"""Session management service for chat agent.""" import json import logging from datetime import datetime, timedelta from typing import Optional, List, Dict, Any from uuid import uuid4 import redis from sqlalchemy.exc import SQLAlchemyError from ..models.chat_session import ChatSession from ..models.base import db logger = logging.getLogger(__name__) class SessionManagerError(Exception): """Base exception for session manager errors.""" pass class SessionNotFoundError(SessionManagerError): """Raised when a session is not found.""" pass class SessionExpiredError(SessionManagerError): """Raised when a session has expired.""" pass class SessionManager: """Manages user chat sessions with Redis caching and PostgreSQL persistence.""" def __init__(self, redis_client: redis.Redis, session_timeout: int = 3600): """ Initialize the session manager. Args: redis_client: Redis client instance for caching session_timeout: Session timeout in seconds (default: 1 hour) """ self.redis_client = redis_client self.session_timeout = session_timeout self.cache_prefix = "session:" self.user_sessions_prefix = "user_sessions:" def create_session(self, user_id: str, language: str = 'python', session_metadata: Optional[Dict[str, Any]] = None) -> ChatSession: """ Create a new chat session. Args: user_id: User identifier language: Programming language for the session (default: python) session_metadata: Additional session metadata Returns: ChatSession: The created session Raises: SessionManagerError: If session creation fails """ try: # Create session in database session = ChatSession.create_session( user_id=user_id, language=language, session_metadata=session_metadata or {} ) # Cache session in Redis self._cache_session(session) # Add session to user's session list self._add_to_user_sessions(user_id, session.id) logger.info(f"Created new session {session.id} for user {user_id}") return session except SQLAlchemyError as e: logger.error(f"Database error creating session: {e}") raise SessionManagerError(f"Failed to create session: {e}") except redis.RedisError as e: logger.error(f"Redis error caching session: {e}") # Session was created in DB, continue without cache return session def get_session(self, session_id: str) -> ChatSession: """ Get a session by ID, checking cache first then database. Args: session_id: Session identifier Returns: ChatSession: The session object Raises: SessionNotFoundError: If session doesn't exist SessionExpiredError: If session has expired """ # Try to get from cache first cached_session = self._get_cached_session(session_id) if cached_session: # Check if session is expired if self._is_session_expired(cached_session): self._expire_session(session_id) raise SessionExpiredError(f"Session {session_id} has expired") return cached_session # Get from database try: session = db.session.query(ChatSession).filter( ChatSession.id == session_id, ChatSession.is_active == True ).first() if not session: raise SessionNotFoundError(f"Session {session_id} not found") # Check if session is expired if session.is_expired(self.session_timeout): session.deactivate() raise SessionExpiredError(f"Session {session_id} has expired") # Cache the session self._cache_session(session) return session except SQLAlchemyError as e: logger.error(f"Database error getting session {session_id}: {e}") raise SessionManagerError(f"Failed to get session: {e}") def update_session_activity(self, session_id: str) -> None: """ Update session activity timestamp. Args: session_id: Session identifier Raises: SessionNotFoundError: If session doesn't exist """ try: session = self.get_session(session_id) session.update_activity() # Update cache self._cache_session(session) logger.debug(f"Updated activity for session {session_id}") except (SessionNotFoundError, SessionExpiredError): raise except Exception as e: logger.error(f"Error updating session activity: {e}") raise SessionManagerError(f"Failed to update session activity: {e}") def get_user_sessions(self, user_id: str, active_only: bool = True) -> List[ChatSession]: """ Get all sessions for a user. Args: user_id: User identifier active_only: Whether to return only active sessions Returns: List[ChatSession]: List of user sessions """ try: query = db.session.query(ChatSession).filter(ChatSession.user_id == user_id) if active_only: query = query.filter(ChatSession.is_active == True) sessions = query.order_by(ChatSession.last_active.desc()).all() # Filter out expired sessions if active_only: active_sessions = [] for session in sessions: if not session.is_expired(self.session_timeout): active_sessions.append(session) else: # Mark as inactive session.deactivate() self._remove_from_cache(session.id) return active_sessions return sessions except SQLAlchemyError as e: logger.error(f"Database error getting user sessions: {e}") raise SessionManagerError(f"Failed to get user sessions: {e}") def cleanup_inactive_sessions(self) -> int: """ Clean up inactive and expired sessions. Returns: int: Number of sessions cleaned up """ try: # Clean up expired sessions in database cleaned_count = ChatSession.cleanup_expired_sessions(self.session_timeout) # Clean up expired sessions from cache self._cleanup_expired_cache_sessions() logger.info(f"Cleaned up {cleaned_count} expired sessions") return cleaned_count except SQLAlchemyError as e: logger.error(f"Database error during cleanup: {e}") raise SessionManagerError(f"Failed to cleanup sessions: {e}") def delete_session(self, session_id: str) -> None: """ Delete a session completely. Args: session_id: Session identifier Raises: SessionNotFoundError: If session doesn't exist """ try: session = db.session.query(ChatSession).filter( ChatSession.id == session_id ).first() if not session: raise SessionNotFoundError(f"Session {session_id} not found") user_id = session.user_id # Delete from database (cascade will handle related records) db.session.delete(session) db.session.commit() # Remove from cache self._remove_from_cache(session_id) # Remove from user sessions list self._remove_from_user_sessions(user_id, session_id) logger.info(f"Deleted session {session_id}") except SQLAlchemyError as e: logger.error(f"Database