hl_getLatestBlockNumber - Get Latest Block Number

Return the highest block number currently available for a given stream.

When to Use This Method

hl_getLatestBlockNumber is essential for:

• Synchronization — Determine the current head before fetching batch blocks
• Polling — Check for new blocks at regular intervals
• Catch-up Logic — Calculate how far behind your consumer is
• Health Monitoring — Verify the data pipeline is advancing

Common Use Cases

1. Poll for New Blocks

Check for new data at regular intervals:

async function pollForNewBlocks(callback, intervalMs = 5000) {
  let lastSeen = await getLatestBlockNumber();
  console.log(`Starting poll from block ${lastSeen}`);

  setInterval(async () => {
    const latest = await getLatestBlockNumber();

    if (latest > lastSeen) {
      console.log(`New blocks: ${lastSeen + 1} to ${latest}`);
      callback(lastSeen + 1, latest);
      lastSeen = latest;
    }
  }, intervalMs);
}

// Usage
pollForNewBlocks((from, to) => {
  console.log(`Processing blocks ${from}–${to}`);
});

2. Calculate Consumer Lag

Monitor how far behind a consumer is:

def check_lag(consumer_block: int) -> dict:
    latest = get_latest_block_number()
    lag = latest - consumer_block

    return {
        'consumer_block': consumer_block,
        'latest_block': latest,
        'lag_blocks': lag,
        'status': 'healthy' if lag < 100 else 'behind'
    }

Best Practices

1. Poll responsibly — Don't poll more frequently than every few seconds
2. Use as a cursor — Combine with hl_getBatchBlocks for sequential data retrieval
3. Monitor lag — Track the difference between your consumer position and the latest block
4. Handle stale data — If the latest block number hasn't advanced, the upstream may be paused

Related Methods

• hl_getBatchBlocks — Retrieve fill blocks in a range

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