nautechsystems/nautilus_trader · error

data-connect timeout

Error message

data-connect timeout

What it means

connect_data_phase wraps self.kernel.connect_data_clients() in a timeout bounded by the remaining time until the shared connection deadline. If connecting all data clients does not finish in time, the future is cancelled and this error is returned; start() then aborts startup with "Data client connection timed out". A zero timeout_connection is intentionally still allowed (fails-closed-on-poll semantics), so this only fires when a real connect hangs or the budget is exhausted.

Source

Thrown at crates/live/src/node/mod.rs:2100

        };

        AsyncRunner::handle_exec_event(evt);

        if let Some(fill) = &recent_fill_candidate {
            self.exec_manager.commit_recent_fill_if_applied(fill);
        }
    }

    async fn connect_data_phase(&mut self, deadline: dst::time::Instant) -> anyhow::Result<()> {
        // A zero remaining budget still admits an immediately-ready connect (an
        // empty/ready client set completes on the first poll); a pending connect
        // fails closed on that same poll. This keeps a zero `timeout_connection`
        // - a supported "do not wait, but allow ready work" configuration -
        // working, while still bounding a hung connect.
        let remaining = deadline.saturating_duration_since(dst::time::Instant::now());
        dst::time::timeout(remaining, self.kernel.connect_data_clients())
            .await
            .map_err(|_| anyhow::anyhow!("data-connect timeout"))
    }

    async fn connect_exec_clients(&mut self, deadline: dst::time::Instant) -> anyhow::Result<()> {
        let remaining = deadline.saturating_duration_since(dst::time::Instant::now());
        dst::time::timeout(remaining, self.kernel.connect_exec_clients())
            .await
            .map_err(|_| anyhow::anyhow!("exec-connect timeout"))
    }

    /// Connects execution clients and checks all engines are connected.
    ///
    /// Returns the final connection wait status.
    /// Must be called after data clients are connected and instrument events drained.
    async fn connect_exec_phase(
        &mut self,
        deadline: dst::time::Instant,
    ) -> anyhow::Result<EngineConnectionStatus> {
        self.connect_exec_clients(deadline).await?;

View on GitHub (pinned to 18893faf8b)

Solutions

1. Increase timeout_connection to comfortably cover data client connects plus instrument event draining.
2. Verify market-data endpoint reachability and credentials; fix any adapter-level connect error surfaced in logs.
3. Reduce the number or cost of initial subscriptions if venue onboarding is slow.
4. Check DNS/proxy configuration on the host that could stall TCP/TLS establishment.

Example fix

// before
timeout_connection: Duration::from_secs(15)
// after
timeout_connection: Duration::from_secs(120)

// Ensure the shared connection deadline can cover data connect
let deadline_needed = expected_data_connect_secs + instrument_drain_secs;
assert!(config.timeout_connection.as_secs() >= deadline_needed);

match node.start().await {
    Err(e) if e.to_string().contains("data-connect timeout") => {
        // raise timeout_connection / check market-data endpoints, then retry
    }
    other => other?,
}

When it happens

Trigger: dst::time::timeout(remaining, connect_data_clients()) elapses in connect_data_phase (mod.rs:2096-2101); remaining is deadline.saturating_duration_since(now), so earlier startup phases may have already consumed the deadline.

Common situations: Slow market-data venue handshakes; instrument subscription floods taking longer than timeout_connection; DNS or TLS stalls; the exec/data phase ordering consuming the shared deadline so data connect gets little time on retry paths.

Understand the failure class

Background: Request timed out: what client-side request timeouts mean across libraries (Request timed out, TIMED_OUT, APITimeoutError) — this error's family across 39 libraries.

• Timeouts: ETIMEDOUT, deadlines, and hung requests — what actually expires when a request times out.

Related errors

• readiness timeout while waiting for engine connections
• exec-connect timeout
• Timeout waiting for account {account_id} to be registered af
• subscription confirmation failed: {e}
• Lighter WebSocket initial connection timeout after {} second

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/7d6232d10c9a23d4. Report an issue: GitHub.