# Dev Log: Artificial Backfill Limiter

**Date:** 2026-01-12
**Author:** Jules (AI Agent)
**Status:** Successful
**Related Files:** `wsgi_handler.py`, `templates/deals.html`, `keepa_deals/backfiller.py`, `keepa_deals/db_utils.py`

## Task Overview
The objective was to implement a configurable "Artificial Limit" for the Backfiller process. This allows the user to manually stop the backfill task after a specific number of deals (e.g., 3,000) have been processed. The primary use case is to simulate a "Database Full" state, which stops the resource-intensive backfill and allows the "Refiller" (`update_recent_deals`) to take over its high-frequency delta-sync operations. Without this, the Refiller is often blocked by the Backfiller's long-running lock or token consumption.

## Challenges Faced

1.  **Architecture Separation:** 
    *   The initial approach considered adding raw SQL queries directly into the `backfiller.py` business logic loop to check the deal count.
    *   **Issue:** This violated the separation of concerns, as `backfiller.py` should rely on `db_utils.py` for all database interactions. It also introduced potential import errors (missing `sqlite3`).
    *   **Solution:** Refactored the counting logic into a dedicated `get_deal_count()` function within `keepa_deals/db_utils.py`, keeping the business logic clean.

2.  **Persistence of Configuration:**
    *   The limit setting needed to persist across server restarts and be accessible by independent background workers (Celery) that do not share the Flask session.
    *   **Solution:** Utilized the existing `system_state` table (via `get_system_state` / `set_system_state`) to store `backfill_limit_enabled` and `backfill_limit_count`. This ensures all processes verify the same source of truth.

3.  **UI Integration:**
    *   The "Deals" configuration page (`/deals`) already had a form for the Keepa Query.
    *   **Solution:** Added a secondary form for the Backfill Limiter. To prevent conflicts, a hidden input (`name="action"`) was implemented to distinguish between `update_query` and `update_limit` POST requests handled by the same route.

## Actions Taken

1.  **Backend Logic (`keepa_deals/backfiller.py`):**
    *   Modified the main processing loop to check the system state before fetching each new page of deals.
    *   Implemented a check: `if enabled and current_count >= limit: break`.
    *   This ensures the task stops gracefully, releasing its Redis lock, which is the trigger for the Refiller to resume.

2.  **Database Utility (`keepa_deals/db_utils.py`):**
    *   Added `get_deal_count()`: A safe, context-managed function to return the total row count of the `deals` table.

3.  **Frontend (`templates/deals.html`):**
    *   Added a "Backfill Limiter" card with a checkbox and number input.
    *   Styled to match the existing "Settings Card" aesthetic.

4.  **Controller (`wsgi_handler.py`):**
    *   Updated the `/deals` route to handle the new `update_limit` action.
    *   Added logic to fetch current settings on page load to pre-fill the form.

5.  **Verification:**
    *   Created and ran a script `verify_limit_logic_v2.py` that mocked the database state and verified that the backfiller logic correctly identified when to stop and when to continue based on the configured limit.

## Outcome
The task was **Successful**. The Backfill Limiter is now active and configurable via the Admin UI. This feature enables precise control over the system's lifecycle, allowing the user to force a transition from "Bulk History Collection" (Backfill) to "Real-Time Updates" (Refiller) at a chosen database size.

## Reference: How to Use
1.  Navigate to **Admin > Deals**.
2.  In the **Backfill Limiter** card, check "Enable Artificial Limit".
3.  Enter the desired maximum number of deals (e.g., 2800).
4.  Click **Update Limit**.
5.  **Behavior:**
    *   The Backfiller will continue running until the `deals` table count meets or exceeds this number.
    *   Once reached, it will log "Artificial backfill limit reached" and exit.
    *   The Redis lock `backfill_deals_lock` will be released.
    *   The Refiller (`update_recent_deals`), running every minute, will detect the released lock and begin processing new updates.