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"""
Multi-level caching system with memory and disk storage, TTL, and LRU eviction.
"""
import os
import pickle
import time
import threading
from pathlib import Path
from typing import Any, Dict, Optional, Set, Tuple
from collections import OrderedDict
import hashlib
import json
from .error_handler import ResourceError
class CacheEntry:
"""Represents a cache entry with metadata."""
def __init__(self, value: Any, ttl: Optional[int] = None):
self.value = value
self.created_at = time.time()
self.last_accessed = self.created_at
self.access_count = 0
self.ttl = ttl
def is_expired(self) -> bool:
"""Check if cache entry has expired."""
if self.ttl is None:
return False
return time.time() - self.created_at > self.ttl
def touch(self) -> None:
"""Update access time and count."""
self.last_accessed = time.time()
self.access_count += 1
class CacheManager:
"""Multi-level cache manager with memory and disk storage."""
def __init__(self, config: Dict[str, Any]):
self.config = config
self.cache_config = config.get("cache", {})
# Configuration
self.memory_cache_size = self.cache_config.get("embedding_cache_size", 10000)
self.default_ttl = self.cache_config.get("cache_ttl", 3600)
self.enable_disk_cache = self.cache_config.get("enable_disk_cache", True)
self.cache_dir = Path(self.cache_config.get("cache_dir", "./cache"))
# Memory cache (LRU)
self._memory_cache: OrderedDict[str, CacheEntry] = OrderedDict()
self._lock = threading.RLock()
# Disk cache setup
if self.enable_disk_cache:
self.cache_dir.mkdir(parents=True, exist_ok=True)
self._disk_cache_index = self._load_disk_cache_index()
else:
self._disk_cache_index = {}
# Statistics
self.stats = {
"memory_hits": 0,
"disk_hits": 0,
"misses": 0,
"evictions": 0,
"disk_writes": 0,
"disk_reads": 0,
"errors": 0
}
def get(self, key: str) -> Optional[Any]:
"""Get value from cache."""
with self._lock:
# Check memory cache first
if key in self._memory_cache:
entry = self._memory_cache[key]
if entry.is_expired():
del self._memory_cache[key]
else:
# Move to end (most recently used)
self._memory_cache.move_to_end(key)
entry.touch()
self.stats["memory_hits"] += 1
return entry.value
# Check disk cache
if self.enable_disk_cache and key in self._disk_cache_index:
try:
value = self._load_from_disk(key)
if value is not None:
# Add to memory cache
self._set_memory_cache(key, value, self.default_ttl)
self.stats["disk_hits"] += 1
return value
except Exception as e:
self.stats["errors"] += 1
print(f"Error loading from disk cache: {e}")
self.stats["misses"] += 1
return None
def set(self, key: str, value: Any, ttl: Optional[int] = None) -> None:
"""Set value in cache."""
ttl = ttl if ttl is not None else self.default_ttl
with self._lock:
# Set in memory cache
self._set_memory_cache(key, value, ttl)
# Set in disk cache if enabled
if self.enable_disk_cache:
try:
self._save_to_disk(key, value, ttl)
except Exception as e:
self.stats["errors"] += 1
print(f"Error saving to disk cache: {e}")
def _set_memory_cache(self, key: str, value: Any, ttl: Optional[int]) -> None:
"""Set value in memory cache with LRU eviction."""
# Remove if already exists
if key in self._memory_cache:
del self._memory_cache[key]
# Add new entry
self._memory_cache[key] = CacheEntry(value, ttl)
# Enforce size limit
while len(self._memory_cache) > self.memory_cache_size:
oldest_key = next(iter(self._memory_cache))
del self._memory_cache[oldest_key]
self.stats["evictions"] += 1
def delete(self, key: str) -> bool:
"""Delete key from cache."""
with self._lock:
removed = False
# Remove from memory cache
if key in self._memory_cache:
del self._memory_cache[key]
removed = True
# Remove from disk cache
if self.enable_disk_cache and key in self._disk_cache_index:
try:
cache_file = self._get_cache_file_path(key)
if cache_file.exists():
cache_file.unlink()
del self._disk_cache_index[key]
self._save_disk_cache_index()
removed = True
except Exception as e:
self.stats["errors"] += 1
print(f"Error deleting from disk cache: {e}")
return removed
def clear(self) -> None:
"""Clear all cache entries."""
with self._lock:
# Clear memory cache
self._memory_cache.clear()
# Clear disk cache
if self.enable_disk_cache:
try:
for cache_file in self.cache_dir.glob("cache_*.pkl"):
cache_file.unlink()
self._disk_cache_index.clear()
self._save_disk_cache_index()
except Exception as e:
self.stats["errors"] += 1
print(f"Error clearing disk cache: {e}")
def _save_to_disk(self, key: str, value: Any, ttl: Optional[int]) -> None:
"""Save value to disk cache."""
