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5c9b605 afd6eeb 5c9b605 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 | """Database-backed response cache with stale fallback support."""
from __future__ import annotations
import hashlib
import os
import re
from dataclasses import dataclass
from datetime import datetime, timedelta, timezone
from typing import Any
from sqlalchemy import create_engine, text
from sqlalchemy.engine import Engine
from app.core.config import settings
from app.utils.serialization import dumps_json, loads_json, to_jsonable
UTC = timezone.utc
TABLE_NAME_PATTERN = re.compile(r"^[A-Za-z_][A-Za-z0-9_]{0,63}$")
@dataclass(frozen=True)
class CacheEntry:
key: str
namespace: str
payload: Any
source: str
created_at: datetime
expires_at: datetime
row_count: int | None
@property
def expired(self) -> bool:
return self.expires_at <= datetime.now(UTC)
class ResponseCache:
def __init__(self, database_url: str, enabled: bool = True) -> None:
self.enabled = enabled
self.database_url = self._normalize_database_url(database_url)
self.table_name = self._validate_table_name(settings.cache_table_name)
self.engine: Engine | None = None
if self.enabled:
self._init_engine()
def _normalize_database_url(self, database_url: str) -> str:
if database_url.startswith("mysql://"):
return database_url.replace("mysql://", "mysql+pymysql://", 1)
return database_url
def _validate_table_name(self, table_name: str) -> str:
value = table_name.strip()
if not TABLE_NAME_PATTERN.fullmatch(value):
raise ValueError(f"Invalid CACHE_TABLE_NAME: {table_name!r}")
return value
def _init_engine(self) -> None:
if self.database_url.startswith("sqlite:///"):
path = self.database_url.removeprefix("sqlite:///")
dirname = os.path.dirname(path)
if dirname:
os.makedirs(dirname, exist_ok=True)
connect_args: dict[str, Any] = {}
if settings.database_ssl and self.database_url.startswith("mysql+pymysql://"):
connect_args["ssl"] = {"ssl": True}
self.engine = create_engine(
self.database_url,
pool_pre_ping=True,
future=True,
connect_args=connect_args,
)
with self.engine.begin() as conn:
conn.execute(
text(
f"""
CREATE TABLE IF NOT EXISTS {self.table_name} (
cache_key VARCHAR(191) PRIMARY KEY,
namespace VARCHAR(96) NOT NULL,
request_hash VARCHAR(64) NOT NULL,
payload_json LONGTEXT NOT NULL,
source_name VARCHAR(160) NOT NULL,
row_count INTEGER NULL,
created_at DATETIME NOT NULL,
expires_at DATETIME NOT NULL
)
"""
)
)
def make_key(self, namespace: str, params: dict[str, Any]) -> str:
canonical = dumps_json(
{
"version": settings.cache_schema_version,
"namespace": namespace,
"params": to_jsonable(params),
}
)
digest = hashlib.sha256(canonical.encode("utf-8")).hexdigest()
return f"{namespace}:{digest}"
def get(self, key: str, allow_expired: bool = False) -> CacheEntry | None:
if not self.enabled or self.engine is None:
return None
with self.engine.begin() as conn:
row = conn.execute(
text(
f"""
SELECT cache_key, namespace, payload_json, source_name, row_count, created_at, expires_at
FROM {self.table_name}
WHERE cache_key = :key
"""
),
{"key": key},
).mappings().first()
if not row:
return None
entry = CacheEntry(
key=str(row["cache_key"]),
namespace=str(row["namespace"]),
payload=loads_json(str(row["payload_json"])),
source=str(row["source_name"]),
row_count=row["row_count"],
created_at=self._as_utc(row["created_at"]),
expires_at=self._as_utc(row["expires_at"]),
)
if entry.expired and not allow_expired:
return None
return entry
def set(
self,
key: str,
namespace: str,
payload: Any,
source: str,
ttl_seconds: int,
row_count: int | None = None,
) -> CacheEntry | None:
if not self.enabled or self.engine is None:
return None
now = datetime.now(UTC)
expires_at = now + timedelta(seconds=ttl_seconds)
request_hash = key.rsplit(":", 1)[-1]
with self.engine.begin() as conn:
conn.execute(
text(
f"""
DELETE FROM {self.table_name}
WHERE cache_key = :key
"""
),
{"key": key},
)
conn.execute(
text(
f"""
INSERT INTO {self.table_name} (
cache_key, namespace, request_hash, payload_json, source_name,
row_count, created_at, expires_at
)
VALUES (
:key, :namespace, :request_hash, :payload_json, :source_name,
:row_count, :created_at, :expires_at
)
"""
),
{
"key": key,
"namespace": namespace,
"request_hash": request_hash,
"payload_json": dumps_json(payload),
"source_name": source,
"row_count": row_count,
"created_at": now.replace(tzinfo=None),
"expires_at": expires_at.replace(tzinfo=None),
},
)
return CacheEntry(key, namespace, payload, source, now, expires_at, row_count)
def purge_expired(self) -> int:
if not self.enabled or self.engine is None:
return 0
now = datetime.now(UTC).replace(tzinfo=None)
with self.engine.begin() as conn:
result = conn.execute(
text(f"DELETE FROM {self.table_name} WHERE expires_at < :now"),
{"now": now},
)
return int(result.rowcount or 0)
def purge_all(self) -> int:
if not self.enabled or self.engine is None:
return 0
with self.engine.begin() as conn:
result = conn.execute(text(f"DELETE FROM {self.table_name}"))
return int(result.rowcount or 0)
def stats(self) -> dict[str, Any]:
if not self.enabled or self.engine is None:
return {"enabled": False}
with self.engine.begin() as conn:
total = conn.execute(text(f"SELECT COUNT(*) FROM {self.table_name}")).scalar_one()
expired = conn.execute(
text(f"SELECT COUNT(*) FROM {self.table_name} WHERE expires_at < :now"),
{"now": datetime.now(UTC).replace(tzinfo=None)},
).scalar_one()
return {
"enabled": True,
"backend": self.database_url.split(":", 1)[0],
"total_entries": int(total),
"expired_entries": int(expired),
}
def _as_utc(self, value: Any) -> datetime:
if isinstance(value, datetime):
if value.tzinfo is None:
return value.replace(tzinfo=UTC)
return value.astimezone(UTC)
return datetime.fromisoformat(str(value)).replace(tzinfo=UTC)
cache = ResponseCache(settings.database_url, enabled=settings.cache_enabled)
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