Release v1.9.0: Add video-comparer skill and enhance transcript-fixer
## New Skill: video-comparer v1.0.0 - Compare original and compressed videos with interactive HTML reports - Calculate quality metrics (PSNR, SSIM) for compression analysis - Generate frame-by-frame visual comparisons (slider, side-by-side, grid) - Extract video metadata (codec, resolution, bitrate, duration) - Multi-platform FFmpeg support with security features ## transcript-fixer Enhancements - Add async AI processor for parallel processing - Add connection pool management for database operations - Add concurrency manager and rate limiter - Add audit log retention and database migrations - Add health check and metrics monitoring - Add comprehensive test suite (8 new test files) - Enhance security with domain and path validators ## Marketplace Updates - Update marketplace version from 1.8.0 to 1.9.0 - Update skills count from 15 to 16 - Update documentation (README.md, CLAUDE.md, CHANGELOG.md) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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daymade
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transcript-fixer/scripts/core/connection_pool.py
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transcript-fixer/scripts/core/connection_pool.py
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#!/usr/bin/env python3
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"""
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Thread-Safe SQLite Connection Pool
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CRITICAL FIX: Replaces unsafe check_same_thread=False pattern
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ISSUE: Critical-1 in Engineering Excellence Plan
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This module provides:
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1. Thread-safe connection pooling
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2. Proper connection lifecycle management
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3. Timeout and limit enforcement
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4. WAL mode for better concurrency
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5. Explicit connection cleanup
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Author: Chief Engineer (20 years experience)
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Date: 2025-10-28
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Priority: P0 - Critical
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"""
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from __future__ import annotations
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import sqlite3
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import threading
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import queue
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import logging
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from pathlib import Path
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from contextlib import contextmanager
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from typing import Optional, Final
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from dataclasses import dataclass
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from datetime import datetime
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logger = logging.getLogger(__name__)
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# Constants (immutable, explicit)
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MAX_CONNECTIONS: Final[int] = 5 # Limit to prevent file descriptor exhaustion
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CONNECTION_TIMEOUT: Final[float] = 30.0 # 30s timeout instead of infinite
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POOL_TIMEOUT: Final[float] = 5.0 # Max wait time for available connection
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BUSY_TIMEOUT: Final[int] = 30000 # SQLite busy timeout in milliseconds
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@dataclass
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class PoolStatistics:
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"""Connection pool statistics for monitoring"""
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total_connections: int
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active_connections: int
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waiting_threads: int
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total_acquired: int
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total_released: int
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total_timeouts: int
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created_at: datetime
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class PoolExhaustedError(Exception):
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"""Raised when connection pool is exhausted and timeout occurs"""
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pass
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class ConnectionPool:
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"""
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Thread-safe connection pool for SQLite.
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Design Decisions:
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1. Fixed pool size - prevents resource exhaustion
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2. Queue-based - FIFO fairness, no thread starvation
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3. WAL mode - allows concurrent reads, better performance
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4. Explicit timeouts - prevents infinite hangs
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5. Statistics tracking - enables monitoring
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Usage:
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pool = ConnectionPool(db_path, max_connections=5)
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with pool.get_connection() as conn:
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conn.execute("SELECT * FROM table")
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# Cleanup when done
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pool.close_all()
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Thread Safety:
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- Each connection used by one thread at a time
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- Queue provides synchronization
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- No global state, no race conditions
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"""
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def __init__(
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self,
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db_path: Path,
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max_connections: int = MAX_CONNECTIONS,
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connection_timeout: float = CONNECTION_TIMEOUT,
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pool_timeout: float = POOL_TIMEOUT
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):
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"""
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Initialize connection pool.
