Epic: DO_WHILE iteration cleanup and Timeline UI rendering fixes (Q4 Roadmap 1.2)

[nthmost-orkes]

DO_WHILE Iteration Cleanup and Timeline UI Rendering

Context

DO_WHILE tasks accumulate iterations indefinitely in the database without cleanup, causing database bloat, memory exhaustion, and production outages. Additionally, the Timeline UI becomes blank when viewing DO_WHILE workflows with nested SWITCH defaultCase or FORK_JOIN_DYNAMIC tasks, creating a critical user experience issue.

Current State vs. Desired State

Current:

• DO_WHILE iterations accumulate indefinitely in database
• No cleanup mechanism for completed iterations
• Timeline UI renders blank for DO_WHILE with nested SWITCH defaultCase
• Timeline UI renders blank for DO_WHILE with nested FORK_JOIN_DYNAMIC
• Production outages due to database bloat and memory exhaustion

Desired:

• Configurable iteration cleanup with keepLastN parameter
• Database remains stable even with 1000+ iterations
• Timeline UI renders correctly for all DO_WHILE workflow patterns
• Opt-in cleanup behavior, fully backward compatible

Technical Scope

What Needs to Be Implemented

• [ ] Implement removeIterations() method in DO_WHILE task handler
• [ ] Add ExecutionDAO dependency for database cleanup operations
• [ ] Add keepLastN parameter to control iteration retention (configurable, opt-in)
• [ ] Fix Timeline UI rendering for DO_WHILE with SWITCH defaultCase
• [ ] Fix Timeline UI rendering for DO_WHILE with FORK_JOIN_DYNAMIC
• [ ] Add configuration options for cleanup behavior

Implementation Approach

Implement iteration cleanup logic in the DO_WHILE task handler with configurable retention policy. Fix Timeline UI rendering issues for nested task scenarios. Ensure all changes are backward compatible and opt-in.

Files/Components Affected

• Backend: DoWhile.java (add cleanup logic ~50 lines)
• Backend: ExecutionDAO integration
• Frontend: Timeline UI rendering logic
• Configuration: Add cleanup parameters

Dependencies

• No blocking dependencies on other issues
• Builds foundation for Phase 2 DO_WHILE list iteration (#624)

Related Issues

• Fixes #534 - Timeline UI blank with DO_WHILE loop
• Fixes #613 - DO_WHILE database bloat and memory issues

Success Criteria

• [ ] DO_WHILE workflows can run 1000+ iterations without database bloat
• [ ] Database performance remains stable with iteration cleanup enabled
• [ ] Timeline UI renders correctly for DO_WHILE with nested SWITCH defaultCase
• [ ] Timeline UI renders correctly for DO_WHILE with nested FORK_JOIN_DYNAMIC
• [ ] Cleanup is configurable via keepLastN parameter
• [ ] Backward compatibility maintained - existing workflows work unchanged
• [ ] No performance regression for workflows not using cleanup

Testing Requirements

• [ ] Unit tests for removeIterations() method
• [ ] Integration tests with 100+ iterations verifying cleanup
• [ ] UI tests verifying Timeline rendering with SWITCH scenarios
• [ ] UI tests verifying Timeline rendering with FORK_JOIN_DYNAMIC scenarios
• [ ] Database compatibility tests across supported databases
• [ ] Performance validation for large iteration counts
• [ ] Backward compatibility tests with existing DO_WHILE workflows

Documentation Needs

• [ ] Documentation for keepLastN parameter configuration
• [ ] Configuration guide for iteration cleanup behavior
• [ ] Release notes highlighting database bloat fix
• [ ] Release notes highlighting Timeline UI rendering fixes
• [ ] Migration guide for enabling cleanup on existing workflows
• [ ] Best practices for choosing keepLastN values

Notes

Backward Compatibility: Cleanup is opt-in via keepLastN parameter. Workflows without this parameter behave exactly as before, ensuring zero breaking changes.

UI Impact: Fixing Timeline rendering is critical for user experience and perception. Blank UI creates impression of broken software.

Foundation for Phase 2: This cleanup mechanism must work correctly with Phase 2's DO_WHILE list iteration feature (#624).