LedgerLine/services/ledger/app.py

from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
from pydantic import BaseModel, field_validator
from opentelemetry import trace
from opentelemetry.trace import StatusCode
from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor
from opentelemetry.instrumentation.sqlalchemy import SQLAlchemyInstrumentor

from common.logging_config import configure_logging
from common.metrics import observe_db_pools
from common.telemetry import setup_telemetry

from . import chaos
from .db import normal_engine, session_factory, starved_engine
from . import repository

SERVICE_NAME = "ledger"
logger = configure_logging(SERVICE_NAME)
tracer = trace.get_tracer(__name__)
setup_telemetry(service_name=SERVICE_NAME)
app = FastAPI(title=SERVICE_NAME)

FastAPIInstrumentor.instrument_app(
    app,
    excluded_urls="/healthz",
    exclude_spans=["receive", "send"],
)
SQLAlchemyInstrumentor().instrument(
    engines=[normal_engine.sync_engine, starved_engine.sync_engine]
)
observe_db_pools({"normal": normal_engine, "starved": starved_engine})


class CreateTransactionRequest(BaseModel):
    account_id: str
    kind: str
    amount_minor: int
    currency: str
    merchant_name: str
    category_id: int | None = None

    @field_validator("amount_minor")
    @classmethod
    def deposit_amount_must_be_non_negative(cls, v, info):
        kind = info.data.get("kind")
        if kind == "deposit" and v < 0:
            raise ValueError("amount_minor must be non-negative for a deposit")
        return v


class SettleRequest(BaseModel):
    risk_score: float


@app.exception_handler(Exception)
async def unhandled_exception_handler(request: Request, exc: Exception):
    logger.exception("unhandled_exception", path=request.url.path)
    return JSONResponse(status_code=500, content={"error": "internal error"})


@app.get("/")
async def root():
    return {"service": SERVICE_NAME, "version": "0.1.0"}


@app.get("/healthz")
async def healthz(request: Request):
    if request.headers.get("X-Ledgerline-Probe") == "chatty-health":
        logger.info("healthz_probe_received", probe="chatty-health")
    return {"status": "ok", "service": SERVICE_NAME}


@app.get("/readyz")
async def readyz():
    try:
        async with normal_engine.connect() as conn:
            await conn.exec_driver_sql("SELECT 1")
    except Exception as exc:
        span = trace.get_current_span()
        span.record_exception(exc)
        span.set_status(StatusCode.ERROR, str(exc))
        logger.exception("readyz_check_failed")
        return JSONResponse(status_code=503, content={"status": "unavailable"})
    return {"status": "ok"}


@app.get("/internal/accounts")
async def list_accounts():
    async with session_factory(starved=False) as session:
        rows = await repository.list_accounts(session)
    return [dict(row) for row in rows]


@app.post("/internal/transactions")
async def create_transaction(body: CreateTransactionRequest):
    logger.info(
        "transaction_received",
        account_id=body.account_id,
        kind=body.kind,
        amount_minor=body.amount_minor,
    )

    starved = await chaos.pool_starvation_enabled()
    poison_enabled = await chaos.poison_data_enabled()
    poison_tx_id = await chaos.find_poison_transaction_id(body.account_id)

    async with session_factory(starved=starved) as session:
        account = await repository.get_account(session, body.account_id)
        if account is None:
            return JSONResponse(status_code=404, content={"error": "account not found"})

        if poison_tx_id is not None and poison_enabled:
            poison_row = await repository.get_transaction_currency(session, poison_tx_id)
            # poison_data: skip input validation on the seeded malformed rows
            # (§8) -- this naive access raises on the NULL currency on purpose.
            _ = poison_row.currency.upper()

        tx_id = await repository.create_transaction(
            session,
            account_id=body.account_id,
            kind=body.kind,
            amount_minor=body.amount_minor,
            currency=body.currency,
            merchant_name=body.merchant_name,
            category_id=body.category_id,
        )

    return JSONResponse(
        status_code=201,
        content={
            "transaction_id": tx_id,
            "account_id": body.account_id,
            "holder_name": account.holder_name,
            "kind": body.kind,
            "amount_minor": body.amount_minor,
            "category_id": body.category_id,
            "status": "pending",
        },
    )


@app.post("/internal/transactions/{tx_id}/settle")
async def settle(tx_id: str, body: SettleRequest):
    starved = await chaos.pool_starvation_enabled()
    row_lock = await chaos.row_lock_contention_enabled()

    with tracer.start_as_current_span(
        "ledger.settle",
        attributes={"ledgerline.tx.id": tx_id, "ledgerline.risk.score": body.risk_score},
    ) as span:
        async with session_factory(starved=starved) as session:
            tx = await repository.get_transaction(session, tx_id)
            if tx is None:
                return JSONResponse(status_code=404, content={"error": "transaction not found"})
            span.set_attribute("ledgerline.account.id", str(tx.account_id))
            span.set_attribute("ledgerline.tx.amount_minor", tx.amount_minor)
            account = await repository.get_account(session, tx.account_id)
            use_lock = row_lock and bool(account.is_hot)
            balance = await repository.settle_transaction(session, tx=tx, risk_score=body.risk_score, use_row_lock=use_lock)

    logger.info("transaction_settled", transaction_id=tx_id, risk_score=body.risk_score)
    return {"status": "settled", "balance_minor": balance}


@app.post("/internal/transactions/{tx_id}/reject")
async def reject(tx_id: str, body: SettleRequest):
    starved = await chaos.pool_starvation_enabled()

    async with session_factory(starved=starved) as session:
        tx = await repository.get_transaction(session, tx_id)
        if tx is None:
            return JSONResponse(status_code=404, content={"error": "transaction not found"})
        balance = await repository.reject_transaction(session, tx=tx, risk_score=body.risk_score)

    logger.info("transaction_rejected", transaction_id=tx_id, risk_score=body.risk_score)
    return {"status": "rejected", "balance_minor": balance}