Multiple process engine with different DB

Camunda 7 Topics Discussion & Questions
1

Hello,
I am novice to use camunda platform and i am working with camunda community version 7.15.0 on wildfly 22 and openjdk 11.
I have compiled two very similar applications which contain the same named “MyEjb extends JavaDelegate”, and both bpmn invoke this by delegateExpression ${myEjb}
I want these two applications to run on two different engines connected to two different DB.
Is it possible to do this with the community version or i need the enterprise version?
NB.: I’m not setting up any tenants, it’s a problem?

In my standalone.xml i’ve

defaultEngine → DB_GENERICS (h2)
engineAppA → DB_A ( postgres)
engineAppB → DB_B (postgres)

AppA

    • pom.xml
    • AppA.ear
        • AppA.war
        • pom.xml
        • src / main /
            • java
                • MyEjb.java
            • resources
                • AppA.bpmn
                • META-INF / processes.xml ( engineAppA)
                  AppB
    • pom.xml
    • AppB.ear
        • AppB.war
        • pom.xml
        • src / main /
            • java
                • MyEjb.java
            • resources
                • AppB.bpmn
                • META-INF / processes.xml ( engineAppB)
2

Hi @Giuseppe_Infurna
Welcome to the forum.
You mentioned:

This seems to indicate that they’re completely independent of one another so there’s not likely to be any problem here at all.
Is there a problem that you’re expecting from this setup?

3

HI @Niall ,
So, when i tried with only one ear on one engine, everything worked fine.
when i tried with two ears and two engines i got the error

ENGINE-16004 Exception while closing command context: Unknown property used in expression: $ {myEjb}. Cause: Cannot resolve identifier ‘myEjb’: org.camunda.bpm.engine.ProcessEngineException: Unknown property used in expression: $ {myEjb}. Cause: Cannot resolve identifier ‘myEjb’ …

I cleaned up both DBs and restarted wildfly and everything worked.

4

Oh, sorry i misunderstood - you’re deploying two engines to a wildfly container?
Is there a reason that you don’t want to use a single engine?
Also is myEJB exactly the same in each deployment?

5

The idea is to have the same process but with separate db one for each client.
So I thought about cloning the process and renaming the ids for each client
<bpmn: process id = “processA” name = “processA”> for customer A
<bpmn: process id = “processB” name = “processB”> for customer B

The logic (myEjb) is the same for all clients.

6

You could probably move the common EJB code and have it available on the Wildfly server for all applications to access

7

Being two separate ears why should camunda have trouble finding the correct javaDelegate (ejb)?
How does camunda to be find javaDelegate by identifier?

8

I found the problem. The archive-name in processes.xml was the same for both ear, when deploying a new version of ear, camunda struggles to associate the correct process with its archive.
Solution: I removed archive-name in processes.xml so that camunda uses applicationName instead of archive-name in act_re_deployment.