Multichain Indexing

This page explains how to index from multiple chains in a single indexer.

This means that events from contracts deployed on multiple chains can be used to create and update entities defined in the schema file.

Users are required to populate the network section in config.yaml file for each chain and specify a contract to index from.

Users can then specify event loader/handler for each of the contracts specified in config.yaml file.

Multichain Indexing on Greeter template

Config file

name: Greeter
description: Greeter indexer
networks:
  - id: 137 # Polygon
    start_block: 45336336
    contracts:
      - name: PolygonGreeter
        abi_file_path: abis/greeter-abi.json
        address: "0x9D02A17dE4E68545d3a58D3a20BbBE0399E05c9c"
        handler: ./src/EventHandlers.bs.js
        events:
          - event: "NewGreeting"
            requiredEntities:
              - name: "Greeting"
          - event: "ClearGreeting"
            requiredEntities:
              - name: "Greeting"
  - id: 59144 # Linea
    start_block: 367801
    contracts:
      - name: LineaGreeter
        abi_file_path: abis/greeter-abi.json
        address: "0xdEe21B97AB77a16B4b236F952e586cf8408CF32A"
        handler: ./src/EventHandlers.bs.js
        events:
          - event: "NewGreeting"
            requiredEntities:
              - name: "Greeting"
          - event: "ClearGreeting"
            requiredEntities:
              - name: "Greeting"

The Greeter indexer listens to NewGreeting and ClearGreeting events from both PolygonGreeter and LineaGreeter contracts to update the Greeting entity.

Schema file

type Greeting {
  id: ID!
  greetings: [String!]!
  latestGreeting: String!
  numberOfGreetings: Int!
}

Event Handler file

Javascript

let {
  PolygonGreeterContract,
  LineaGreeterContract,
} = require("../generated/src/Handlers.bs.js");

PolygonGreeterContract.NewGreeting.loader((event, context) => {
  context.Greeting.load(event.params.user);
  ...
});

PolygonGreeterContract.NewGreeting.handler((event, context) => {
  let existingGreeter = context.Greeting.get(event.params.user);
  ...
});

PolygonGreeterContract.ClearGreeting.loader((event, context) => {
  context.Greeting.load(event.params.user);
  ...
});

PolygonGreeterContract.ClearGreeting.handler((event, context) => {
  let existingGreeter = context.Greeting.get(event.params.user);
  ...
});

LineaGreeterContract.NewGreeting.loader((event, context) => {
  context.Greeting.load(event.params.user);
  ...
});

LineaGreeterContract.NewGreeting.handler((event, context) => {
  let existingGreeter = context.Greeting.get(event.params.user);
  ...
});

LineaGreeterContract.ClearGreeting.loader((event, context) => {
  context.Greeting.load(event.params.user);
  ...
});

LineaGreeterContract.ClearGreeting.handler((event, context) => {
  let existingGreeter = context.Greeting.get(event.params.user);
  ...
});

Typescript

import {
  PolygonGreeterContract_NewGreeting_loader,
  PolygonGreeterContract_NewGreeting_handler,
  PolygonGreeterContract_ClearGreeting_loader,
  PolygonGreeterContract_ClearGreeting_handler,
  LineaGreeterContract_NewGreeting_loader,
  LineaGreeterContract_NewGreeting_handler,
  LineaGreeterContract_ClearGreeting_loader,
  LineaGreeterContract_ClearGreeting_handler,
} from "../generated/src/Handlers.gen";

import { GreetingEntity } from "../generated/src/Types.gen";

PolygonGreeterContract_NewGreeting_loader(({ event, context }) => {
  context.Greeting.load(event.params.user.toString());
  ...
});

PolygonGreeterContract_NewGreeting_handler(({ event, context }) => {
  let currentGreeter = context.Greeting.get(event.params.user);
  ...
});

PolygonGreeterContract_ClearGreeting_loader(({ event, context }) => {
  context.Greeting.load(event.params.user.toString());
  ...
});

PolygonGreeterContract_ClearGreeting_handler(({ event, context }) => {
  let currentGreeter = context.Greeting.get(event.params.user);
  ...
});

LineaGreeterContract_NewGreeting_loader(({ event, context }) => {
  context.Greeting.load(event.params.user.toString());
  ...
});

LineaGreeterContract_NewGreeting_handler(({ event, context }) => {
  let currentGreeter = context.Greeting.get(event.params.user);
  ...
});

LineaGreeterContract_ClearGreeting_loader(({ event, context }) => {
  context.Greeting.load(event.params.user.toString());
  ...
});

LineaGreeterContract_ClearGreeting_handler(({ event, context }) => {
  let currentGreeter = context.Greeting.get(event.params.user);
  ...
});

Rescript

open Types

Handlers.PolygonGreeterContract.NewGreeting.loader((~event, ~context) => {
  context.greeting.load(event.params.user->Ethers.ethAddressToString)
  ...
})

Handlers.PolygonGreeterContract.NewGreeting.handler((~event, ~context) => {
  let currentGreeterOpt = context.greeting.get(event.params.user->Ethers.ethAddressToString)
  ...
})

Handlers.PolygonGreeterContract.ClearGreeting.loader((~event, ~context) => {
  context.greeting.load(event.params.user->Ethers.ethAddressToString)
  ...
})

Handlers.PolygonGreeterContract.ClearGreeting.handler((~event, ~context) => {
  let currentGreeterOpt = context.greeting.get(event.params.user->Ethers.ethAddressToString)
  ...
})
Handlers.LineaGreeterContract.NewGreeting.loader((~event, ~context) => {
  context.greeting.load(event.params.user->Ethers.ethAddressToString)
  ...
})

Handlers.LineaGreeterContract.NewGreeting.handler((~event, ~context) => {
  let currentGreeterOpt = context.greeting.get(event.params.user->Ethers.ethAddressToString)
  ...
})

Handlers.LineaGreeterContract.ClearGreeting.loader((~event, ~context) => {
  context.greeting.load(event.params.user->Ethers.ethAddressToString)
  ...
})

Handlers.LineaGreeterContract.ClearGreeting.handler((~event, ~context) => {
  let currentGreeterOpt = context.greeting.get(event.params.user->Ethers.ethAddressToString)
  ...
})

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