This is mainly aimed at John M, but I figure I might as well post this
here rather than through private correspondence.

As you (John) know, I'm writing a Camping-based server (Fluxr) that
will act as a front-end for OpenWFEru. The server will be responsible
for launching workflows, reporting on their status, etc.

One use pattern I see in our immediate needs is for a workflow to stop
and wait for some external event. So for example, the Camping server
receives an order to launch a workflow, and the workflow progresses up
to a point (for example, a branch) where it must wait for an external
trigger or for some additional external input data. I'm looking for
some opinions as to the best way to implement this.

I know that OpenWFEru has a when/wait expression, so it probably makes
sense to use this to wait for external events. However, the way I
understand it, OpenWFEru creates a separate process for each workflow
launched, and this process keeps running until the workflow is
completed. Since the event could be triggered days or weeks later, I'm
weary of keeping all these processes running. Instead, I'm wondering
if it might make more sense for the Fluxr server to persist the
workflow's state and shut it down. It would then be up to the Fluxr
server to listen for the trigger event, and re-instantiate and resume
the workflow from the persisted state.

Is this the right way to go? What would you suggest as the best way to
do this? I'm not exactly sure how I could go about pausing,
persisting, and then resuming an entire workflow in mid-process... the
fact that this seems difficult makes me wonder if I'm going about it
the wrong way.

Also, I realize that wrapping the OpenWFEru engine inside a Camping
server is a bit redundant, since OpenWFEru is meant to act as it's own
server (hence the old REST interface), but I think the added layer of
abstraction between the web application (i.e. Camping) and the
business process executor (i.e. OpenWFEru) makes sense.


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