SubQuery Academy (Documentation)

Ethereum Quick Start - Gravatar (Simple)

SubQuery TeamAbout 6 min

Ethereum Quick Start - Gravatar (Simple)

Goals

The goal of this quick start guide is to index all Ethereum Gravatars created or updated on the Ethereum mainnet.

Note

Before we begin, make sure that you have initialised your project using the provided steps in the Start Here section. Please initialise a Ethereum project

Now, let's move forward and update these configurations.

Previously, in the 1. Create a New Project section, you must have noted 3 key files. Let's begin updating them one by one.

Note

The final code of this project can be found hereopen in new window.

1. Update Your Project Manifest File

The Project Manifest (project.yaml) file works as an entry point to your Ethereum project. It defines most of the details on how SubQuery will index and transform the chain data. For Ethereum, there are three types of mapping handlers (and you can have more than one in each project):

  • BlockHanders: On each and every block, run a mapping function
  • TransactionHandlers: On each and every transaction that matches optional filter criteria, run a mapping function
  • LogHanders: On each and every log that matches optional filter criteria, run a mapping function

Note that the manifest file has already been set up correctly and doesn’t require significant changes, but you need to import the correct contract definitions and update the datasource handlers.

We are indexing all Gravatars from the Gravatar contract, first you will need to import the contract abi defintion. You can copy the entire JSON and save as a file ./Gravity.json in the /abis directory.

This section in the Project Manifest now imports all the correct definitions and lists the triggers that we look for on the blockchain when indexing.

Since you are going to index all Gravatars, you need to update the datasources section as follows:

dataSources:
  - kind: ethereum/Runtime
    startBlock: 6175243 # This is when the Gravatar contract was deployed
    options:
      # Must be a key of assets
      abi: gravity
      address: "0x2E645469f354BB4F5c8a05B3b30A929361cf77eC" # The contract address of the Gravatar on Ethereum
    assets:
      gravity:
        file: "./abis/Gravity.json"
    mapping:
      file: "./dist/index.js"
      handlers:
        - handler: handleNewGravatar
          kind: ethereum/LogHandler
          filter:
            topics:
              ## Follows standard log filters https://docs.ethers.io/v5/concepts/events/
              - NewGravatar(uint256,address,string,string)
        - handler: handleUpdatedGravatar
          kind: ethereum/LogHandler
          filter:
            topics:
              ## Follows standard log filters https://docs.ethers.io/v5/concepts/events/
              - UpdatedGravatar(uint256,address,string,string)

The above code indicates that you will be running a handleLog mapping function whenever there is an NewGravatar or UpdatedGravatar log on any transaction from the Gravatar contractopen in new window.

Check out our Manifest File documentation to get more information about the Project Manifest (project.yaml) file.

2. Update Your GraphQL Schema File

The schema.graphql file determines the shape of your data from SubQuery due to the mechanism of the GraphQL query language. Hence, updating the GraphQL Schema file is the perfect place to start. It allows you to define your end goal right at the start.

Remove all existing entities and update the schema.graphql file as follows. Here you can see we are indexing the id, owner, display name, imagine URL and the block the gravatar was created in.

type Gravatar @entity {
  id: ID!
  owner: Bytes!
  displayName: String!
  imageUrl: String!
  createdBlock: BigInt!
}

Important

When you make any changes to the schema file, please ensure that you regenerate your types directory.

SubQuery makes it easy and type-safe to work with your GraphQL entities, as well as smart contracts, events, transactions, and logs. SubQuery CLI will generate types from your project's GraphQL schema and any contract ABIs included in the data sources.

This will create a new directory (or update the existing) src/types which contain generated entity classes for each type you have defined previously in schema.graphql. These classes provide type-safe entity loading, read and write access to entity fields - see more about this process in the GraphQL Schema. All entites can be imported from the following directory:

import { Gravatar } from "../types";

If you're creating a new Etheruem based project, this command will also generate ABI types and save them into src/types using the npx typechain --target=ethers-v5 command, allowing you to bind these contracts to specific addresses in the mappings and call read-only contract methods against the block being processed. It will also generate a class for every contract event to provide easy access to event parameters, as well as the block and transaction the event originated from. All of these types are written to src/typs/abi-interfaces and src/typs/contracts directories. In the example Gravatar SubQuery project, you would import these types like so.

import {
  NewGravatarLog,
  UpdatedGravatarLog,
} from "../types/abi-interfaces/Gravity";

Check out the GraphQL Schema documentation to get in-depth information on schema.graphql file.

Now that you have made essential changes to the GraphQL Schema file, let’s proceed ahead with the Mapping Function’s configuration.

3. Add a Mapping Function

Mapping functions define how chain data is transformed into the optimised GraphQL entities that we previously defined in the schema.graphql file.

