rohitg00/ai-engineering-from-scratch · error · ReliabilityError

charge must be positive

Error message

charge must be positive

What it means

Error "charge must be positive" thrown in rohitg00/ai-engineering-from-scratch.

Source

Thrown at phases/13-tools-and-protocols/29-mcp-reliability-cancellation-and-flow-control/code/main.py:335

    @staticmethod
    def _fingerprint(account: str, cents: int) -> str:
        payload = json.dumps(
            {"account": account, "cents": cents},
            sort_keys=True,
            separators=(",", ":"),
        )
        return hashlib.sha256(payload.encode("utf-8")).hexdigest()

    def charge(
        self,
        account: str,
        cents: int,
        *,
        rpc_id: int | str,
        idempotency_key: str | None = None,
    ) -> dict[str, Any]:
        if cents <= 0:
            raise ReliabilityError("charge must be positive")
        fingerprint = self._fingerprint(account, cents)
        with self._lock:
            self._connection.execute("BEGIN IMMEDIATE")
            try:
                if idempotency_key is not None:
                    stored = self._connection.execute(
                        """
                        SELECT fingerprint, result_json
                        FROM idempotency_records
                        WHERE idempotency_key = ?
                        """,
                        (idempotency_key,),
                    ).fetchone()
                    if stored is not None:
                        stored_fingerprint, stored_json = stored
                        if stored_fingerprint != fingerprint:
                            raise ReliabilityError(
                                "idempotency key was reused with different arguments"

View on GitHub (pinned to 39ea8a1c6d)

When it happens

Trigger: Thrown at phases/13-tools-and-protocols/29-mcp-reliability-cancellation-and-flow-control/code/main.py:335 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of rohitg00/ai-engineering-from-scratch@39ea8a1c6d (2026-08-26). Data as JSON: /api/errors/cba1e9c4b643e247. Report an issue: GitHub.