Graph middleware

Middleware acts as a bridge between your blockchain network and applications, providing essential services like data indexing, API access, and event monitoring. Before adding middleware, ensure you have an application and blockchain node in place.

How to add middleware

Manage middleware

The graph middleware

The Graph provides powerful indexing capabilities for EVM chains through subgraphs. Use this middleware when you need:

• Custom indexing logic through subgraph manifests
• Complex GraphQL queries
• Real-time data updates

Using the graph sdk

import { createTheGraphClient } from "@settlemint/sdk-thegraph";
 
const { client: graphClient, graphql } = createTheGraphClient({
  instances: JSON.parse(
    process.env.SETTLEMINT_THEGRAPH_SUBGRAPHS_ENDPOINTS || "[]"
  ),
  accessToken: process.env.SETTLEMINT_ACCESS_TOKEN!,
  subgraphName: "your-subgraph",
});

Using the graph middleware

The Graph is a protocol for indexing and querying blockchain data from networks. It can be used with all EVM-compatible chains like Ethereum, Hyperledger Besu, Polygon, Avalanche, etc. You can run it on your own blockchain nodes (both public and permissioned).

Using the Graph protocol, you can create subgraphs that define which blockchain data will be indexed. The middleware will then use these subgraphs to correctly index your smart contracts and expose a developer-friendly and efficient GraphQL API, allowing you to query the data you need.

We have some prebuilt subgraph indexing modules included in the smart contract set, and you can build your own modules if you have a custom smart contract set.

When the middleware is deployed, follow these steps to start using it:

Define and deploy a subgraph

Navigate to the smart contract set which you want to index, go the details and open the IDE. Here you will define the subgraph to set the indexing specifications, and deploy it so it can be loaded into the middleware. There are instructions included in the IDE to help you.

Subgraph raw configuration

Inside the root you will find a file called subgraph.config.json that contains the raw configuration of the subgraph. The important section is the datasources section.

• Name - here we defined the smart contracts with their name (the name of the artifact created in the 'deployments' folder when running the deploy task)
• Address & Startblock - You will notice the startblock and address to be 0. You must fill these in when your contract has been deployed. The block number and the address can be found in the deployment folder, under ignition.
• Module - In the modules array all the indexing modules to activate for this smart contract.

About the indexing modules

We provide two libraries of indexing modules: one by the OpenZeppelin team for all the common smart contracts in their smart contract library, and one by the SettleMint team to extend the capabilities of the OpenZeppelin one, and to provide indexing of the specific SettleMint smart contract sets.

The OpenZeppelin set contains the following indexing modules:

• accesscontrol
• erc1155
• erc1967upgrade
• erc20
• erc721
• governor
• ownable
• pausable
• timelock
• voting

The SettleMint set contains the following indexing modules:

• erc721ipfs: to extend the ERC-721 from OpenZeppelin to index IPFS metadata of your ERC-721 tokens
• crowdsale/vestingvault/vestingwallet: to index and expose all the data for the crowdsale contract set
• forwarder: for the ERC-20 Meta transactions forwarder data
• statemachinemetadata: to index IPFS metadata for state machines

These are available in the subgraph folder in your IDE. You can create your own modules for any other data you want to index, or for custom smart contracts not part of the default sets. And you can modify the existing ones if you want to index things a bit different.

Write your own indexing module

You can also write your own custom indexing module for smart contracts that are not part of the default sets.

Follow these steps to create a custom indexing module:

• Primitives to generate a GraphQL schema: subgraph/datasource/x.gql.json - In order to allow composability, the schema are not defined in the GraphQL format but rather in a dedicated JSON format which is can be assembled and compiled to GraphQL.
• Template to generate a subgraph manifest: subgraph/datasource/x.yaml - This file lists all the events that the datasources should listen to, and links that to the corresponding indexing logic.
• Indexing logic: subgraph/datasources/x.ts and (optionally) subgraph/fetch/x.ts - This is the core logic that processes the events to index the onchain activity.

To learn more, check it out on Github.

Start your subgraph

The following tasks need to be run in this sequence:

• bunx settlemint scs subgraph codegen - Generates the AssemblyScript types for your contracts ABI.
• bunx settlemint scs subgraph build - Compiles the WASM files based on the outputs generated by bunx settlemint scs subgraph codegen.
• bunx settlemint scs subgraph deploy - Deploys the WASM files to IPFS and updates the middleware to start or update the indexing.

The indexing of your smart contracts has now started. This can take a while, but once done you can query the middleware for your data in seconds using the GraphQL API. You can find the endpoint in the Connect-tab.