changeround

README

QBFT Speedup

Fast sync for current running instances, in order to speedup change round.

Background

SSV nodes broadcast a change round msg when their internal timeout clock elapses. Timeout are exponential, that is some base timeout to the round x^r (x - base timeout, r - round number).

When there are less than 2f+1 nodes online, existing (and later joining nodes) play a catchup game with the goal of all of them to land on the same round number. There are 2 ways to catchup:

1. just timeout until you reach a round where 2f+1 nodes are (that's why the timeouts are exponential).
2. An IBFT "faster" sync protocol that can bump a node to a higher round if f+1 change round msgs are received.

The above helps somewhat but is still very slow as timeouts are exponential and quickly get to very long timeouts (hours and days).

Solution - Fast Sync

A solution is to actively ask other nodes for their latest change rounds when a node boots.
Doing so will bump the node immediately forward, still using the f+1 IBFT speedup but now not needing to wait passively for other nodes to send the change round msg.

This fast sync is a huge time efficiency increase in situations where less than 2f+1 nodes are online.

Documentation

Index

• Variables
• type Fetcher
  • func NewLastRoundFetcher(logger *zap.Logger, syncer p2pprotocol.Syncer) Fetcher
• type MsgHandler

Variables

var ErrNotFound = fmt.Errorf("not found")

ErrNotFound represents a not found error

Types

type Fetcher

type Fetcher interface {
	// GetChangeRoundMessages fetches change round messages for the given identifier and height
	GetChangeRoundMessages(identifier spectypes.MessageID, height specqbft.Height, handler MsgHandler) error
}

Fetcher is responsible for fetching change round messages from other peers in the subnet

func NewLastRoundFetcher

func NewLastRoundFetcher(logger *zap.Logger, syncer p2pprotocol.Syncer) Fetcher

NewLastRoundFetcher returns an instance of changeRoundFetcher

type MsgHandler

type MsgHandler func(*specqbft.SignedMessage) error

MsgHandler handles incoming change round messages