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state: gate reconnect PolicyChange on NodeNeedsPeerRecompute

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Connect and Disconnect appended change.PolicyChange() on every reconnect. PolicyChange sets RequiresRuntimePeerComputation, so the batcher rebuilt a full netmap (packet filters, SSH policy, peer serialization) for every connected node — O(N) per reconnect, O(N^2) on a restart storm. On a small VM this saturated CPU after the v0.28 -> v0.29 upgrade.

Emit it only when the node's online state changes what peers compute: subnet routers, relay targets, and via targets. An ordinary reconnect now sends just the lightweight online/offline peer patch. Relay and via targets still recompute, so peers drop a stale PeerRelay allocation when a relay goes offline.

Fixes #3293
This commit is contained in:
Kristoffer Dalby 2026-06-03 10:25:52 +00:00
parent bceac495f9
commit 7706552c99
2 changed files with 185 additions and 10 deletions
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27
hscontrol/state/state.go
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@ -594,9 +594,14 @@ func (s *State) Connect(id types.NodeID) ([]change.Change, uint64) {
c = append(c, change.NodeAdded(id))
}
// Coming online may re-enable cap/relay grants and identity-based
// aliases targeting this node, so peers need a fresh netmap.
c = append(c, change.PolicyChange())
// Only a node whose online state changes what peers compute (a subnet
// router, relay target, or via target) needs a full peer recompute.
// An ordinary node coming online just sends the lightweight online
// patch above; emitting a PolicyChange for it would force every peer
// to rebuild its netmap on every reconnect.
if s.polMan.NodeNeedsPeerRecompute(node) {
c = append(c, change.PolicyChange())
}
return c, epoch
}
@ -648,13 +653,15 @@ func (s *State) Disconnect(id types.NodeID, epoch uint64) ([]change.Change, erro
c = change.Change{}
}
// Going offline can affect policy compilation beyond subnet routes
// (cap/relay grants, tag/group aliases, via routes), so peers need
// a fresh netmap regardless of whether the primary moved.
//
// TODO(kradalby): fires one full netmap recompute per peer on
// every connect/disconnect. Coalesce in mapper/batcher.go:addToBatch.
cs := []change.Change{change.NodeOfflineFor(node), c, change.PolicyChange()}
// Only a node whose online state changes what peers compute (a subnet
// router, relay target, or via target) needs a full peer recompute.
// An ordinary node going offline just sends the lightweight offline
// patch; emitting a PolicyChange for it would force every peer to
// rebuild its netmap on every disconnect.
cs := []change.Change{change.NodeOfflineFor(node), c}
if s.polMan.NodeNeedsPeerRecompute(node) {
cs = append(cs, change.PolicyChange())
}
return cs, nil
}