Follow these steps to add a mapping function:

Navigate to the default mapping function in the src/mappings directory. You will be able to see three exported functions: handleBlock, handleLog, and handleTransaction. Replace these functions with the following code (note the additional imports):

import {
  NewGravatarLog,
  UpdatedGravatarLog,
} from "../types/abi-interfaces/Gravity";
import { Gravatar } from "../types";

export async function handleNewGravatar(log: NewGravatarLog): Promise<void> {
  logger.info("New Gravar at block " + log.blockNumber.toString());
  const gravatar = Gravatar.create({
    id: log.args.id.toHexString(),
    owner: log.args.owner,
    displayName: log.args.displayName,
    imageUrl: log.args.imageUrl,
    createdBlock: BigInt(log.blockNumber),
  });

  await gravatar.save();
}

export async function handleUpdatedGravatar(
  log: UpdatedGravatarLog
): Promise<void> {
  logger.info("Updated Gravar at block " + log.blockNumber.toString());
  const id = log.args.id.toHexString();

  // We first check if the Gravatar already exists, if not we create it
  let gravatar = await Gravatar.get(id);
  if (gravatar == null || gravatar == undefined) {
    gravatar = new Gravatar(id);
    gravatar.createdBlock = BigInt(log.blockNumber);
  }
  // Update with new data
  gravatar.owner = log.args.owner;
  gravatar.displayName = log.args.displayName;
  gravatar.imageUrl = log.args.imageUrl;
  await gravatar.save();
}

Let’s understand how the above code works.

For handleNewGravatar, the function here receives an NewGravatarEvent which includes transaction log data in the payload. We extract this data and then create a new Gravatar entity that we defined in our schema.graphql and then save this to the store using the .save() function (Note that SubQuery will automatically save this to the database).

For handleUpdatedGravatar, the function here receives an UpdatedGravatarEvent which includes transaction log data in the payload. We extract this data and then first check that the Gravatar already exists, if not we instantiate a new one and then update that Gravatar with the correct updated details. This is then saved to the store using the .save() function (Note that SubQuery will automatically save this to the database).

Check out our Mappings documentation to get more information on mapping functions.

4. Build Your Project

Next, build your work to run your new SubQuery project. Run the build command from the project's root directory as given here:

Important

Whenever you make changes to your mapping functions, you must rebuild your project.

Now, you are ready to run your first SubQuery project. Let’s check out the process of running your project in detail.

5. Run Your Project Locally with Docker

Whenever you create a new SubQuery Project, first, you must run it locally on your computer and test it and using Docker is the easiest and quickiest way to do this.

The docker-compose.yml file defines all the configurations that control how a SubQuery node runs. For a new project, which you have just initialised, you won't need to change anything.

However, visit the Running SubQuery Locally to get more information on the file and the settings.

Run the following command under the project directory:

Note

It may take a few minutes to download the required images and start the various nodes and Postgres databases.

6. Query your Project

Next, let's query our project. Follow these three simple steps to query your SubQuery project:

  1. Open your browser and head to http://localhost:3000.

  2. You will see a GraphQL playground in the browser and the schemas which are ready to query.

  3. Find the Docs tab on the right side of the playground which should open a documentation drawer. This documentation is automatically generated and it helps you find what entities and methods you can query.

Try the following query to understand how it works for your new SubQuery starter project. Don’t forget to learn more about the GraphQL Query language.

query {
  gravatars(first: 2, orderBy: CREATED_BLOCK_DESC) {
    nodes {
      id
      owner
      displayName
      imageUrl
      createdBlock
    }
  }
}

You will see the result similar to below:

{
  "data": {
    "gravatars": {
      "nodes": [
        {
          "id": "0x47",
          "owner": "\\xbc8dafeaca658ae0857c80d8aa6de4d487577c63",
          "displayName": "Victor",
          "imageUrl": "https://ucarecdn.com/295e4ba5-ad1c-48bf-9957-093424709881/-/crop/152x152/1,0/-/preview/",
          "createdBlock": "6469958"
        },
        {
          "id": "0x46",
          "owner": "\\x0773cbc2c55cd6354a61b7bcbca52d9dccd56534",
          "displayName": "dgogel",
          "imageUrl": "https://ucarecdn.com/c44402a0-30f8-4c0c-bf1f-b13918903211/-/crop/512x512/0,0/-/preview/",
          "createdBlock": "6460716"
        }
      ]
    }
  }
}

Note

The final code of this project can be found hereopen in new window.

What's next?

Congratulations! You have now a locally running SubQuery project that accepts GraphQL API requests for transferring data.

Tip

Find out how to build a performant SubQuery project and avoid common mistakes in Project Optimisation.

Click here to learn what should be your next step in your SubQuery journey.