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Add database transaction support with atomic operations

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- Create transaction.py with @transactional decorator, atomic() context manager
- Add TransactionPropagation modes: REQUIRED, REQUIRES_NEW, NESTED
- Add savepoint support for nested transactions with partial rollback
- Update connection.py with TransactionManager, get_transactional_session
- Update service.py with bulk operations (bulk_mark_downloaded, bulk_delete)
- Wrap QueueRepository.save_item() and clear_all() in atomic transactions
- Add comprehensive tests (66 transaction tests, 90% coverage)
- All 1090 tests passing
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Lukas
2025-12-25 18:05:33 +01:00
parent b2728a7cf4
commit 1ba67357dc
15 changed files with 3385 additions and 202 deletions
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17
docs/CHANGELOG.md
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@@ -71,6 +71,23 @@ This changelog follows [Keep a Changelog](https://keepachangelog.com/) principle
_Changes that are in development but not yet released._
### Added
- Database transaction support with `@transactional` decorator and `atomic()` context manager
- Transaction propagation modes (REQUIRED, REQUIRES_NEW, NESTED) for fine-grained control
- Savepoint support for nested transactions with partial rollback capability
- `TransactionManager` helper class for manual transaction control
- Bulk operations: `bulk_mark_downloaded`, `bulk_delete`, `clear_all` for batch processing
- `rotate_session` atomic operation for secure session rotation
- Transaction utilities: `is_session_in_transaction`, `get_session_transaction_depth`
- `get_transactional_session` for sessions without auto-commit
### Changed
- `QueueRepository.save_item()` now uses atomic transactions for data consistency
- `QueueRepository.clear_all()` now uses atomic transactions for all-or-nothing behavior
- Service layer documentation updated to reflect transaction-aware design
### Fixed
- Scan status indicator now correctly shows running state after page reload during active scan

117
docs/DATABASE.md
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@@ -197,14 +197,97 @@ Source: [src/server/models/download.py](../src/server/models/download.py#L63-L11
---
## 6. Repository Pattern
## 6. Transaction Support
### 6.1 Overview
The database layer provides comprehensive transaction support to ensure data consistency across compound operations. All write operations can be wrapped in explicit transactions.
Source: [src/server/database/transaction.py](../src/server/database/transaction.py)
### 6.2 Transaction Utilities
| Component | Type | Description |
| ------------------------- | ----------------- | ---------------------------------------- |
| `@transactional` | Decorator | Wraps function in transaction boundary |
| `atomic()` | Async context mgr | Provides atomic operation block |
| `atomic_sync()` | Sync context mgr | Sync version of atomic() |
| `TransactionContext` | Class | Explicit sync transaction control |
| `AsyncTransactionContext` | Class | Explicit async transaction control |
| `TransactionManager` | Class | Helper for manual transaction management |
### 6.3 Transaction Propagation Modes
| Mode | Behavior |
| -------------- | ------------------------------------------------ |
| `REQUIRED` | Use existing transaction or create new (default) |
| `REQUIRES_NEW` | Always create new transaction |
| `NESTED` | Create savepoint within existing transaction |
### 6.4 Usage Examples
**Using @transactional decorator:**
```python
from src.server.database.transaction import transactional
@transactional()
async def compound_operation(db: AsyncSession, data: dict):
# All operations commit together or rollback on error
series = await AnimeSeriesService.create(db, ...)
episode = await EpisodeService.create(db, series_id=series.id, ...)
return series, episode
```
**Using atomic() context manager:**
```python
from src.server.database.transaction import atomic
async def some_function(db: AsyncSession):
async with atomic(db) as tx:
await operation1(db)
await operation2(db)
# Auto-commits on success, rolls back on exception
```
**Using savepoints for partial rollback:**
```python
async with atomic(db) as tx:
await outer_operation(db)
async with tx.savepoint() as sp:
await risky_operation(db)
if error_condition:
await sp.rollback() # Only rollback nested ops
await final_operation(db) # Still executes
```
Source: [src/server/database/transaction.py](../src/server/database/transaction.py)
### 6.5 Connection Module Additions
| Function | Description |
| ------------------------------- | -------------------------------------------- |
| `get_transactional_session` | Session without auto-commit for transactions |
| `TransactionManager` | Helper class for manual transaction control |
| `is_session_in_transaction` | Check if session is in active transaction |
| `get_session_transaction_depth` | Get nesting depth of transactions |
Source: [src/server/database/connection.py](../src/server/database/connection.py)
---
## 7. Repository Pattern
The `QueueRepository` class provides data access abstraction.
