Newbee consulting question

[Tomer Paz]

Hi.

I am examining RabbitMQ as an AMQP broker for a workflow system that we wish to develop in-house, on-premise.

The closest description to our architecture is Amazon SWF. it is ~95% the solution concept to our requirements, but we can't use it as it is a cloud SaaS and our requirement is 'on-premise' :)

I was wondering How to manage distributed Tasks where the task manager ('orchestrator') is at the data-center, 

 the workers are distributed in different physical sites (some on the same site, some far in other site separated by WAN),

 where the connection between the datacenter and the sites might be disrupted sometimes.

We don't have a major performance requirement, we need not thousands of msg/sec, more like 1-3k messages a minute. Each worker might work for minutes on a single task...

Since the requirement is for WorkFlow management, it means we want tasks marked done by a remote worker, will be reported back to the manager, to keep the State of all tasks managed in central manner.

We use that for monitoring and reports (statistics).

I have read about the RPC like pattern, prefer to avoid it (!)

I also read the tutorials about task/worker pattern which is closer to what we need, but we also need the capability to parallelise 'steps' (that's what workflow orchestration is about) within a parent task so that

some tasks in the workflow tree will be processed consequently, some in parallel. 

Assume workers are not necessarily the same. i.e. there are different task "types" thus different workers processing them (hence this is not a simple pub/sub pattern either).

It sounds like we need some kind of mixture of three patterns to pull this out, but I am not sure: task/worker, pub/sub and the "Topic" Exchange kind of routing.

Oh, and did I mention we want the architecture to be "pull" rather than "push" in terms of workers 'asking' the workflow manager to get new tasks when they are free, 

 rather than task manager pushing tasks to workers blindly.

Would love to hear some experience if there is such, with such pattern using AMQ and RubbitMQ in particular to communicate the tasks.

TIA

Tomer