Use pull consumers (#2140)

* Pull consumers

* Pull consumers

* Only nuke consumers if they are push consumers

* Clean up old consumers

* Better error handling

* Update comments

appservice/consumers/roomserver.go

@@ -34,7 +34,7 @@ import (
 type OutputRoomEventConsumer struct {
 	ctx          context.Context
 	jetstream    nats.JetStreamContext
-	durable      nats.SubOpt
+	durable      string
 	topic        string
 	asDB         storage.Database
 	rsAPI        api.RoomserverInternalAPI
@@ -66,37 +66,37 @@ func NewOutputRoomEventConsumer(
 
 // Start consuming from room servers
 func (s *OutputRoomEventConsumer) Start() error {
-	_, err := s.jetstream.Subscribe(s.topic, s.onMessage, s.durable)
+	return jetstream.JetStreamConsumer(
-	return err
+		s.ctx, s.jetstream, s.topic, s.durable, s.onMessage,
+		nats.DeliverAll(), nats.ManualAck(),
+	)
 }
 
 // onMessage is called when the appservice component receives a new event from
 // the room server output log.
-func (s *OutputRoomEventConsumer) onMessage(msg *nats.Msg) {
+func (s *OutputRoomEventConsumer) onMessage(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	// Parse out the event JSON
-		// Parse out the event JSON
+	var output api.OutputEvent
-		var output api.OutputEvent
+	if err := json.Unmarshal(msg.Data, &output); err != nil {
-		if err := json.Unmarshal(msg.Data, &output); err != nil {
+		// If the message was invalid, log it and move on to the next message in the stream
-			// If the message was invalid, log it and move on to the next message in the stream
+		log.WithError(err).Errorf("roomserver output log: message parse failure")
-			log.WithError(err).Errorf("roomserver output log: message parse failure")
-			return true
-		}
-
-		if output.Type != api.OutputTypeNewRoomEvent {
-			return true
-		}
-
-		events := []*gomatrixserverlib.HeaderedEvent{output.NewRoomEvent.Event}
-		events = append(events, output.NewRoomEvent.AddStateEvents...)
-
-		// Send event to any relevant application services
-		if err := s.filterRoomserverEvents(context.TODO(), events); err != nil {
-			log.WithError(err).Errorf("roomserver output log: filter error")
-			return true
-		}
-
 		return true
-	})
+	}
+
+	if output.Type != api.OutputTypeNewRoomEvent {
+		return true
+	}
+
+	events := []*gomatrixserverlib.HeaderedEvent{output.NewRoomEvent.Event}
+	events = append(events, output.NewRoomEvent.AddStateEvents...)
+
+	// Send event to any relevant application services
+	if err := s.filterRoomserverEvents(context.TODO(), events); err != nil {
+		log.WithError(err).Errorf("roomserver output log: filter error")
+		return true
+	}
+
+	return true
 }
 
 // filterRoomserverEvents takes in events and decides whether any of them need

federationapi/consumers/eduserver.go

@@ -34,7 +34,7 @@ import (
 type OutputEDUConsumer struct {
 	ctx               context.Context
 	jetstream         nats.JetStreamContext
-	durable           nats.SubOpt
+	durable           string
 	db                storage.Database
 	queues            *queue.OutgoingQueues
 	ServerName        gomatrixserverlib.ServerName
@@ -66,13 +66,22 @@ func NewOutputEDUConsumer(
 
 // Start consuming from EDU servers
 func (t *OutputEDUConsumer) Start() error {
-	if _, err := t.jetstream.Subscribe(t.typingTopic, t.onTypingEvent, t.durable); err != nil {
+	if err := jetstream.JetStreamConsumer(
+		t.ctx, t.jetstream, t.typingTopic, t.durable, t.onTypingEvent,
+		nats.DeliverAll(), nats.ManualAck(),
+	); err != nil {
 		return err
 	}
-	if _, err := t.jetstream.Subscribe(t.sendToDeviceTopic, t.onSendToDeviceEvent, t.durable); err != nil {
+	if err := jetstream.JetStreamConsumer(
+		t.ctx, t.jetstream, t.sendToDeviceTopic, t.durable, t.onSendToDeviceEvent,
+		nats.DeliverAll(), nats.ManualAck(),
+	); err != nil {
 		return err
 	}
-	if _, err := t.jetstream.Subscribe(t.receiptTopic, t.onReceiptEvent, t.durable); err != nil {
+	if err := jetstream.JetStreamConsumer(
+		t.ctx, t.jetstream, t.receiptTopic, t.durable, t.onReceiptEvent,
+		nats.DeliverAll(), nats.ManualAck(),
+	); err != nil {
 		return err
 	}
 	return nil
@@ -80,175 +89,169 @@ func (t *OutputEDUConsumer) Start() error {
 
