nautechsystems/nautilus_trader · error

Missing poolId topic

Error message

Missing poolId topic

What it means

parse_initialize_event_hypersync for Uniswap V4 throws this when topics[1] is absent, since the Pool ID (the unique V4 pool identifier, e.g. the salt/poolId) lives in the second indexed topic. Unlike V3, V4 pools are identified by this ID rather than a pool address, so the parser cannot proceed without it. The error distinguishes a missing topic from a malformed one.

Source

Thrown at crates/adapters/blockchain/src/exchanges/parsing/uniswap_v4/initialize.rs:101

    );

    // Extract currency0 and currency1 from topics
    // topics[0] = event signature
    // topics[1] = poolId (bytes32)
    // topics[2] = currency0 (indexed)
    // topics[3] = currency1 (indexed)
    let topics = &log.topics;
    if topics.len() < 4 {
        anyhow::bail!(
            "Initialize event missing topics: expected 4, was {}",
            topics.len()
        );
    }

    // Extract Pool ID from topics[1] - this is the unique identifier for V4 pools
    let pool_id_bytes = topics[1]
        .as_ref()
        .ok_or_else(|| anyhow::anyhow!("Missing poolId topic"))?
        .as_ref();
    let pool_identifier = Ustr::from(&hex::encode_prefixed(pool_id_bytes));

    let currency0 = Address::from_slice(
        topics[2]
            .as_ref()
            .ok_or_else(|| anyhow::anyhow!("Missing currency0 topic"))?
            .as_ref()
            .get(12..32)
            .ok_or_else(|| anyhow::anyhow!("Invalid currency0 topic length"))?,
    );

    let currency1 = Address::from_slice(
        topics[3]
            .as_ref()
            .ok_or_else(|| anyhow::anyhow!("Missing currency1 topic"))?
            .as_ref()
            .get(12..32)

View on GitHub (pinned to 18893faf8b)

Solutions

1. Verify the log is a genuine Uniswap V4 PoolManager Initialize event with 4 topics (signature, poolId, currency0, currency1).
2. Check topics.len() >= 2 and topics[1].is_some() before calling the parser and skip otherwise.
3. Ensure you are routing V3 logs to the v3 parser and V4 logs to the v4 parser — the signatures differ.
4. Fix test fixtures to include the poolId as an indexed topic.

Example fix

// before
let event = parse_initialize_event_hypersync(&log)?;
// after
if log.topics.len() < 2 || log.topics[1].is_none() {
    tracing::warn!(tx = ?log.transaction_hash, "v4 Initialize log missing poolId topic; skipping");
    return Ok(None);
}
let event = parse_initialize_event_hypersync(&log)?;

if log.topics.len() < 2 || log.topics[1].is_none() {
    // skip: v4 Initialize requires poolId as topics[1]
    return Ok(None);
}

fn has_pool_id_topic(log: &Log) -> bool {
    log.topics.len() >= 2 && log.topics[1].is_some()
}

match parse_initialize_event_hypersync(&log) {
    Ok(event) => handle(event),
    Err(e) if e.to_string().contains("Missing poolId topic") => {
    tracing::warn!("v4 initialize log without poolId; skipping");
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: Calling parse_initialize_event_hypersync (v4) with a log that has fewer than 2 topics or topics[1] = None — e.g. an Initialize-shaped topic0 emitted by a non-standard contract, or a log fixture built with only the event signature topic.

Common situations: Consuming logs from forked V4-like contracts with different topic layouts; hand-built test logs missing indexed parameters; provider payloads that drop optional/None topic slots; mixing V3 Initialize logs into the V4 parser.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Missing currency0 topic
• Invalid currency0 topic length
• Missing data in burn event log
• Missing data in collect event log
• Missing data in initialize event log

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/75ccf1d2e665d0ff. Report an issue: GitHub.