avalanche123

What a mind blowing achievement. Wow!

I think this is also getting at the difference between pub/sub and state synchronization. While one might think they want the former, what they really want is the latter. Get some state and receive updates continuously rather than deal with unreliable stream of updates

I believe anti trust is triggered when it negatively affects consumers, with Amazon’s aggressive competition consumers usually win. At least short term...

Well, success of a job is transient and not permanent in this case. Like I mentioned before, successful boot of a dependency doesn't mean that dependency exists by the time we get to boot a host. You need to continuously check the status of your group to determine actions that can be taken for current state. A stateful system that marks a job as complete upon successful execution wouldn't work. DAG computation does happen, but inside MoreHostsCanBeBooted condition that is a pre-requisite for BootMoreHosts action. If what you're proposing is to re-run the same job until target state transition has been achieved and code job in idempotent way, then this is essentially what's being done with the current approach, except there are no jobs, and idempotency is a side-effect of not tracking progress. I hope my explanations make sense :)

This was my initial idea. However, consider this scenario. I need to boot a web stack (db master, pool of db slaves, webservers and a load balancer). I boot a master, job succeeds, then I boot slaves, job succeeds. I boot webservers, but by this time master is shut down or becomes unavailable. Because of a job-based approach, this will never be detected and fixed by the controller. The chosen approach would detect the state of the environment and determine that a master is missing and proceed to correct the situation or abort the process altogether. Hope this makes sense!

Thanks for feedback. Indeed, complex emergent behaviors are not demonstrated in the provided example. But they are possible when changes in environment affect other control loops. Which might result in conflicts, at which point control loop for conflict resolution can be added, this is why MAPE-K tower is a useful abstraction.

I feel the example I built for our demo is a good one. Here I implemented presence and chat servers to build online chatroom. Servers and clients were initially built in Ruby, to be used in a private network behind firewall. I was then able to re-use client code with minimal changes and port it into JavaScript. This client code gave presence and chat to the browser. So effectively we solved an interesting networking problem once and were able to re-use the solution in two vastly different environments - private networks and the browser, where different authentication, authorization, performance and guarantees requirements apply.

heh, best I can do yet

You are right, however C bindings in other languages usually look quite ugly and non-idiomatic, but ZeroMQ did great job in that sense and their higher level language bindings are written with language specifics in mind

Yup, I'm sure that will get updated

NullMQ multiplexing protocol is built on top of STOMP. The main advantage of NullMQ is same socket primitives as ZeroMQ, so same patterns and solutions can be built in the browser.