Nifi is unable to import a flow from Nifi Registry, if that flow contain one or more process groups that
- have a parameter context
- is already under source control.
To reproduce the error, create a process group (groupA), add some processor, add a parameter context, and map the parameter(s) to processor properties. Check in groupA to Registry, and remove it from the canvas. Create a new group, groupB, that acts as the root group in the flow. Enter groupB, and import groupA from Registry. Check in groupB.
From a different Nifi instance, import groupB from Registry. Nifi gives the following error message:
An unexpected error has occurred. Please check the logs for additional details (the logs do not contain any further error message)
A different error message is produced if the flow is already on the Nifi canvas, and updated via the Version->Change version menu:
Failed to update flow to new version due to java.lang.NullPointerException
A work-around is to remove the sub-groups from source control. E.g. in the example above, navigate to groupA on the Nifi instance where the flow was created, and stop version control of groupA. Check in the changes of groupB. You should now be able to import groupB from Registry on a different Nifi instance.