KB-2144 XOR node with multiple incoming flows hangs on second execution

Symptoms

When an XOR node with more than one input evaluates for the second time in a process instance, the process remains active on that node and never continues:

Cause

This is expected behavior as per the XOR gateway documentation:

"When multiple incoming flows are connected to the XOR gateway, it allows the first flow token through to an exclusive outgoing flow. Subsequent flow tokens wait for all incoming flows to arrive before executing the output flow decision."

Action

For any XOR node with multiple incoming flows that is both:

1. Expected to execute multiple times.
2. Expected to evaluate after only 1 input is provided.

Modify the process model so that each incoming flow has a separate XOR node with only a single input.

Workaround

For active process instances affected by this, there are two possible options.

Option 1

Manually start the next node that is expected to execute based on the XOR gateway logic.

Option 2

Manually edit the process instance flow according to the Action section above.

Last Reviewed: August 2020