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import json
import logging
import os
import tempfile
import threading
import time
from contextlib import contextmanager
from pathlib import Path
from typing import Any
if os.name == "nt":
import msvcrt
else:
import fcntl
LOCK_POLL_SECONDS = 0.05
LOCK_TIMEOUT_SECONDS = 5.0
DEFAULT_CACHE_TTL_SECONDS = 86400
class ResponseCache:
def __init__(
self,
path: str | Path,
enabled: bool = True,
ttl_seconds: int = DEFAULT_CACHE_TTL_SECONDS,
) -> None:
self.path = Path(path)
self.enabled = bool(enabled)
self.ttl_seconds = max(1, int(ttl_seconds))
self._data: dict[str, Any] = {}
self._lock = threading.RLock()
self._load()
def get(self, key: str) -> dict[str, Any] | None:
if not self.enabled:
return None
with self._lock:
value = self._data.get(key)
cached = self._unwrap_entry(value)
if cached is None and key in self._data:
self._data.pop(key, None)
self.save()
return cached
def set(self, key: str, value: dict[str, Any]) -> None:
if not self.enabled:
return
with self._lock:
self._data[key] = {
"created_at": time.time(),
"value": value,
}
self.save()
def save(self) -> None:
if not self.enabled:
return
with self._lock:
self.path.parent.mkdir(parents=True, exist_ok=True)
with self._file_lock():
fd, tmp_name = tempfile.mkstemp(
dir=self.path.parent,
prefix=f".{self.path.name}.",
suffix=".tmp",
text=True,
)
try:
with os.fdopen(fd, "w", encoding="utf-8") as f:
json.dump(
self._data, f, ensure_ascii=False, indent=2, default=str
)
f.write("\n")
os.replace(tmp_name, self.path)
except Exception:
try:
os.unlink(tmp_name)
except OSError:
pass
raise
def make_cache_key(
self,
query: str,
retrieval_result: dict[str, Any],
selected_citations: list[dict[str, Any]] | None,
cohort: str | None = None,
context_fingerprint: dict[str, Any] | None = None,
pipeline_version: str | None = None,
) -> str:
payload = {
"query": query,
"cohort": cohort,
"pipeline_version": pipeline_version,
"context_fingerprint": context_fingerprint or {},
"retrieval_query": retrieval_result.get("retrieval_query"),
"citations": [
{
"chunk_id": citation.get("chunk_id"),
"title": citation.get("title"),
"chunk_type": citation.get("chunk_type"),
"source_pages": citation.get("source_pages"),
}
for citation in (selected_citations or [])
],
"structured_result": retrieval_result.get("structured_result"),
"tool_result": retrieval_result.get("tool_result"),
}
stable_json = json.dumps(
payload, ensure_ascii=False, sort_keys=True, default=str
)
return hashlib.sha256(stable_json.encode("utf-8")).hexdigest()
def _load(self) -> None:
if not self.enabled or not self.path.exists():
self._data = {}
return
try:
with self._lock:
with self._file_lock():
with self.path.open("r", encoding="utf-8") as f:
loaded = json.load(f)
except (json.JSONDecodeError, OSError, TimeoutError):
self._data = {}
return
self._data = loaded if isinstance(loaded, dict) else {}
def _unwrap_entry(self, entry: Any) -> dict[str, Any] | None:
if not isinstance(entry, dict):
return None
if "created_at" not in entry or "value" not in entry:
# Backward compatible with cache files written before TTL metadata.
return entry
value = entry.get("value")
if not isinstance(value, dict):
return None
try:
age_seconds = time.time() - float(entry.get("created_at"))
except (TypeError, ValueError):
return None
if age_seconds > self.ttl_seconds:
return None
return value
@contextmanager
def _file_lock(self) -> Any:
lock_path = self.path.with_suffix(f"{self.path.suffix}.lock")
lock_path.parent.mkdir(parents=True, exist_ok=True)
with lock_path.open("a+b") as lock_file:
_acquire_file_lock(lock_file)
try:
yield
finally:
_release_file_lock(lock_file)
def _acquire_file_lock(lock_file: Any) -> None:
deadline = time.monotonic() + LOCK_TIMEOUT_SECONDS
while True:
try:
if os.name == "nt":
lock_file.seek(0)
msvcrt.locking(lock_file.fileno(), msvcrt.LK_NBLCK, 1)
else:
fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
return
except OSError:
if time.monotonic() >= deadline:
raise TimeoutError("Timed out waiting for response cache lock")
time.sleep(LOCK_POLL_SECONDS)
def _release_file_lock(lock_file: Any) -> None:
if os.name == "nt":
lock_file.seek(0)
msvcrt.locking(lock_file.fileno(), msvcrt.LK_UNLCK, 1)
else:
fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)
class RedisResponseCache(ResponseCache):
def __init__(
self,
redis_url: str,
path: str | Path,
enabled: bool = True,
ttl_seconds: int = DEFAULT_CACHE_TTL_SECONDS,
) -> None:
super().__init__(path=path, enabled=enabled, ttl_seconds=ttl_seconds)
self.redis_url = redis_url
import redis
self.client = redis.from_url(self.redis_url)
def get(self, key: str) -> dict[str, Any] | None:
if not self.enabled:
return None
try:
cached_json = self.client.get(key)
if cached_json:
print(f"[Redis Cache] HIT for key {key[:8]}...")
entry = json.loads(cached_json)
return self._unwrap_entry(entry)
except Exception as e:
logging.warning(f"Redis get failed: {e}. Falling back to local cache.")
# If not in Redis (or Redis failed), fallback to local
return super().get(key)
def set(self, key: str, value: dict[str, Any]) -> None:
if not self.enabled:
return
entry = {
"created_at": time.time(),
"value": value,
}
try:
self.client.set(
key,
json.dumps(entry, ensure_ascii=False, default=str),
ex=self.ttl_seconds,
)
print(f"[Redis Cache] Wrote key {key[:8]}...")
except Exception as e:
logging.warning(f"Redis set failed: {e}. Falling back to local cache.")
# Write to local cache as well (Two-Tier caching)
super().set(key, value)
def get_response_cache(
path: str | Path,
enabled: bool = True,
ttl_seconds: int = DEFAULT_CACHE_TTL_SECONDS,
) -> ResponseCache:
if os.environ.get("STUDENT_RAG_DISABLE_REDIS", "").strip().lower() in {
"1",
"true",
"yes",
"on",
}:
print("[Cache] Redis disabled by STUDENT_RAG_DISABLE_REDIS. Using Local JSON.")
return ResponseCache(path, enabled, ttl_seconds)
redis_url = os.environ.get("REDIS_URL")
if redis_url:
try:
import redis
r = redis.from_url(redis_url)
r.ping()
print("[Cache] Connected to Redis. Enabling Two-Tier Caching.")
return RedisResponseCache(redis_url, path, enabled, ttl_seconds)
except Exception as e:
print(f"[Cache] Redis connection failed: {e}. Falling back to Local JSON.")
print("[Cache] Using Local JSON Caching.")
return ResponseCache(path, enabled, ttl_seconds)
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