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ipn/ipnlocal: do not stall event processing for appc route updates (#17663)

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A follow-up to #17411. Put AppConnector events into a task queue, as they may
take some time to process. Ensure that the queue is stopped at shutdown so that
cleanup will remain orderly.

Because events are delivered on a separate goroutine, slow processing of an
event does not cause an immediate problem; however, a subscriber that blocks
for a long time will push back on the bus as a whole. See
https://godoc.org/tailscale.com/util/eventbus#hdr-Expected_subscriber_behavior
for more discussion.

Updates #17192
Updates #15160

Change-Id: Ib313cc68aec273daf2b1ad79538266c81ef063e3
Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>
(cherry picked from commit 06b092388e)
This commit is contained in:
M. J. Fromberger
2025-10-29 08:37:19 -07:00
committed by Tom Proctor
parent faca4c08b7
commit 6e2f2bb31a
1 changed files with 11 additions and 6 deletions
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17
ipn/ipnlocal/local.go
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@@ -87,6 +87,7 @@ import (
"tailscale.com/util/clientmetric"
"tailscale.com/util/dnsname"
"tailscale.com/util/eventbus"
"tailscale.com/util/execqueue"
"tailscale.com/util/goroutines"
"tailscale.com/util/mak"
"tailscale.com/util/osuser"
@@ -187,6 +188,7 @@ type LocalBackend struct {
statsLogf logger.Logf // for printing peers stats on change
sys *tsd.System
eventSubs eventbus.Monitor
appcTask execqueue.ExecQueue // handles updates from appc
health *health.Tracker // always non-nil
polc policyclient.Client // always non-nil
@@ -642,12 +644,14 @@ func (b *LocalBackend) consumeEventbusTopics(ec *eventbus.Client) func(*eventbus
// We need to find a way to ensure that changes to the backend state are applied
// consistently in the presnce of profile changes, which currently may not happen in
// a single atomic step. See: https://github.com/tailscale/tailscale/issues/17414
if err := b.AdvertiseRoute(ru.Advertise...); err != nil {
b.logf("appc: failed to advertise routes: %v: %v", ru.Advertise, err)
}
if err := b.UnadvertiseRoute(ru.Unadvertise...); err != nil {
b.logf("appc: failed to unadvertise routes: %v: %v", ru.Unadvertise, err)
}
b.appcTask.Add(func() {
if err := b.AdvertiseRoute(ru.Advertise...); err != nil {
b.logf("appc: failed to advertise routes: %v: %v", ru.Advertise, err)
}
if err := b.UnadvertiseRoute(ru.Unadvertise...); err != nil {
b.logf("appc: failed to unadvertise routes: %v: %v", ru.Unadvertise, err)
}
})
case ri := <-storeRoutesSub.Events():
// Whether or not routes should be stored can change over time.
shouldStoreRoutes := b.ControlKnobs().AppCStoreRoutes.Load()
@@ -1113,6 +1117,7 @@ func (b *LocalBackend) Shutdown() {
// they can deadlock with c.Shutdown().
// 2. LocalBackend.consumeEventbusTopics event handlers may not guard against
// undesirable post/in-progress LocalBackend.Shutdown() behaviors.
b.appcTask.Shutdown()
b.eventSubs.Close()
b.em.close()