What causes "Blockchain execution client is not connected" in nautechsystems/nautilus_trader?

Await a successful connect() (and any required post-connect reconciliation) before calling wrap, approve, or submit_order.

nautechsystems/nautilus_trader · error

Blockchain execution client is not connected

Error message

Blockchain execution client is not connected

What it means

ensure_transaction_ready() is the pre-flight gate for submitting any transaction (wrap, approve, swap). It first requires the execution client to be connected to the chain via core.is_connected(); if not, it fails closed so no transaction is signed or submitted while the client is offline.

Source

Thrown at crates/adapters/blockchain/src/execution/client.rs:1522

        match purpose {
            TransactionPurpose::Wrap => {
                verify_wrap_balance_increase(executor, &to, value, included).await
            }
            TransactionPurpose::Approve => {
                let call = ERC20::approveCall::abi_decode(&input)
                    .with_context(|| "persisted approve calldata is invalid")?;
                verify_approve_allowance(executor, &to, &call.spender, call.amount, included).await
            }
            TransactionPurpose::Swap => {
                unreachable!("swap intents restore a swap plan")
            }
        }
    }

    fn ensure_transaction_ready(&self, purpose: TransactionPurpose) -> anyhow::Result<()> {
        if !self.core.is_connected() {
            anyhow::bail!("Blockchain execution client is not connected");
        }

        {
            let slot = self.in_flight.lock();
            if let Some(in_flight) = *slot {
                return Err(in_flight_limit_error(&in_flight));
            }
        }

        if !self.cache.has_database() {
            anyhow::bail!(
                "No durable store configured; refusing to submit a {} transaction",
                purpose.as_str()
            );
        }
        Ok(())
    }

View on GitHub (pinned to 18893faf8b)

Solutions

Await a successful connect() (and any required post-connect reconciliation) before calling wrap, approve, or submit_order.
Check connection state (client.is_connected()) in your strategy loop and gate order submission on it.
Verify the RPC endpoint/URL and network reachability, then reconnect; re-establish the WebSocket/HTTP provider if it dropped.
Handle the not-connected error by pausing trading and retrying connect with backoff instead of resubmitting transactions.

Example fix

// before: submit immediately, fails if not yet connected
client.submit_order(order)?;

// after: gate on connection before trading
if !client.is_connected() {
    client.connect().await.expect("execution client connect");
}
assert!(client.is_connected());
client.submit_order(order)?;

Defensive patterns

Strategy: try-catch

Validate before calling

// Gate submission on connection state before calling wrap/approve/submit_order
if !client.is_connected() {
    client.connect().await?; // or defer submission until connected
}

Try / catch

match client.submit_order(order) {
    Err(e) if e.to_string().contains("not connected") => {
        log::warn!("execution client offline; pausing trading");
        client.connect().await?; // reconnect with backoff, then resubmit
    }
    result => result?,
}

Prevention

Await connect() (and post-connect reconciliation) completion before enabling order submission.
Subscribe to connection-state changes and pause trading on disconnect.
Configure RPC reconnect/backoff and health checks so is_connected() recovers promptly.
Use a connection watchdog that reconnects automatically during provider outages.

When it happens

Trigger: Calling wrap(), approve(), or prepare_swap() (e.g. via submit_order) before connect() succeeded, or after the connection dropped/was closed (RPC endpoint down, network interruption, client explicitly disconnected).

Common situations: Submitting an order at startup before the async connect completed; RPC provider outage or WebSocket disconnect mid-session; calling wrap/approve on a fresh client without connecting; a dropped network causing is_connected() to flip false while the strategy keeps trading.

Understand the failure class

Background: ECONNREFUSED and "connection refused" / "could not connect to server" errors: what they mean and how to fix them — this error's family across 44 libraries.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/c18d3d287dae695e. Report an issue: GitHub.