Timer start event in a cluster

Camunda 7 Topics Discussion & Questions
1

Hello,

if I have a process application in a cluster and have a process model with a timer start event which starts a process instance, say, every hour,

  • will an instance be started on each cluster node (e.g. every hour I’ll have N instances)
    or
  • will just one process instance be started every hour?

What is the intended behaviour in this case?

Thank you!

2

Each node should hold no state.
All state is in the DB - so no matter how many clusters you have there will only ever be one job that’s waiting to fired.
So it will never run more than once.

3

I have another related question. How is this job identified? I.e. how does the engine decide whether it’s the same timer or not?

If I deploy two process models with a timer start event, how will the engine know that these are two different models? Or, if I deploy a newer version of an existing model, how will the engine know that it’s the same model and hence only one instance per hour should be started?

I’d assume it’s done based on the process model key + timer event id, but it’s just my assumption and not knowlege. Do you know it for sure?