Move OnPoll into the Service method set

This feels a lot better because now `OnPoll` works in a similar way to
`OnReceiveWebhook` (called on a `Service`) rather than have this strange
global-per-service-type struct.

src/github.com/matrix-org/go-neb/api.go

@@ -309,7 +309,7 @@ func (s *configureServiceHandler) OnIncomingRequest(req *http.Request) (interfac
 
 	// Start any polling NOW because they may decide to stop it in PostRegister, and we want to make
 	// sure we'll actually stop.
-	if service.Poller() != nil {
+	if _, ok := service.(types.Poller); ok {
 		if err := polling.StartPolling(service); err != nil {
 			log.WithFields(log.Fields{
 				"service_id": service.ServiceID(),

src/github.com/matrix-org/go-neb/polling/polling.go

@@ -1,7 +1,6 @@
 package polling
 
 import (
-	"fmt"
 	log "github.com/Sirupsen/logrus"
 	"github.com/matrix-org/go-neb/clients"
 	"github.com/matrix-org/go-neb/database"
@@ -27,10 +26,7 @@ func SetClients(clis *clients.Clients) {
 // Start polling already existing services
 func Start() error {
 	// Work out which service types require polling
-	for serviceType, poller := range types.PollersByType() {
-		if poller == nil {
-			continue
-		}
+	for _, serviceType := range types.PollingServiceTypes() {
 		// Query for all services with said service type
 		srvs, err := database.GetServiceDB().LoadServicesByType(serviceType)
 		if err != nil {
@@ -50,15 +46,11 @@ func Start() error {
 // so there may be a brief period of overlap. It is safe to immediately call `StopPolling(service)` to immediately terminate
 // this poll.
 func StartPolling(service types.Service) error {
-	p := types.PollersByType()[service.ServiceType()]
-	if p == nil {
-		return fmt.Errorf("Service %s (type=%s) doesn't have a Poller", service.ServiceID(), service.ServiceType())
-	}
 	// Set the poll time BEFORE spinning off the goroutine in case the caller immediately stops us. If we don't do this here,
 	// we risk them setting the ts to 0 BEFORE we've set the start time, resulting in a poll when one was not intended.
 	ts := time.Now().UnixNano()
 	setPollStartTime(service, ts)
-	go pollLoop(service, p, ts)
+	go pollLoop(service, ts)
 	return nil
 }
 
@@ -73,13 +65,17 @@ func StopPolling(service types.Service) {
 
 // pollLoop begins the polling loop for this service. Does not return, so call this
 // as a goroutine!
-func pollLoop(service types.Service, poller types.Poller, ts int64) {
+func pollLoop(service types.Service, ts int64) {
 	logger := log.WithFields(log.Fields{
-		"timestamp":     ts,
-		"service_id":    service.ServiceID(),
-		"service_type":  service.ServiceType(),
-		"interval_secs": poller.IntervalSecs(),
+		"timestamp":    ts,
+		"service_id":   service.ServiceID(),
+		"service_type": service.ServiceType(),
 	})
+	poller, ok := service.(types.Poller)
+	if !ok {
+		logger.Error("Service is not a Poller.")
+		return
+	}
 	logger.Info("Starting polling loop")
 	cli, err := clientPool.Client(service.ServiceUserID())
 	if err != nil {
@@ -87,12 +83,21 @@ func pollLoop(service types.Service, poller types.Poller, ts int64) {
 		return
 	}
 	for {
-		poller.OnPoll(service, cli)
+		logger.Info("OnPoll")
+		nextTime := poller.OnPoll(cli)
 		if pollTimeChanged(service, ts) {
 			logger.Info("Terminating poll.")
 			break
 		}
-		time.Sleep(time.Duration(poller.IntervalSecs()) * time.Second)
+		// work out how long to sleep
+		if nextTime.Unix() == 0 {
+			logger.Info("Terminating poll - OnPoll returned 0")
+			break
+		}
+		now := time.Now()
+		logger.Info("Sleeping for ", nextTime.Sub(now))
+		time.Sleep(nextTime.Sub(now))
+
 		if pollTimeChanged(service, ts) {
 			logger.Info("Terminating poll.")
 			break

src/github.com/matrix-org/go-neb/services/rssbot/rssbot.go

@@ -15,25 +15,75 @@ import (
 
 const minPollingIntervalSeconds = 60 // 1 min (News feeds can be genuinely spammy)
 
