Пример #1
0
// listenForNodeChanges listens for changes to node status using change feeds.
// This function will block until the query fails
func (c *Cluster) listenForNodeChanges() error {
	// Start listening to changes from a random active node
	node, err := c.GetRandomNode()
	if err != nil {
		return err
	}

	q, err := newQuery(
		DB("rethinkdb").Table("server_status").Changes(),
		map[string]interface{}{},
		c.opts,
	)
	if err != nil {
		return fmt.Errorf("Error building query %s", err)
	}

	cursor, err := node.Query(q)
	if err != nil {
		return err
	}

	// Keep reading node status updates from changefeed
	var result struct {
		NewVal nodeStatus `gorethink:"new_val"`
		OldVal nodeStatus `gorethink:"old_val"`
	}
	for cursor.Next(&result) {
		addr := fmt.Sprintf("%s:%d", result.NewVal.Network.Hostname, result.NewVal.Network.ReqlPort)
		addr = strings.ToLower(addr)

		switch result.NewVal.Status {
		case "connected":
			// Connect to node using exponential backoff (give up after waiting 5s)
			// to give the node time to start-up.
			b := backoff.NewExponentialBackOff()
			b.MaxElapsedTime = time.Second * 5

			backoff.Retry(func() error {
				node, err := c.connectNodeWithStatus(result.NewVal)
				if err == nil {
					if !c.nodeExists(node) {
						c.addNode(node)

						Log.WithFields(logrus.Fields{
							"id":   node.ID,
							"host": node.Host.String(),
						}).Debug("Connected to node")
					}
				}

				return err
			}, b)
		}
	}

	return cursor.Err()
}
Пример #2
0
// discover attempts to find new nodes in the cluster using the current nodes
func (c *Cluster) discover() {
	// Keep retrying with exponential backoff.
	b := backoff.NewExponentialBackOff()
	// Never finish retrying (max interval is still 60s)
	b.MaxElapsedTime = 0

	// Keep trying to discover new nodes
	for {
		backoff.RetryNotify(func() error {
			// If no hosts try seeding nodes
			if len(c.GetNodes()) == 0 {
				c.connectNodes(c.getSeeds())
			}

			return c.listenForNodeChanges()
		}, b, func(err error, wait time.Duration) {
			Log.Debugf("Error discovering hosts %s, waiting %s", err, wait)
		})
	}
}