Mark Payne created NIFI-6503:
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Summary: Cleanup code around Controller Service management
Key: NIFI-6503
URL: https://issues.apache.org/jira/browse/NIFI-6503
Project: Apache NiFi
Issue Type: Improvement
Components: Core Framework
Reporter: Mark Payne
Assignee: Mark Payne
In reviewing code for the Controller Services, I see a lot of overlapping code
that is not very clean. `StandardControllerServiceProvider` maintains a cache
of all Controller Services. `StandardFlowManager` also keeps a cache of the
Controller Services that exist at the 'root' or 'controller' level. There's no
need to be caching these services twice. `StandardFlowManager` should be simply
delegating calls to `StandardControllerServiceProvider` or vice-versa.
When a Controller Service is removed from the
`StandardControllerServiceProvider`, it first gets the Process Group of the
service. If there is none, it's a root-level controller service so the class
delegates to `StandardFlowManager` to handle the cleanup of the removed
Controller Service. If there is a Process Group, it delegates the cleanup to
the associated Process Group. Both of those pieces of code are nearly
identical. This code should be removed from both places and instead relocated
to the `StandardControllerServiceProvider` to handle.
`ComponentNode` should probably have a method along the lines of
`List<ControllerServiceNode>
getReferencedControllerServices(ControllerServiceProvider provider)` so that
places that need to iterate over the referenced services can do so much more
easily. Depending on the actions taken against this List, it may make more
sense to instead return a `ControllerServiceReferences` type of object that is
capable of performing those actions instead of requiring the caller iterate
over each of them. For example, a `removeReference(ComponentNode
referencingComponent)` method to remove references from all services. This
would more easily facilitate logging, etc. Also note that this is denoted as a
`List`, not a `Set` because if a Processor references a Controller Service
multiple times, it's important to evaluate things like `removeReference`
multiples times. A convenience method of `ControllerServiceReferences
distinct()` could be useful here as well.
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