nautechsystems/nautilus_trader · error

Missing block number

Error message

Missing block number

What it means

This error indicates the RpcLog's block_number field is None when extract_block_number is called. Ethereum RPC logs always carry a block number in confirmed receipts, so a missing value means the log came from a pending/unmined transaction or a partially populated response. It is thrown before any hex parsing occurs.

Solutions

1. Only process logs once the transaction is confirmed (wait for receipt or block confirmation).
2. Handle the None case explicitly: skip or queue pending logs instead of unwrapping.
3. Check your RPC subscription type — switch from pending to confirmed log streams.
4. If constructing RpcLog manually in tests, populate block_number with a hex quantity like "0x1".

Example fix

// before
let block = extract_block_number(&log)?;
// after
match extract_block_number(&log) {
    Ok(block) => process(block),
    Err(_) if log.block_number.is_none() => skip_pending_log(),
    Err(e) => return Err(e),
}

if log.block_number.is_none() {
    // pending or synthetic log — defer or skip
}

fn has_block_number(log: &RpcLog) -> bool { log.block_number.is_some() }

match extract_block_number(&log) {
    Ok(b) => handle(b),
    Err(e) if log.block_number.is_none() => defer_pending(&log),
    Err(e) => return Err(e),
}

When it happens

Trigger: Calling extract_block_number on a log from a pending transaction receipt (block_number null), on a manually constructed RpcLog, or on deserialized JSON where the field was omitted/null.

Common situations: Subscribing to pending logs via newPendingTransactions or newPendingReceipts, provider-specific responses where pending receipts omit block_number, or partial mock/test data.

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 log index
• Missing transaction hash
• Missing transaction index
• Finalized Swap log has no block hash
• Initialize event missing topics: expected 4, was

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/abda0ce795195540. Report an issue: GitHub.

Appendix: source

Thrown at crates/adapters/blockchain/src/rpc/log.rs:62

///
/// # Errors
///
/// Returns an error if the hex string cannot be parsed as u32.
pub fn parse_hex_u32(hex: &str) -> anyhow::Result<u32> {
    u32::from_str_radix(hex.trim_start_matches("0x"), 16)
        .map_err(|e| anyhow::anyhow!("Invalid hex u32: {e}"))
}

/// Extract block number from RPC log.
///
/// # Errors
///
/// Returns an error if the block number is missing or cannot be parsed.
pub fn extract_block_number(log: &RpcLog) -> anyhow::Result<u64> {
    let hex = log
        .block_number
        .as_ref()
        .ok_or_else(|| anyhow::anyhow!("Missing block number"))?;
    parse_hex_u64(hex)
}

/// Extract transaction hash from RPC log.
///
/// # Errors
///
/// Returns an error if the transaction hash is missing.
pub fn extract_transaction_hash(log: &RpcLog) -> anyhow::Result<String> {
    log.transaction_hash
        .clone()
        .ok_or_else(|| anyhow::anyhow!("Missing transaction hash"))
}

/// Extract transaction index from RPC log.
///
/// # Errors
///

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