-type feedPoller struct{}
+type rssBotService struct {
+	types.DefaultService
+	id            string
+	serviceUserID string
+	Feeds         map[string]struct { // feed_url => { }
+		PollIntervalMins         int      `json:"poll_interval_mins"`
+		Rooms                    []string `json:"rooms"`
+		NextPollTimestampSecs    int64    // Internal: When we should poll again
+		FeedUpdatedTimestampSecs int64    // Internal: The last time the feed was updated
+	} `json:"feeds"`
+}
+
+func (s *rssBotService) ServiceUserID() string { return s.serviceUserID }
+func (s *rssBotService) ServiceID() string     { return s.id }
+func (s *rssBotService) ServiceType() string   { return "rssbot" }
+
+// Register will check the liveness of each RSS feed given. If all feeds check out okay, no error is returned.
+func (s *rssBotService) Register(oldService types.Service, client *matrix.Client) error {
+	if len(s.Feeds) == 0 {
+		// this is an error UNLESS the old service had some feeds in which case they are deleting us :(
+		var numOldFeeds int
+		oldFeedService, ok := oldService.(*rssBotService)
+		if !ok {
+			log.WithField("service", oldService).Error("Old service isn't a rssBotService")
+		} else {
+			numOldFeeds = len(oldFeedService.Feeds)
+		}
+		if numOldFeeds == 0 {
+			return errors.New("An RSS feed must be specified.")
+		}
+		return nil
+	}
+	// Make sure we can parse the feed
+	for feedURL, feedInfo := range s.Feeds {
+		fp := gofeed.NewParser()
+		if _, err := fp.ParseURL(feedURL); err != nil {
+			return fmt.Errorf("Failed to read URL %s: %s", feedURL, err.Error())
+		}
+		if len(feedInfo.Rooms) == 0 {
+			return fmt.Errorf("Feed %s has no rooms to send updates to", feedURL)
+		}
+	}
+	return nil
+}
 
-func (p *feedPoller) IntervalSecs() int64 { return 10 }
-func (p *feedPoller) OnPoll(s types.Service, cli *matrix.Client) {
+func (s *rssBotService) PostRegister(oldService types.Service) {
+	if len(s.Feeds) == 0 { // bye-bye :(
+		logger := log.WithFields(log.Fields{
+			"service_id":   s.ServiceID(),
+			"service_type": s.ServiceType(),
+		})
+		logger.Info("Deleting service: No feeds remaining.")
+		polling.StopPolling(s)
+		if err := database.GetServiceDB().DeleteService(s.ServiceID()); err != nil {
+			logger.WithError(err).Error("Failed to delete service")
+		}
+	}
+}
+
+func (s *rssBotService) OnPoll(cli *matrix.Client) time.Time {
 	logger := log.WithFields(log.Fields{
 		"service_id":   s.ServiceID(),
 		"service_type": s.ServiceType(),
 	})
-
-	frService, ok := s.(*rssBotService)
-	if !ok {
-		logger.Error("RSSBot: OnPoll called without a Feed Service instance")
-		return
-	}
 	now := time.Now().Unix() // Second resolution
 
 	// Work out which feeds should be polled
 	var pollFeeds []string
-	for u, feedInfo := range frService.Feeds {
+	for u, feedInfo := range s.Feeds {
 		if feedInfo.NextPollTimestampSecs == 0 || now >= feedInfo.NextPollTimestampSecs {
 			// re-query this feed
 			pollFeeds = append(pollFeeds, u)
@@ -41,12 +91,12 @@ func (p *feedPoller) OnPoll(s types.Service, cli *matrix.Client) {
 	}
 
 	if len(pollFeeds) == 0 {
-		return
+		return s.nextTimestamp()
 	}
 
 	// Query each feed and send new items to subscribed rooms
 	for _, u := range pollFeeds {
-		feed, items, err := p.queryFeed(frService, u)
+		feed, items, err := s.queryFeed(u)
 		if err != nil {
 			logger.WithField("feed_url", u).WithError(err).Error("Failed to query feed")
 			continue
@@ -54,7 +104,7 @@ func (p *feedPoller) OnPoll(s types.Service, cli *matrix.Client) {
 		// Loop backwards since [0] is the most recent and we want to send in chronological order
 		for i := len(items) - 1; i >= 0; i-- {
 			item := items[i]
-			if err := p.sendToRooms(frService, cli, u, feed, item); err != nil {
+			if err := s.sendToRooms(cli, u, feed, item); err != nil {
 				logger.WithFields(log.Fields{
 					"feed_url":   u,
 					log.ErrorKey: err,
@@ -65,13 +115,26 @@ func (p *feedPoller) OnPoll(s types.Service, cli *matrix.Client) {
 	}
 
