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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
//go:build linux
package main
import (
"context"
"fmt"
"log"
"time"
"tailscale.com/client/local"
"tailscale.com/ipn"
)
// ensureServicesNotAdvertised is a function that gets called on containerboot
// termination and ensures that any currently advertised VIPServices get
// unadvertised to give clients time to switch to another node before this one
// is shut down.
func ensureServicesNotAdvertised(ctx context.Context, lc *local.Client) error {
prefs, err := lc.GetPrefs(ctx)
if err != nil {
return fmt.Errorf("error getting prefs: %w", err)
}
if len(prefs.AdvertiseServices) == 0 {
return nil
}
log.Printf("unadvertising services: %v", prefs.AdvertiseServices)
if _, err := lc.EditPrefs(ctx, &ipn.MaskedPrefs{
AdvertiseServicesSet: true,
Prefs: ipn.Prefs{
AdvertiseServices: nil,
},
}); err != nil {
// EditPrefs only returns an error if it fails _set_ its local prefs.
// If it fails to _persist_ the prefs in state, we don't get an error
// and we continue waiting below, as control will failover as usual.
return fmt.Errorf("error setting prefs AdvertiseServices: %w", err)
}
// Services use the same (failover XOR regional routing) mechanism that
// HA subnet routers use. Unfortunately we don't yet get a reliable signal
// from control that it's responded to our unadvertisement, so the best we
// can do is wait for 20 seconds, where 15s is the approximate maximum time
// it should take for control to choose a new primary, and 5s is for buffer.
//
// Note: There is no guarantee that clients have been _informed_ of the new
// primary no matter how long we wait. We would need a mechanism to await
// netmap updates for peers to know for sure.
//
// See https://tailscale.com/kb/1115/high-availability for more details.
// TODO(tomhjp): Wait for a netmap update instead of sleeping when control
// supports that.
select {
case <-ctx.Done():
return nil
case <-time.After(20 * time.Second):
return nil
}
}
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