File size: 4,698 Bytes
c94194a | 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 | """Result caching for the verification engine.
Two things are expensive and highly reusable in bulk verification:
- **DNS/MX** for a domain (every address at that domain needs the same answer)
- **the mailbox verdict** for an address (lists overlap; users re-run lists)
Both are cached here, with one hard correctness rule: **only definitive results
are cached**. Transient failures — a DNS timeout, a greylist 4xx, an unreachable
MX — are never stored, because remembering them would freeze a temporary
condition into a 24h "verdict" and suppress a later successful probe.
A cache outage degrades to "no cache"; it must never break validation.
"""
from __future__ import annotations
import json
from typing import Any, Callable, Coroutine, Optional
from ..config import settings
from ..models import DNSResult, SMTPResult
from ..utils.cache import get_cache as _default_get, set_cache as _default_set
# A DNS timeout/resolver error is inconclusive — never a cacheable fact.
_UNRESOLVED_DNS_CODES = frozenset({"timeout", "resolver_error"})
DNS_TTL = 24 * 3600 # MX/SPF/DMARC change slowly
VERDICT_TTL = 24 * 3600 # a mailbox verdict is stable within a day
class ValidationCache:
"""Thin typed layer over the shared Redis/memory cache."""
def __init__(
self,
get: Optional[Callable[[str], Coroutine[Any, Any, Optional[str]]]] = None,
set: Optional[Callable[..., Coroutine[Any, Any, None]]] = None,
ttl_seconds: int = DNS_TTL,
):
self._get = get or _default_get
self._set = set or _default_set
self.ttl_seconds = ttl_seconds
# ---- keys ------------------------------------------------------
@staticmethod
def dns_key(domain: str) -> str:
return f"vx:dns:{domain.strip().lower()}"
@staticmethod
def verdict_key(email: str, deep: bool) -> str:
# `deep` is part of the identity: a fast-mode result carries no mailbox
# proof and must never satisfy a deep request.
return f"vx:v:{'d' if deep else 'f'}:{email.strip().lower()}"
# ---- low level -------------------------------------------------
async def _read_json(self, key: str) -> Optional[dict]:
try:
raw = await self._get(key)
except Exception:
return None # cache outage -> treat as a miss
if not raw:
return None
try:
data = json.loads(raw)
except Exception:
return None # corrupt payload -> miss, never raise
return data if isinstance(data, dict) else None
async def _write_json(self, key: str, payload: dict, ttl: int) -> None:
try:
await self._set(key, json.dumps(payload), ttl)
except Exception:
pass # a cache write failure must not break validation
# ---- DNS -------------------------------------------------------
async def get_dns(self, domain: str) -> Optional[DNSResult]:
data = await self._read_json(self.dns_key(domain))
if not data:
return None
try:
return DNSResult(**data)
except Exception:
return None
async def put_dns(self, domain: str, result: DNSResult) -> None:
if result.error_code in _UNRESOLVED_DNS_CODES:
return # transient -> never cache
await self._write_json(
self.dns_key(domain), result.model_dump(), self.ttl_seconds
)
# ---- mailbox verdict ------------------------------------------
async def get_verdict(
self, email: str, deep: bool
) -> Optional[tuple[SMTPResult, Optional[bool]]]:
data = await self._read_json(self.verdict_key(email, deep))
if not data:
return None
try:
smtp = SMTPResult(**data["smtp"])
catch_all = data.get("catch_all")
return smtp, catch_all
except Exception:
return None
async def put_verdict(
self,
email: str,
deep: bool,
smtp: SMTPResult,
catch_all: Optional[bool],
) -> None:
# Cacheable only when the mailbox question was actually answered, or the
# domain is definitively catch-all (a domain fact, not a probe failure).
definitive = smtp.verified is not None or catch_all is True
if not definitive:
return
await self._write_json(
self.verdict_key(email, deep),
{"smtp": smtp.model_dump(), "catch_all": catch_all},
VERDICT_TTL,
)
# Shared instance used by the engine.
validation_cache = ValidationCache(
ttl_seconds=getattr(settings, "dns_cache_ttl_seconds", DNS_TTL)
) |