Method publishBeacon

kv/memberlist/propagation_tracker.go:311–351

(ctx context.Context)

}

func (t *PropagationDelayTracker) publishBeacon(ctx context.Context) {
	// Generate a non-zero beacon ID. We need beaconID > 0 because 0 is used as
	// the "no pending beacon" sentinel value in pendingBeaconID.
	beaconID := rand.Uint64()
	if beaconID == 0 {
		beaconID = 1
	}
	now := time.Now()

	// Set pendingBeaconID before marking as seen to prevent cleanupSeenBeacons
	// from removing it during the CAS operation window.
	t.pendingBeaconID.Store(beaconID)
	defer t.pendingBeaconID.Store(0)

	// Mark as seen before publishing to avoid measuring our own beacon.
	t.markAsSeen(beaconID)

	err := t.kv.CAS(ctx, propagationDelayTrackerKey, t.codec, func(in interface{}) (out interface{}, retry bool, err error) {
		desc := GetOrCreatePropagationDelayTrackerDesc(in)

		// Skip publishing if we already have a beacon with the same ID (extremely rare beacon ID collision).
		// In case of a collision, the beacon ID is tracked as seen anyway, but we don't care given it's a rare case.
		if _, exists := desc.Beacons[beaconID]; exists {
			return nil, false, nil
		}

		desc.Beacons[beaconID] = BeaconDesc{
			PublishedAt: now.UnixMilli(),
			PublishedBy: t.nodeName,
		}

		return desc, true, nil
	})

	if err != nil {
		level.Warn(t.logger).Log("msg", "failed to publish beacon", "err", err)
		return
	}

	t.beaconsPublishedTotal.Inc()
}

// deleteBeacons marks the specified beacons as tombstones by setting their DeletedAt timestamp.
func (t *PropagationDelayTracker) deleteBeacons(ctx context.Context, beaconIDs []uint64) {