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https://issues.apache.org/jira/browse/NIFI-16470?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mark Payne resolved NIFI-16470.
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Fix Version/s: nifi-api-2.14.0
Assignee: Bob Paulin
Resolution: Fixed
> Implement nifi-api changes to enable evolve flow functionality
> --------------------------------------------------------------
>
> Key: NIFI-16470
> URL: https://issues.apache.org/jira/browse/NIFI-16470
> Project: Apache NiFi
> Issue Type: Improvement
> Reporter: Bob Paulin
> Assignee: Bob Paulin
> Priority: Major
> Fix For: nifi-api-2.14.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> h2. *Proposed nifi-api changes*
> All additions are backward compatible. Existing connectors compile and run
> unchanged.
> h3. *FlowEvolutionContext*
> {code:java}
> public interface FlowEvolutionContext {
> /**
> * The pre-upgrade Active flow. Its flow, parameters, and bundle are from
> the authoritative snapshot.
> * Its configuration has already been migrated and filtered for the
> loaded Connector version.
> */
> FlowContext getPreUpgradeActiveFlowContext();
> /** The bundle of the loaded Connector code, whether loaded at startup or
> changed at runtime. */
> Bundle getPostUpgradeBundle();
> }
> {code}
> The context provides the pre-upgrade flow and the loaded Connector bundle. If
> flow evolution fails, the framework replaces the supplied context with a
> wrapper that rejects every method declared by {{{}FlowEvolutionContext{}}},
> including {{getPreUpgradeActiveFlowContext()}} and
> {{{}getPostUpgradeBundle(){}}}. This covers timeout, cancellation, and any
> other evolution failure, so a connector that retained the context cannot
> continue using it.
> h3. *Connector.prepareForFlowEvolution*
> {code:java}
> default CompletableFuture<Void> prepareForFlowEvolution(FlowEvolutionContext
> context) throws FlowUpdateException {
> return CompletableFuture.completedFuture(null);
> } {code}
> The framework invokes this hook while the pre-upgrade flow is still installed
> and before the upgraded flow removes connections. The method returns promptly
> with a non-null future that owns all preparation work. The hook empties
> pre-upgrade connections the upgraded flow no longer contains before that
> future completes. Synchronous setup can throw {{{}FlowUpdateException{}}};
> asynchronous failures complete the future exceptionally. The hook is not
> called when the Connector leaves Troubleshooting; the managed flow must
> already be empty then.
> The framework cancels the future on evolution timeout, user drain
> cancellation or stop, coordinator interruption, and cluster monitoring
> failure. {{CompletableFuture.cancel(true)}} does not interrupt arbitrary
> executor tasks, so connector implementations must make delegated work
> cooperatively cancellable and must not complete the future while
> fire-and-forget work can still mutate the pre-upgrade flow. Connector-created
> asynchronous threads must preserve the Connector NAR classloader context.
> Only normal completion advances phase one. The framework then predicts the
> upgraded flow with {{getActiveFlow}} and the Working context, and fails
> evolution if a removed connection still holds FlowFiles.
> h3. *Connector.getActiveFlow*
> The method must remain idempotent and build the flow only from the supplied
> context's configuration. When called with the Working context, its result
> predicts what {{applyUpdate}} will install.
> h3. *VersionedConnector*
> * managedProcessGroup, managedParameterContext, and managedFlowBundle
> persist the authoritative flow, its parameters, and the Connector version
> that built it.
> * troubleshootingProcessGroup separately persists user edits made in
> troubleshooting.
> * bundle identifies the Connector code to load and remains independent from
> managedFlowBundle.
> ConnectorInitializationContext is unchanged. It does not gain a bundle getter.
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