```python
class QueueRepository:
async def save_item(self, item: DownloadItem) -> None:
"""Save or update a download item."""
"""Save or update a download item (atomic operation)."""
async def get_all_items(self) -> List[DownloadItem]:
"""Get all items from database."""
@@ -212,17 +295,17 @@ class QueueRepository:
async def delete_item(self, item_id: str) -> bool:
"""Delete item by ID."""
async def get_items_by_status(
self, status: DownloadStatus
) -> List[DownloadItem]:
"""Get items filtered by status."""
async def clear_all(self) -> int:
"""Clear all items (atomic operation)."""
```
Note: Compound operations (`save_item`, `clear_all`) are wrapped in `atomic()` transactions.
Source: [src/server/services/queue_repository.py](../src/server/services/queue_repository.py)
---
## 7. Database Service
## 8. Database Service
The `AnimeSeriesService` provides async CRUD operations.
@@ -246,11 +329,23 @@ class AnimeSeriesService:
"""Get series by primary key identifier."""
```
### Bulk Operations
Services provide bulk operations for transaction-safe batch processing:
| Service | Method | Description |
| ---------------------- | ---------------------- | ------------------------------ |
| `EpisodeService` | `bulk_mark_downloaded` | Mark multiple episodes at once |
| `DownloadQueueService` | `bulk_delete` | Delete multiple queue items |
| `DownloadQueueService` | `clear_all` | Clear entire queue |
| `UserSessionService` | `rotate_session` | Revoke old + create new atomic |
| `UserSessionService` | `cleanup_expired` | Bulk delete expired sessions |
Source: [src/server/database/service.py](../src/server/database/service.py)
---
## 8. Data Integrity Rules
## 9. Data Integrity Rules
### Validation Constraints
@@ -269,7 +364,7 @@ Source: [src/server/database/models.py](../src/server/database/models.py#L89-L11
---
## 9. Migration Strategy
## 10. Migration Strategy
Currently, SQLAlchemy's `create_all()` is used for schema creation.
@@ -286,7 +381,7 @@ Source: [src/server/database/connection.py](../src/server/database/connection.py
---
## 10. Common Query Patterns
## 11. Common Query Patterns
### Get all series with missing episodes
@@ -317,7 +412,7 @@ items = await db.execute(
---
## 11. Database Location
## 12. Database Location
| Environment | Default Location |
| ----------- | ------------------------------------------------- |

311
docs/instructions.md
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@@ -121,147 +121,202 @@ For each task completed:
---
## 🔧 Current Task: Make MP4 Scanning Progress Visible in UI
---
### Problem Statement
## Task: Add Database Transaction Support
When users trigger a library rescan (via the "Rescan Library" button on the anime page), the MP4 file scanning happens silently in the background. Users only see a brief toast message, but there's no visual feedback showing:
### Objective
1. That scanning is actively happening
2. How many files/directories have been scanned
3. The progress through the scan operation
4. When scanning is complete with results
Implement proper transaction handling across all database write operations using SQLAlchemy's transaction support. This ensures data consistency and prevents partial writes during compound operations.
Currently, the only indication is in server logs:
### Background
```
INFO: Starting directory rescan
INFO: Scanning for .mp4 files
Currently, the application uses SQLAlchemy sessions with auto-commit behavior through the `get_db_session()` generator. While individual operations are atomic, compound operations (multiple writes) can result in partial commits if an error occurs mid-operation.
