feat: initialize Kurdistan SDK - independent fork of Polkadot SDK

This commit is contained in:
2025-12-13 15:44:15 +03:00
commit e4778b4576
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// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Pezkuwi.
// Pezkuwi is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Pezkuwi is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Pezkuwi. If not, see <http://www.gnu.org/licenses/>.
//! This subsystem is responsible for keeping track of session changes
//! and issuing a connection request to the relevant validators
//! on every new session.
//!
//! In addition to that, it creates a gossip overlay topology
//! which limits the amount of messages sent and received
//! to be an order of sqrt of the validators. Our neighbors
//! in this graph will be forwarded to the network bridge with
//! the `NetworkBridgeRxMessage::NewGossipTopology` message.
use std::{
collections::{HashMap, HashSet},
fmt,
time::{Duration, Instant},
u32,
};
use futures::{channel::oneshot, select, FutureExt as _};
use futures_timer::Delay;
use rand::{Rng, SeedableRng};
use rand_chacha::ChaCha20Rng;
use sc_network::{config::parse_addr, Multiaddr};
use sp_application_crypto::{AppCrypto, ByteArray};
use sp_keystore::{Keystore, KeystorePtr};
use pezkuwi_node_network_protocol::{
authority_discovery::AuthorityDiscovery, peer_set::PeerSet, GossipSupportNetworkMessage,
PeerId, ValidationProtocols,
};
use pezkuwi_node_subsystem::{
messages::{
ChainApiMessage, GossipSupportMessage, NetworkBridgeEvent, NetworkBridgeRxMessage,
NetworkBridgeTxMessage, RuntimeApiMessage, RuntimeApiRequest,
},
overseer, ActiveLeavesUpdate, FromOrchestra, OverseerSignal, SpawnedSubsystem, SubsystemError,
};
use pezkuwi_node_subsystem_util as util;
use pezkuwi_primitives::{AuthorityDiscoveryId, Hash, SessionIndex, SessionInfo, ValidatorIndex};
#[cfg(test)]
mod tests;
mod metrics;
use metrics::Metrics;
const LOG_TARGET: &str = "teyrchain::gossip-support";
// How much time should we wait to reissue a connection request
// since the last authority discovery resolution failure.
#[cfg(not(test))]
const BACKOFF_DURATION: Duration = Duration::from_secs(5);
#[cfg(test)]
const BACKOFF_DURATION: Duration = Duration::from_millis(500);
// The authorithy_discovery queries runs every ten minutes,
// so it make sense to run a bit more often than that to
// detect changes as often as we can, but not too often since
// it won't help.
#[cfg(not(test))]
const TRY_RERESOLVE_AUTHORITIES: Duration = Duration::from_secs(5 * 60);
#[cfg(test)]
const TRY_RERESOLVE_AUTHORITIES: Duration = Duration::from_secs(2);
/// Duration after which we consider low connectivity a problem.
///
/// Especially at startup low connectivity is expected (authority discovery cache needs to be
/// populated). Authority discovery on Kusama takes around 8 minutes, so warning after 10 minutes
/// should be fine:
///
/// https://github.com/paritytech/substrate/blob/fc49802f263529160635471c8a17888846035f5d/client/authority-discovery/src/lib.rs#L88
const LOW_CONNECTIVITY_WARN_DELAY: Duration = Duration::from_secs(600);
/// If connectivity is lower than this in percent, issue warning in logs.
const LOW_CONNECTIVITY_WARN_THRESHOLD: usize = 85;
/// The Gossip Support subsystem.
pub struct GossipSupport<AD> {
keystore: KeystorePtr,
last_session_index: Option<SessionIndex>,
/// Whether we are currently an authority or not.
is_authority_now: bool,
/// The minimum known session we build the topology for.
min_known_session: SessionIndex,
// Some(timestamp) if we failed to resolve
// at least a third of authorities the last time.
// `None` otherwise.
last_failure: Option<Instant>,
// Validators can restart during a session, so if they change
// their PeerID, we will connect to them in the best case after
// a session, so we need to try more often to resolved peers and
// reconnect to them. The authorithy_discovery queries runs every ten
// minutes, so we can't detect changes in the address more often
// that that.
last_connection_request: Option<Instant>,
/// First time we did not reach our connectivity threshold.
