Block Monitoring

The Open Ethereum Indexer provides a robust system for monitoring new blocks on the blockchain. This page explains how to set up block handlers and process blockchain blocks in your application. It is similar to event listening, but triggers for blocks instead of events.

Registering Block Handlers

You can register block handlers using the onBlock function:

import { onBlock } from '@open-ethereum/indexer';
 
onBlock({
  onIndex: async (payload) => {
    // This code runs when a block is indexed
    console.log('Block indexed:', payload);
 
    // Access block data
    const { number, hash, timestamp } = payload;
    console.log(
      `Block #${number} with hash ${hash} at ${new Date(timestamp * 1000)}`,
    );
 
    // Store block data or trigger other actions
  },
  onDeindex: async (payload) => {
    // This code runs if a block is deindexed (during a chain reorganization)
    console.log('Block deindexed:', payload);
 
    // Remove or update stored data as necessary
  },
});

Block Payload

The block handler receives a payload with the following structure:

import { Log } from '@ethersproject/abstract-provider';
 
export interface BlockEvent {
  hash: string;
  number: number;
  parent: string;
  timestamp: number;
  logs: Array<Log>;
}

Example: Block Notifier

The block notifier example shows how to use block listening to notify every 1,000,000 blocks.

Event Listening Storing data in the database