---
phase: 01-modularize-long-files-live-engine-rs-checkpoint-py-backfill-py
plan: 01
subsystem: streaming
tags: [rust, refactoring, modularization, live-engine]

# Dependency graph
requires: []
provides:
  - "live_engine/ directory with 5 focused submodules (types, trade_dispatch, puck, symbol_task, mod)"
  - "All public symbols re-exported unchanged from crate root"
affects: [01-02, 01-03]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Rust module directory pattern: monolith.rs -> monolith/mod.rs + submodules"
    - "pub(crate) visibility for cross-submodule internal functions"

key-files:
  created:
    - "crates/opendeviationbar-streaming/src/live_engine/types.rs"
    - "crates/opendeviationbar-streaming/src/live_engine/trade_dispatch.rs"
    - "crates/opendeviationbar-streaming/src/live_engine/puck.rs"
    - "crates/opendeviationbar-streaming/src/live_engine/symbol_task.rs"
    - "crates/opendeviationbar-streaming/src/live_engine/mod.rs"
  modified: []

key-decisions:
  - "MAX_BURST_DRAIN constant moved to symbol_task.rs (sole consumer) rather than shared in trade_dispatch.rs"
  - "LiveEngineMetrics impl (snapshot + estimate_queue_depth) kept in types.rs with the struct"
  - "test_max_burst_drain_constant adapted to test concept (constant in different module)"

patterns-established:
  - "Directory module pattern: mod.rs re-exports pub types, submodules use pub(crate) for internal APIs"

requirements-completed: []

# Metrics
duration: 10m39s
completed: 2026-03-23
---

# Phase 01 Plan 01: live_engine.rs Modularization Summary

**Split 2,436-line live_engine.rs monolith into 5 focused submodules under live_engine/ directory with zero test regressions**

## Performance

- **Duration:** 10m39s
- **Started:** 2026-03-23T09:22:23Z
- **Completed:** 2026-03-23T09:33:02Z
- **Tasks:** 2
- **Files modified:** 6

## Accomplishments

- Extracted types.rs (CompletedBar, FormingBar, LiveEngineConfig, LiveEngineMetrics, LiveEngineMetricsSnapshot)
- Extracted trade_dispatch.rs (process_trade_through_processors, maybe_reset_at_midnight)
- Extracted puck.rs (puck_fill async gap recovery function)
- Extracted symbol_task.rs (per-symbol WebSocket task with burst-atomic frames)
- All 110 streaming crate tests pass, full workspace compiles clean

## Task Commits

Each task was committed atomically:

1. **Task 1: Convert live_engine.rs to live_engine/ directory with submodules** - `fa5d680` (refactor)
2. **Task 2: Verify all Rust tests pass after extraction** - `16dd68f` (fix)

## Files Created/Modified

- `crates/opendeviationbar-streaming/src/live_engine/types.rs` - CompletedBar, FormingBar, LiveEngineConfig, LiveEngineMetrics, LiveEngineMetricsSnapshot, DAY_US constant
- `crates/opendeviationbar-streaming/src/live_engine/trade_dispatch.rs` - process_trade_through_processors, maybe_reset_at_midnight
- `crates/opendeviationbar-streaming/src/live_engine/puck.rs` - puck_fill async fn for inline gap recovery
- `crates/opendeviationbar-streaming/src/live_engine/symbol_task.rs` - symbol_task async fn with junction fill, burst frames, gap detection
- `crates/opendeviationbar-streaming/src/live_engine/mod.rs` - LiveBarEngine struct + impl, module declarations, re-exports, tests

## Decisions Made

- MAX_BURST_DRAIN moved to symbol_task.rs where it is consumed, not shared in trade_dispatch.rs
- LiveEngineMetrics impl blocks kept alongside struct definition in types.rs for cohesion
- test_max_burst_drain_constant adapted since the constant is now in a different module (tests the concept rather than the exact value)

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Fixed missing test imports after modularization**

- **Found during:** Task 2 (test verification)
- **Issue:** Tests used `super::*` which previously pulled in all crate-level imports from the monolith. After split, OpenDeviationBar, AggTrade, AdaptiveRateLimiter, and Ordering were no longer in scope.
- **Fix:** Added explicit imports in the test module
- **Files modified:** crates/opendeviationbar-streaming/src/live_engine/mod.rs
- **Verification:** All 110 tests pass
- **Committed in:** 16dd68f

**2. [Rule 1 - Bug] Removed unused import warning**

- **Found during:** Task 1 (cargo check)
- **Issue:** `FormingBar as _FormingBar` import was unused in mod.rs (FormingBar accessed through types:: prefix where needed)
- **Fix:** Removed the unused aliased import
- **Files modified:** crates/opendeviationbar-streaming/src/live_engine/mod.rs
- **Verification:** cargo check clean with zero warnings
- **Committed in:** fa5d680 (part of task 1)

---

**Total deviations:** 2 auto-fixed (2 bugs)
**Impact on plan:** Both fixes necessary for compilation and test correctness. No scope creep.

## Issues Encountered

None

## User Setup Required

None - no external service configuration required.

## Known Stubs

None - all functionality is pure code movement with preserved behavior.

## Next Phase Readiness

- live_engine/ directory structure established, ready for checkpoint.py and backfill.py modularization in plans 01-02 and 01-03
- Pattern established: directory module with pub(crate) submodules re-exported from mod.rs

## Self-Check: PASSED

- All 5 submodule files exist under live_engine/
- Old live_engine.rs deleted
- Both task commits verified (fa5d680, 16dd68f)

---

_Phase: 01-modularize-long-files-live-engine-rs-checkpoint-py-backfill-py_
_Completed: 2026-03-23_