///
/// This is the time of the first failed attempt to connect to >2/3 of all validators in a
/// potential sequence of failed attempts. It will be cleared once we reached >2/3
/// connectivity.
failure_start: Option<Instant>,
/// Successfully resolved connections
///
/// waiting for actual connection.
resolved_authorities: HashMap<AuthorityDiscoveryId, HashSet<Multiaddr>>,
/// Actually connected authorities.
connected_authorities: HashMap<AuthorityDiscoveryId, PeerId>,
/// By `PeerId`.
///
/// Needed for efficient handling of disconnect events.
connected_peers: HashMap<PeerId, HashSet<AuthorityDiscoveryId>>,
/// Authority discovery service.
authority_discovery: AD,
/// The oldest session we need to build a topology for because
/// the finalized blocks are from a session we haven't built a topology for.
finalized_needed_session: Option<u32>,
/// Subsystem metrics.
metrics: Metrics,
}
#[overseer::contextbounds(GossipSupport, prefix = self::overseer)]
impl<AD> GossipSupport<AD>
where
AD: AuthorityDiscovery,
{
/// Create a new instance of the [`GossipSupport`] subsystem.
pub fn new(keystore: KeystorePtr, authority_discovery: AD, metrics: Metrics) -> Self {
// Initialize metrics to `0`.
metrics.on_is_not_authority();
metrics.on_is_not_teyrchain_validator();
Self {
keystore,
last_session_index: None,
last_failure: None,
last_connection_request: None,
failure_start: None,
resolved_authorities: HashMap::new(),
connected_authorities: HashMap::new(),
connected_peers: HashMap::new(),
min_known_session: u32::MAX,
authority_discovery,
finalized_needed_session: None,
is_authority_now: false,
metrics,
}
}
async fn run<Context>(mut self, mut ctx: Context) -> Self {
fn get_connectivity_check_delay() -> Delay {
Delay::new(LOW_CONNECTIVITY_WARN_DELAY)
}
let mut next_connectivity_check = get_connectivity_check_delay().fuse();
loop {
let message = select!(
_ = next_connectivity_check => {
self.check_connectivity();
next_connectivity_check = get_connectivity_check_delay().fuse();
continue
}
result = ctx.recv().fuse() =>
match result {
Ok(message) => message,
Err(e) => {
gum::debug!(
target: LOG_TARGET,
err = ?e,
"Failed to receive a message from Overseer, exiting",
);
return self
},
}
);
match message {
FromOrchestra::Communication {
msg: GossipSupportMessage::NetworkBridgeUpdate(ev),
} => self.handle_connect_disconnect(ev),
FromOrchestra::Signal(OverseerSignal::ActiveLeaves(ActiveLeavesUpdate {
activated,
..
})) => {
gum::trace!(target: LOG_TARGET, "active leaves signal");
let leaves = activated.into_iter().map(|a| a.hash);
if let Err(e) = self.handle_active_leaves(ctx.sender(), leaves).await {
gum::debug!(target: LOG_TARGET, error = ?e);
}
},
FromOrchestra::Signal(OverseerSignal::BlockFinalized(_hash, _number)) =>
if let Some(session_index) = self.last_session_index {
if let Err(e) = self
.build_topology_for_last_finalized_if_needed(
ctx.sender(),
session_index,
)
.await
{
gum::warn!(
target: LOG_TARGET,
"Failed to build topology for last finalized session: {:?}",
e
);
}
},
FromOrchestra::Signal(OverseerSignal::Conclude) => return self,
}
}
}
/// 1. Determine if the current session index has changed.
