kevdoran opened a new pull request, #10876:
URL: https://github.com/apache/nifi/pull/10876

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   # Summary
   
   [NIFI-15255](https://issues.apache.org/jira/browse/NIFI-15255)
   
   ## Motivation
   
   Connector working configuration currently lives only in memory and is 
persisted to `flow.json.gz`. There is no way for an external system to manage 
or override it. This PR introduces `ConnectorConfigurationProvider`, a 
framework extension point that allows Connector name and working flow 
configuration to be persisted in and loaded from an external store.
   
   ## Architecture
   
   `ConnectorConfigurationProvider` is a nullable collaborator of 
`StandardConnectorRepository`. When absent (the default), all behavior is 
unchanged. When present, the repository calls it on every read and write:
   
   ```mermaid
   graph TB
       subgraph "REST / Service / DAO Layers"
           CR["ConnectorResource"]
           SF["NiFiServiceFacade"]
           DAO["ConnectorDAO"]
       end
   
       subgraph "Controller Layer"
           FC["FlowController"]
           FM["FlowManager"]
       end
   
       subgraph "Repository Layer"
           REPO["ConnectorRepository (StandardConnectorRepository)"]
           ASSETREPO["ConnectorAssetRepository"]
           CCP["🆕 ConnectorConfigurationProvider (nullable, NAR-discovered)"]
       end
   
       subgraph "In-Memory"
           CN["ConnectorNode"]
           AFC["activeFlowContext"]
           WFC["workingFlowContext"]
       end
   
       subgraph "Persistence"
           FLOW["flow.json.gz"]
           EXT["🆕 External Store (database, etc.)"]
       end
   
       CR --> SF --> DAO --> REPO
       DAO --> FM --> CN
       REPO --> CN
       REPO --> ASSETREPO
       REPO -->|"load / save / discard / delete / verifyCreate"| CCP
       CCP --> EXT
       CN --> AFC
       CN --> WFC
       SF -.->|"saveFlow()"| FLOW
   ```
   
   **Read operations** (`getConnector`, `getConnectors`, `addConnector`, 
`applyUpdate`) call `provider.load()` and override the in-memory name and 
working flow configuration with the provider's values.
   
   **Write operations** (`configureConnector`, `discardWorkingConfiguration`, 
`updateConnector`) sync with the provider *before* modifying in-memory state. 
If the provider throws, the `ConnectorNode` is unchanged.
   
   **Cluster sync** (`inheritConfiguration`) does *not* interact with the 
provider, as the design is that cluster operations such as a new node joining 
the cluster should always inherit the current, local connector state.
   
   Provider failures propagate as `ConnectorConfigurationProviderException` 
rather than being silently swallowed, giving implementations control over 
failure semantics.
   
   ## New Types (`nifi-framework-api`)
   
   - **`ConnectorConfigurationProvider`** -- Extension point interface: 
`initialize`, `load`, `save`, `discard`, `delete`, `verifyCreate`
   - **`ConnectorConfigurationProviderInitializationContext`** -- Exposes 
`Map<String, String>` properties (following the established NiFi initialization 
context pattern)
   - **`ConnectorWorkingConfiguration`** -- Mutable POJO carrying `name` and 
`List<VersionedConfigurationStep> workingFlowConfiguration`
   - **`ConnectorConfigurationProviderException`** -- RuntimeException for 
provider failures
   
   ## Other Changes
   
   - **Centralized `ConnectorNode` metadata updates** -- All name modifications 
now go through `ConnectorRepository.updateConnector()` instead of calling 
`connectorNode.setName()` directly. Updated call sites: 
`StandardNiFiServiceFacade` (via new `ConnectorDAO.updateConnector()`), 
`VersionedFlowSynchronizer`.
   - **Centralized create verification** -- 
`ConnectorRepository.verifyCreate()` checks for duplicate IDs and delegates to 
`provider.verifyCreate()`. `StandardConnectorDAO.verifyCreate()` now delegates 
to the repository.
   - **Removed redundant `addConnector()`** -- 
`StandardConnectorDAO.createConnector()` no longer calls `addConnector()` since 
`FlowManager.createConnector()` already does this.
   
   ## Configuration
   
   ```properties
   
nifi.components.connectors.configuration.provider.implementation=com.example.MyProvider
   
nifi.components.connectors.configuration.provider.db.url=jdbc:postgresql://localhost/nifi
   ```
   
   ## Testing
   
   25 unit tests in `TestStandardConnectorRepository` covering read overrides, 
write-through atomicity, partial merge semantics, lifecycle delegation, 
exception propagation, cluster sync exclusion, and `verifyCreate` / 
`addConnector` atomicity. Updated `StandardConnectorDAOTest` for `verifyCreate` 
delegation.
   
   ## Files Changed
   
   17 files, +975 / -30. Four new types in `nifi-framework-api`, one new 
implementation in `nifi-framework-core`, twelve modified files across 
`nifi-framework-core`, `nifi-framework-core-api`, `nifi-web-api`, and 
`nifi-properties`.
   


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