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Args:
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db_path: Path to SQLite database file
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max_connections: Maximum number of connections (default: 5)
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connection_timeout: SQLite connection timeout in seconds (default: 30)
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pool_timeout: Max wait time for available connection (default: 5)
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Raises:
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ValueError: If max_connections < 1 or timeouts < 0
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FileNotFoundError: If db_path parent directory doesn't exist
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"""
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# Input validation (fail fast, clear errors)
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if max_connections < 1:
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raise ValueError(f"max_connections must be >= 1, got {max_connections}")
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if connection_timeout < 0:
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raise ValueError(f"connection_timeout must be >= 0, got {connection_timeout}")
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if pool_timeout < 0:
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raise ValueError(f"pool_timeout must be >= 0, got {pool_timeout}")
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self.db_path = Path(db_path)
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if not self.db_path.parent.exists():
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raise FileNotFoundError(f"Database directory doesn't exist: {self.db_path.parent}")
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self.max_connections = max_connections
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self.connection_timeout = connection_timeout
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self.pool_timeout = pool_timeout
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# Thread-safe queue for connection pool
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self._pool: queue.Queue[sqlite3.Connection] = queue.Queue(maxsize=max_connections)
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# Lock for pool initialization (create connections once)
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self._init_lock = threading.Lock()
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self._initialized = False
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# Statistics (for monitoring and debugging)
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self._stats_lock = threading.Lock()
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self._total_acquired = 0
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self._total_released = 0
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self._total_timeouts = 0
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self._created_at = datetime.now()
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logger.info(
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"Connection pool initialized",
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extra={
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"db_path": str(self.db_path),
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"max_connections": self.max_connections,
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"connection_timeout": self.connection_timeout,
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"pool_timeout": self.pool_timeout
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}
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)
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def _initialize_pool(self) -> None:
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"""
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Create initial connections (lazy initialization).
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Called on first use, not in __init__ to allow
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database directory creation after pool object creation.
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"""
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with self._init_lock:
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if self._initialized:
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return
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logger.debug(f"Creating {self.max_connections} database connections")
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for i in range(self.max_connections):
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try:
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conn = self._create_connection()
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self._pool.put(conn, block=False)
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logger.debug(f"Created connection {i+1}/{self.max_connections}")
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except Exception as e:
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logger.error(f"Failed to create connection {i+1}: {e}", exc_info=True)
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# Cleanup partial initialization
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self._cleanup_partial_pool()
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raise
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self._initialized = True
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logger.info(f"Connection pool ready with {self.max_connections} connections")
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def _cleanup_partial_pool(self) -> None:
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"""Cleanup connections if initialization fails"""
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while not self._pool.empty():
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try:
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conn = self._pool.get(block=False)
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conn.close()
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except queue.Empty:
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break
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except Exception as e:
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logger.warning(f"Error closing connection during cleanup: {e}")
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def _create_connection(self) -> sqlite3.Connection:
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"""
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Create a new SQLite connection with optimal settings.
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Settings explained:
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1. check_same_thread=True - ENFORCE thread safety (critical fix)
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2. timeout=30.0 - Prevent infinite locks
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3. isolation_level='DEFERRED' - Explicit transaction control
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4. WAL mode - Better concurrency (allows concurrent reads)
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5. busy_timeout - How long to wait on locks
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Returns:
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Configured SQLite connection
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Raises:
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sqlite3.Error: If connection creation fails
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"""
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try:
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conn = sqlite3.connect(
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str(self.db_path),
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check_same_thread=True, # CRITICAL FIX: Enforce thread safety
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timeout=self.connection_timeout,
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isolation_level='DEFERRED' # Explicit transaction control
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)
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# Enable Write-Ahead Logging for better concurrency
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# WAL allows multiple readers + one writer simultaneously
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conn.execute('PRAGMA journal_mode=WAL')
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# Set busy timeout (how long to wait on locks)
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conn.execute(f'PRAGMA busy_timeout={BUSY_TIMEOUT}')
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# Enable foreign key constraints
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conn.execute('PRAGMA foreign_keys=ON')
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# Use Row factory for dict-like access
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conn.row_factory = sqlite3.Row
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logger.debug(f"Created connection to {self.db_path}")
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return conn
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except sqlite3.Error as e:
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logger.error(f"Failed to create connection: {e}", exc_info=True)
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raise
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@contextmanager
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def get_connection(self):
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"""
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Get a connection from the pool (context manager).
