k1nq
130 lines
4.3 KiB
Python
130 lines
4.3 KiB
Python
import asyncio
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import logging
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import random
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from collections.abc import Awaitable, Callable
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from datetime import UTC, datetime
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import httpx
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from sqlalchemy import select
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from sqlalchemy.ext.asyncio import async_sessionmaker
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from app.config import Settings
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from app.models import Payment, PaymentStatus
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from app.schemas import PaymentCreatedEvent, PaymentWebhook
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logger = logging.getLogger(__name__)
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class PaymentNotFoundError(Exception):
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pass
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class PaymentGateway:
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def __init__(self, settings: Settings) -> None:
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self._min_seconds = settings.processing_min_seconds
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self._max_seconds = settings.processing_max_seconds
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self._success_rate = settings.processing_success_rate
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async def charge(self) -> PaymentStatus:
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await asyncio.sleep(random.uniform(self._min_seconds, self._max_seconds))
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if random.random() < self._success_rate:
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return PaymentStatus.SUCCEEDED
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return PaymentStatus.FAILED
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class WebhookClient:
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def __init__(self, timeout: float) -> None:
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self._timeout = timeout
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async def send(self, url: str, payload: PaymentWebhook) -> None:
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async with httpx.AsyncClient(timeout=self._timeout) as client:
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response = await client.post(url, json=payload.model_dump(mode="json"))
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response.raise_for_status()
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async def retry_async[T](
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operation: Callable[[], Awaitable[T]],
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*,
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attempts: int,
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base_delay: float,
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sleep: Callable[[float], Awaitable[None]] = asyncio.sleep,
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) -> T:
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for attempt in range(attempts):
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try:
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return await operation()
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except Exception:
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if attempt == attempts - 1:
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raise
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delay = base_delay * (2**attempt)
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logger.warning(
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"Payment handling attempt %d/%d failed; retrying in %.2fs",
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attempt + 1,
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attempts,
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delay,
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exc_info=True,
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)
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await sleep(delay)
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raise RuntimeError("Retry loop completed without a result")
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class PaymentProcessor:
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def __init__(
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self,
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session_factory: async_sessionmaker,
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gateway: PaymentGateway,
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webhook_client: WebhookClient,
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settings: Settings,
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) -> None:
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self._session_factory = session_factory
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self._gateway = gateway
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self._webhook_client = webhook_client
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self._attempts = settings.processing_max_attempts
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self._base_delay = settings.retry_base_delay
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async def process(self, event: PaymentCreatedEvent) -> None:
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await retry_async(
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lambda: self._process_once(event),
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attempts=self._attempts,
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base_delay=self._base_delay,
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)
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async def _process_once(self, event: PaymentCreatedEvent) -> None:
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async with self._session_factory() as session:
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payment = await session.scalar(
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select(Payment).where(Payment.id == event.payment_id).with_for_update()
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)
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if payment is None:
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raise PaymentNotFoundError(str(event.payment_id))
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if payment.status is PaymentStatus.PENDING:
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payment.status = await self._gateway.charge()
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payment.processed_at = datetime.now(UTC)
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await session.commit()
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if payment.webhook_delivered_at is not None:
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return
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if payment.processed_at is None:
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raise RuntimeError("A terminal payment has no processing timestamp")
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webhook_url = payment.webhook_url
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webhook = PaymentWebhook(
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payment_id=payment.id,
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amount=payment.amount,
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currency=payment.currency,
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status=payment.status,
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processed_at=payment.processed_at,
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metadata=payment.metadata_,
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)
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await self._webhook_client.send(webhook_url, webhook)
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async with self._session_factory() as session:
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payment = await session.scalar(
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select(Payment).where(Payment.id == event.payment_id).with_for_update()
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)
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if payment is None:
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raise PaymentNotFoundError(str(event.payment_id))
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if payment.webhook_delivered_at is None:
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payment.webhook_delivered_at = datetime.now(UTC)
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await session.commit()
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