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> For the 'asynchronous manner' discussion see http://tinyurl.com/n3v9lt8; I'm still not sure why u would want to make is_sync/is_async a primitive concept in a workflow system, shouldn't this be only up to the entity running the workflow to decide? Why is a task allowed to be sync/async, that has major side-effects for state-persistence, resumption (and to me is a incorrect abstraction to provide) and general workflow execution control, I'd be very careful with this (which is why I am hesitant to add it without much much more discussion).


Let's remove the confusion caused by "async". All tasks [may] run async from the engine standpoint, agreed. 

"Long running tasks" - that's it.

Examples: wait_5_days, run_hadoop_job, take_human_input. 
The Task doesn't do the job: it delegates to an external system. The flow execution needs to wait  (5 days passed, hadoob job finished with data x, user inputs y), and than continue with the received results.

The requirement is to survive a restart of any WF component without loosing the state of the long running operation.

Does TaskFlow already have a way to do it? Or ongoing ideas, considerations? If yes let's review. Else let's brainstorm together. 

I agree,
> that has major side-effects for state-persistence, resumption (and to me is a incorrect abstraction to provide) and general workflow execution control, I'd be very careful with this

But these requirement  comes from customers'  use cases: wait_5_day - lifecycle management workflow, long running external system - Murano requirements, user input - workflow for operation automations with control gate checks, provisions which require 'approval' steps, etc. 

DZ> 

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