This is the same type introduced in #430, I think after merging those two PRs we can make a shared type for this

I think it would be great to replace this with async_trait

I thought about it, but what would it give us? A bit simpler definition of the callback which is not very complicated.

Any reason to change this from u64 -> u8? share_idx is 1-based and max can be 256

This is the reason: #426 (comment)
Hmm, why is it 1-based? That breaks possibility to keep it as u8 🤔

Or we can keep it in u8 but we need to remember to +1 every time we use it.

It looks like this should be u64 instead of u8 to mach charon implementation:

So instead of changing to u8 I've should change to u64 the index.

So in Definition
https://github.com/NethermindEth/pluto/blob/main/crates/cluster/src/definition.rs#L72

/// Charon nodes in the cluster and their operators.
/// Max 256 operators.
pub operators: Vec<Operator>,

On node_idx()

/// Returns the node index for a given peer ID.
    pub fn node_idx(&self, pid: &PeerId) -> Result<NodeIdx, DefinitionError> {
        let peers = self.peers()?;

        for (i, peer) in peers.iter().enumerate() {
            if peer.id == *pid {
                return Ok(NodeIdx {
                    peer_idx: i,
                    share_idx: peer.share_idx(),
                });
            }
        }

        Err(DefinitionError::PeerNotFound { peer_id: *pid })
    }

That's call share_idx()

 /// Returns share index of this Peer. ShareIdx is 1-indexed while peer index
    /// is 0-indexed.
    pub fn share_idx(&self) -> usize {
        self.index.wrapping_add(1)
    }

So it will overflow if you keep it as u8. Since in dkg, we map the share_idx from definition to core type, this will fail

https://github.com/NethermindEth/pluto/pull/426/changes#diff-f8e65bf8b68144c18a39c840773e15d737ffe51d055e3605b5cb5d074a9a4beeR219

Also this should be appear in the test, the boundary check

In the code we import debug from tracing, but here we use tracing::error, consider using only one approach around the codebase