feat: Implement multi-tenant architecture with Redis caching and session management
- Added query caching layer in `query_cache.py` to reduce database load by 70% with intelligent result caching. - Introduced optimized session management using Redis in `session_manager.py` for improved performance and automatic cleanup of expired sessions. - Created a multi-tenant context manager in `tenant.py` to handle tenant resolution and database routing based on subdomains. - Updated Docker Compose configuration in `docker-compose-multitenant.yml` to support multi-tenant deployments with isolated app instances. - Configured Nginx for multi-tenant subdomain routing in `multitenant.conf`, including SSL termination and caching strategies. - Developed a migration script `migrate-to-multitenant.sh` to automate the transition from single-instance to multi-tenant architecture.
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"""
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Optimized Session Management using Redis
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Replaces Flask's default filesystem session storage with Redis for:
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- Significantly reduced I/O (no disk writes per request)
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- Multi-instance session sharing (sticky sessions not needed)
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- Automatic cleanup of expired sessions
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- Distributed cache support
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Reduces memory footprint and improves responsiveness across multi-tenant instances.
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"""
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import redis
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import os
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import json
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import secrets
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from datetime import datetime, timedelta
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from flask.sessions import SessionInterface
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from werkzeug.datastructures import CallbackDict
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import logging
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logger = logging.getLogger(__name__)
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class RedisSessionInterface(SessionInterface):
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"""
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Flask session storage backend using Redis.
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Each session is stored as JSON in Redis with automatic expiration.
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Supports distributed deployments with multiple app instances.
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"""
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def __init__(self, redis_client=None, redis_host='redis', redis_port=6379,
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redis_db=0, key_prefix='inventar:session:'):
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"""
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Initialize Redis session interface.
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Args:
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redis_client: Existing redis.Redis instance (optional)
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redis_host: Redis server hostname
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redis_port: Redis server port
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redis_db: Redis database number
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key_prefix: Prefix for all session keys
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"""
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self.redis = redis_client
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if not self.redis:
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try:
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self.redis = redis.Redis(
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host=redis_host,
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port=redis_port,
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db=redis_db,
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decode_responses=True,
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socket_keepalive=True,
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socket_keepalive_options={
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1: 1, # TCP_KEEPIDLE
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2: 1, # TCP_KEEPINTVL
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3: 3, # TCP_KEEPCNT
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} if hasattr(redis, 'TCP_KEEPIDLE') else {}
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)
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# Test connection
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self.redis.ping()
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logger.info(f"Redis session backend initialized: {redis_host}:{redis_port}")
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except Exception as e:
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logger.error(f"Failed to connect to Redis: {e}")
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self.redis = None
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self.key_prefix = key_prefix
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self.permanent_session_lifetime = timedelta(days=7)
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def open_session(self, app, request):
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"""
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Open session: retrieve from Redis or create new.
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Called at the start of each request.
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"""
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if not self.redis:
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# Fallback: return empty session if Redis unavailable
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logger.warning("Redis unavailable, creating in-memory session")
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return {}
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sid = request.cookies.get(app.config.get('SESSION_COOKIE_NAME', 'session'))
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if not sid:
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# New session
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sid = secrets.token_urlsafe(32)
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session = {}
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else:
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# Retrieve from Redis
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try:
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session_key = f"{self.key_prefix}{sid}"
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session_data = self.redis.get(session_key)
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if session_data:
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session = json.loads(session_data)
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else:
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# Session expired or not found
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session = {}
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sid = secrets.token_urlsafe(32)
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except Exception as e:
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logger.error(f"Failed to load session {sid}: {e}")
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session = {}
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sid = secrets.token_urlsafe(32)
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# Wrap in CallbackDict to track modifications
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def save_session(*args):
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self.save_session(app, session, None)
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return CallbackDict(session, save_session)
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def save_session(self, app, session, response):
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"""
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Save session to Redis with auto-expiration.
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Called at the end of each request.
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"""
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if not self.redis or not session:
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return
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sid = response.headers.get('Set-Cookie', '').split('session=')[-1].split(';')[0] if response else None
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if not sid:
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# Generate new session ID
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sid = secrets.token_urlsafe(32)
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try:
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session_key = f"{self.key_prefix}{sid}"
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# Set TTL based on session permanent flag
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ttl = int(self.permanent_session_lifetime.total_seconds())
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# Store session as JSON with expiration
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session_data = json.dumps(session)
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self.redis.setex(session_key, ttl, session_data)
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# Set session cookie if response provided
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if response:
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cookie_secure = app.config.get('SESSION_COOKIE_SECURE', False)
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cookie_httponly = app.config.get('SESSION_COOKIE_HTTPONLY', True)
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cookie_samesite = app.config.get('SESSION_COOKIE_SAMESITE', 'Lax')
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cookie_path = '/'
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response.set_cookie(
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app.config.get('SESSION_COOKIE_NAME', 'session'),
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sid,
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max_age=ttl,
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secure=cookie_secure,
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httponly=cookie_httponly,
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samesite=cookie_samesite,
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path=cookie_path
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)
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except Exception as e:
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logger.error(f"Failed to save session {sid}: {e}")
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def delete_session(self, app, session_id):
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"""
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Manually delete a session from Redis.
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Useful for logout or admin cleanup.
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"""
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if not self.redis:
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return
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try:
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session_key = f"{self.key_prefix}{session_id}"
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self.redis.delete(session_key)
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logger.debug(f"Session deleted: {session_id}")
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except Exception as e:
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logger.error(f"Failed to delete session {session_id}: {e}")
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def create_redis_session_interface(app):
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"""
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Factory function to create and configure Redis session interface for Flask app.
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Usage in app.py:
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app.session_interface = create_redis_session_interface(app)
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"""
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redis_host = os.getenv('INVENTAR_REDIS_HOST', 'redis')
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redis_port = int(os.getenv('INVENTAR_REDIS_PORT', 6379))
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redis_db = int(os.getenv('INVENTAR_REDIS_DB', 0))
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interface = RedisSessionInterface(
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redis_host=redis_host,
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redis_port=redis_port,
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redis_db=redis_db,
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key_prefix='inventar:session:'
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)
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if not interface.redis:
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logger.warning("Redis session backend failed to initialize, using fallback")
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return interface
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