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ipn/ipnlocal: use eventbus.SubscribeFunc in LocalBackend (#17524)
This does not change which subscriptions are made, it only swaps them to use the SubscribeFunc API instead of Subscribe. Updates #15160 Updates #17487 Change-Id: Id56027836c96942206200567a118f8bcf9c07f64 Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>
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M. J. Fromberger
GitHub
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@ -180,13 +180,13 @@ var (
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// state machine generates events back out to zero or more components.
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type LocalBackend struct {
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// Elements that are thread-safe or constant after construction.
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ctx context.Context // canceled by [LocalBackend.Shutdown]
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ctxCancel context.CancelCauseFunc // cancels ctx
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logf logger.Logf // general logging
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keyLogf logger.Logf // for printing list of peers on change
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statsLogf logger.Logf // for printing peers stats on change
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sys *tsd.System
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eventSubs eventbus.Monitor
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ctx context.Context // canceled by [LocalBackend.Shutdown]
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ctxCancel context.CancelCauseFunc // cancels ctx
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logf logger.Logf // general logging
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keyLogf logger.Logf // for printing list of peers on change
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statsLogf logger.Logf // for printing peers stats on change
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sys *tsd.System
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eventClient *eventbus.Client
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health *health.Tracker // always non-nil
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polc policyclient.Client // always non-nil
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@ -589,74 +589,44 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, sys *tsd.System, lo
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// Start the event bus late, once all the assignments above are done.
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// (See previous race in tailscale/tailscale#17252)
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ec := b.Sys().Bus.Get().Client("ipnlocal.LocalBackend")
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b.eventSubs = ec.Monitor(b.consumeEventbusTopics(ec))
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b.eventClient = ec
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eventbus.SubscribeFunc(ec, b.onClientVersion)
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eventbus.SubscribeFunc(ec, func(au controlclient.AutoUpdate) {
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b.onTailnetDefaultAutoUpdate(au.Value)
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})
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eventbus.SubscribeFunc(ec, func(cd netmon.ChangeDelta) { b.linkChange(&cd) })
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if buildfeatures.HasHealth {
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eventbus.SubscribeFunc(ec, b.onHealthChange)
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}
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if buildfeatures.HasPortList {
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eventbus.SubscribeFunc(ec, b.setPortlistServices)
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}
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eventbus.SubscribeFunc(ec, b.onAppConnectorRouteUpdate)
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eventbus.SubscribeFunc(ec, b.onAppConnectorStoreRoutes)
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return b, nil
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}
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// consumeEventbusTopics consumes events from all relevant
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// [eventbus.Subscriber]'s and passes them to their related handler. Events are
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// always handled in the order they are received, i.e. the next event is not
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// read until the previous event's handler has returned. It returns when the
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// [eventbus.Client] is closed.
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func (b *LocalBackend) consumeEventbusTopics(ec *eventbus.Client) func(*eventbus.Client) {
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clientVersionSub := eventbus.Subscribe[tailcfg.ClientVersion](ec)
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autoUpdateSub := eventbus.Subscribe[controlclient.AutoUpdate](ec)
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var healthChange <-chan health.Change
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if buildfeatures.HasHealth {
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healthChangeSub := eventbus.Subscribe[health.Change](ec)
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healthChange = healthChangeSub.Events()
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func (b *LocalBackend) onAppConnectorRouteUpdate(ru appctype.RouteUpdate) {
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// TODO(creachadair, 2025-10-02): It is currently possible for updates produced under
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// one profile to arrive and be applied after a switch to another profile.
