feat(gossipsub): Add Message Batch Publishing in Gossipsub

Description

Adding a MessageBatch API to the libp2p::gossipsub to support batch publishing. This feature allows publishing a batch of related messages by prioritizing the transmission of one copy of each message to different peers before sending redundant copies.

Motivation

The Gossipsub protocol in rust-libp2p (implemented in the libp2p-gossipsub crate) currently allows publishing messages to topics individually, with each message being sent to connected peers as soon as it is published.

However, in scenarios with bandwidth-constrained peers or high message volumes, sending messages individually can lead to inefficiencies, such as redundant message propagation, dropped messages due to outbound queue limits, ..

One solution could be adding a MessageBatch mechanism to allow users to group related messages into a batch and publish them together (the implementation on go pubsub -> https://github.com/libp2p/go-libp2p-pubsub/pull/607).

This would optimize bandwidth usage by ensuring that a single copy of each unique message is sent to each peer before additional copies.

Requirements

• MessageBatch Struct: A new struct to collect messages for batch publishing, with methods to add messages and trigger publication.

• Batch Publishing Logic: A mechanism to prioritize sending one copy of each message to peers before sending duplicates, similar to the Go implementation’s rarest-first strategy.

• Integration with Gossipsub: Extend the Gossipsub behaviour to handle batched messages, ensuring compatibility with existing message ID generation and peer outbound queues.

• Configurable Queue Size: Recommend setting the peer outbound queue size to accommodate the expected number of batched messages, plus additional slack for gossip overhead.

Open questions

No response

Are you planning to do it yourself in a pull request?

Maybe

Start by reading the existing publishing API and message flow in the libp2p-gossipsub crate, then compare the proposed behavior with the referenced Go pubsub pull request. Done means agreeing on a MessageBatch API, implementing rarest-first batch propagation, and covering queue sizing and compatibility with existing message IDs and outbound queues.