Files
plm-lottery/app/api/routes/withdrawals.py
T
davideandClaude Opus 5 d528c5b475 Let the system recover from a broadcast that never confirms
The code treated a broadcast as final: money moved on-chain and the DB was
updated on the assumption it would either confirm or be fee-bumped until it
did. Neither is guaranteed, and every way that assumption broke was permanent
(BUGS.md B-02, B-03, B-04, B-07, B-08, B-20, B-21).

Persist before broadcasting. place_bet and request_withdrawal now write their
rows in a "building" state and commit, then broadcast, then promote to
broadcast/pending in a second commit. Before, a failure or crash between the
broadcast and the commit left the coins irreversibly spent with no trace: no
participant (so no entry in the draw), no pending row (so no RBF and no
confirmation tracking), and the UTXOs not even marked spent, so the next bet
would try to double-spend them. A refused broadcast now releases the reserved
UTXOs, restores the balance, removes the participant (or marks the withdrawal
failed), audit-logs it, and answers a translatable broadcast_failed — as 502,
since the network refused it, not the caller, where it used to be an opaque 500.

Reconcile what's in flight against the chain. New PendingTransactionReconciler
(app/tx/reconcile.py, every 120s and once at startup) asks whether each
non-terminal tx exists: present -> promote, gone -> mark failed with a reason,
release the inputs, roll the domain row back, audit-log it. Grace periods differ
by state (120s for "building", 6h for "pending", so the RBF bumper gets its
attempts first). It is deliberately biased to inaction: only a server that
positively doesn't know the tx counts as absent, and a transport failure never
abandons anything, because releasing a UTXO whose tx is actually alive would
invite a double-spend. Verified against the live server, which answers "No such
mempool or blockchain transaction" for an unknown txid.

Stop keying on a value that changes. An RBF bump changes the txid, and
_on_bet_confirmed looked the participant up by bet_txid — so a bumped bet
confirmed under a txid no participant carried, the row stayed "broadcast"
forever, and the scheduler waited on it forever: the round could never close and
the lottery stopped. Handlers now resolve by immutable ids (round_id/user_id,
withdrawal_id), and bump_fee retargets every stored txid — bet_txid,
Withdrawal.txid, Round.payout_txid and UtxoEvent.spent_txid — plus records the
previous one in replaced_by_txid, which was never written at all.

One bad row no longer blocks the rest. The confirmation poller's per-tx lookup
is guarded: a txid the server can't resolve used to abort the whole pass, so
nothing confirmed again until an operator intervened. It also selects plain
columns instead of hydrating entities that outlive their session.

Tests: 6 reconciler cases including "a broken connection must not release coins";
the bet-ordering test probes committed state from an independent session during
the broadcast, and caught a real mistake in the first draft of this change (the
_pending_transaction helper still hardcoded status="pending", so rows were born
already-broadcast and would have got the 6-hour grace instead of 120s).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-07-27 00:31:24 +02:00

60 lines
1.9 KiB
Python

from fastapi import APIRouter, Depends, Request, status
from pydantic import BaseModel
from sqlalchemy.ext.asyncio import AsyncSession
from app.api.errors import from_api_error, http_error
from app.auth.dependencies import get_current_user
from app.db.models import User
from app.db.session import get_session
from app.withdrawals.service import WithdrawalError, request_withdrawal
router = APIRouter(prefix="/withdrawals", tags=["withdrawals"])
class WithdrawalRequest(BaseModel):
external_address: str
amount_sats: int
class WithdrawalResponse(BaseModel):
txid: str
amount_requested_sats: int
amount_sent_sats: int
status: str
@router.post("", response_model=WithdrawalResponse, status_code=status.HTTP_201_CREATED)
async def create_withdrawal(
body: WithdrawalRequest,
request: Request,
user: User = Depends(get_current_user),
session: AsyncSession = Depends(get_session),
) -> WithdrawalResponse:
listener = request.app.state.electrum_listener
if listener.client is None:
raise http_error(
status.HTTP_503_SERVICE_UNAVAILABLE,
"network_unavailable",
"not connected to the network, try again shortly",
)
async with request.app.state.user_locks.acquire(user.id):
try:
withdrawal = await request_withdrawal(
session, listener.client, user, body.external_address, body.amount_sats
)
except WithdrawalError as exc:
code = (
status.HTTP_502_BAD_GATEWAY # the network refused it, not the caller (B-07)
if exc.code == "broadcast_failed"
else status.HTTP_400_BAD_REQUEST
)
raise from_api_error(code, exc) from exc
return WithdrawalResponse(
txid=withdrawal.txid,
amount_requested_sats=withdrawal.amount_requested_sats,
amount_sent_sats=withdrawal.amount_sent_sats,
status=withdrawal.status,
)