onBlock API

Please refer to the documentation website for a thorough guide on all Envio indexer features

The onBlock API of HyperIndex lets you run custom logic on every block or at fixed block intervals. This is useful for aggregations, time-series operations, and bulk updates.

In this example, we'll walk through how to use the onBlock handler to take a snapshot of a token's total supply every 1000 blocks.

Creating the Handler

First, import onBlock from generated:

import { onBlock } from "generated";

The onBlock function takes two arguments:

1. Options – configure the handler's name, the chain it should run on, and interval-related settings such as interval, startBlock, and stopBlock.
2. Handler function – contains your custom logic. Similar event handlers, it has access to relevant data, which in this case is block values like timestamp and chainId.

Example usage:

onBlock(
    {
        name: "MY_BLOCK_HANDLER",
        chain: CHAIN_ID,
        interval: BLOCK_INTERVAL
    },
    async ({ block, context }) => {
        // your onBlock logic here
    }
)

Prerequisites

Before running the indexer locally, make sure you have the following installed:

• Node.js 18+
• pnpm
• Docker Desktop

Running the Indexer

Add your Envio API key to the .env file, then start the indexer:

pnpm dev

If you make changes to config.yaml or schema.graphql, regenerate the type files:

pnpm codegen

GraphQL Playground

While indexer is running, visit the Envio Console(https://envio.dev/console) to open the GraphQL Playground and query your indexed data.