No differentiation between Message Start and Intermediate Events for the correlation key

[hkupitz]

Describe the bug

When checking a process with a Message Start Event that has a message name configured, the check results in the following task:

TASK: Please define a correlation key.

As a message start event does not allow to define a message correlation key directly in the BPMN for Camunda 8, this is not accurate.

Steps to reproduce

1. Create a Camunda 7 BPMN diagram starting with a Message Start Event.
2. Assign a Global message reference to the event.
3. Run the diagram converter.

Expected Behaviour

The above mentioned converter check should not result in a "correlation key" task.

Library version

0.6.2

Camunda version

7.19

[jonathanlukas]

@hkupitz thank you for this bug report.

Indeed, this is a complex topic as the correlationKey is defined in the message element itself, which has no knowledge about where is is referenced.

I see 2 alternatives:

• remove the task message completely and rely on the native linting the modeler has embedded already (I prefer that one)
• adjust the task message to state something like Please define a correlation key if the element is no start event (which is a bit verbose)

cc: @ingorichtsmeier wdyt?

[ingorichtsmeier]

@hkupitz and @jonathanlukas,

all Zeebe clients always require a correlation key for publishing messages. My assumption is, that we need a new command for the GRPC spec like publishStartMessage where the correlation key is optional.

As long as we don't have a solution for an optional correlation key, we should keep it as it is.

[jonathanlukas]

@ingorichtsmeier it works on zeebe side. The only "flaw" is that correlation keys are not required on the model as long as only a start message event uses the message.

[ingorichtsmeier]

it works on zeebe side

May be. But in the Java client I have to write

zeebeClient.newPublishMessageCommand().messageName(messageName).correlationKey(correlationKey)

before I can add .send().

And zbctl says

$ zbctl publish message a
Error: required flag(s) "correlationKey" not set

The command cannot be sent without a correlation key.

[jonathanlukas]

True. The correlation key for a start event is "hidden" for the rest of the process instance execution, but required for implementation of messaging pattern:

https://docs.camunda.io/docs/components/concepts/messages/#message-patterns