Kris Verlaenen [
https://community.jboss.org/people/KrisVerlaenen] created the discussion
"Re: jbpm5 scale out reference architecture.."
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Hi,
This looks like a decent session management strategy for large deployments (where you need
to be able to manage a lot more than just a few thousand of active process instances).
It is indeed possible to migrate sessions and process instances to a different DB. Note
that a lot more is actually be possible, that your strategy is not using (which might not
mean that there is an issue with this of course, just mentioning as this could give you
more options to scale as well).
You can move a session from one node to other. So if node1 instantiated a session, but at
some point later, node1 is busy, you can restore the same session on node2 and continue
execution of the process instance there. So this gives you more flexibility than defined
in "For requests pertaining to a specific process instance, consult the table in (5)
& (6) and route to appropriate node". But this is probably a trade of between
cpu and db (as moving to another node probably means that the session needs to be restored
from db while it might be in cache on the original node). We do however recommend to not
run the same session in parallel on multiple nodes (as that would usually lead to
conflicts and decreased performance. So binding a session to a node isn't necessarily
a bad strategy (just means you have some flexibility to reallocate if necessary).
You can even move a process instance to another session. Node that you should only
consider this if your process instance is not linked to its session state (otherwise you
should always use them together). Examples where session state is used is for example
when you are using timers or when you are using business rules anywhere in your process.
We're working on setting up improved session management for cases like this
(instantiate session remotely on nodes based on a specific strategy and distribute
requests). If you believe this would be something we could collaborate on, let me know !
Kris
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