Lightning talk given at the Server-side Javascript Meetup in San Francisco on Jan 28th, 2010.

1. Communicating Event Loops
Tom Van Cutsem
Mark S. Miller

2. Threads vs Event Loops

3. Communicating Event Loops
Events = asynchronous messages
Event handlers = methods

4. Properties
Within a vat: plain sequential OOP
Between vats: strictly asynchronous communication
no deadlock
hides latency
Explicit unit of interleaving (turns )
turns run to completion: no races on vat-local state
easy to add new events without breaking existing code
control flow across turns "inverted"
Explicit locality boundaries (vats )
no synchronously accessible shared state
easy to add new vats without breaking existing vats
partitioning state across vats requires consideration
Non-determinism is restricted to message arrival order

5. Key abstractions: promises + closures
var obj = {
foo: function(x,y) { return x + y; }
}
// in another vat:
var promise = Q(obj).foo(1,2); // asynchronous send
var promise2 = Q(promise).bar(3,4); // data-flow
f(promise2);
function f(p) {
// control-flow synchronization
Q.when(p, function(result) {
... // closure: local vars still in scope
});
}