/// 2. If it has, determine relevant validators and issue a connection request.
async fn handle_active_leaves(
&mut self,
sender: &mut impl overseer::GossipSupportSenderTrait,
leaves: impl Iterator<Item = Hash>,
) -> Result<(), util::Error> {
for leaf in leaves {
let current_index = util::request_session_index_for_child(leaf, sender).await.await??;
let since_failure = self.last_failure.map(|i| i.elapsed()).unwrap_or_default();
let since_last_reconnect =
self.last_connection_request.map(|i| i.elapsed()).unwrap_or_default();
let force_request = since_failure >= BACKOFF_DURATION;
let re_resolve_authorities = since_last_reconnect >= TRY_RERESOLVE_AUTHORITIES;
let leaf_session = Some((current_index, leaf));
let maybe_new_session = match self.last_session_index {
Some(i) if current_index <= i => None,
_ => leaf_session,
};
let maybe_issue_connection = if force_request || re_resolve_authorities {
leaf_session
} else {
maybe_new_session
};
if let Some((session_index, relay_parent)) = maybe_issue_connection {
let session_info =
util::request_session_info(leaf, session_index, sender).await.await??;
let session_info = match session_info {
Some(s) => s,
None => {
gum::warn!(
relay_parent = ?leaf,
session_index = self.last_session_index,
"Failed to get session info.",
);
continue;
},
};
// Note: we only update `last_session_index` once we've
// successfully gotten the `SessionInfo`.
let is_new_session = maybe_new_session.is_some();
if is_new_session {
gum::debug!(
target: LOG_TARGET,
%session_index,
"New session detected",
);
self.last_session_index = Some(session_index);
self.is_authority_now =
ensure_i_am_an_authority(&self.keystore, &session_info.discovery_keys)
.is_ok();
}
// Connect to authorities from the past/present/future.
//
// This is maybe not the right place for this logic to live,
// but at the moment we're limited by the network bridge's ability
// to handle connection requests (it only allows one, globally).
//
// Certain network protocols - mostly req/res, but some gossip,
// will require being connected to past/future validators as well
// as current. That is, the old authority sets are not made obsolete
// by virtue of a new session being entered. Therefore we maintain
// connections to a much broader set of validators.
{
let mut connections = authorities_past_present_future(sender, leaf).await?;
self.last_connection_request = Some(Instant::now());
// Remove all of our locally controlled validator indices so we don't connect to
// ourself.
let connections =
if remove_all_controlled(&self.keystore, &mut connections) != 0 {
connections
} else {
// If we control none of them, issue an empty connection request
// to clean up all connections.
Vec::new()
};
if force_request || is_new_session {
self.issue_connection_request(sender, connections).await;
} else if re_resolve_authorities {
self.issue_connection_request_to_changed(sender, connections).await;
}
}
if is_new_session {
if let Err(err) = self
.build_topology_for_last_finalized_if_needed(sender, session_index)
.await
{
gum::warn!(
target: LOG_TARGET,
"Failed to build topology for last finalized session: {:?}",
err
);
}
// Gossip topology is only relevant for authorities in the current session.
let our_index = self.get_key_index_and_update_metrics(&session_info)?;
update_gossip_topology(
sender,
our_index,
session_info.discovery_keys.clone(),
relay_parent,
session_index,
)
.await?;
}
// authority_discovery is just a cache so let's try every time we try to re-connect
// if new authorities are present.
self.update_authority_ids(sender, session_info.discovery_keys).await;
}
}
Ok(())
}
/// Build the gossip topology for the session of the last finalized block if we haven't built
/// one.
///
/// This is needed to ensure that if finality is lagging accross session boundary and a restart
/// happens after the new session started, we built a topology from the session we haven't
/// finalized the blocks yet.
/// Once finalized blocks start to be from a session we've built a topology for, we can stop.
