The Babylon Finality Gadget is a program that can be run by users of OP stack L2s to track consecutive L2 block quorum and query the BTC-finalised status of blocks.

See our proposal on Optimism for more details.

Modules

cmd : entry point for opfgd finality gadget daemon
finalitygadget : top-level umbrella module that exposes query methods and coordinates calls to other clients
client : grpc client to query the finality gadget
server : grpc server for the finality gadget
proto : protobuf definitions for the grpc server
config : configs for the finality gadget
btcclient : wrapper around Bitcoin RPC client
bbnclient : wrapper around Babylon RPC client
ethl2client : wrapper around OP stack L2 ETH RPC client
cwclient : client to query CosmWasm smart contract deployed on BabylonChain
db : handler for local database to store finalized block state
types : common types
log : custom logger
testutil : test utilities and helpers

Instructions

Download and configuration

To get started, clone the repository.

git clone https://github.com/babylonlabs-io/finality-gadget.git

Copy the config.toml.example file to config.toml:

cp config.toml.example config.toml

Configure the config.toml file with the following parameters:

L2RPCHost = # RPC URL of OP stack L2 chain
BitcoinRPCHost = # Bitcoin RPC URL
DBFilePath = # Path to local bbolt DB file
FGContractAddress = # Babylon finality gadget contract address
BBNChainID = # Babylon chain id
BBNRPCAddress = # Babylon RPC host URL
GRPCListener = # Host:port to listen for gRPC connections
PollInterval = # Interval to poll for new L2 blocks

Building and installing the binary

At the top-level directory of the project

make install

The above command will build and install the opfgd binary to $GOPATH/bin.

If your shell cannot find the installed binaries, make sure $GOPATH/bin is in the $PATH of your shell. Usually these commands will do the job

export PATH=$HOME/go/bin:$PATH
echo 'export PATH=$HOME/go/bin:$PATH' >> ~/.profile

Running the daemon

To start the daemon, run:

opfgd start --cfg config.toml

Running tests

To run tests:

make test

Build Docker image

Prerequisites

Docker Desktop: Install from Docker's official website.
Make: Required for building service binaries. Installation guide available here.
GitHub SSH Key:
- Create a non-passphrase-protected SSH key.
- Add it to GitHub (instructions).
- Export the key path:
```
export BBN_PRIV_DEPLOY_KEY=FULL_PATH_TO_PRIVATE_KEY/.ssh/id_ed25519
```

Repository Setup:

git clone https://github.com/babylonlabs-io/finality-gadget.git

To build the docker image:

make build-docker