micro/router/watcher.go

package router

import (
	"errors"
	"time"
)

// ErrWatcherStopped is returned when routing table watcher has been stopped
var ErrWatcherStopped = errors.New("watcher stopped")

// EventType defines routing table event
type EventType int

const (
	// Create is emitted when a new route has been created
	Create EventType = iota
	// Delete is emitted when an existing route has been deleted
	Delete
	// Update is emitted when an existing route has been updated
	Update
)

// String returns human readable event type
func (t EventType) String() string {
	switch t {
	case Create:
		return "create"
	case Delete:
		return "delete"
	case Update:
		return "update"
	default:
		return "unknown"
	}
}

// Event is returned by a call to Next on the watcher.
type Event struct {
	// Timestamp is event timestamp
	Timestamp time.Time
	// ID of the event
	ID string
	// Route is table route
	Route Route
	// Type defines type of event
	Type EventType
}

// Watcher defines routing table watcher interface
// Watcher returns updates to the routing table
type Watcher interface {
	// Next is a blocking call that returns watch result
	Next() (*Event, error)
	// Chan returns event channel
	Chan() (<-chan *Event, error)
	// Stop stops watcher
	Stop()
}

// WatchOption is used to define what routes to watch in the table
type WatchOption func(*WatchOptions)

// WatchOptions are table watcher options
// TODO: expand the options to watch based on other criteria
type WatchOptions struct {
	// Service allows to watch specific service routes
	Service string
}

// WatchService sets what service routes to watch
// Service is the microservice name
func WatchService(s string) WatchOption {
	return func(o *WatchOptions) {
		o.Service = s
	}
}