This crate provides gossiping capabilities on top of a network.
Gossip messages are separated by two categories: "topics" and consensus engine ID. The consensus engine ID is sent over the wire with the message, while the topic is not, with the expectation that the topic can be derived implicitly from the content of the message, assuming it is valid.
Topics are a single 32-byte tag associated with a message, used to group those messages
in an opaque way. Consensus code can invoke
broadcast_topic to attempt to send all messages
under a single topic to all peers who don't have them yet, and
send all messages under a single topic to a specific peer.
- Implement the
Networktrait, representing the low-level networking primitives. It is already implemented on
- Implement the
Validatortrait. See the section below.
- Decide on a protocol name. Each gossiping protocol should have a different one.
- Build a
GossipEngineusing these three elements.
- Use the methods of the
GossipEnginein order to send out messages and receive incoming messages.
GossipEngine will automatically use
Network::remove_set_reserved to maintain a set of peers equal to the set of peers the
node is syncing from. See the documentation of
sc-network for more explanations about the
concepts of peer sets.
The primary role of a
Validator is to process incoming messages from peers, and decide
whether to discard them or process them. It also decides whether to re-broadcast the message.
The secondary role of the
Validator is to check if a message is allowed to be sent to a given
peer. All messages, before being sent, will be checked against this filter.
This enables the validator to use information it's aware of about connected peers to decide
whether to send messages to them at any given moment in time - In particular, to wait until
peers can accept and process the message before sending it.
Lastly, the fact that gossip validators can decide not to rebroadcast messages opens the door for neighbor status packets to be baked into the gossip protocol. These status packets will typically contain light pieces of information used to inform peers of a current view of protocol state.
A gossip message validator that discards all messages.
Wraps around an implementation of the
Topic stream message with sender.
The reason for sending out the message.
Message validation result.
Abstraction over a network.
Validates consensus messages.
Validation context. Allows reacting to incoming messages by sending out further messages.