Terra Quick Start

... 2022-6-23 About 6 min

# Terra Quick Start

In this Quick start guide, we're going to start with a simple Terra starter project and then finish by indexing some actual real data. This is an excellent basis to start with when developing your own SubQuery Project.

If your are looking for guides for Substrate/Polkadot, you can read the Substrate/Polkadot specific quick start guide.

At the end of this guide, you'll have a working SubQuery project running on a SubQuery node with a GraphQL endpoint that you can query data from.

If you haven't already, we suggest that you familiarise yourself with the terminology used in SubQuery.

The goal of this quick start guide is to adapt the standard starter project to begin indexing all transfers from Terra, it should only take 10-15 minutes

# Preparation

# Local Development Environment

# Install the SubQuery CLI

Install SubQuery CLI globally on your terminal by using NPM:

# NPM
npm install -g @subql/cli
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Please note that we DO NOT encourage the use of yarn global for installing @subql/cli due to its poor dependency management which may lead to an errors down the line.

You can then run help to see available commands and usage provide by CLI

subql help
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# Initialise the SubQuery Starter Project

Inside the directory in which you want to create a SubQuery project, simply run the following command to get started.

subql init
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You'll be asked certain questions as the SubQuery project is initalised:

  • Project Name: A name for your SubQuery project
  • Network Family: The layer-1 blockchain network family that this SubQuery project will be developed to index, use the arrow keys on your keyboard to select from the options, for this guide we will use "Terra"
  • Network: The specific network that this SubQuery project will be developed to index, use the arrow keys on your keyboard to select from the options, for this guide we will use "Terra"
  • Template: Select a SubQuery project template that will provide a starting point to begin development, we suggest selecting the "Starter project"
  • Git repository (Optional): Provide a Git URL to a repo that this SubQuery project will be hosted in (when hosted in SubQuery Explorer)
  • RPC endpoint (Required): Provide a HTTPS URL to a running RPC endpoint that will be used by default for this project. This RPC node must be an archive node (have the full chain state). For this guide we will use the default value "https://terra-columbus-5.beta.api.onfinality.io"
  • Authors (Required): Enter the owner of this SubQuery project here (e.g. your name!)
  • Description (Optional): You can provide a short paragraph about your project that describe what data it contains and what users can do with it
  • Version (Required): Enter a custom version number or use the default (1.0.0)
  • License (Required): Provide the software license for this project or accept the default (Apache-2.0)

After the initialisation process is complete, you should see a folder with your project name has been created inside the directory. The contents of this directoy should be identical to what's listed in the Directory Structure.

Last, under the project directory, run following command to install the new project's dependencies.

cd PROJECT_NAME
yarn install
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cd PROJECT_NAME
npm install
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# Making Changes to your Project

In the starter package that you just initialised, we have provided a standard configuration for your new project. You will mainly be working on the following files:

  1. The GraphQL Schema in schema.graphql
  2. The Project Manifest in project.yaml
  3. The Mapping functions in src/mappings/ directory

The goal of this quick start guide is to adapt the standard starter project to begin indexing all transfers from the bLuna smart contract.

# Updating your GraphQL Schema File

The schema.graphql file defines the various GraphQL schemas. Due to the way that the GraphQL query language works, the schema file essentially dictates the shape of your data from SubQuery. Its a great place to start becuase it allows you to define your end goal up front.

We're going to update the schema.graphql file to read as follows

type Transfer @entity {
  id: ID! # id field is always required and must look like this
  txHash: String!
  blockHeight: BigInt # The block height of the transfer
  sender: String! # The account that transfers are made from
  recipient: String! # The account that transfers are made to
  amount: String! # Amount that is transferred
}
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Important: When you make any changes to the schema file, please ensure that you regenerate your types directory. Do this now.

yarn codegen
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npm run-script codegen
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You'll find the generated models in the /src/types/models directory. For more information about the schema.graphql file, check out our documentation under Build/GraphQL Schema

# Updating the Project Manifest File

The Projet Manifest (project.yaml) file can be seen as an entry point of your project and it defines most of the details on how SubQuery will index and transform the chain data.

We won't do many changes to the manifest file as it already has been setup correctly, but we need to change our handlers. Remember we are planning to index all Terra transfer events, as a result, we need to update the datasources section to read the following.

dataSources:
  - kind: terra/Runtime
    startBlock: 4724001 # Colombus-5 Starts at this height
    mapping:
      file: ./dist/index.js
      handlers:
        - handler: handleEvent
          kind: terra/EventHandler
          # this will trigger on all events that match the following smart contract filter condition
          filter:
            type: transfer
            messageFilter:
              type: /terra.wasm.v1beta1.MsgExecuteContract
              values:
                # We are subscribing to the bLuna smart contract (e.g. only transfer events from this contract)
                contract: terra1j66jatn3k50hjtg2xemnjm8s7y8dws9xqa5y8w
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This means we'll run a handleEvent mapping function each and every time there is a transfer event from the bLuna smart contract.