 	// Persist the service to save the next poll times
-	if _, err := database.GetServiceDB().StoreService(frService); err != nil {
+	if _, err := database.GetServiceDB().StoreService(s); err != nil {
 		logger.WithError(err).Error("Failed to persist next poll times for service")
 	}
+
+	return s.nextTimestamp()
+}
+
+func (s *rssBotService) nextTimestamp() time.Time {
+	// return the earliest next poll ts
+	var earliestNextTs int64
+	for _, feedInfo := range s.Feeds {
+		if earliestNextTs == 0 || feedInfo.NextPollTimestampSecs < earliestNextTs {
+			earliestNextTs = feedInfo.NextPollTimestampSecs
+		}
+	}
+	return time.Unix(earliestNextTs, 0)
 }
 
 // Query the given feed, update relevant timestamps and return NEW items
-func (p *feedPoller) queryFeed(s *rssBotService, feedURL string) (*gofeed.Feed, []gofeed.Item, error) {
+func (s *rssBotService) queryFeed(feedURL string) (*gofeed.Feed, []gofeed.Item, error) {
 	log.WithField("feed_url", feedURL).Info("Querying feed")
 	var items []gofeed.Item
 	fp := gofeed.NewParser()
@@ -115,11 +178,11 @@ func (p *feedPoller) queryFeed(s *rssBotService, feedURL string) (*gofeed.Feed,
 	// TODO: Handle the 'sy' Syndication extension to control update interval.
 	// See http://www.feedforall.com/syndication.htm and http://web.resource.org/rss/1.0/modules/syndication/
 
-	p.updateFeedInfo(s, feedURL, nextPollTsSec, feedLastUpdatedTs)
+	s.updateFeedInfo(feedURL, nextPollTsSec, feedLastUpdatedTs)
 	return feed, items, nil
 }
 
-func (p *feedPoller) updateFeedInfo(s *rssBotService, feedURL string, nextPollTs, feedUpdatedTs int64) {
+func (s *rssBotService) updateFeedInfo(feedURL string, nextPollTs, feedUpdatedTs int64) {
 	for u := range s.Feeds {
 		if u != feedURL {
 			continue
@@ -131,7 +194,7 @@ func (p *feedPoller) updateFeedInfo(s *rssBotService, feedURL string, nextPollTs
 	}
 }
 
-func (p *feedPoller) sendToRooms(s *rssBotService, cli *matrix.Client, feedURL string, feed *gofeed.Feed, item gofeed.Item) error {
+func (s *rssBotService) sendToRooms(cli *matrix.Client, feedURL string, feed *gofeed.Feed, item gofeed.Item) error {
 	logger := log.WithField("feed_url", feedURL).WithField("title", item.Title)
 	logger.Info("New feed item")
 	for _, roomID := range s.Feeds[feedURL].Rooms {
@@ -150,66 +213,6 @@ func itemToHTML(feed *gofeed.Feed, item gofeed.Item) matrix.HTMLMessage {
 	))
 }
 
-type rssBotService struct {
-	types.DefaultService
-	id            string
-	serviceUserID string
-	Feeds         map[string]struct { // feed_url => { }
-		PollIntervalMins         int      `json:"poll_interval_mins"`
-		Rooms                    []string `json:"rooms"`
-		NextPollTimestampSecs    int64    // Internal: When we should poll again
-		FeedUpdatedTimestampSecs int64    // Internal: The last time the feed was updated
-	} `json:"feeds"`
-}
-
-func (s *rssBotService) ServiceUserID() string { return s.serviceUserID }
-func (s *rssBotService) ServiceID() string     { return s.id }
-func (s *rssBotService) ServiceType() string   { return "rssbot" }
-func (s *rssBotService) Poller() types.Poller  { return &feedPoller{} }
-
-// Register will check the liveness of each RSS feed given. If all feeds check out okay, no error is returned.
-func (s *rssBotService) Register(oldService types.Service, client *matrix.Client) error {
-	if len(s.Feeds) == 0 {
-		// this is an error UNLESS the old service had some feeds in which case they are deleting us :(
-		var numOldFeeds int
-		oldFeedService, ok := oldService.(*rssBotService)
-		if !ok {
-			log.WithField("service", oldService).Error("Old service isn't a rssBotService")
-		} else {
-			numOldFeeds = len(oldFeedService.Feeds)
-		}
-		if numOldFeeds == 0 {
-			return errors.New("An RSS feed must be specified.")
-		}
-		return nil
-	}
-	// Make sure we can parse the feed
-	for feedURL, feedInfo := range s.Feeds {
-		fp := gofeed.NewParser()
-		if _, err := fp.ParseURL(feedURL); err != nil {
-			return fmt.Errorf("Failed to read URL %s: %s", feedURL, err.Error())
-		}
-		if len(feedInfo.Rooms) == 0 {
-			return fmt.Errorf("Feed %s has no rooms to send updates to", feedURL)
-		}
-	}
-	return nil
-}
-
-func (s *rssBotService) PostRegister(oldService types.Service) {
-	if len(s.Feeds) == 0 { // bye-bye :(
-		logger := log.WithFields(log.Fields{
-			"service_id":   s.ServiceID(),
-			"service_type": s.ServiceType(),
-		})
-		logger.Info("Deleting service: No feeds remaining.")
-		polling.StopPolling(s)
-		if err := database.GetServiceDB().DeleteService(s.ServiceID()); err != nil {
-			logger.WithError(err).Error("Failed to delete service")
-		}
-	}
-}
-
 func init() {
 	types.RegisterService(func(serviceID, serviceUserID, webhookEndpointURL string) types.Service {
 		r := &rssBotService{