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// We need to find a way to ensure that changes to the backend state are applied
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// consistently in the presnce of profile changes, which currently may not happen in
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// a single atomic step. See: https://github.com/tailscale/tailscale/issues/17414
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if err := b.AdvertiseRoute(ru.Advertise...); err != nil {
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b.logf("appc: failed to advertise routes: %v: %v", ru.Advertise, err)
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}
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changeDeltaSub := eventbus.Subscribe[netmon.ChangeDelta](ec)
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routeUpdateSub := eventbus.Subscribe[appctype.RouteUpdate](ec)
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storeRoutesSub := eventbus.Subscribe[appctype.RouteInfo](ec)
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var portlist <-chan PortlistServices
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if buildfeatures.HasPortList {
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portlistSub := eventbus.Subscribe[PortlistServices](ec)
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portlist = portlistSub.Events()
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if err := b.UnadvertiseRoute(ru.Unadvertise...); err != nil {
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b.logf("appc: failed to unadvertise routes: %v: %v", ru.Unadvertise, err)
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}
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}
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return func(ec *eventbus.Client) {
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for {
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select {
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case <-ec.Done():
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return
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case clientVersion := <-clientVersionSub.Events():
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b.onClientVersion(&clientVersion)
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case au := <-autoUpdateSub.Events():
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b.onTailnetDefaultAutoUpdate(au.Value)
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case change := <-healthChange:
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b.onHealthChange(change)
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case changeDelta := <-changeDeltaSub.Events():
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b.linkChange(&changeDelta)
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case pl := <-portlist:
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if buildfeatures.HasPortList { // redundant, but explicit for linker deadcode and humans
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b.setPortlistServices(pl)
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}
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case ru := <-routeUpdateSub.Events():
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// TODO(creachadair, 2025-10-02): It is currently possible for updates produced under
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// one profile to arrive and be applied after a switch to another profile.
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// We need to find a way to ensure that changes to the backend state are applied
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// consistently in the presnce of profile changes, which currently may not happen in
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// a single atomic step. See: https://github.com/tailscale/tailscale/issues/17414
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if err := b.AdvertiseRoute(ru.Advertise...); err != nil {
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b.logf("appc: failed to advertise routes: %v: %v", ru.Advertise, err)
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}
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if err := b.UnadvertiseRoute(ru.Unadvertise...); err != nil {
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b.logf("appc: failed to unadvertise routes: %v: %v", ru.Unadvertise, err)
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}
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case ri := <-storeRoutesSub.Events():
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// Whether or not routes should be stored can change over time.
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shouldStoreRoutes := b.ControlKnobs().AppCStoreRoutes.Load()
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if shouldStoreRoutes {
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if err := b.storeRouteInfo(ri); err != nil {
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b.logf("appc: failed to store route info: %v", err)
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}
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}
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}
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func (b *LocalBackend) onAppConnectorStoreRoutes(ri appctype.RouteInfo) {
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// Whether or not routes should be stored can change over time.
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shouldStoreRoutes := b.ControlKnobs().AppCStoreRoutes.Load()
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if shouldStoreRoutes {
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if err := b.storeRouteInfo(ri); err != nil {
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b.logf("appc: failed to store route info: %v", err)
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}
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}
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}
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@ -1107,13 +1077,12 @@ func (b *LocalBackend) ClearCaptureSink() {
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// Shutdown halts the backend and all its sub-components. The backend
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// can no longer be used after Shutdown returns.
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func (b *LocalBackend) Shutdown() {
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// Close the [eventbus.Client] and wait for LocalBackend.consumeEventbusTopics
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// to return. Do this before acquiring b.mu:
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// 1. LocalBackend.consumeEventbusTopics event handlers also acquire b.mu,
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// they can deadlock with c.Shutdown().
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// 2. LocalBackend.consumeEventbusTopics event handlers may not guard against
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// undesirable post/in-progress LocalBackend.Shutdown() behaviors.
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b.eventSubs.Close()
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// Close the [eventbus.Client] to wait for subscribers to
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// return before acquiring b.mu:
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// 1. Event handlers also acquire b.mu, they can deadlock with c.Shutdown().
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// 2. Event handlers may not guard against undesirable post/in-progress
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// LocalBackend.Shutdown() behaviors.
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b.eventClient.Close()
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b.em.close()
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