ATLAS-4766: java.lang.IllegalStateException from JanuGraph while purg…

[sheetalshah1007]

…ing entities at Atlas

What changes were proposed in this pull request?

Problem: DeleteHandlerV1 throws java.lang.IllegalStateException when purging entities because it tries to access graph vertices/edges that have already been removed in the same transaction during batch operations.

Solution:

1. isRelationshipEdge() method - Wrapped vertex type retrieval in try-catch to gracefully handle IllegalStateException when vertices are already removed
2. deleteVertex() method - Added edge.exists() and outVertex.exists() checks to skip edges with removed endpoints; wrapped loop in try-catch for resilience

How was this patch tested?

New test suite DeleteHandlerV1Test.java:

• testIsRelationshipEdgeWithPurgedEndpoint() - Verifies method handles purged endpoints safely
• testPurgeManagerAfterSubordinateAlreadyPurged() - Tests sequential purge of related entities
• testBatchPurgeManagerAndSubordinates() - Tests batch purge of multiple entities in one transaction

All tests confirm no IllegalStateException is thrown during delete/purge operations.

[chaitalicod]

LGTM +1

[sheetalshah1007]

Added the attached implementation notes for ATLAS-4766. The document provides additional context on the JanusGraph IllegalStateException failure scenario, the DeleteHandlerV1 resilience changes, the dual-layer protection strategy, and the associated test coverage.
ATLAS-4766_JanusGraph_IllegalStateException_Purge_Resilience_Implementation_Notes.md