nautechsystems/nautilus_trader · error · anyhow::Error

Failed to serialize subscription: {e}

Error message

Failed to serialize subscription: {e}

What it means

`handle_subscribe` serializes the OKXSubscription (op=subscribe with args) to JSON before sending. Serialization of these strongly-typed structs should never fail in practice; if it does (corrupt/invalid subscription args producing unserializable data), the error is surfaced wrapped in this message.

Source

Thrown at crates/adapters/okx/src/websocket/handler.rs:538

        self.handle_subscription_ack(&event, arg, Some(code), Some(msg))
    }

    async fn handle_subscribe(&self, args: Vec<OKXSubscriptionArg>) -> anyhow::Result<()> {
        for arg in &args {
            log::debug!(
                "Subscribing to channel: channel={:?}, inst_id={:?}",
                arg.channel,
                arg.inst_id
            );
        }

        let message = OKXSubscription {
            op: OKXWsOperation::Subscribe,
            args,
        };

        let json_txt = serde_json::to_string(&message)
            .map_err(|e| anyhow::anyhow!("Failed to serialize subscription: {e}"))?;

        self.send_with_retry(json_txt, Some(OKX_RATE_LIMIT_KEY_SUBSCRIPTION.as_slice()))
            .await
            .map_err(|e| anyhow::anyhow!("Failed to send subscription after retries: {e}"))?;
        Ok(())
    }

    async fn handle_unsubscribe(&self, args: Vec<OKXSubscriptionArg>) -> anyhow::Result<()> {
        for arg in &args {
            log::debug!(
                "Unsubscribing from channel: channel={:?}, inst_id={:?}",
                arg.channel,
                arg.inst_id
            );
        }

        let message = OKXSubscription {
            op: OKXWsOperation::Unsubscribe,

View on GitHub (pinned to 18893faf8b)

Solutions

1. Inspect the inner `{e}` and the args being subscribed; fix the arg construction to use plain strings/numbers.
2. Validate subscription parameters (inst_id, channel, depth) are normal UTF-8 strings before subscribing.
3. Report as a bug if it occurs with standard subscription args; serde serialization of these structs is expected to always succeed.

// rust
// ensure args are plain strings before subscribing
assert!(args.iter().all(|a| !a.inst_id.as_deref().unwrap_or("").is_empty()));

When it happens

Trigger: `serde_json::to_string(&OKXSubscription{...})` returns Err while handling a subscribe command — e.g. arg values containing types that fail serialization.

Common situations: Extremely rare; usually indicates a bug in constructed subscription args (e.g. non-finite floats or invalid map keys in custom arg fields) rather than a user configuration issue.

Understand the failure class

Background: json.Marshal / "failed to marshal" errors in Go: why "unsupported type" happens and how to fix it — this error's family across 22 libraries.

Related errors

• Failed to send subscription after retries: {e}
• Failed to serialize unsubscription: {e}
• Invalid OKX websocket channel
• Failed to send subscribe command: {e}
• Invalid `BarSpecification` for channel, was {bar_spec}

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/b1e27a147a5f5ef7. Report an issue: GitHub.