nautechsystems/nautilus_trader · error

Duplicate data catalog name '{name}'

Error message

Duplicate data catalog name '{name}'

What it means

When building the kernel with streaming/catalog configuration, each configured data catalog is assigned a name (explicit or auto-generated catalog_N). Names are collected into a set, and if two catalogs resolve to the same name the kernel refuses to start with this error, because catalog lookups by name would be ambiguous.

Source

Thrown at crates/system/src/kernel.rs:346

        let exec_engine = Rc::new(RefCell::new(exec_engine));

        let order_emulator = OrderEmulatorAdapter::new(clock.clone(), cache.clone());

        let data_engine = DataEngine::new(clock.clone(), cache.clone(), config.data_engine());
        #[cfg(feature = "streaming")]
        let mut data_engine = data_engine;
        #[cfg(feature = "streaming")]
        {
            let mut unnamed_index = 0;
            let mut catalog_names = HashSet::new();

            for catalog_config in config.catalogs() {
                let name = catalog_config.name.clone().unwrap_or_else(|| {
                    let name = format!("catalog_{unnamed_index}");
                    unnamed_index += 1;
                    name
                });
                anyhow::ensure!(
                    catalog_names.insert(name.clone()),
                    "Duplicate data catalog name '{name}'",
                );
                let catalog = catalog_config.create_catalog().with_context(|| {
                    format!(
                        "Failed to create data catalog from '{}'",
                        catalog_config.path
                    )
                })?;
                data_engine.register_catalog(catalog, Some(&name));
            }
        }
        let data_engine = Rc::new(RefCell::new(data_engine));

        DataEngine::register_msgbus_handlers(&data_engine);
        RiskEngine::register_msgbus_handlers(&risk_engine);
        ExecutionEngine::register_msgbus_handlers(&exec_engine);
        OrderEmulator::register_msgbus_handlers(&order_emulator.emulator());

View on GitHub (pinned to 18893faf8b)

Solutions

  1. Give every catalog in config.catalogs() a unique explicit name
  2. Check for duplicated catalog blocks in the config file (copy-paste errors)
  3. Rename any manual catalog name that could collide with generated names (catalog_0, catalog_1, ...) — prefer descriptive names like "parquet-main"
  4. Log the resolved catalog names during startup to spot collisions before the kernel builds

Example fix

// before: duplicate names
catalogs: [CatalogConfig { name: Some("main"), .. }, CatalogConfig { name: Some("main"), .. }]
// after
catalogs: [CatalogConfig { name: Some("main"), .. }, CatalogConfig { name: Some("archive"), .. }]
Defensive patterns

Strategy: validation

Validate before calling

fn catalog_names_unique(configs: &[CatalogConfig]) -> Result<(), String> {
    let mut seen = std::collections::HashSet::new();
    for (i, c) in configs.iter().enumerate() {
        let name = c.name.clone().unwrap_or(format!("catalog_{i}"));
        if !seen.insert(name.clone()) {
            return Err(format!("duplicate catalog name: {name}"));
        }
    }
    Ok(())
}

Try / catch

match Kernel::new_with_dependencies(...) {
    Err(e) if e.to_string().contains("Duplicate data catalog name") => {
        eprintln!("fix catalog names in config: {e}");
        std::process::exit(2);
    }
    other => other?,
}

Prevention

When it happens

Trigger: Configuring two or more catalogs in the TradingKernelConfig with the same explicit name, or relying on auto-generated names that collide after a manual name equals a generated one (e.g. an explicit "catalog_0" plus an unnamed catalog).

Common situations: Copy-pasting a catalog block in the config without renaming it; merging config files that each define a default-named catalog; an explicitly named catalog like catalog_1 colliding with the second unnamed catalog's generated name.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/0df839eaaaf6c864. Report an issue: GitHub.