async fn build_topology_for_last_finalized_if_needed(
&mut self,
sender: &mut impl overseer::GossipSupportSenderTrait,
current_session_index: u32,
) -> Result<(), util::Error> {
self.min_known_session = self.min_known_session.min(current_session_index);
if self
.finalized_needed_session
.map(|oldest_needed_session| oldest_needed_session < self.min_known_session)
.unwrap_or(true)
{
let (tx, rx) = oneshot::channel();
sender.send_message(ChainApiMessage::FinalizedBlockNumber(tx)).await;
let finalized_block_number = match rx.await? {
Ok(block_number) => block_number,
_ => return Ok(()),
};
let (tx, rx) = oneshot::channel();
sender
.send_message(ChainApiMessage::FinalizedBlockHash(finalized_block_number, tx))
.await;
let finalized_block_hash = match rx.await? {
Ok(Some(block_hash)) => block_hash,
_ => return Ok(()),
};
let finalized_session_index =
util::request_session_index_for_child(finalized_block_hash, sender)
.await
.await??;
if finalized_session_index < self.min_known_session &&
Some(finalized_session_index) != self.finalized_needed_session
{
gum::debug!(
target: LOG_TARGET,
?finalized_block_hash,
?finalized_block_number,
?finalized_session_index,
"Building topology for finalized block session",
);
let finalized_session_info = match util::request_session_info(
finalized_block_hash,
finalized_session_index,
sender,
)
.await
.await??
{
Some(session_info) => session_info,
_ => return Ok(()),
};
let our_index = self.get_key_index_and_update_metrics(&finalized_session_info)?;
update_gossip_topology(
sender,
our_index,
finalized_session_info.discovery_keys.clone(),
finalized_block_hash,
finalized_session_index,
)
.await?;
}
self.finalized_needed_session = Some(finalized_session_index);
}
Ok(())
}
// Checks if the node is an authority and also updates `pezkuwi_node_is_authority` and
// `pezkuwi_node_is_teyrchain_validator` metrics accordingly.
// On success, returns the index of our keys in `session_info.discovery_keys`.
fn get_key_index_and_update_metrics(
&mut self,
session_info: &SessionInfo,
) -> Result<usize, util::Error> {
let authority_check_result =
ensure_i_am_an_authority(&self.keystore, &session_info.discovery_keys);
match authority_check_result.as_ref() {
Ok(index) => {
gum::trace!(target: LOG_TARGET, "We are now an authority",);
self.metrics.on_is_authority();
// The subset of authorities participating in teyrchain consensus.
let teyrchain_validators_this_session = session_info.validators.len();
// First `maxValidators` entries are the teyrchain validators. We'll check
// if our index is in this set to avoid searching for the keys.
// https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148
if *index < teyrchain_validators_this_session {
gum::trace!(target: LOG_TARGET, "We are now a teyrchain validator",);
self.metrics.on_is_teyrchain_validator();
} else {
gum::trace!(target: LOG_TARGET, "We are no longer a teyrchain validator",);
self.metrics.on_is_not_teyrchain_validator();
}
},
Err(util::Error::NotAValidator) => {
gum::trace!(target: LOG_TARGET, "We are no longer an authority",);
self.metrics.on_is_not_authority();
self.metrics.on_is_not_teyrchain_validator();
},
// Don't update on runtime errors.
Err(_) => {},
};
authority_check_result
}
async fn resolve_authorities(
&mut self,
authorities: Vec<AuthorityDiscoveryId>,
) -> (Vec<HashSet<Multiaddr>>, HashMap<AuthorityDiscoveryId, HashSet<Multiaddr>>, usize) {
let mut validator_addrs = Vec::with_capacity(authorities.len());
let mut resolved = HashMap::with_capacity(authorities.len());
let mut failures = 0;
for authority in authorities {
if let Some(addrs) =
self.authority_discovery.get_addresses_by_authority_id(authority.clone()).await
{
validator_addrs.push(addrs.clone());
resolved.insert(authority, addrs);
} else {
failures += 1;
gum::debug!(
