I am not allowed to describe the use case and it will sound weird, but we're
trying to figure out the best way of handling thousands of small, event-driven
state machines in a Web environment.
We have a standard Moose, Catalyst, DBIx::Class, TT, Postgres database
stack and the potential for hundreds or thousands of users using the site at
the same time. Each user can one one or more "workflows" attached to a given
profile. Users choose which workflows they need or don't need. They'll have
maybe three to five workflows at a time. Each workflow is a small state
machine that should switch when the user takes a given action (which we're
calling "events", so the term "event-driven" is misleading), such as checking
out a document, editing it, visiting a new section of the site, etc.
We're trying to figure out the best way of writing this. Our primary
concerns are performance and accuracy. It's better that the Web site crash
than to have inaccurate workflows. We've considered having a small state
machine module and representing all of the state machines as JSON and having
all of them loaded into memory at once. With thousands of workflows, maybe
this works, maybe it doesn't?
More importantly, what's the best way to trigger an "event"? Are we going
to have to hardcode all of the actions everywhere? I suppose we can start
applying roles at runtime to everything, but we're unsure of the best
approach. We're not asking you to write the code for us, but any speculation
on the best approach would be helpful.