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GhostCrab 👻🦀

Ethereum smart contracts indexer SDK written in Rust


Introduction

GhostCrab is a rust library that allows you to index Ethereum smart contracts. It provides a simple and easy-to-use API for building performant and scalable indexers.

Getting Started

To get started with GhostCrab, you need to install the Rust toolchain and the ghost-crab crate. You can find the installation instructions in the Rust documentation.

Once you have installed the Rust toolchain, you can add the ghost-crab crate to your project's Cargo.toml file:

[dependencies]
ghost-crab = "0.2.0"

Usage

To use GhostCrab, you need to create a new instance of the Indexer struct. This struct provides methods for loading event handlers and block handlers, as well as starting the indexer.

use ghost_crab::prelude::*;

use handlers::etherfi;
use handlers::stader;

#[tokio::main]
async fn main() {
    let mut indexer = ghost_crab::Indexer::new().unwrap();

    indexer
        .load_event_handler(etherfi::EtherFiTVLUpdated::new())
        .await
        .unwrap();

    indexer
        .load_block_handler(stader::StaderBlockHandler::new())
        .await
        .unwrap();

    indexer.start().await.unwrap();
}

Event Handlers

Event handlers are used to process events emitted by smart contracts. They are defined as closures that implement the Handler trait. The Handler trait provides methods for accessing the event data, the contract address, and other useful information.

Here's an example of an event handler that processes TVLUpdated events emitted by the EtherFi Oracle contract:

use alloy::eips::BlockNumberOrTag;
use ghost_crab::prelude::*;

#[event_handler(EtherFi.TVLUpdated)]
async fn EtherFiTVLUpdated(ctx: Context) {
    let block_number = ctx.log.block_number.unwrap() as i64;
    let current_tvl = event._currentTvl.to_string();
    let log_index = ctx.log.log_index.unwrap() as i64;

    let block = ctx.block().await.unwrap().unwrap();

    let block_timestamp = block.header.timestamp as i64;

    // Save the data to your database
}

In the current version, we do not offer any kind of abstractions for the DB interactions, so you will have to use an external library like sqlx to interact with the DB, and save the data in your desired format.

In the above example, EtherFi is defined in the configuration as follows:

{
  "database": "$DATABASE_URL",
  "dataSources": {
    "EtherFi": {
      "startBlock": 105927637,
      "address": "0x6329004E903B7F420245E7aF3f355186f2432466",
      "abi": "abis/etherfi/TVLOracle.json",
      "network": "optimism"
    }
  },
  "networks": {
    "optimism": {
      "rpcUrl": "$OPT_RPC_URL",
      "requestsPerSecond": 30
    }
  }
}

Block Handlers

Block handlers are used to process blocks. They are defined as closures that implement the BlockHandler trait. The BlockHandler trait provides methods for accessing the block data and other useful information.

Here's an example of a block handler that processes blocks:

use alloy::{eips::BlockId, sol};
use ghost_crab::prelude::*;

sol!(
    #[sol(rpc)]
    StaderStakePoolsManager,
    "abis/stader/StaderStakePoolsManager.json"
);

const STADER: Address = address!("cf5EA1b38380f6aF39068375516Daf40Ed70D299");

#[block_handler(Stader)]
async fn StaderBlockHandler(ctx: BlockContext) {
    let stader_staking_manager = StaderStakePoolsManager::new(STADER, &ctx.provider);

    let total_assets = stader_staking_manager
        .totalAssets()
        .block(BlockId::from(ctx.block_number))
        .call()
        .await
        .unwrap();

    let db = db::get().await;

    let eth = total_assets._0.to_string();
    let block_number = ctx.block_number as i64;
    let block = ctx.block().await.unwrap().unwrap();
    let block_timestamp = block.header.timestamp as i64;

    // Save the data to your database
}

In the above example, Stader is defined in the configuration as follows:

{
  "database": "$DATABASE_URL",
  "blockHandlers": {
    "Stader": {
      "startBlock": 17416153,
      "network": "ethereum",
      "step": 720
    }
  },
  "networks": {
    "ethereum": {
      "rpcUrl": "$ETH_RPC_URL",
      "requestsPerSecond": 30
    }
  }
}

Templates

Templates are ideal to dynamically trigger new indexing processes. They are defined as closures that implement the Handler trait. The Handler trait provides methods for accessing the event data, the contract address, and other useful information.

Here's an example on how to use templates:

use alloy::eips::BlockNumberOrTag;
use ghost_crab::prelude::*;

#[template(ETHVault.Deposited)]
async fn ETHVaultDeposited(ctx: Context) {
    // Handler Logic
}

#[event_handler(VaultsRegistry.VaultAdded)]
async fn VaultsRegistry(ctx: Context) {
    ctx.templates
        .start(Template {
            address: vault.clone(),
            start_block: ctx.log.block_number.unwrap(),
            handler: ETHVaultDeposited::new(),
        })
        .await;
}

In the above example, we are tracking a VaultsRegistry contract which emits a VaultAdded event every time a new vault is added. Under the hood, GhostCrab is using the TemplateManager to start a new indexing process for the ETHVault contract on the specified address, and start block.

In this particular case, there is no way we could have known the address of the ETHVault contract before the VaultAdded event was emitted, so this is when templates come handy to dynamically start the indexing processes for new contracts.

Configuration

GhostCrab uses a configuration file to specify the data sources, templates, and block handlers. Here's an example of a configuration file:

{
  "dataSources": {
    "MyDataSourceName": {
      "abi": "my_contract_abi.json",
      "address": "0x1234567890123456789012345678901234567890",
      "start_block": 1000000,
      "network": "mainnet"
    }
  },
  "templates": {
    "MySecondDataSourceName": {
      "abi": "my_second_contract_abi.json",
      "network": "mainnet"
    }
  },
  "networks": {
    "mainnet": {
      "rpcUrl": "$MAINNET_RPC_URL",
      "requestsPerSecond": 30
    }
  },
  "blockHandlers": {
    "MyThirdDataSourceName": {
      "start_block": 1000000,
      "network": "mainnet"
    }
  }
}

In summary:

  • If you want to use an environment variable, you can use the $ENV_VAR syntax within the configuration file.
  • If you want to create an event handler, you need to define a data source. This data source will be loaded by the proc macro event_handler.
  • If you want to create a template, you need to define a template. This template will be loaded by the proc macro template.
  • If you want to create a block handler, you need to define a block handler. This block handler will be loaded by the procedural macro block_handler.

Examples

If you want to see some examples of how to use GhostCrab, you can check out our indexers repo, where we maintain a collection of smart contracts indexers for our staking analytics dashboard.