For more information about the Project Manifest (project.yaml) file, check out our documentation under Build/Manifest File

# Add a Mapping Function

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

Navigate to the default mapping function in the src/mappings directory. You'll see three exported functions, handleBlock, handleEvent, and handleCall. You can delete both the handleBlock and handleCall functions, we are only dealing with the handleEvent function.

The handleEvent function recieved event data whenever event matches the filters that we specify previously in our project.yaml. We are going to update it to process all transfer events and save them to the GraphQL entities that we created earlier.

You can update the handleEvent function to the following (note the additional imports):

import { TerraEvent } from "@subql/types-terra";
import { Transfer } from "../types";
import { MsgExecuteContract } from "@terra-money/terra.js";

export async function handleEvent(
  event: TerraEvent<MsgExecuteContract>
): Promise<void> {
    // Print debugging data from the event
    // logger.info(JSON.stringify(event));
    
    // Create the new transfer entity with a unique ID
    const transfer = new Transfer(
      `${event.tx.tx.txhash}-${event.msg.idx}-${event.idx}`
    );
    transfer.blockHeight = BigInt(event.block.block.block.header.height);
    transfer.txHash = event.tx.tx.txhash;
    for (const attr of event.event.attributes) {
      switch (attr.key) {
        case "sender":
          transfer.sender = attr.value;
          break;
        case "recipient":
          transfer.recipient = attr.value;
          break;
        case "amount":
          transfer.amount = attr.value;
          break;
        default:
      }
    }
    await transfer.save();
}
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What this is doing is receiving a SubstrateEvent which includes transfer data on the payload. We extract this data and then instantiate a new Transfer entity that we defined earlier in the schema.graphql file. We add additional information and then use the .save() function to save the new entity (SubQuery will automatically save this to the database).

For more information about mapping functions, check out our documentation under Build/Mappings

# Build the Project

In order run your new SubQuery Project we first need to build our work. Run the build command from the project's root directory.

yarn build
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npm run-script build
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Important: Whenever you make changes to your mapping functions, you'll need to rebuild your project

# Running and Querying your Project

# Run your Project with Docker

Whenever you create a new SubQuery Project, you should always run it locally on your computer to test it first. The easiest way to do this is by using Docker.

All configuration that controls how a SubQuery node is run is defined in this docker-compose.yml file. For a new project that has been just initalised you won't need to change anything here, but you can read more about the file and the settings in our Run a Project section

Under the project directory run following command:

yarn start:docker
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npm run-script start:docker
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It may take some time to download the required packages (@subql/node (opens new window), @subql/query (opens new window), and Postgres) for the first time but soon you'll see a running SubQuery node. Be patient here.

# Query your Project

Open your browser and head to http://localhost:3000 (opens new window).

You should see a GraphQL playground is showing in the explorer and the schemas that are ready to query. On the top right of the playground, you'll find a Docs button that will open a documentation draw. This documentation is automatically generated and helps you find what entities and methods you can query.

For a new SubQuery starter project, you can try the following query to get a taste of how it works or learn more about the GraphQL Query language.

{
  query {
    transfers(
      first: 10,
      orderBy: ID_DESC
    ) {
      nodes {
        id
        txHash
        amount
        blockHeight
        sender
        recipient
      }
    }
  }
}
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# Publish your SubQuery Project

SubQuery provides a free managed service when you can deploy your new project to. You can deploy it to SubQuery Projects (opens new window) and query it using our Explorer (opens new window).

Read the guide to publish your new project to SubQuery Projects

# Next Steps

Congratulations, you now have a locally running SubQuery project that accepts GraphQL API requests for transfers data from bLuna.

Now that you've had an insight into how to build a basic SubQuery project, the question is where to from here? If you are feeling confident, you can jump into learning more about the three key files. The manifest file, the GraphQL schema, and the mappings file under the Build section of these docs.

Otherwise, continue to our Academy section where have more in depth workshops, tutorials, and example projects. There we'll look at more advanced modifications, and we'll take a deeper dive at running SubQuery projects by running readily available and open source projects.

Finally, if you're looking for more ways to run and publish your project, our Run & Publish section provides detailed informatation about all the ways to run your SubQuery project and other advanced GraphQL aggregation and subscription features.

Last update: June 23, 2022 09:54