Topaz

A distributed actor-model virtual machine that runs in the browser & on the server.

Setup

hub clone joshnuss/topaz
yarn && yarn build

Running on the server

yarn example examples/spawn.js

Running in the browser

ruby -run -e httpd . -p 8000
open localhost:8000/examples

How it works

Schedulers

The VM contains multiple schedulers running in parallel (each one is a WebWorker). For example, a machine with 8 CPUs would have 8 schedulers.

Spawning an Actor

Calling VM.spawn(code) creates a new actor object and places it on a random scheduler.

Multitasking

The CPUs are time sliced using a pre-emptive multitasking model.

Each scheduler has a "run queue", it pops actors off the queue, gives it 2000 iterations, pauses it and pushes it back to the end of the queue. It then pops the next actor and repeats in an endless loop. This ensures that no actor hogs the CPU.

Linking

Actors can be linked to each other: When a linked actor terminates, every link is terminated as well. (Links are bi-directional)

Monitoring

Actor can monitor each-other: When a monitored actor terminates, all monitoring actors are notified about the termination. The notifcation is sent to their mailbox. (Monitoring is uni-directional)

Messaging

Actors can send & receive messages between each other. Sending is non-blocking, but receiving can block (when the mailbox is empty).

Sometimes, a message will need to go to an actor on different scheduler. In that case, it's routed thru the VM, which uses a MessageChannel to notify the correct WebWorkers.

Actor Object

Each actor is represented as a plain JavaScript Object. It contains the following data:

id: [nodeId, actorId] an 2-cell array, first element is the node, second is the actor id
mailbox: [] an array of messages that are waiting to be processed.
waiting: true | false true if mailbox is empty and the actor issued a receive call. Actors in waiting state are not executed until they receive a new message.
terminated: true | false true when the actor has terminated. This happens when an error occurs or when an actor call the exit function. Actors in terminated state are never executed and will be culled.
links: [] an array of actor ids that are linked to this actor.
monitors: [] an array of actor ids that are monitoring this actor.
code: [] a list of operations (currently using s-expressions).
state: {} contains the state data of the actor. Similar to this in JavaScript or self in Ruby.
reductions: integer total number of statements processed.

Examples

See examples folder

License

MIT

mattbmoorin/topaz