### Requirements
1. **All database write operations must be wrapped in explicit transactions**
2. **Compound operations must be atomic** - either all writes succeed or all fail
3. **Nested operations should use savepoints** for partial rollback capability
4. **Existing functionality must not break** - backward compatible changes only
5. **All tests must pass after implementation**
---
### Step 1: Create Transaction Utilities Module
**File**: `src/server/database/transaction.py`
Create a new module providing transaction management utilities:
1. **`@transactional` decorator** - Wraps a function in a transaction boundary
- Accepts a session parameter or retrieves one via dependency injection
- Commits on success, rolls back on exception
- Re-raises exceptions after rollback
- Logs transaction start, commit, and rollback events
2. **`TransactionContext` class** - Context manager for explicit transaction control
- Supports `with` statement usage
- Provides `savepoint()` method for nested transactions using `begin_nested()`
- Handles commit/rollback automatically
3. **`atomic()` function** - Async context manager for async operations
- Same behavior as `TransactionContext` but for async code
**Interface Requirements**:
- Decorator must work with both sync and async functions
- Must handle the case where session is already in a transaction
- Must support optional `propagation` parameter (REQUIRED, REQUIRES_NEW, NESTED)
---
### Step 2: Update Connection Module
**File**: `src/server/database/connection.py`
Modify the existing session management:
1. Add `get_transactional_session()` generator that does NOT auto-commit
2. Add `TransactionManager` class for manual transaction control
3. Keep `get_db_session()` unchanged for backward compatibility
4. Add session state inspection utilities (`is_in_transaction()`, `get_transaction_depth()`)
---
### Step 3: Wrap Service Layer Operations
**File**: `src/server/database/service.py`
Apply transaction handling to all compound write operations:
**AnimeService**:
- `create_anime_with_episodes()` - if exists, wrap in transaction
- Any method that calls multiple repository methods
**EpisodeService**:
- `bulk_update_episodes()` - if exists
- `mark_episodes_downloaded()` - if handles multiple episodes
**DownloadQueueService**:
- `add_batch_to_queue()` - if exists
- `clear_and_repopulate()` - if exists
- Any method performing multiple writes
**SessionService**:
- `rotate_session()` - delete old + create new must be atomic
- `cleanup_expired_sessions()` - bulk delete operation
**Pattern to follow**:
```python
@transactional
def compound_operation(self, session: Session, data: SomeModel) -> Result:
# Multiple write operations here
# All succeed or all fail
```
### Desired Outcome
---
Users should see real-time progress in the UI during library scanning with:
### Step 4: Update Queue Repository
1. **Progress overlay** showing scan is active with a spinner animation
2. **Live counters** showing directories scanned and files found
3. **Current directory display** showing which folder is being scanned (truncated if too long)
4. **Completion summary** showing total files found, directories scanned, and elapsed time
5. **Auto-dismiss** the overlay after showing completion summary
**File**: `src/server/services/queue_repository.py`
Ensure atomic operations for:
1. `save_item()` - check existence + insert/update must be atomic
2. `remove_item()` - if involves multiple deletes
3. `clear_all_items()` - bulk delete should be transactional
4. `reorder_queue()` - multiple position updates must be atomic
---
### Step 5: Update API Endpoints
**Files**: `src/server/api/anime.py`, `src/server/api/downloads.py`, `src/server/api/auth.py`
Review and update endpoints that perform multiple database operations:
1. Identify endpoints calling multiple service methods
2. Wrap in transaction boundary at the endpoint level OR ensure services handle it
3. Prefer service-level transactions over endpoint-level for reusability
---
### Step 6: Add Unit Tests
**File**: `tests/unit/test_transactions.py`
Create comprehensive tests:
1. **Test successful transaction commit** - verify all changes persisted
2. **Test rollback on exception** - verify no partial writes
3. **Test nested transaction with savepoint** - verify partial rollback works
4. **Test decorator with sync function**
5. **Test decorator with async function**
6. **Test context manager usage**
7. **Test transaction propagation modes**
**File**: `tests/unit/test_service_transactions.py`
1. Test each service's compound operations for atomicity
2. Mock exceptions mid-operation to verify rollback
3. Verify no orphaned data after failed operations
---
### Step 7: Update Integration Tests
**File**: `tests/integration/test_db_transactions.py`
1. Test real database transaction behavior
2. Test concurrent transaction handling
3. Test transaction isolation levels if applicable
---
### Step 7: Update Dokumentation
1. Check Docs folder and updated the needed files
---
### Implementation Notes
- **SQLAlchemy Pattern**: Use `session.begin_nested()` for savepoints
- **Error Handling**: Always log transaction failures with full context
- **Performance**: Transactions have overhead - don't wrap single operations unnecessarily
- **Testing**: Use `session.rollback()` in test fixtures to ensure clean state
### Files to Modify
#### 1. `src/server/services/websocket_service.py`
Add three new broadcast methods for scan events:
- **broadcast_scan_started**: Notify clients that a scan has begun, include the root directory path
- **broadcast_scan_progress**: Send periodic updates with directories scanned count, files found count, and current directory name
- **broadcast_scan_completed**: Send final summary with total directories, total files, and elapsed time in seconds
Follow the existing pattern used by `broadcast_download_progress` for message structure consistency.
