nautechsystems/nautilus_trader · error · anyhow::Error

`synthetic` {synthetic.id} does not exist

Error message

`synthetic` {synthetic.id} does not exist

What it means

`DataActor::update_synthetic` requires the synthetic to already exist in the cache; it performs an update by re-adding. If no instrument with that `synthetic.id` is cached, updating is meaningless and the call bails.

Source

Thrown at crates/common/src/actor/data_actor.rs:4326

        if cache.borrow().synthetic(&synthetic.id).is_some() {
            anyhow::bail!("`synthetic` {} already exists", synthetic.id);
        }
        cache.borrow_mut().add_synthetic(synthetic)
    }

    /// Updates the `synthetic` instrument in the cache, replacing the existing entry.
    ///
    /// # Errors
    ///
    /// Returns an error if no synthetic with the same ID already exists, or if the
    /// backing cache fails to persist the replacement. Panics if the actor is not
    /// registered with a trader. // panics-doc-ok
    pub fn update_synthetic(&self, synthetic: SyntheticInstrument) -> anyhow::Result<()> {
        self.check_registered();

        let cache = self.cache_rc();
        if cache.borrow().synthetic(&synthetic.id).is_none() {
            anyhow::bail!("`synthetic` {} does not exist", synthetic.id);
        }
        cache.borrow_mut().add_synthetic(synthetic)
    }

    /// Subscribes the actor to data.
    ///
    /// # Panics
    ///
    /// Panics if the actor is not properly registered.
    pub fn subscribe_data(
        &mut self,
        handler: ShareableMessageHandler,
        data_type: DataType,
        client_id: Option<ClientId>,
        params: Option<Params>,
    ) {
        assert!(
            self.is_properly_registered(),

View on GitHub (pinned to 18893faf8b)

Solutions

1. Add the synthetic first with `add_synthetic`, then update
2. Verify the synthetic ID matches the one previously added
3. Ensure the same cache database is in use as when the synthetic was added

Example fix

// before
actor.update_synthetic(spread)?; // may bail if never added
// after
if actor.cache_rc().borrow().synthetic(&spread.id).is_some() {
    actor.update_synthetic(spread)?;
} else {
    actor.add_synthetic(spread)?;
}

if cache.borrow().synthetic(&id).is_none() {
    actor.add_synthetic(synthetic)?; // add instead of update
} else {
    actor.update_synthetic(synthetic)?;
}

if let Err(e) = actor.update_synthetic(synthetic.clone()) {
    if e.to_string().contains("does not exist") {
        actor.add_synthetic(synthetic)?;
    } else { return Err(e); }
}

When it happens

Trigger: Calling `actor.update_synthetic(synthetic)` when `cache.synthetic(&synthetic.id)` is None — the synthetic was never added, was created with a typo'd ID, or was removed earlier.

Common situations: Typo in the synthetic ID; updating in a fresh process/cache where the synthetic was never registered; config change renamed the ID so the update targets a nonexistent key.

Understand the failure class

Background: "Not found" and "does not exist" errors: why "Task not found", "No such folder", and "Can't find" fire when a lookup comes back empty — this error's family across 14 libraries.

Related errors

• Pool {pool_identifier} is not registered
• `synthetic` {synthetic.id} already exists
• Cannot update position {}: not found in cache
• Cannot update position {position_id}: not found in cache
• Instrument {instrument_id} not found in cache

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/5d182c2be73d3a89. Report an issue: GitHub.