nautechsystems/nautilus_trader · error

ticker channel present

Error message

ticker channel present

What it means

Same internal-invariant panic as the book case, but for ticker channels: when registering a `ChannelOwner::Ticker { instrument_id, feed }` owner, the adapter stores the active channel name per instrument and marks the subscription under its feed. The `channel` Option is expected to be `Some` here; `None` means the registration was invoked without an established channel.

Source

Thrown at crates/adapters/derive/src/data.rs:1920

            ChannelOwner::BookDeltas(instrument_id) => {
                self.active_book_delta_channels.insert(
                    instrument_id,
                    channel.expect("book channel present").to_string(),
                );
            }
            ChannelOwner::BookDepth10(instrument_id) => {
                self.active_book_depth10_channels.insert(
                    instrument_id,
                    channel.expect("book channel present").to_string(),
                );
            }
            ChannelOwner::Ticker {
                instrument_id,
                feed,
            } => {
                self.active_ticker_channels.insert(
                    instrument_id,
                    channel.expect("ticker channel present").to_string(),
                );
                self.ticker_subscriptions(feed).insert(instrument_id);
            }
            ChannelOwner::Trades(instrument_id) => {
                self.active_trade_subs.insert(instrument_id);
            }
        }
    }

    fn deactivate(&self, owner: ChannelOwner, channel_empty: bool) {
        match owner {
            ChannelOwner::BookDeltas(instrument_id) => {
                self.active_book_delta_channels.remove(&instrument_id);
            }
            ChannelOwner::BookDepth10(instrument_id) => {
                self.active_book_depth10_channels.remove(&instrument_id);
            }
            ChannelOwner::Ticker {

View on GitHub (pinned to 18893faf8b)

Solutions

1. Only call the ticker registration path with a resolved channel name; guarantee Some(channel) for Ticker owners.
2. Check the ticker subscribe response parsing to ensure the channel string is extracted and forwarded.
3. Replace the expect with an explicit error path that logs the feed/instrument and rejects the registration gracefully.
4. Keep ticker registrations paired with the feed-based subscription set update so state stays consistent.

Example fix

// before
self.active_ticker_channels.insert(
    instrument_id,
    channel.expect("ticker channel present").to_string(),
);
// after
match channel {
    Some(ch) => {
        self.active_ticker_channels.insert(instrument_id, ch.to_string());
        self.ticker_subscriptions(feed).insert(instrument_id);
    }
    None => tracing::error!(?feed, %instrument_id, "ticker channel missing"),
}

if channel.is_none() {
    tracing::error!(?feed, "ticker channel missing at registration");
    return false;
}

When it happens

Trigger: Registering a ticker subscription owner without a channel name — e.g. the subscribe flow calls the registry with `channel: None` for a Ticker owner, or the websocket channel string was never assigned before insertion into `active_ticker_channels`.

Common situations: Seen when developing or modifying Derive ticker subscription handling, after refactors of the channel-owner map, or if ticker subscribe responses from the exchange no longer include the channel identifier the parser expects.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

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• Stream receiver already taken or client not connected - stre

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/16c19ecd299e92c8. Report an issue: GitHub.