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control/controlclient: remove optimization that was more convoluted than useful

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While working on #13390, I ran across this non-idiomatic
pointer-to-view and parallel-sorted-map accounting code that was all
just to avoid a sort later.

But the sort later when building a new netmap.NetworkMap is already a
drop in the bucket of CPU compared to how much work & allocs
mapSession.netmap and LocalBackend's spamming of the full netmap
(potentially tens of thousands of peers, MBs of JSON) out to IPNBus
clients for any tiny little change (node changing online status, etc).

Removing the parallel sorted slice let everything be simpler to reason
about, so this does that. The sort might take a bit more CPU time now
in theory, but in practice for any netmap size for which it'd matter,
the quadratic netmap IPN bus spam (which we need to fix soon) will
overshadow that little sort.

Updates #13390
Updates #1909

Change-Id: I3092d7c67dc10b2a0f141496fe0e7e98ccc07712
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2025-01-03 10:10:16 -08:00
committed by Brad Fitzpatrick
parent 1e2e319e7d
commit 402fc9d65f
2 changed files with 30 additions and 51 deletions
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68
control/controlclient/map.go
View File

@@ -14,7 +14,6 @@ import (
"runtime"
"runtime/debug"
"slices"
"sort"
"strconv"
"sync"
"time"
@@ -31,6 +30,7 @@ import (
"tailscale.com/util/clientmetric"
"tailscale.com/util/mak"
"tailscale.com/util/set"
"tailscale.com/util/slicesx"
"tailscale.com/wgengine/filter"
)
@@ -75,8 +75,7 @@ type mapSession struct {
lastPrintMap time.Time
lastNode tailcfg.NodeView
lastCapSet set.Set[tailcfg.NodeCapability]
peers map[tailcfg.NodeID]*tailcfg.NodeView // pointer to view (oddly). same pointers as sortedPeers.
sortedPeers []*tailcfg.NodeView // same pointers as peers, but sorted by Node.ID
peers map[tailcfg.NodeID]tailcfg.NodeView
lastDNSConfig *tailcfg.DNSConfig
lastDERPMap *tailcfg.DERPMap
lastUserProfile map[tailcfg.UserID]tailcfg.UserProfile
@@ -366,16 +365,11 @@ var (
patchifiedPeerEqual = clientmetric.NewCounter("controlclient_patchified_peer_equal")
)
// updatePeersStateFromResponseres updates ms.peers and ms.sortedPeers from res. It takes ownership of res.
// updatePeersStateFromResponseres updates ms.peers from resp.
// It takes ownership of resp.
func (ms *mapSession) updatePeersStateFromResponse(resp *tailcfg.MapResponse) (stats updateStats) {
defer func() {
if stats.removed > 0 || stats.added > 0 {
ms.rebuildSorted()
}
}()
if ms.peers == nil {
ms.peers = make(map[tailcfg.NodeID]*tailcfg.NodeView)
ms.peers = make(map[tailcfg.NodeID]tailcfg.NodeView)
}
if len(resp.Peers) > 0 {
@@ -384,12 +378,12 @@ func (ms *mapSession) updatePeersStateFromResponse(resp *tailcfg.MapResponse) (s
keep := make(map[tailcfg.NodeID]bool, len(resp.Peers))
for _, n := range resp.Peers {
keep[n.ID] = true
if vp, ok := ms.peers[n.ID]; ok {
lenBefore := len(ms.peers)
ms.peers[n.ID] = n.View()
if len(ms.peers) == lenBefore {
stats.changed++
*vp = n.View()
} else {
stats.added++
ms.peers[n.ID] = ptr.To(n.View())
}
}
for id := range ms.peers {
@@ -410,12 +404,12 @@ func (ms *mapSession) updatePeersStateFromResponse(resp *tailcfg.MapResponse) (s
}
for _, n := range resp.PeersChanged {
if vp, ok := ms.peers[n.ID]; ok {
lenBefore := len(ms.peers)
ms.peers[n.ID] = n.View()
if len(ms.peers) == lenBefore {
stats.changed++
*vp = n.View()
} else {
stats.added++
ms.peers[n.ID] = ptr.To(n.View())
}
}
@@ -427,7 +421,7 @@ func (ms *mapSession) updatePeersStateFromResponse(resp *tailcfg.MapResponse) (s
} else {
mut.LastSeen = nil
}
*vp = mut.View()
ms.peers[nodeID] = mut.View()
stats.changed++
}
}
@@ -436,7 +430,7 @@ func (ms *mapSession) updatePeersStateFromResponse(resp *tailcfg.MapResponse) (s
if vp, ok := ms.peers[nodeID]; ok {
mut := vp.AsStruct()
mut.Online = ptr.To(online)
*vp = mut.View()
ms.peers[nodeID] = mut.View()
stats.changed++
}
}
@@ -488,31 +482,12 @@ func (ms *mapSession) updatePeersStateFromResponse(resp *tailcfg.MapResponse) (s
mut.CapMap = v
patchCapMap.Add(1)
}
*vp = mut.View()
ms.peers[pc.NodeID] = mut.View()
}
return
}
// rebuildSorted rebuilds ms.sortedPeers from ms.peers. It should be called
// after any additions or removals from peers.
func (ms *mapSession) rebuildSorted() {
if ms.sortedPeers == nil {
ms.sortedPeers = make([]*tailcfg.NodeView, 0, len(ms.peers))
} else {
if len(ms.sortedPeers) > len(ms.peers) {
clear(ms.sortedPeers[len(ms.peers):])
}
ms.sortedPeers = ms.sortedPeers[:0]
}
for _, p := range ms.peers {
ms.sortedPeers = append(ms.sortedPeers, p)
}
sort.Slice(ms.sortedPeers, func(i, j int) bool {
return ms.sortedPeers[i].ID() < ms.sortedPeers[j].ID()
})
}
func (ms *mapSession) addUserProfile(nm *netmap.NetworkMap, userID tailcfg.UserID) {
if userID == 0 {
return
@@ -576,7 +551,7 @@ func (ms *mapSession) patchifyPeer(n *tailcfg.Node) (_ *tailcfg.PeerChange, ok b
if !ok {
return nil, false
}
return peerChangeDiff(*was, n)
return peerChangeDiff(was, n)
}
// peerChangeDiff returns the difference from 'was' to 'n', if possible.
@@ -778,14 +753,19 @@ func peerChangeDiff(was tailcfg.NodeView, n *tailcfg.Node) (_ *tailcfg.PeerChang
return ret, true
}
func (ms *mapSession) sortedPeers() []tailcfg.NodeView {
ret := slicesx.MapValues(ms.peers)
slices.SortFunc(ret, func(a, b tailcfg.NodeView) int {
return cmp.Compare(a.ID(), b.ID())
})
return ret
}
// netmap returns a fully populated NetworkMap from the last state seen from
// a call to updateStateFromResponse, filling in omitted
// information from prior MapResponse values.
func (ms *mapSession) netmap() *netmap.NetworkMap {
peerViews := make([]tailcfg.NodeView, len(ms.sortedPeers))
for i, vp := range ms.sortedPeers {
peerViews[i] = *vp
}
peerViews := ms.sortedPeers()
nm := &netmap.NetworkMap{
NodeKey: ms.publicNodeKey,