src/github.com/matrix-org/go-neb/types/types.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"net/url"
 	"strings"
+	"time"
 )
 
 // A ClientConfig is the configuration for a matrix client for a bot to use.
@@ -40,10 +41,11 @@ type BotOptions struct {
 	Options     map[string]interface{}
 }
 
-// Poller represents a thing that can be polled at a given rate.
+// Poller represents a thing which can poll. Services should implement this method signature to support polling.
 type Poller interface {
-	IntervalSecs() int64
-	OnPoll(service Service, client *matrix.Client)
+	// OnPoll is called when the poller should poll. Return the timestamp when you want to be polled again.
+	// Return 0 to never be polled again.
+	OnPoll(client *matrix.Client) time.Time
 }
 
 // A Service is the configuration for a bot service.
@@ -66,11 +68,6 @@ type Service interface {
 	// concurrent modifications to this service whilst this function executes. This lifecycle hook should be used to clean
 	// up resources which are no longer needed (e.g. removing old webhooks).
 	PostRegister(oldService Service)
-	// Return a Poller object if you wish to be invoked every N seconds. This struct MUST NOT conditionally change: either
-	// ALWAYS return a new Poller interface or NEVER return a Poller. The Poller will exist outside of the lifetime of the
-	// Service upon which it is being called on, so DO NOT wrap this inside a closure or else you will introduce a memory
-	// leak. An instantiated service will be passed into the `OnPoll(Service)` for you to extract state.
-	Poller() Poller
 }
 
 // DefaultService NO-OPs the implementation of optional Service interface methods. Feel free to override them.
@@ -89,9 +86,6 @@ func (s *DefaultService) Register(oldService Service, client *matrix.Client) err
 // PostRegister does nothing.
 func (s *DefaultService) PostRegister(oldService Service) {}
 
-// Poller returns no poller.
-func (s *DefaultService) Poller() Poller { return nil }
-
 // OnReceiveWebhook does nothing but 200 OK the request.
 func (s *DefaultService) OnReceiveWebhook(w http.ResponseWriter, req *http.Request, cli *matrix.Client) {
 	w.WriteHeader(200) // Do nothing
@@ -116,18 +110,24 @@ func BaseURL(u string) error {
 }
 
 var servicesByType = map[string]func(string, string, string) Service{}
-var pollersByType = map[string]Poller{}
+var serviceTypesWhichPoll = map[string]bool{}
 
 // RegisterService registers a factory for creating Service instances.
 func RegisterService(factory func(string, string, string) Service) {
 	s := factory("", "", "")
 	servicesByType[s.ServiceType()] = factory
-	pollersByType[s.ServiceType()] = s.Poller()
+
+	if _, ok := s.(Poller); ok {
+		serviceTypesWhichPoll[s.ServiceType()] = true
+	}
 }
 
-// PollersByType returns a map of service type to poller, which may be nil
-func PollersByType() map[string]Poller {
-	return pollersByType
+// PollingServiceTypes returns a list of service types which meet the Poller interface
+func PollingServiceTypes() (types []string) {
+	for t := range serviceTypesWhichPoll {
+		types = append(types, t)
+	}
+	return
 }
 
 // CreateService creates a Service of the given type and serviceID.