target: LOG_TARGET,
"Couldn't resolve addresses of authority: {:?}",
authority
);
}
}
(validator_addrs, resolved, failures)
}
async fn issue_connection_request_to_changed<Sender>(
&mut self,
sender: &mut Sender,
authorities: Vec<AuthorityDiscoveryId>,
) where
Sender: overseer::GossipSupportSenderTrait,
{
let (_, resolved, _) = self.resolve_authorities(authorities).await;
let mut changed = Vec::new();
for (authority, new_addresses) in &resolved {
let new_peer_ids = new_addresses
.iter()
.flat_map(|addr| parse_addr(addr.clone()).ok().map(|(p, _)| p))
.collect::<HashSet<_>>();
match self.resolved_authorities.get(authority) {
Some(old_addresses) => {
let old_peer_ids = old_addresses
.iter()
.flat_map(|addr| parse_addr(addr.clone()).ok().map(|(p, _)| p))
.collect::<HashSet<_>>();
if !old_peer_ids.is_superset(&new_peer_ids) {
changed.push(new_addresses.clone());
}
},
None => changed.push(new_addresses.clone()),
}
}
gum::debug!(
target: LOG_TARGET,
num_changed = ?changed.len(),
?changed,
"Issuing a connection request to changed validators"
);
if !changed.is_empty() {
self.resolved_authorities = resolved;
sender
.send_message(NetworkBridgeTxMessage::AddToResolvedValidators {
validator_addrs: changed,
peer_set: PeerSet::Validation,
})
.await;
}
}
async fn issue_connection_request<Sender>(
&mut self,
sender: &mut Sender,
authorities: Vec<AuthorityDiscoveryId>,
) where
Sender: overseer::GossipSupportSenderTrait,
{
let num = authorities.len();
let (validator_addrs, resolved, failures) = self.resolve_authorities(authorities).await;
self.resolved_authorities = resolved;
gum::debug!(target: LOG_TARGET, %num, "Issuing a connection request");
sender
.send_message(NetworkBridgeTxMessage::ConnectToResolvedValidators {
validator_addrs,
peer_set: PeerSet::Validation,
})
.await;
// issue another request for the same session
// if at least a third of the authorities were not resolved.
if num != 0 && 3 * failures >= num {
let timestamp = Instant::now();
match self.failure_start {
None => self.failure_start = Some(timestamp),
Some(first) if first.elapsed() >= LOW_CONNECTIVITY_WARN_DELAY => {
gum::warn!(
target: LOG_TARGET,
connected = ?(num - failures),
target = ?num,
"Low connectivity - authority lookup failed for too many validators."
);
},
Some(_) => {
gum::debug!(
target: LOG_TARGET,
connected = ?(num - failures),
target = ?num,
"Low connectivity (due to authority lookup failures) - expected on startup."
);
},
}
self.last_failure = Some(timestamp);
} else {
self.last_failure = None;
self.failure_start = None;
};
}
async fn update_authority_ids<Sender>(
&mut self,
sender: &mut Sender,
authorities: Vec<AuthorityDiscoveryId>,
) where
Sender: overseer::GossipSupportSenderTrait,
{
let mut authority_ids: HashMap<PeerId, HashSet<AuthorityDiscoveryId>> = HashMap::new();
for authority in authorities {
let peer_ids = self
.authority_discovery
.get_addresses_by_authority_id(authority.clone())
.await
.into_iter()
.flat_map(|list| list.into_iter())
.flat_map(|addr| parse_addr(addr).ok().map(|(p, _)| p))
.collect::<HashSet<_>>();
gum::trace!(
target: LOG_TARGET,
?peer_ids,
?authority,
"Resolved to peer ids"
);
for p in peer_ids {
authority_ids.entry(p).or_default().insert(authority.clone());
}
}
// peer was authority and now isn't
for (peer_id, current) in self.connected_peers.iter_mut() {
// empty -> nonempty is handled in the next loop
if !current.is_empty() && !authority_ids.contains_key(peer_id) {
sender
.send_message(NetworkBridgeRxMessage::UpdatedAuthorityIds {
peer_id: *peer_id,
authority_ids: HashSet::new(),
})
.await;
for a in current.drain() {
self.connected_authorities.remove(&a);
}
}
}
// peer has new authority set.
for (peer_id, new) in authority_ids {
// If the peer is connected _and_ the authority IDs have changed.
