  function(socket) {
    // Valid
    console.log(socket.getpeername());
    createDomain(socket, function() {
      socket.on('data', function(buf) {
        console.log(buf.toString());
      })
    });
  }
).listen(8080);

net.createServer(
  function(socket) {
    // Invalid - will make createDomain throw
    socket.on('error', console.log);
    // Also invalid - will make createDomain throw
    socket.write("bla", afterWrite);
    
    createDomain(socket, function() {
      // ...
    });
  }
).listen(8080);