blocksync

Documentation

Overview

Package blocksync implements two versions of a reactor Service that are responsible for block propagation and gossip between peers. This mechanism was formerly known as fast-sync.

In order for a full node to successfully participate in consensus, it must have the latest view of state. The blocksync protocol is a mechanism in which peers may exchange and gossip entire blocks with one another, in a request/response type model, until they've successfully synced to the latest head block. Once succussfully synced, the full node can switch to an active role in consensus and will no longer blocksync and thus no longer run the blocksync process.

Note, the blocksync reactor Service gossips entire block and relevant data such that each receiving peer may construct the entire view of the blocksync state.

There are currently two versions of the blocksync reactor Service:

• v0: The initial implementation that is battle-tested, but whose test coverage is lacking and is not formally verifiable.
• v2: The latest implementation that has much higher test coverage and is formally verified. However, the current implementation of v2 is not as battle-tested and is known to have various bugs that could make it unreliable in production environments.

The v0 blocksync reactor Service has one p2p channel, BlockchainChannel. This channel is responsible for handling messages that both request blocks and respond to block requests from peers. For every block request from a peer, the reactor will execute respondToPeer which will fetch the block from the node's state store and respond to the peer. For every block response, the node will add the block to its pool via AddBlock.

Internally, v0 runs a poolRoutine that constantly checks for what blocks it needs and requests them. The poolRoutine is also responsible for taking blocks from the pool, saving and executing each block.

Index

• Constants

Constants

const (
	MaxMsgSize = types.MaxBlockSizeBytes +
		bcproto.BlockResponseMessagePrefixSize +
		bcproto.BlockResponseMessageFieldKeySize
)