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Fix: PeerManager doesn't remove "outbound only" peers which should be pruned (#3236)

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## Issue Addressed

This is one step to address https://github.com/sigp/lighthouse/issues/3092 before introducing `quickcheck`.

I noticed an issue while I was reading the pruning implementation `PeerManager::prune_excess_peers()`. If a peer with the following condition, **`outbound_peers_pruned` counter increases but the peer is not pushed to `peers_to_prune`**.

- [outbound only](1e4ac8a4b9/beacon_node/lighthouse_network/src/peer_manager/mod.rs (L1018))
- [min_subnet_count <= MIN_SYNC_COMMITTEE_PEERS](1e4ac8a4b9/beacon_node/lighthouse_network/src/peer_manager/mod.rs (L1047))

As a result, PeerManager doesn't remove "outbound" peers which should be pruned.

Note: [`subnet_to_peer`](e0d673ea86/beacon_node/lighthouse_network/src/peer_manager/mod.rs (L999)) (HashMap) doesn't guarantee a particular order of iteration. So whether the test fails depend on the order of iteration.
This commit is contained in:
Akihito Nakano 2022-06-06 05:51:10 +00:00
parent 3d51f24717
commit a6d2ed6119
1 changed files with 179 additions and 13 deletions
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192
beacon_node/lighthouse_network/src/peer_manager/mod.rs
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@ -1015,20 +1015,17 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
let mut removed_peer_index = None; let mut removed_peer_index = None;
for (index, (candidate_peer, info)) in peers_on_subnet.iter().enumerate() { for (index, (candidate_peer, info)) in peers_on_subnet.iter().enumerate() {
// Ensure we don't remove too many outbound peers // Ensure we don't remove too many outbound peers
if info.is_outbound_only() { if info.is_outbound_only()
if self.target_outbound_peers() && self.target_outbound_peers()
< connected_outbound_peer_count >= connected_outbound_peer_count
.saturating_sub(outbound_peers_pruned) .saturating_sub(outbound_peers_pruned)
{ {
outbound_peers_pruned += 1; // Restart the main loop with the outbound peer removed from
} else { // the list. This will lower the peers per subnet count and
// Restart the main loop with the outbound peer removed from // potentially a new subnet may be chosen to remove peers. This
// the list. This will lower the peers per subnet count and // can occur recursively until we have no peers left to choose
// potentially a new subnet may be chosen to remove peers. This // from.
// can occur recursively until we have no peers left to choose continue;
// from.
continue;
}
} }
// Check the sync committee // Check the sync committee
@ -1051,6 +1048,9 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
} }
} }
if info.is_outbound_only() {
outbound_peers_pruned += 1;
}
// This peer is suitable to be pruned // This peer is suitable to be pruned
removed_peer_index = Some(index); removed_peer_index = Some(index);
break; break;
@ -1885,4 +1885,170 @@ mod tests {
assert!(!connected_peers.contains(&peers[1])); assert!(!connected_peers.contains(&peers[1]));
assert!(!connected_peers.contains(&peers[2])); assert!(!connected_peers.contains(&peers[2]));
} }
/// This test is for reproducing the issue:
/// https://github.com/sigp/lighthouse/pull/3236#issue-1256432659
///
/// Whether the issue happens depends on `subnet_to_peer` (HashMap), since HashMap doesn't
/// guarantee a particular order of iteration. So we repeat the test case to try to reproduce
/// the issue.
#[tokio::test]
async fn test_peer_manager_prune_based_on_subnet_count_repeat() {
for _ in 0..100 {
test_peer_manager_prune_based_on_subnet_count().await;
}
}
/// Test the pruning logic to prioritize peers with the most subnets. This test specifies
/// the connection direction for the peers.
/// Either Peer 4 or 5 is expected to be removed in this test case.
///
/// Create 8 peers.
/// Peer0 (out) : Subnet 1, Sync-committee-1
/// Peer1 (out) : Subnet 1, Sync-committee-1
/// Peer2 (out) : Subnet 2, Sync-committee-2
/// Peer3 (out) : Subnet 2, Sync-committee-2
/// Peer4 (out) : Subnet 3
/// Peer5 (out) : Subnet 3
/// Peer6 (in) : Subnet 4
/// Peer7 (in) : Subnet 5
async fn test_peer_manager_prune_based_on_subnet_count() {
let target = 7;
let mut peer_manager = build_peer_manager(target).await;
// Create 8 peers to connect to.
let mut peers = Vec::new();
for x in 0..8 {
let peer = PeerId::random();
// Have some of the peers be on a long-lived subnet
let mut attnets = crate::types::EnrAttestationBitfield::<E>::new();
let mut syncnets = crate::types::EnrSyncCommitteeBitfield::<E>::new();
match x {
0 => {
peer_manager.inject_connect_outgoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(1, true).unwrap();
syncnets.set(1, true).unwrap();
}
1 => {
peer_manager.inject_connect_outgoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(1, true).unwrap();
syncnets.set(1, true).unwrap();
}
2 => {
peer_manager.inject_connect_outgoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(2, true).unwrap();
syncnets.set(2, true).unwrap();
}
3 => {
peer_manager.inject_connect_outgoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(2, true).unwrap();
syncnets.set(2, true).unwrap();
}
4 => {
peer_manager.inject_connect_outgoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(3, true).unwrap();
}
5 => {
peer_manager.inject_connect_outgoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(3, true).unwrap();
}
6 => {
peer_manager.inject_connect_ingoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(4, true).unwrap();
}
7 => {
peer_manager.inject_connect_ingoing(
&peer,
"/ip4/0.0.0.0".parse().unwrap(),
None,
);
attnets.set(5, true).unwrap();
}
_ => unreachable!(),
}
let metadata = crate::rpc::MetaDataV2 {
seq_number: 0,
attnets,
syncnets,
};
peer_manager
.network_globals
.peers
.write()
.peer_info_mut(&peer)
.unwrap()
.set_meta_data(MetaData::V2(metadata));
let long_lived_subnets = peer_manager
.network_globals
.peers
.read()
.peer_info(&peer)
.unwrap()
.long_lived_subnets();
println!("{},{}", x, peer);
for subnet in long_lived_subnets {
println!("Subnet: {:?}", subnet);
peer_manager
.network_globals
.peers
.write()
.add_subscription(&peer, subnet);
}
peers.push(peer);
}
// Perform the heartbeat.
peer_manager.heartbeat();
// Tests that when we are over the target peer limit, after disconnecting an unhealthy peer,
// the number of connected peers updates and we will not remove too many peers.
assert_eq!(
peer_manager.network_globals.connected_or_dialing_peers(),
target
);
let connected_peers: std::collections::HashSet<_> = peer_manager
.network_globals
.peers
.read()
.connected_or_dialing_peers()
.cloned()
.collect();
// Either peer 4 or 5 should be removed.
// Check that we keep 6 and 7 peers, which we have few on a particular subnet.
assert!(connected_peers.contains(&peers[6]));
assert!(connected_peers.contains(&peers[7]));
}
} }