NIFI-16344 Preserve Swap File Ordering during Selective Drop

[markap14]

Summary

NIFI-16344

Selective FlowFile drop rewrites swap files containing matching records. Rewritten files were appended after unchanged swap files, allowing newer FlowFiles to be polled before retained older FlowFiles. This change replaces rewritten swap locations in their original positions and adds a multiple-swap-file regression test that verifies FIFO polling order.

Tracking

Issue Tracking

• Apache NiFi Jira issue created

Pull Request Tracking

• Pull Request title starts with Apache NiFi Jira issue number
• Pull Request commit message starts with Apache NiFi Jira issue number
• Pull request contains a commit with Verified signature status

Pull Request Formatting

• Pull Request based on current revision of the main branch
• Pull Request refers to a feature branch with one commit containing changes

Verification

Build

Targeted reactor build and queue tests completed using JDK 21:

./mvnw -pl nifi-framework-bundle/nifi-framework/nifi-framework-core -am -Dtest=org.apache.nifi.controller.queue.clustered.TestSwappablePriorityQueue,org.apache.nifi.controller.TestStandardFlowFileQueue,org.apache.nifi.controller.queue.clustered.TestSocketLoadBalancedFlowFileQueue -Dsurefire.failIfNoSpecifiedTests=false test

Tests run: 73, Failures: 0, Errors: 0, Skipped: 0.

Licensing

• No new dependencies

Documentation

• No documentation changes required

[bobpaulin]

Hi @markap14 the new code preserves the order as intended. One nit comment just for readability. Otherwise test coverage and functionality matches as expected.

[markap14]

[grok-4.6] Good catch on the incomplete rename from @bobpaulin's suggestion — the declaration was updated to rewrittenSwapLocations but three uses in dropFlowFiles still referenced updatedSwapLocations, which failed code-compliance / Validate with:

[WARNING] SwappablePriorityQueue.java:[1042,19] (coding) UnusedLocalVariable: Unused named local variable 'rewrittenSwapLocations'.

Fixed in 28249a3 (signed); all references in that block now use rewrittenSwapLocations.

[bobpaulin]

Thanks for the update @markap14. This looks good.