Possible to open multiple message subscriptions for the same event

[korthout]

Describe the bug

When a user deploys the same process multiple times without changes, additional message start event subscriptions are opened, if there are top-level message start events present in the process.

This does not lead to issues because published messages only create a single instance, but strangely, additional message subscriptions are opened.

To Reproduce

• run Zeebe Play
• deploy a simple process with a top-level message start event
• deploy the same process again
• in Zeebe Play, notice the secondary message subscription

Expected behavior

Only a single message subscription exist for any message event at any time.

[korthout]

I'm giving this low severity because there is no user impact.

[skayliu]

Hey, @korthout, i dig a little bit, when deploy the same process again, we can find the processesMetadata.duplicate is true.

We have check top-level time start event isDuplicate at DeploymentCreateProcessor.java#L129, bud the others are not.

Hey, @korthout @Zelldon could #6314 #6480 caused by this?

"processesMetadata":[
            {
                "version":6,
                "bpmnProcessId":"Process_0k1nnh5",
                "processDefinitionKey":2251799813685489,
                "checksum":"+tH+Q1NPNoxIlEKqMgHBQw==",
                "resourceName":"Process_0k1nnh5.bpmn",
                "duplicate":true
            }
        ]

[korthout]

@skayliu Thanks for looking into this.

We have check top-level time start event isDuplicate at DeploymentCreateProcessor.java#L129, bud the others are not.

👍 Good find! Adding that check for the other start event subscriptions could be a good solution.

• CREATE Deployment command processing can reach easily max message size #6314

This is not related.

• Do not distribute duplicate deployments #6480

This is not caused by this, but could probably be solved similarly using your suggestion.