if let Some(prev) = self.connected_peers.get(&peer_id).filter(|x| x != &&new) {
sender
.send_message(NetworkBridgeRxMessage::UpdatedAuthorityIds {
peer_id,
authority_ids: new.clone(),
})
.await;
prev.iter().for_each(|a| {
self.connected_authorities.remove(a);
});
new.iter().for_each(|a| {
self.connected_authorities.insert(a.clone(), peer_id);
});
self.connected_peers.insert(peer_id, new);
}
}
}
fn handle_connect_disconnect(&mut self, ev: NetworkBridgeEvent<GossipSupportNetworkMessage>) {
match ev {
NetworkBridgeEvent::PeerConnected(peer_id, _, _, o_authority) => {
if let Some(authority_ids) = o_authority {
authority_ids.iter().for_each(|a| {
self.connected_authorities.insert(a.clone(), peer_id);
});
self.connected_peers.insert(peer_id, authority_ids);
} else {
self.connected_peers.insert(peer_id, HashSet::new());
}
},
NetworkBridgeEvent::PeerDisconnected(peer_id) => {
if let Some(authority_ids) = self.connected_peers.remove(&peer_id) {
authority_ids.into_iter().for_each(|a| {
self.connected_authorities.remove(&a);
});
}
},
NetworkBridgeEvent::UpdatedAuthorityIds(_, _) => {
// The `gossip-support` subsystem itself issues these messages.
},
NetworkBridgeEvent::OurViewChange(_) => {},
NetworkBridgeEvent::PeerViewChange(_, _) => {},
NetworkBridgeEvent::NewGossipTopology { .. } => {},
NetworkBridgeEvent::PeerMessage(_, message) => {
// match void -> LLVM unreachable
match message {
ValidationProtocols::V3(m) => match m {},
}
},
}
}
/// Check connectivity and report on it in logs.
fn check_connectivity(&mut self) {
let absolute_connected = self.connected_authorities.len();
let absolute_resolved = self.resolved_authorities.len();
let connected_ratio =
(100 * absolute_connected).checked_div(absolute_resolved).unwrap_or(100);
let unconnected_authorities = self
.resolved_authorities
.iter()
.filter(|(a, _)| !self.connected_authorities.contains_key(a));
if connected_ratio <= LOW_CONNECTIVITY_WARN_THRESHOLD && self.is_authority_now {
gum::error!(
target: LOG_TARGET,
session_index = self.last_session_index.as_ref().map(|s| *s).unwrap_or_default(),
"Connectivity seems low, we are only connected to {connected_ratio}% of available validators (see debug logs for details), if this persists more than a session action needs to be taken"
);
}
let pretty = PrettyAuthorities(unconnected_authorities);
gum::debug!(
target: LOG_TARGET,
?connected_ratio,
?absolute_connected,
?absolute_resolved,
unconnected_authorities = %pretty,
"Connectivity Report"
);
}
}
// Get the authorities of the past, present, and future.
async fn authorities_past_present_future(
sender: &mut impl overseer::GossipSupportSenderTrait,
relay_parent: Hash,
) -> Result<Vec<AuthorityDiscoveryId>, util::Error> {
let authorities = util::request_authorities(relay_parent, sender).await.await??;
gum::debug!(
target: LOG_TARGET,
authority_count = ?authorities.len(),
"Determined past/present/future authorities",
);
Ok(authorities)
}
/// Return an error if we're not a validator in the given set (do not have keys).
/// Otherwise, returns the index of our keys in `authorities`.
fn ensure_i_am_an_authority(
keystore: &KeystorePtr,
authorities: &[AuthorityDiscoveryId],
) -> Result<usize, util::Error> {
for (i, v) in authorities.iter().enumerate() {
if Keystore::has_keys(&**keystore, &[(v.to_raw_vec(), AuthorityDiscoveryId::ID)]) {
return Ok(i);
}
}
Err(util::Error::NotAValidator)
}
/// Filter out all controlled keys in the given set. Returns the number of keys removed.
fn remove_all_controlled(
keystore: &KeystorePtr,
authorities: &mut Vec<AuthorityDiscoveryId>,
) -> usize {
let mut to_remove = Vec::new();
for (i, v) in authorities.iter().enumerate() {
if Keystore::has_keys(&**keystore, &[(v.to_raw_vec(), AuthorityDiscoveryId::ID)]) {
to_remove.push(i);
}
}
for i in to_remove.iter().rev().copied() {
authorities.remove(i);
}
to_remove.len()
}
/// We partition the list of all sorted `authorities` into `sqrt(len)` groups of `sqrt(len)` size
/// and form a matrix where each validator is connected to all validators in its row and column.
