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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) |