Multi Rust: From Threads to Nodes

3) Make it distributed

Now we make one node become a network.

Peer discovery

• Start from static bootnodes.
• Enable optional mDNS for local development clusters.

Data propagation and sync

• Use pubsub gossip for tx and block announcements.
• On startup, request missing blocks using request/response.

Fork choice (simple by design)

For this capstone keep fork choice simple: highest height / longest chain.

That is enough to demonstrate distributed behavior, while also being honest that consensus is much deeper than this chapter.

Observability

Instrument key spans:

• block_validate
• mempool_insert
• block_import
• sync_request
• sync_apply

#![allow(unused)]
fn main() {
use tracing::{info_span, Instrument};

let span = info_span!("block_import", height = block.header.height);
async move {
    import_block(block).await
}
.instrument(span)
.await?;
}

Try it: 3 local nodes

cargo run -p blockchain_node -- --id n1 --port 7001 --bootnodes ""
cargo run -p blockchain_node -- --id n2 --port 7002 --bootnodes "/ip4/127.0.0.1/tcp/7001"
cargo run -p blockchain_node -- --id n3 --port 7003 --bootnodes "/ip4/127.0.0.1/tcp/7001"

Then submit one tx to n2 and verify n1/n3 logs show propagation and block import.

Deliverable

A local 3-node demo where a block observed on one node is imported by the other two.