Golang Datastore.FindLock方法代碼示例

// Run updates the vulnerability database at regular intervals.
func Run(config *config.UpdaterConfig, datastore database.Datastore, st *utils.Stopper) {
	defer st.End()

	// Do not run the updater if there is no config or if the interval is 0.
	if config == nil || config.Interval == 0 {
		log.Infof("updater service is disabled.")
		return
	}

	whoAmI := uuid.New()
	log.Infof("updater service started. lock identifier: %s", whoAmI)

	for {
		var stop bool

		// Determine if this is the first update and define the next update time.
		// The next update time is (last update time + interval) or now if this is the first update.
		nextUpdate := time.Now().UTC()
		lastUpdate, firstUpdate, err := getLastUpdate(datastore)
		if err != nil {
			log.Errorf("an error occured while getting the last update time")
			nextUpdate = nextUpdate.Add(config.Interval)
		} else if firstUpdate == false {
			nextUpdate = lastUpdate.Add(config.Interval)
		}

		// If the next update timer is in the past, then try to update.
		if nextUpdate.Before(time.Now().UTC()) {
			// Attempt to get a lock on the the update.
			log.Debug("attempting to obtain update lock")
			hasLock, hasLockUntil := datastore.Lock(lockName, whoAmI, lockDuration, false)
			if hasLock {
				// Launch update in a new go routine.
				doneC := make(chan bool, 1)
				go func() {
					Update(datastore, firstUpdate)
					doneC <- true
				}()

				for done := false; !done && !stop; {
					select {
					case <-doneC:
						done = true
					case <-time.After(refreshLockDuration):
						// Refresh the lock until the update is done.
						datastore.Lock(lockName, whoAmI, lockDuration, true)
					case <-st.Chan():
						stop = true
					}
				}

				// Unlock the update.
				datastore.Unlock(lockName, whoAmI)

				if stop {
					break
				}
				continue
			} else {
				lockOwner, lockExpiration, err := datastore.FindLock(lockName)
				if err != nil {
					log.Debug("update lock is already taken")
					nextUpdate = hasLockUntil
				} else {
					log.Debugf("update lock is already taken by %s until %v", lockOwner, lockExpiration)
					nextUpdate = lockExpiration
				}
			}
		}

		// Sleep, but remain stoppable until approximately the next update time.
		now := time.Now().UTC()
		waitUntil := nextUpdate.Add(time.Duration(rand.ExpFloat64()/0.5) * time.Second)
		log.Debugf("next update attempt scheduled for %v.", waitUntil)
		if !waitUntil.Before(now) {
			if !st.Sleep(waitUntil.Sub(time.Now())) {
				break
			}
		}
	}

	// Clean resources.
	for _, metadataFetcher := range metadataFetchers {
		metadataFetcher.Clean()
	}
	for _, fetcher := range fetchers {
		fetcher.Clean()
	}

	log.Info("updater service stopped")
}