go-abci-service

Go ABCI Service

Introduction

The Chainpoint Network's blockchain is based around the Tendermint blockchain library, a Byzantine Fault Tolerant (BFT) peer-to-peer consensus layer. Tendermint allows anyone to interact with a self-generated Tendermint blockchain using an Application-BlockChain Interface (ABCI) app written in Go.

This service module encompasses a Tendermint Core, Chainpoint ABCI app, and various submodules for connecting to C_Level_DB, PostgreSQL, and Redis. The result is one dockerized binary run in a Docker Swarm capable of coordinating all Core services on a single host.

Operation Modes

When initialized, Tendermint will create Genesis, Config, and Node_Key files in ~/.chainpoint/core/config/node_1. All other data, including ECDSA, redis, and postgresql files, can be found in ~/.chainpoint/core/data.

A Tendermint full-node can become a validator, and share greater responsibilities such as confirming new Cores, generating proofs, and injecting DRAND Beacon entropy into the blockchain.

Deeper Dive

When a Chainpoint Core starts up, it first retrieves all configuration options from the environment variables listed in the swarm-compose.yaml file in the project root. It then instantiates both an ABCI application and a Tendermint Core. These become bound together for the duration of operation.

Every block epoch (60 seconds by default), the ABCI application is set to perform a number of functions:

• Authenticate transactions from all other Cores.
• Aggregate all hashes received from the API into a CAL transaction and submit it to the Calendar.
• Elect a leader to send a DRAND Beacon Entropy transaction to the blockchain.
• Monitor for public keys from new Cores, which are broadcast via a JWK message.
• Monitor sync status with the rest of the Network (and shutdown critical functions if not synced yet).

Every anchor epoch (60 minutes by default), the ABCI application is set to perform the following anchor/reward functions:

• Elect a leader to anchor all hashes received since last anchor epoch by broadcasting their Merkle Root to Bitcoin via the lnd service. The resulting Bitcoin TX ID is placed in a BTC-A transaction and submitted to the Calendar.
• Monitor for the confirmation of a successful anchor to Bitcoin. The resulting Bitcoin header info containing the anchor is placed in a BTC-C transaction and submitted to the Calendar.

Anchor Interface

The go-abci-service/anchor package contains an interface which allows alternate blockchain anchor engine to be implemented. Chainpoint's bitcoin anchoring implementation is included in the bitcoin subpackage.

Any new blockchain anchor must implement the methods in the anchor_interface.go file, as well as assign the new anchor to the AnchorEngine in the ABCI AnchorApplication.

Useful Packages

The following packages contain go language utilities which may be useful in the following ways:

• lightning : Methods for interacting with tierion/lnd modified lightning nodes. Most methods can also interact with the lightninglabs lnd nodes.
• aggregator : Multithreaded method of creating Merkle trees from large numbers of hashes
• beacon : Retrieves timestamped entropy from the drand network
• blake2s : Implements the BLAKE hash function
• fee : Retrieves bitcoin fees from the bitcoinerlive service
• leader_election : Methods for deterministically electing a leader from a group of Tendermint nodes
• merkletools : Chainpoint Merkle tree implementation
• tendermint_rpc : RPC methods for interacting with a Tendermint node
• util : Various utilities for doing everything from verifying ECDSA signatures to generically finding array elements

Troubleshooting

• If the Tendermint Core crashes, it will log a panic message. Usually this is due to the Tendermint Core having a corrupt copy of the chain. When in doubt, don't be afraid to make remove and make clean to stop the node and delete the chainstate, then redeploy with make deploy. A fast-sync with the rest of the Network should fix the issue.
• If the Tendermint Core returns connection errors to other services, make sure all URIs and API keys are correct in your configuration.
• If you need to move hosts, be sure to save the ~/.chainpoint directory and move it to the new host. You will want to adjust the Core's public IP in ~/.chainpoint/core/.env to reflect the new host.