Indexing on Fuel Network

Introduction

Envio has expanded its indexing capabilities beyond EVM-compatible blockchains to now fully support the Fuel Network (both mainnet and testnet). This documentation covers how to use Envio's products with Fuel's unique architecture and features. ⛽⚡

Fuel offers several advantages as a modular execution layer including:

• Parallel transaction execution
• State-minimized design
• UTXO-based architecture
• Advanced FuelVM capabilities

HyperIndex for Fuel

HyperIndex enables developers to easily index and query real-time and historical data on Fuel Network with the same powerful features available for EVM chains.

Getting Started with Fuel Indexing

You can start indexing Fuel contracts in two ways:

1. Quick Start (5-minute tutorial): Follow our step-by-step tutorial to create your first Fuel indexer quickly.

2. No-Code Contract Import: Use our Contract Import tool to automatically generate configuration and schema files for your Fuel contracts.

Example Fuel Indexers

Looking for inspiration? Check out these indexers built by projects in the Fuel ecosystem:

Project	Type	GitHub Repository
Spark	Orderbook DEX	github
Mira	AMM DEX	github
Thunder	NFT Marketplace	github
Swaylend	Lending Protocol	github
Greeter	Tutorial	github

Features Supported on Fuel

HyperIndex for Fuel supports all the core features available in the EVM version:

• ✅ No-code Contract Import
• ✅ Dynamic Contracts / Factory Tracking
• ✅ Testing Framework
• ✅ Hosted Service
• ✅ Wildcard Indexing

Fuel-Specific Event Types

Understanding Fuel's Event Model

Fuel's event model differs significantly from EVM. Instead of predefined events, Fuel uses a more flexible approach with various receipt types that can be indexed.

LOG_DATA Receipts (Primary Event Type)

The most common event type in Fuel is the LOG_DATA receipt, created by the log instruction in Sway contracts.

Unlike Solidity's emit which requires predefined event structures, Sway's log function allows passing any data, providing greater flexibility.

Configuration Example:

ecosystem: fuel
network:
  name: "fuel_testnet"

contracts:
  - name: SwayContract
    abi_file_path: "./abis/SwayContract.json"
    start_block: 1
    address: "0x123..."
    events:
      - name: NewGreeting
        logId: "8500535089865083573"

The logId is a unique identifier for the logged struct, which you can find in your contract's ABI file.

Auto-detection of logId:

If your event name matches the logged struct name in Sway, you can omit the logId:

events:
  - name: NewGreeting # Will automatically detect logId if it matches the struct name

Tip: Instead of manually configuring events, use the Contract Import tool which automatically detects events and generates the proper configuration.

Additional Fuel Event Types

Fuel allows indexing several additional receipt types not available in EVM:

Event Type	Description	Example Configuration
Mint	Triggered when a contract mints tokens	- name: Mint
Burn	Triggered when a contract burns tokens	- name: Burn
Transfer	Combines TRANSFER and TRANSFER_OUT receipts	- name: Transfer
Call	Triggered when a contract calls another contract	- name: Call

Using Custom Names:

You can rename these events while maintaining their type:

events:
  - name: MintMyNft # Custom name
    type: mint # Actual event type

Note: All event types can be used with Wildcard Indexing.

Transfer Event Specifics

The Transfer event type combines two Fuel receipt types:

• TRANSFER: Emitted when a contract transfers tokens to another contract
• TRANSFER_OUT: Emitted when a contract transfers tokens to a wallet

Important: Transfers between wallets are not included in the Transfer event type.

Event Object Structure in Handlers

When handling Fuel events, the event object structure differs from EVM:

// Example Fuel event handler
SwayContract.NewGreeting.handler(async ({ event, context }) => {
  // Access event parameters
  const message = event.params.message;

  // Access block information
  const blockHeight = event.block.height;
  const blockTime = event.block.time;
  const blockId = event.block.id;

  // Access transaction information
  const txId = event.transaction.id;

  // Access source contract address
  const sourceContract = event.srcAddress;

  // Access log position
  const logIndex = event.logIndex;

  // Store data
  context.Greeting.set({
    id: event.transaction.id,
    message: message,
    timestamp: blockTime,
  });
});

Migration Guide from v2.x.x-fuel

Starting with V2.3, the Fuel indexer has been integrated into the main envio package. If you were using the Fuel-specific version (envio@2.x.x-fuel), follow these steps to migrate:

1. Update Package Version

# Update local dependency
pnpm i envio@latest

# If installed globally
pnpm i -g envio@latest

2. Update Configuration

Add the ecosystem: fuel field to your config.yaml:

ecosystem: fuel # Required for Fuel indexers
network:
  name: "fuel_testnet"
  # other network config...

3. Update Event Handler Code

Several field names have changed in the event object:

Old Field	New Field
event.data.x	event.params.x
event.time	event.block.time
event.blockHeight	event.block.height
(none)	event.block.id
event.transactionId	event.transaction.id
event.contractId	event.srcAddress
event.receiptIndex	event.logIndex
event.receiptType	(removed)

Example migration:

SwayContract.NewGreeting.handler(async ({ event, context }) => {
  context.Greeting.set({
-   id: event.data.id,
-   message: event.data.message,
-   createdAt: event.time,
-   blockHeight: event.blockHeight,
+   id: event.params.id,
+   message: event.params.message,
+   createdAt: event.block.time,
+   blockHeight: event.block.height,
    transaction: event.transaction.id,
  });
});

Note: If you use loaders, also follow the v1 to v2 migration guide for loader-specific changes.

HyperFuel

HyperFuel is Envio's low-level data API for the Fuel Network (equivalent to HyperSync for EVM chains).

HyperFuel provides:

• High-performance data access
• Flexible query capabilities
• Multiple data formats (Parquet, Arrow, typed data)
• Complete historical data

Available Clients

Access HyperFuel data using any of these clients:

• Rust: hyperfuel-client-rust
• Python: hyperfuel-client-python
• Node.js: hyperfuel-client-node
• JSON API: hyperfuel-json-api

HyperFuel Endpoints

• Mainnet: https://fuel.hypersync.xyz
• Testnet: https://fuel-testnet.hypersync.xyz

For detailed information, see the HyperFuel documentation.

About Fuel Network

Fuel is an operating system purpose-built for Ethereum rollups with unique architecture focused on:

• Parallelization: Execute transactions concurrently for higher throughput
• State-minimized execution: Efficient storage and computation model
• Interoperability: Seamless integration with other blockchain systems

Powered by the FuelVM, Fuel expands Ethereum's capabilities without compromising security or decentralization.

Resources

• Website
• Twitter
• Discord
• Documentation

Need Help?

If you encounter any issues with Fuel indexing, please:

1. Check our Troubleshooting guides
2. Join our Discord for community support
3. Create an issue in our GitHub repository