nautechsystems/nautilus_trader · error

event-store replay did not start

Error message

event-store replay did not start

What it means

The engine detected that an event-store replay was configured but the replay never actually started before the run proceeded. run_impl bails to avoid silently trading without replaying the requested event-store data.

Source

Thrown at crates/backtest/src/engine.rs:809

            self.force_stop = false;
            self.kernel.reset_shutdown_flag();

            // Initialize sync command senders (once per thread)
            Self::init_command_senders();

            // Set logging to static clock mode for deterministic timestamps
            logging_clock_set_static_mode();
            logging_clock_set_static_time(start_ns.as_u64());

            // Start kernel, then stop before trader startup for event-store replay
            self.kernel.start();
            if self.kernel.is_event_store_replay() {
                self.log_pre_run();
                return Ok(());
            }

            if self.kernel.is_event_store_replay_configured() {
                anyhow::bail!("event-store replay did not start");
            }
            self.kernel.start_trader()?;

            // Drain on_start data subscriptions so aggregators subscribe before the first data
            // point, else internal aggregation drops the first tick. Trading/exec stay queued
            while !data_cmd_queue_is_empty() {
                drain_data_cmd_queue();
            }

            self.log_pre_run();
        }

        self.log_run();

        // Skip data before start_ns
        while let Some(d) = self.data_iterator.peek() {
            if d.ts_init() >= start_ns {
                break;

View on GitHub (pinned to 18893faf8b)

Solutions

1. Verify the event-store replay configuration (catalog path, stream/session ids) points to existing replayable data
2. Check kernel event-replay setup so replay is actually initiated before trading starts
3. Confirm data exists in the event store for the requested time range

Example fix

// before
let engine = get_backtest_engine_with_event_replay("/wrong/path");
engine.run(None, None, None, false)?;
// after
let engine = get_backtest_engine_with_event_replay("/correct/catalog"); // contains replay data
engine.run(None, None, None, false)?;

match engine.run(...) {
    Err(e) if e.to_string() == "event-store replay did not start" => {
        eprintln!("check event-store replay config and data availability: {e}");
    }
    other => other?,
}

When it happens

Trigger: Event-store replay configured (e.g. via kernel/catalog event replay settings) but the replay did not begin: misconfigured replay source, empty/unreachable event store, or replay not initiated before reaching this check.

Common situations: Pointing replay at a non-existent or empty event-store stream; wrong session/storage configuration; streaming flags suppressing replay start.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• catalog marker join plan failed for {data_cls}: {error}
• catalog marker join load failed for {data_cls}: {error}
• Cannot handle command: {command:?}
• Latency model should be initialized
• Execution client should be initialized

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/b821e27e39ee0b96. Report an issue: GitHub.