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Commits
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  Brad FitzpatrickandBrad Fitzpatrick
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aa5da2e5f2 |
ipn/ipnlocal, control/controlclient: process node adds/removes in constant time
For large tailnets (~50k+ nodes) with frequent peer churn (ephemeral
GitHub Actions workers etc.), tailscaled used to rebuild the full
netmap and fan it out on the IPN bus on every MapResponse that
added or removed a peer. There were two O(N) costs per delta: the
full netmap rebuild + every Notify.NetMap encode to every bus watcher.
This change tackles both:
1. Plumb O(1) peer add/remove through the delta path. PeersChanged
and PeersRemoved no longer prevent the delta happy path; instead,
they mutate the per-node-backend peer map in place.
2. Restrict ipn.Notify.NetMap emission to the platforms whose host
GUIs still depend on it (Windows, macOS, iOS) and migrate
in-tree consumers off it everywhere else:
- Migrate reactive consumers (containerboot, kube agents,
sniproxy, tsconsensus, etc.) off Notify.NetMap to the
previously-added Notify.SelfChange signal so they no longer
have to subscribe to the full netmap.
- Add ipn.NotifyNoNetMap so GUI clients on "legacy-emit" platforms
that have already migrated can opt out of the per-watcher
NetMap encode.
- Gate Notify.NetMap emission on the producer side by a compile-
time GOOS check, so the supporting code is dead-code-eliminated
on Linux and other geese where no GUI consumer needs it.
Re-running BenchmarkGiantTailnet from tstest/largetailnet, which was
added along with baseline numbers on unmodified main in
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Brad FitzpatrickandBrad Fitzpatrick
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ad5436af0d |
tstest/largetailnet, tstest/integration/testcontrol: add in-process large-tailnet benchmark
Add a Go benchmark that exercises a single tailnet client (a [tsnet.Server]
running in the test process) against a synthetic large initial netmap and
a stream of caller-driven peer add/remove deltas, all in-process.
The harness is split in two parts:
- tstest/largetailnet, a reusable package containing a [Streamer]
that hijacks the map long-poll on a [testcontrol.Server] via the new
AltMapStream hook, sends one initial MapResponse with N synthetic
peers, and forwards caller-supplied delta MapResponses on the same
stream. Helpers like MakePeer / AllocPeer build synthetic peers with
unique IDs and addresses derived from the Tailscale ULA range.
- tstest/largetailnet/largetailnet_test.go, BenchmarkGiantTailnet
(headless tailscaled workload, no IPN bus subscriber) and
BenchmarkGiantTailnetBusWatcher (GUI-client workload with one
Notify subscriber attached). Both are gated on
--actually-test-giant-tailnet (skipped by default), stand up an
in-process testcontrol + tsnet.Server, let Up block until the
initial N-peer netmap has been processed, then ResetTimer and run
add+remove pairs via b.Loop. Per-delta sync is via a test-only
[ipnlocal.LocalBackend.AwaitNodeKeyForTest] channel that closes
once the just-added peer key appears in the netmap (no-watcher
variant) or via bus-Notify drain (bus-watcher variant).
To support the hijack, [testcontrol.Server] grows an AltMapStream hook
and a small MapStreamWriter interface for benchmarks/stress tests that
need to drive a controlled MapResponse sequence; the normal serveMap
path is untouched when AltMapStream is nil. The streamer answers
non-streaming "lite" map polls (which controlclient issues before the
streaming long-poll to push HostInfo) with an empty MapResponse and
returns immediately, so the streaming poll that follows is the one
that gets the initial netmap.
The benchmark is intended for before/after comparisons of netmap- and
delta-handling changes targeted at large tailnets. CPU profiles on
unmodified main show the expected O(N) hotspots:
setControlClientStatusLocked / authReconfigLocked /
userspaceEngine.Reconfig / setNetMapLocked, plus JSON encoding of the
full Notify.NetMap to bus watchers (which dominates the BusWatcher
variant).
Median ms/op over 10 runs on unmodified main, by tailnet size N:
N no-watcher bus-watcher
10000 32 166
50000 222 865
100000 504 1765
250000 1551 4696
Recommended invocation:
go test ./tstest/largetailnet/ -run=^$ \
-bench='BenchmarkGiantTailnet(BusWatcher)?$' \
-benchtime=2000x -timeout=10m \
--actually-test-giant-tailnet \
--giant-tailnet-n=250000 \
-cpuprofile=/tmp/giant.cpu.pprof
Updates #12542
Change-Id: I4f5b2bb271a36ba853d5a0ffe82054ef2b15c585
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
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