cache_file = self._get_cache_file_path(key)
cache_data = {
"value": value,
"created_at": time.time(),
"ttl": ttl
}
with open(cache_file, "wb") as f:
pickle.dump(cache_data, f, protocol=pickle.HIGHEST_PROTOCOL)
# Update index
self._disk_cache_index[key] = {
"file": cache_file.name,
"created_at": cache_data["created_at"],
"ttl": ttl
}
self._save_disk_cache_index()
self.stats["disk_writes"] += 1
def _load_from_disk(self, key: str) -> Optional[Any]:
"""Load value from disk cache."""
if key not in self._disk_cache_index:
return None
cache_info = self._disk_cache_index[key]
# Check if expired
if cache_info["ttl"] is not None:
age = time.time() - cache_info["created_at"]
if age > cache_info["ttl"]:
# Remove expired entry
self.delete(key)
return None
cache_file = self.cache_dir / cache_info["file"]
if not cache_file.exists():
# Remove from index if file doesn't exist
del self._disk_cache_index[key]
self._save_disk_cache_index()
return None
try:
with open(cache_file, "rb") as f:
cache_data = pickle.load(f)
self.stats["disk_reads"] += 1
return cache_data["value"]
except Exception:
# Remove corrupted cache file
try:
cache_file.unlink()
del self._disk_cache_index[key]
self._save_disk_cache_index()
except Exception:
pass
return None
def _get_cache_file_path(self, key: str) -> Path:
"""Get cache file path for key."""
# Hash key to create valid filename
key_hash = hashlib.md5(key.encode()).hexdigest()
return self.cache_dir / f"cache_{key_hash}.pkl"
def _load_disk_cache_index(self) -> Dict[str, Dict[str, Any]]:
"""Load disk cache index."""
index_file = self.cache_dir / "cache_index.json"
if not index_file.exists():
return {}
try:
with open(index_file, "r") as f:
return json.load(f)
except Exception as e:
print(f"Error loading cache index: {e}")
return {}
def _save_disk_cache_index(self) -> None:
"""Save disk cache index."""
index_file = self.cache_dir / "cache_index.json"
try:
with open(index_file, "w") as f:
json.dump(self._disk_cache_index, f, indent=2)
except Exception as e:
print(f"Error saving cache index: {e}")
def cleanup_expired(self) -> int:
"""Remove expired entries from cache."""
removed_count = 0
with self._lock:
# Clean memory cache
expired_keys = []
for key, entry in self._memory_cache.items():
if entry.is_expired():
expired_keys.append(key)
for key in expired_keys:
del self._memory_cache[key]
removed_count += 1
# Clean disk cache
if self.enable_disk_cache:
expired_disk_keys = []
current_time = time.time()
for key, info in self._disk_cache_index.items():
if info["ttl"] is not None:
age = current_time - info["created_at"]
if age > info["ttl"]:
expired_disk_keys.append(key)
for key in expired_disk_keys:
try:
cache_file = self.cache_dir / self._disk_cache_index[key]["file"]
if cache_file.exists():
cache_file.unlink()
del self._disk_cache_index[key]
removed_count += 1
except Exception as e:
print(f"Error removing expired cache file: {e}")
if expired_disk_keys:
self._save_disk_cache_index()
return removed_count
def get_size_info(self) -> Dict[str, Any]:
"""Get cache size information."""
with self._lock:
memory_size = len(self._memory_cache)
disk_size = len(self._disk_cache_index)
# Calculate disk usage
disk_usage = 0
if self.enable_disk_cache and self.cache_dir.exists():
try:
for cache_file in self.cache_dir.glob("cache_*.pkl"):
disk_usage += cache_file.stat().st_size
except Exception:
pass
return {
"memory_entries": memory_size,
"disk_entries": disk_size,
"disk_usage_bytes": disk_usage,
"disk_usage_mb": disk_usage / (1024 * 1024),
"memory_limit": self.memory_cache_size
}
def get_stats(self) -> Dict[str, Any]:
"""Get cache statistics."""
stats = self.stats.copy()
total_requests = stats["memory_hits"] + stats["disk_hits"] + stats["misses"]
if total_requests > 0:
stats["hit_rate"] = (stats["memory_hits"] + stats["disk_hits"]) / total_requests
stats["memory_hit_rate"] = stats["memory_hits"] / total_requests
stats["disk_hit_rate"] = stats["disk_hits"] / total_requests
else:
stats["hit_rate"] = 0
stats["memory_hit_rate"] = 0
stats["disk_hit_rate"] = 0
stats["size_info"] = self.get_size_info()
return stats
def optimize(self) -> Dict[str, int]:
"""Optimize cache by removing expired entries and compacting."""
expired_removed = self.cleanup_expired()
# Could add more optimization like defragmenting disk cache
return {
"expired_removed": expired_removed
} |