#### 2. `src/server/services/scanner_service.py`
Modify the scanning logic to emit progress via WebSocket:
- Inject `WebSocketService` dependency into the scanner service
- At scan start, call `broadcast_scan_started`
- During directory traversal, track directories scanned and files found
- Every 10 directories (to avoid WebSocket spam), call `broadcast_scan_progress`
- Track elapsed time using `time.time()`
- At scan completion, call `broadcast_scan_completed` with summary statistics
- Ensure the scan still works correctly even if WebSocket broadcast fails (wrap in try/except)
#### 3. `src/server/static/css/style.css`
Add styles for the scan progress overlay:
- Full-screen semi-transparent overlay (z-index high enough to be on top)
- Centered container with background matching theme (use CSS variables)
- Spinner animation using CSS keyframes
- Styling for current directory text (truncated with ellipsis)
- Styling for statistics display
- Success state styling for completion
- Ensure it works in both light and dark mode themes
#### 4. `src/server/static/js/anime.js`
Add WebSocket message handlers and UI functions:
- Handle `scan_started` message: Create and show progress overlay with spinner
- Handle `scan_progress` message: Update directory count, file count, and current directory text
- Handle `scan_completed` message: Show completion summary, then auto-remove overlay after 3 seconds
- Ensure overlay is properly cleaned up if page navigates away
- Update the existing rescan button handler to work with the new progress system
### WebSocket Message Types
Define three new message types following the existing project patterns:
1. **scan_started**: type, directory path, timestamp
2. **scan_progress**: type, directories_scanned, files_found, current_directory, timestamp
3. **scan_completed**: type, total_directories, total_files, elapsed_seconds, timestamp
### Implementation Steps
1. First modify `websocket_service.py` to add the three new broadcast methods
2. Add unit tests for the new WebSocket methods
3. Modify `scanner_service.py` to use the new broadcast methods during scanning
4. Add CSS styles to `style.css` for the progress overlay
5. Update `anime.js` to handle the new WebSocket messages and display the UI
6. Test the complete flow manually
7. Verify all existing tests still pass
### Testing Requirements
**Unit Tests:**
- Test each new WebSocket broadcast method
- Test that scanner service calls WebSocket methods at appropriate times
- Mock WebSocket service in scanner tests
**Manual Testing:**
- Start server and login
- Navigate to anime page
- Click "Rescan Library" button
- Verify overlay appears immediately with spinner
- Verify counters update during scan
- Verify current directory updates
- Verify completion summary appears
- Verify overlay auto-dismisses after 3 seconds
- Test in both light and dark mode
- Verify no JavaScript console errors
| File | Action |
| ------------------------------------------- | ------------------------------------------ |
| `src/server/database/transaction.py` | CREATE - New transaction utilities |
| `src/server/database/connection.py` | MODIFY - Add transactional session support |
| `src/server/database/service.py` | MODIFY - Apply @transactional decorator |
| `src/server/services/queue_repository.py` | MODIFY - Ensure atomic operations |
| `src/server/api/anime.py` | REVIEW - Check for multi-write endpoints |
| `src/server/api/downloads.py` | REVIEW - Check for multi-write endpoints |
| `src/server/api/auth.py` | REVIEW - Check for multi-write endpoints |
| `tests/unit/test_transactions.py` | CREATE - Transaction unit tests |
| `tests/unit/test_service_transactions.py` | CREATE - Service transaction tests |
| `tests/integration/test_db_transactions.py` | CREATE - Integration tests |
### Acceptance Criteria
- [x] Progress overlay appears immediately when scan starts
- [x] Spinner animation is visible during scanning
- [x] Directory counter updates periodically (every ~10 directories)
- [x] Files found counter updates as MP4 files are discovered
- [x] Current directory name is displayed (truncated if path is too long)
- [x] Scan completion shows total directories, files, and elapsed time
- [x] Overlay auto-dismisses 3 seconds after completion
- [x] Works correctly in both light and dark mode
- [x] No JavaScript errors in browser console
- [x] All existing tests continue to pass
- [x] New unit tests added and passing
- [x] All database write operations use explicit transactions
- [x] Compound operations are atomic (all-or-nothing)
- [x] Exceptions trigger proper rollback
- [x] No partial writes occur on failures
- [x] All existing tests pass (1090 tests passing)
- [x] New transaction tests pass with >90% coverage (90% achieved)
- [x] Logging captures transaction lifecycle events
- [x] Documentation updated in DATABASE.md
- [x] Code follows project coding standards
### Edge Cases to Handle
- Empty directory with no MP4 files
- Very large directory structure (ensure UI remains responsive)
- WebSocket connection lost during scan (scan should still complete)
- User navigates away during scan (cleanup overlay properly)
- Rapid consecutive scan requests (debounce or queue)
### Notes
- Keep progress updates throttled to avoid overwhelming the WebSocket connection
- Use existing CSS variables for colors to maintain theme consistency
- Follow existing JavaScript patterns in the codebase
- The scan functionality must continue to work even if WebSocket fails
---