---
phase: 29-delete-strategy-exchange-gap-floor
plan: 02
subsystem: sidecar
tags: [clickhouse, exchange-gap, aion, resume-tid, kintsugi-log]

requires:
  - phase: 29-delete-strategy-exchange-gap-floor/01
    provides: "_aion_delete_after_resume() extracted to delete_strategy.py"

provides:
  - "_clamp_resume_tid_above_exchange_gaps() prevents futile REST fills for exchange gap TID ranges"
  - "Single CH query to kintsugi_log gets highest exchange gap TID per symbol"

affects: [sidecar-startup, fill-from-rest, kintsugi]

tech-stack:
  added: []
  patterns:
    [
      "exchange gap floor: clamp resume TID above permanent exchange gaps before fill_from_rest",
      "non-fatal guard: query failure logs warning, sidecar starts regardless",
    ]

key-files:
  created:
    - python/opendeviationbar/sidecar/exchange_gap_floor.py
  modified:
    - python/opendeviationbar/sidecar/__init__.py
    - tests/test_sidecar_exchange_gap_floor.py

key-decisions:
  - "Extracted to exchange_gap_floor.py module (not inline in __init__.py) per package structure conventions"
  - "Single query with GROUP BY symbol + max(ariadne_from_id) rather than per-symbol queries"
  - "Max semantics: resume TID is only raised, never lowered by exchange gap floor"
  - "Non-fatal: ConnectionError/OSError/RuntimeError caught, sidecar starts regardless"

patterns-established:
  - "Exchange gap floor: clamp resume TID above known exchange gaps to avoid futile REST fills"

requirements-completed: [RESUME-01]

duration: 5min
completed: 2026-03-28
---

# Phase 29 Plan 02: Exchange Gap Floor Summary

**Exchange gap floor clamping prevents fill_from_rest from attempting unfillable TID ranges using a single kintsugi_log query per startup**

## Performance

- **Duration:** 5 min
- **Started:** 2026-03-28T07:54:21Z
- **Completed:** 2026-03-28T07:59:19Z
- **Tasks:** 1 (TDD: RED + GREEN)
- **Files modified:** 3

## Accomplishments

- `_clamp_resume_tid_above_exchange_gaps()` function queries kintsugi_log for exchange_gap entries and clamps resume TIDs above them
- Call site inserted between Step 2 (resume TID calculation) and Step 3 (DELETE) in `_create_engine()`
- Non-fatal error handling ensures sidecar starts even if kintsugi_log query fails
- 7 unit tests covering all edge cases (clamp, no-op, already above, per-symbol isolation, query failure, None TID)

## Task Commits

Each task was committed atomically:

1. **Task 1 (RED): Failing tests for exchange gap floor** - `4a94977` (test)
2. **Task 1 (GREEN): Implement exchange gap floor clamping** - `fbbd221` (feat)

## Files Created/Modified

- `python/opendeviationbar/sidecar/exchange_gap_floor.py` - Exchange gap floor clamping function (RESUME-01)
- `python/opendeviationbar/sidecar/__init__.py` - Import + call site between Step 2 and Step 3
- `tests/test_sidecar_exchange_gap_floor.py` - 7 unit tests for clamping behavior

## Decisions Made

- Extracted to dedicated `exchange_gap_floor.py` module rather than inline in `__init__.py`, following the established package structure pattern (same as `delete_strategy.py`)
- Used `TYPE_CHECKING` guard for `OpenDeviationBarCache` import to avoid circular imports at runtime

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 3 - Blocking] ANN401 ruff error for `Any` type annotation**

- **Found during:** Task 1 GREEN (commit attempt)
- **Issue:** ruff pre-commit hook rejected `Any` type in `ch_cache` parameter
- **Fix:** Used `TYPE_CHECKING` guard with `OpenDeviationBarCache` type, matching `delete_strategy.py` pattern
- **Files modified:** `python/opendeviationbar/sidecar/exchange_gap_floor.py`
- **Verification:** ruff passes, tests still pass
- **Committed in:** fbbd221 (part of GREEN commit)

---

**Total deviations:** 1 auto-fixed (1 blocking)
**Impact on plan:** Type annotation fix follows established project conventions. No scope creep.

## Issues Encountered

None

## User Setup Required

None - no external service configuration required.

## Known Stubs

None - all data paths are wired to kintsugi_log query.

## Next Phase Readiness

- Exchange gap floor guard is active in sidecar startup path
- Ready for Phase 29 Plan 03 (if any) or next phase
- The guard handles the 2 known exchange gaps across all history

## Self-Check: PASSED

- All 3 files exist on disk
- Both commit hashes (4a94977, fbbd221) verified in git log

---

_Phase: 29-delete-strategy-exchange-gap-floor_
_Completed: 2026-03-28_