error deleting session: {e}") raise SessionManagerError(f"Failed to delete session: {e}") def set_session_language(self, session_id: str, language: str) -> None: """ Set the programming language for a session. Args: session_id: Session identifier language: Programming language Raises: SessionNotFoundError: If session doesn't exist """ try: session = self.get_session(session_id) session.set_language(language) # Update cache self._cache_session(session) logger.info(f"Set language to {language} for session {session_id}") except (SessionNotFoundError, SessionExpiredError): raise except Exception as e: logger.error(f"Error setting session language: {e}") raise SessionManagerError(f"Failed to set session language: {e}") def increment_message_count(self, session_id: str) -> None: """ Increment the message count for a session. Args: session_id: Session identifier """ try: session = self.get_session(session_id) session.increment_message_count() # Update cache self._cache_session(session) except (SessionNotFoundError, SessionExpiredError): raise except Exception as e: logger.error(f"Error incrementing message count: {e}") raise SessionManagerError(f"Failed to increment message count: {e}") def _cache_session(self, session: ChatSession) -> None: """Cache a session in Redis.""" if not self.redis_client: return # Skip caching if Redis is not available try: cache_key = f"{self.cache_prefix}{session.id}" session_data = { 'id': session.id, 'user_id': session.user_id, 'language': session.language, 'created_at': session.created_at.isoformat(), 'last_active': session.last_active.isoformat(), 'message_count': session.message_count, 'is_active': session.is_active, 'session_metadata': session.session_metadata } # Set with expiration self.redis_client.setex( cache_key, self.session_timeout + 300, # Add 5 minutes buffer json.dumps(session_data) ) except redis.RedisError as e: logger.warning(f"Failed to cache session {session.id}: {e}") def _get_cached_session(self, session_id: str) -> Optional[ChatSession]: """Get a session from Redis cache.""" if not self.redis_client: return None # Skip cache lookup if Redis is not available try: cache_key = f"{self.cache_prefix}{session_id}" cached_data = self.redis_client.get(cache_key) if not cached_data: return None session_data = json.loads(cached_data) # Create a ChatSession object from cached data session = ChatSession( user_id=session_data['user_id'], language=session_data['language'], session_metadata=session_data['session_metadata'] ) session.id = session_data['id'] session.created_at = datetime.fromisoformat(session_data['created_at']) session.last_active = datetime.fromisoformat(session_data['last_active']) session.message_count = session_data['message_count'] session.is_active = session_data['is_active'] return session except (redis.RedisError, json.JSONDecodeError, KeyError) as e: logger.warning(f"Failed to get cached session {session_id}: {e}") return None def _remove_from_cache(self, session_id: str) -> None: """Remove a session from Redis cache.""" if not self.redis_client: return # Skip cache removal if Redis is not available try: cache_key = f"{self.cache_prefix}{session_id}" self.redis_client.delete(cache_key) except redis.RedisError as e: logger.warning(f"Failed to remove session {session_id} from cache: {e}") def _add_to_user_sessions(self, user_id: str, session_id: str) -> None: """Add session to user's session list in Redis.""" if not self.redis_client: return # Skip user session tracking if Redis is not available try: user_sessions_key = f"{self.user_sessions_prefix}{user_id}" self.redis_client.sadd(user_sessions_key, session_id) # Set expiration for user sessions list self.redis_client.expire(user_sessions_key, self.session_timeout * 2) except redis.RedisError as e: logger.warning(f"Failed to add session to user sessions list: {e}") def _remove_from_user_sessions(self, user_id: str, session_id: str) -> None: """Remove session from user's session list in Redis.""" if not self.redis_client: return # Skip user session tracking if Redis is not available try: user_sessions_key = f"{self.user_sessions_prefix}{user_id}" self.redis_client.srem(user_sessions_key, session_id) except redis.RedisError as e: logger.warning(f"Failed to remove session from user sessions list: {e}") def _is_session_expired(self, session: ChatSession) -> bool: """Check if a session is expired.""" return session.is_expired(self.session_timeout) def _expire_session(self, session_id: str) -> None: """Mark a session as expired and clean up.""" try: # Mark as inactive in database session = db.session.query(ChatSession).filter( ChatSession.id == session_id ).first() if session: session.deactivate() self._remove_from_user_sessions(session.user_id, session_id) # Remove from cache self._remove_from_cache(session_id) except SQLAlchemyError as e: logger.error(f"Error expiring session {session_id}: {e}") def _cleanup_expired_cache_sessions(self) -> None: """Clean up expired sessions from Redis cache.""" try: # Get all session keys pattern = f"{self.cache_prefix}*" session_keys = self.redis_client.keys(pattern) expired_keys = [] for key in session_keys: try: cached_data = self.redis_client.get(key) if cached_data: session_data = json.loads(cached_data) last_active = datetime.fromisoformat(session_data['last_active']) if datetime.utcnow() - last_active > timedelta(seconds=self.session_timeout): expired_keys.append(key) except (json.JSONDecodeError, KeyError, ValueError): # Invalid data, mark for deletion expired_keys.append(key) # Delete expired keys if expired_keys: self.redis_client.delete(*expired_keys) logger.info(f"Cleaned up {len(expired_keys)} expired cache entries") except redis.RedisError as e: logger.warning(f"Failed to cleanup expired cache sessions: {e}") def create_session_manager(redis_client: redis.Redis, session_timeout: int = 3600) -> SessionManager: """ Factory function to create a SessionManager instance. Args: redis_client: Redis client instance session_timeout: Session timeout in seconds Returns: SessionManager: Configured session manager instance """ return SessionManager(redis_client, session_timeout)