Polkadot Quick Start
Polkadot Quick Start
In this quick start guide, we're going to start with a simple Substrate/Polkadot starter project and then finish by indexing some actual real data. This is an excellent basis to start with when developing your own Substrate/Polkadot SubQuery Project.
このガイドの最後には、SubQuery ノード上で動作する SubQuery プロジェクトを作成し、GraphQL エンドポイントからデータを照会できるようになります。
まだの方は、SubQuery で使われている用語に慣れることをお勧めします。
The goal of this quick start guide is to adapt the standard starter project to begin indexing all transfers from Polkadot, it should only take 10-15 minutes
準備
ローカル開発環境
- Node: A modern (e.g. the LTS version) installation of Node.
- Docker: This tutorial will use require Docker
SubQuery CLI をインストールする
Install SubQuery CLI globally on your terminal by using NPM:
# NPM
npm install -g @subql/cli
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 errors down the line.
You can then run help to see available commands and usage provided by the CLI:
subql help
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
You'll be asked certain questions as the SubQuery project is initalised:
- Project name: A project 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 to select from the available options. For this guide, we will use "Substrate"
- Network: The specific network that this SubQuery project will be developed to index. Use the arrow keys to select from the available options. For this guide, we will use "Polkadot"
- Template project: Select a SubQuery template project that will provide a starting point to begin development. We suggest selecting the "subql-starter" project.
- RPC endpoint: Provide an HTTPS URL to a running RPC endpoint that will be used by default for this project. You can quickly access public endpoints for different Polkadot networks, create your own private dedicated node using OnFinality or just use the default Polkadot endpoint. This RPC node must be an archive node (have the full chain state). For this guide, we will use the default value "https://polkadot.api.onfinality.io"
- Git repository: Provide a Git URL to a repo that this SubQuery project will be hosted in (when hosted in SubQuery Explorer) or accept the provided default.
- Authors: Enter the owner of this SubQuery project here (e.g. your name!) or accept the provided default.
- Description: Provide a short paragraph about your project that describes what data it contains and what users can do with it or accept the provided default.
- Version: Enter a custom version number or use the default (
1.0.0) - License: Provide the software license for this project or accept the default (
MIT)
After the initialisation process is complete, you should see that a folder with your project name has been created inside the directory. The contents of this directory should be identical to what's listed in the Directory Structure.
Last, under the project directory, run the following command to install the new project's dependencies.
::: code-tabs @tab:active yarn shell cd PROJECT_NAME yarn install
Making Changes to your Project
In the starter package that was just initialised, a standard configuration has been provided. These are:
- The GraphQL Schema in
schema.graphql - The Project Manifest in
project.yaml - Mapping functions（
src/mappings/ディレクトリ）
The goal of this quick start guide is to adapt the standard starter project to begin indexing all transfers from Polkadot.
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. It's a great place to start because it allows you to define your end goal upfront.
Update the schema.graphql file to read as follows:
type Transfer @entity {
id: ID! # id field is always required and must look like this
amount: BigInt # Amount that is transferred
blockNumber: BigInt # The block height of the transfer
from: String! # The account that transfers are made from
to: String! # The account that transfers are made to
}
Important: When you make any changes to the schema file, please ensure that you regenerate your types directory.
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 Project 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.
The manifest file has already been set up correctly, but we need to change our handlers. As we are planning to index all Polkadot transfers, we need to update the datasources section as follows:
dataSources:
- kind: substrate/Runtime
startBlock: 1
mapping:
file: ./dist/index.js
handlers:
- handler: handleEvent
kind: substrate/EventHandler
filter:
module: balances
method: Transfer
This means we'll run a handleEvent mapping function each and every time there is a balances.Transfer event.
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. Delete both the handleBlock and handleCall functions as we will only deal with the handleEvent function.
The handleEvent function receives event data whenever an event matches the filters that we specified previously in our project.yaml. We will update it to process all balances.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 { SubstrateEvent } from "@subql/types";
import { Transfer } from "../types";
import { Balance } from "@polkadot/types/interfaces";
export async function handleEvent(event: SubstrateEvent): Promise<void> {
// Get data from the event
// The balances.transfer event has the following payload \[from, to, value\]
// logger.info(JSON.stringify(event));
const from = event.event.data[0];
const to = event.event.data[1];
const amount = event.event.data[2];
// Create the new transfer entity
const transfer = new Transfer(
`${event.block.block.header.number.toNumber()}-${event.idx}`
);
transfer.blockNumber = event.block.block.header.number.toBigInt();
transfer.from = from.toString();
transfer.to = to.toString();
transfer.amount = (amount as Balance).toBigInt();
await transfer.save();
}
What this is doing is receiving a SubstrateEvent which includes transfer data in 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 to run your new SubQuery Project we first need to build our work. Run the build command from the project's root directory.
::: code-tabs @tab:active yarn shell yarn build @tab npm shell npm run-script build :::
Important: Whenever you make changes to your mapping functions, you will 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 the docker-compose.yml file. For a new project that has been just initialised you won't need to change anything, but you can read more about the file and the settings in our Run a Project section.
Under the project directory, run the following command:
::: code-tabs @tab:active yarn shell yarn start:docker @tab npm shell npm run-script start:docker :::
It may take some time to download the required packages (@subql/node, @subql/query, and Postgres) for the first time but soon you should see a running SubQuery node in the terminal screen.
Query your Project
Open your browser and head to http://localhost:3000.
You should see a GraphQL playground in the browser and the schemas that are ready to query. プレイグラウンドの右上には、ドキュメントの描画を開く Docs ボタンがあります。 このドキュメントは自動的に生成され、クエリできるエンティティやメソッドを見つけるのに役立ちます。
For a new SubQuery starter project, try the following query to understand how it works or learn more about the GraphQL Query language.
{
query {
transfers(first: 10, orderBy: AMOUNT_DESC) {
nodes {
id
amount
blockNumber
from
to
}
}
}
}
Publish your SubQuery Project
SubQuery provides a free managed service where you can deploy your new project to. You can deploy it to SubQuery Managed Service and query it using our Explorer.
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.
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 are under the Build section of these docs.
Otherwise, continue to our Academy section where we 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 information about all the ways to run your SubQuery project and other advanced GraphQL aggregation and subscription features.