nautechsystems/nautilus_trader · error

Failed to decode SetFeeProtocol event data: {e}

Error message

Failed to decode SetFeeProtocol event data: {e}

What it means

Thrown by parse_fee_protocol_update_event_hypersync when the data is long enough (>=128 bytes) but alloy's SolType::abi_decode for SetFeeProtocolEventData still fails. This means the byte content does not decode into four uint8-ish parameters per the event ABI — wrong encoding, extra unaligned bytes, or wrong event type.

Source

Thrown at crates/adapters/blockchain/src/exchanges/parsing/uniswap_v3/fee_protocol_update.rs:76

    log: &HypersyncLog,
) -> anyhow::Result<FeeProtocolUpdateEvent> {
    validate_event_signature_hash(
        "SetFeeProtocolEvent",
        FEE_PROTOCOL_UPDATE_EVENT_SIGNATURE_HASH,
        log,
    )?;

    if let Some(data) = &log.data {
        let data_bytes = data.as_ref();

        // Validate the data contains 4 parameters of 32 bytes each
        if data_bytes.len() < 4 * 32 {
            anyhow::bail!("SetFeeProtocol event data is too short");
        }

        let decoded = match <SetFeeProtocolEventData as SolType>::abi_decode(data_bytes) {
            Ok(decoded) => decoded,
            Err(e) => anyhow::bail!("Failed to decode SetFeeProtocol event data: {e}"),
        };

        let pool_address = Address::from_slice(
            log.address
                .clone()
                .expect("Contract address should be set in logs")
                .as_ref(),
        );
        let pool_identifier = PoolIdentifier::Address(Ustr::from(&pool_address.to_string()));

        Ok(FeeProtocolUpdateEvent::new(
            dex,
            pool_identifier,
            extract_block_number(log)?,
            extract_transaction_hash(log)?,
            extract_transaction_index(log)?,
            extract_log_index(log)?,
            u32::from(decoded.fee_protocol0_new),

View on GitHub (pinned to 18893faf8b)

Solutions

1. Log the underlying error {e} to see expected vs actual encoded sizes and fix the payload accordingly.
2. Verify data length is exactly 128 bytes; strip any trailing bytes before decoding.
3. Confirm the hypersync log filter matches the exact SetFeeProtocol event signature (name plus indexed parameter types).
4. Regenerate the SolStruct (SetFeeProtocolEventData) from the verified ABI to ensure parameter order/types are correct.
5. Cross-check with the RPC parser (parse_fee_protocol_update_event_rpc) on the same log to isolate hypersync-specific data issues.

Example fix

// before
Err(e) => anyhow::bail!("Failed to decode SetFeeProtocol event data: {e}"),
// after
Err(e) => anyhow::bail!(
    "Failed to decode SetFeeProtocol event data (len={}): {e}",
    data_bytes.len()
),

fn is_decodeable_set_fee_protocol(data: &[u8]) -> bool {
    data.len() == 128
        && <SetFeeProtocolEventData as SolType>::abi_decode(data).is_ok()
}

match parse_fee_protocol_update_event_hypersync(dex, &log) {
    Ok(event) => handle(event),
    Err(e) if e.to_string().contains("Failed to decode SetFeeProtocol") => {
        tracing::debug!(raw = ?log.data, "undecodeable SetFeeProtocol data: {e}");
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: abi_decode returns Err on a 128+ byte payload for a log whose topic matched SetFeeProtocol — e.g. data belongs to a different event, trailing bytes, or a provider returned a non-canonical encoding.

Common situations: Topic hash collision or alias filtering by signature with a different full signature; decoding logs from a fork/custom pool; corrupted or hand-built log data in tests (test_parse_fee_protocol_update_event_hypersync, test_hypersync_rpc_match).

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• SetFeeProtocol event data is too short
• Flash event data is too short
• Failed to decode flash event data: {e}
• Missing tickLower in topic2 when parsing burn event
• Missing data in SetFeeProtocol event log

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/f6fdab0f853e902c. Report an issue: GitHub.