Camunda BPM execution and variable scope misunderstanding

Question

I work with the camunda BPM process engine and think it is important to understand some concepts. At the moment I struggle a little bit with the concept of Process Executions and Variable Scopes.

To understand what happens during a process execution I designed the following demo process and marked the activities inside the same execution with the same color. I could do this because I debugged the execution id inside each activity.

I understand most of it. What surprised me is that an input parameter opens a new execution (Task 1.3). Thanks meyerdan for clarification on this.

What I do not understand is that "Task 2.2" is inside the same execution of "Task 2.1". A quote from the camunda documentation about Executions is

Internally, the process engine creates two concurrent executions inside the process instance, one for each concurrent path of execution.

So I would have exepcted that Task 2.1 / Task 2.2 and Task 3.1 each live inside an own execution.

Is anyone able to explain this?

My main motivation to understand this is the impact it has on process variable scopes. I did not figure out so far what the Java API methods

VariableScope#getVariable / VariableScope#setVariable

VariableScope#getVariableLocal / VariableScope#setVariableLocal

really do. I first thought that the "Local" variants only refer to the current execution and the other ones only refer to the process instance execution - but that seems to be only half of the truth. These are getters and setters where I miss JavaDoc painfully ;-) Bonus points for also explaining this!

Thanks!

You will find the process in a Maven project with an executable JUnit test on GitHub.

Answer 1

Have a look at Variable Scopes and Variable Visibility

A quote from the documentation (Java Object API) about the setVariable method:

Note that this code sets a variable at the highest possible point in the hierarchy of variable scopes. This means, if the variable is already present (whether in this execution or any of its parent scopes), it is updated. If the variable is not yet present, it is created in the highest scope, i.e. the process instance. If a variable is supposed to be set exactly on the provided execution, the local methods can be used.