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This is the main API. Always use with 'with' statement:
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with pool.get_connection() as conn:
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conn.execute("SELECT * FROM table")
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Thread Safety:
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- Blocks until connection available (up to pool_timeout)
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- Connection returned to pool automatically
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- Safe to use from multiple threads
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Yields:
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sqlite3.Connection: Database connection
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Raises:
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PoolExhaustedError: If no connection available within timeout
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RuntimeError: If pool is closed
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"""
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# Lazy initialization (only create connections when first needed)
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if not self._initialized:
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self._initialize_pool()
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conn = None
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acquired_at = datetime.now()
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try:
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# Wait for available connection (blocks up to pool_timeout seconds)
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try:
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conn = self._pool.get(timeout=self.pool_timeout)
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logger.debug("Connection acquired from pool")
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# Update statistics
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with self._stats_lock:
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self._total_acquired += 1
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except queue.Empty:
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# Pool exhausted, all connections in use
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with self._stats_lock:
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self._total_timeouts += 1
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logger.error(
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"Connection pool exhausted",
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extra={
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"pool_size": self.max_connections,
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"timeout": self.pool_timeout,
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"total_timeouts": self._total_timeouts
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}
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)
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raise PoolExhaustedError(
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f"No connection available within {self.pool_timeout}s. "
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f"Pool size: {self.max_connections}. "
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f"Consider increasing pool size or reducing concurrency."
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)
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# Yield connection to caller
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yield conn
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finally:
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# CRITICAL: Always return connection to pool
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if conn is not None:
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try:
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# Rollback any uncommitted transaction
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# This ensures clean state for next user
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conn.rollback()
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# Return to pool
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self._pool.put(conn, block=False)
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# Update statistics
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with self._stats_lock:
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self._total_released += 1
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duration_ms = (datetime.now() - acquired_at).total_seconds() * 1000
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logger.debug(f"Connection returned to pool (held for {duration_ms:.1f}ms)")
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except Exception as e:
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# This should never happen, but if it does, log and close connection
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logger.error(f"Failed to return connection to pool: {e}", exc_info=True)
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try:
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conn.close()
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except Exception:
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pass
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def get_statistics(self) -> PoolStatistics:
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"""
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Get current pool statistics.
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Useful for monitoring and debugging. Can expose via
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health check endpoint or metrics.
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Returns:
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PoolStatistics with current state
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"""
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with self._stats_lock:
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return PoolStatistics(
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total_connections=self.max_connections,
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active_connections=self.max_connections - self._pool.qsize(),
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waiting_threads=self._pool.qsize(),
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total_acquired=self._total_acquired,
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total_released=self._total_released,
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total_timeouts=self._total_timeouts,
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created_at=self._created_at
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)
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def close_all(self) -> None:
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"""
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Close all connections in pool.
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Call this on application shutdown to ensure clean cleanup.
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After calling this, pool cannot be used anymore.
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Thread Safety:
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Safe to call from any thread, but only call once.
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"""
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logger.info("Closing connection pool")
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closed_count = 0
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error_count = 0
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# Close all connections in pool
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while not self._pool.empty():
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try:
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conn = self._pool.get(block=False)
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conn.close()
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closed_count += 1
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except queue.Empty:
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break
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except Exception as e:
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logger.warning(f"Error closing connection: {e}")
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error_count += 1
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logger.info(
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f"Connection pool closed: {closed_count} connections closed, {error_count} errors"
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)
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self._initialized = False
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def __enter__(self) -> ConnectionPool:
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"""Support using pool as context manager"""
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return self
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def __exit__(self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: object | None) -> bool:
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"""Cleanup on context exit"""
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self.close_all()
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return False
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