nautechsystems/nautilus_trader · error

Cap'n Proto encoding is not supported for Redis cache payloa

Error message

Cap'n Proto encoding is not supported for Redis cache payloads

What it means

serialize_payload in the Redis query/cache layer only implements MsgPack and Json serialization. Cap'n Proto is a recognized SerializationEncoding enum value but has no implementation in this code path, so the function bails immediately to prevent silently writing data in an unsupported format.

Source

Thrown at crates/infrastructure/src/redis/queries.rs:99

    ) -> anyhow::Result<Vec<u8>> {
        match encoding {
            SerializationEncoding::MsgPack => {
                let mut value = serde_json::to_value(payload)?;
                convert_timestamps(&mut value);
                rmp_serde::to_vec(&value)
                    .map_err(|e| anyhow::anyhow!("Failed to serialize msgpack `payload`: {e}"))
            }
            SerializationEncoding::Json => {
                let mut value = serde_json::to_value(payload)?;
                convert_timestamps(&mut value);
                serde_json::to_vec(&value)
                    .map_err(|e| anyhow::anyhow!("Failed to serialize json `payload`: {e}"))
            }
            SerializationEncoding::Sbe => {
                anyhow::bail!("SBE encoding is not supported for Redis cache payloads")
            }
            SerializationEncoding::Capnp => {
                anyhow::bail!("Cap'n Proto encoding is not supported for Redis cache payloads")
            }
        }
    }

    /// Deserializes the given byte slice `payload` into type `T` using the specified `encoding`.
    ///
    /// # Errors
    ///
    /// Returns an error if deserialization from the chosen encoding fails or converting to the target type fails.
    pub fn deserialize_payload<T: DeserializeOwned>(
        encoding: SerializationEncoding,
        payload: &[u8],
    ) -> anyhow::Result<T> {
        let mut value = match encoding {
            SerializationEncoding::MsgPack => rmp_serde::from_slice(payload)
                .map_err(|e| anyhow::anyhow!("Failed to deserialize msgpack `payload`: {e}"))?,
            SerializationEncoding::Json => serde_json::from_slice(payload)
                .map_err(|e| anyhow::anyhow!("Failed to deserialize json `payload`: {e}"))?,

View on GitHub (pinned to 18893faf8b)

Solutions

1. Configure the Redis cache with SerializationEncoding::Json or MsgPack instead of Capnp.
2. Decouple the Redis client's serialization setting from Capnp-configured components.
3. If Capnp support is required, add the Capnp arm to serialize_payload in crates/infrastructure/src/redis/queries.rs.
4. Fail fast at construction time by validating that the configured encoding is Json or MsgPack.

Example fix

// before
let settings = SerializationSettings { encoding: SerializationEncoding::Capnp, .. };
// after
let settings = SerializationSettings { encoding: SerializationEncoding::Json, .. };

fn capnp_allowed_for_redis(e: SerializationEncoding) -> bool {
    matches!(e, SerializationEncoding::MsgPack | SerializationEncoding::Json) // Capnp not implemented
}
assert!(capnp_allowed_for_redis(settings.encoding));

fn cache_encodings() -> [SerializationEncoding; 2] {
    [SerializationEncoding::MsgPack, SerializationEncoding::Json]
}

match serialize_payload(&payload, &settings) {
    Ok(bytes) => { /* store */ }
    Err(e) if e.to_string().contains("Cap'n Proto") => {
        tracing::error!("Redis cache does not support Capnp; reconfigure to Json/MsgPack");
    }
    Err(e) => return Err(e.into()),
}

When it happens

Trigger: Calling serialize_payload (or the Redis cache/query API accepting a SerializationSetting) with SerializationEncoding::Capnp — e.g. a RedisCacheDatabase configured with Capnp serialization.

Common situations: Sharing one serialization setting across integrations where Capnp is supported elsewhere but not in the Redis cache; misconfigured cache clients copied from other backends; assuming enum completeness means all encodings are implemented.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• SBE encoding is not supported for Redis cache payloads
• Cap'n Proto decoding requires the `capnp` feature
• failed to decode Cap'n Proto {}: {}
• CustomData serialization failed: {e}
• Cannot persist position with no events: {}

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/aa53aedadc02075a. Report an issue: GitHub.