/// This is similar to `[web3]` research proposed topology, except for the groups are not teyrchain
/// groups (because not all validators are teyrchain validators and the group size is small),
/// but formed randomly via BABE randomness from two epochs ago.
/// This limits the amount of gossip peers to 2 * `sqrt(len)` and ensures the diameter of 2.
///
/// [web3]: https://research.web3.foundation/en/latest/polkadot/networking/3-avail-valid.html#topology
async fn update_gossip_topology(
sender: &mut impl overseer::GossipSupportSenderTrait,
our_index: usize,
authorities: Vec<AuthorityDiscoveryId>,
relay_parent: Hash,
session_index: SessionIndex,
) -> Result<(), util::Error> {
// retrieve BABE randomness
let random_seed = {
let (tx, rx) = oneshot::channel();
// TODO https://github.com/paritytech/polkadot/issues/5316:
// get the random seed from the `SessionInfo` instead.
sender
.send_message(RuntimeApiMessage::Request(
relay_parent,
RuntimeApiRequest::CurrentBabeEpoch(tx),
))
.await;
let randomness = rx.await??.randomness;
let mut subject = [0u8; 40];
subject[..8].copy_from_slice(b"gossipsu");
subject[8..].copy_from_slice(&randomness);
sp_crypto_hashing::blake2_256(&subject)
};
// shuffle the validators and create the index mapping
let (shuffled_indices, canonical_shuffling) = {
let mut rng: ChaCha20Rng = SeedableRng::from_seed(random_seed);
let len = authorities.len();
let mut shuffled_indices = vec![0; len];
let mut canonical_shuffling: Vec<_> = authorities
.iter()
.enumerate()
.map(|(i, a)| (a.clone(), ValidatorIndex(i as _)))
.collect();
fisher_yates_shuffle(&mut rng, &mut canonical_shuffling[..]);
for (i, (_, validator_index)) in canonical_shuffling.iter().enumerate() {
shuffled_indices[validator_index.0 as usize] = i;
}
(shuffled_indices, canonical_shuffling)
};
sender
.send_message(NetworkBridgeRxMessage::NewGossipTopology {
session: session_index,
local_index: Some(ValidatorIndex(our_index as _)),
canonical_shuffling,
shuffled_indices,
})
.await;
Ok(())
}
// Durstenfeld algorithm for the Fisher-Yates shuffle
// https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
fn fisher_yates_shuffle<T, R: Rng + ?Sized>(rng: &mut R, items: &mut [T]) {
for i in (1..items.len()).rev() {
// invariant: elements with index > i have been locked in place.
let index = rng.gen_range(0u32..(i as u32 + 1));
items.swap(i, index as usize);
}
}
#[overseer::subsystem(GossipSupport, error = SubsystemError, prefix = self::overseer)]
impl<Context, AD> GossipSupport<AD>
where
AD: AuthorityDiscovery + Clone,
{
fn start(self, ctx: Context) -> SpawnedSubsystem {
let future = self.run(ctx).map(|_| Ok(())).boxed();
SpawnedSubsystem { name: "gossip-support-subsystem", future }
}
}
/// Helper struct to get a nice rendering of unreachable authorities.
struct PrettyAuthorities<I>(I);
impl<'a, I> fmt::Display for PrettyAuthorities<I>
where
I: Iterator<Item = (&'a AuthorityDiscoveryId, &'a HashSet<Multiaddr>)> + Clone,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut authorities = self.0.clone().peekable();
if authorities.peek().is_none() {
write!(f, "None")?;
} else {
write!(f, "\n")?;
}
for (authority, addrs) in authorities {
write!(f, "{}:\n", authority)?;
for addr in addrs {
write!(f, " {}\n", addr)?;
}
write!(f, "\n")?;
}
Ok(())
}
}