 // onSendToDeviceEvent is called in response to a message received on the
 // send-to-device events topic from the EDU server.
-func (t *OutputEDUConsumer) onSendToDeviceEvent(msg *nats.Msg) {
+func (t *OutputEDUConsumer) onSendToDeviceEvent(ctx context.Context, msg *nats.Msg) bool {
 	// Extract the send-to-device event from msg.
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	var ote api.OutputSendToDeviceEvent
-		var ote api.OutputSendToDeviceEvent
+	if err := json.Unmarshal(msg.Data, &ote); err != nil {
-		if err := json.Unmarshal(msg.Data, &ote); err != nil {
+		log.WithError(err).Errorf("eduserver output log: message parse failed (expected send-to-device)")
-			log.WithError(err).Errorf("eduserver output log: message parse failed (expected send-to-device)")
-			return true
-		}
-
-		// only send send-to-device events which originated from us
-		_, originServerName, err := gomatrixserverlib.SplitID('@', ote.Sender)
-		if err != nil {
-			log.WithError(err).WithField("user_id", ote.Sender).Error("Failed to extract domain from send-to-device sender")
-			return true
-		}
-		if originServerName != t.ServerName {
-			log.WithField("other_server", originServerName).Info("Suppressing send-to-device: originated elsewhere")
-			return true
-		}
-
-		_, destServerName, err := gomatrixserverlib.SplitID('@', ote.UserID)
-		if err != nil {
-			log.WithError(err).WithField("user_id", ote.UserID).Error("Failed to extract domain from send-to-device destination")
-			return true
-		}
-
-		// Pack the EDU and marshal it
-		edu := &gomatrixserverlib.EDU{
-			Type:   gomatrixserverlib.MDirectToDevice,
-			Origin: string(t.ServerName),
-		}
-		tdm := gomatrixserverlib.ToDeviceMessage{
-			Sender:    ote.Sender,
-			Type:      ote.Type,
-			MessageID: util.RandomString(32),
-			Messages: map[string]map[string]json.RawMessage{
-				ote.UserID: {
-					ote.DeviceID: ote.Content,
-				},
-			},
-		}
-		if edu.Content, err = json.Marshal(tdm); err != nil {
-			log.WithError(err).Error("failed to marshal EDU JSON")
-			return true
-		}
-
-		log.Infof("Sending send-to-device message into %q destination queue", destServerName)
-		if err := t.queues.SendEDU(edu, t.ServerName, []gomatrixserverlib.ServerName{destServerName}); err != nil {
-			log.WithError(err).Error("failed to send EDU")
-			return false
-		}
-
 		return true
-	})
+	}
+
+	// only send send-to-device events which originated from us
+	_, originServerName, err := gomatrixserverlib.SplitID('@', ote.Sender)
+	if err != nil {
+		log.WithError(err).WithField("user_id", ote.Sender).Error("Failed to extract domain from send-to-device sender")
+		return true
+	}
+	if originServerName != t.ServerName {
+		log.WithField("other_server", originServerName).Info("Suppressing send-to-device: originated elsewhere")
+		return true
+	}
+
+	_, destServerName, err := gomatrixserverlib.SplitID('@', ote.UserID)
+	if err != nil {
+		log.WithError(err).WithField("user_id", ote.UserID).Error("Failed to extract domain from send-to-device destination")
+		return true
+	}
+
+	// Pack the EDU and marshal it
+	edu := &gomatrixserverlib.EDU{
+		Type:   gomatrixserverlib.MDirectToDevice,
+		Origin: string(t.ServerName),
+	}
+	tdm := gomatrixserverlib.ToDeviceMessage{
+		Sender:    ote.Sender,
+		Type:      ote.Type,
+		MessageID: util.RandomString(32),
+		Messages: map[string]map[string]json.RawMessage{
+			ote.UserID: {
+				ote.DeviceID: ote.Content,
+			},
+		},
+	}
+	if edu.Content, err = json.Marshal(tdm); err != nil {
+		log.WithError(err).Error("failed to marshal EDU JSON")
+		return true
+	}
+
+	log.Infof("Sending send-to-device message into %q destination queue", destServerName)
+	if err := t.queues.SendEDU(edu, t.ServerName, []gomatrixserverlib.ServerName{destServerName}); err != nil {
+		log.WithError(err).Error("failed to send EDU")
+		return false
+	}
+
+	return true
 }
 
 // onTypingEvent is called in response to a message received on the typing
 // events topic from the EDU server.
-func (t *OutputEDUConsumer) onTypingEvent(msg *nats.Msg) {
+func (t *OutputEDUConsumer) onTypingEvent(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	// Extract the typing event from msg.
-		// Extract the typing event from msg.
+	var ote api.OutputTypingEvent
-		var ote api.OutputTypingEvent
+	if err := json.Unmarshal(msg.Data, &ote); err != nil {
-		if err := json.Unmarshal(msg.Data, &ote); err != nil {
+		// Skip this msg but continue processing messages.
-			// Skip this msg but continue processing messages.
+		log.WithError(err).Errorf("eduserver output log: message parse failed (expected typing)")
-			log.WithError(err).Errorf("eduserver output log: message parse failed (expected typing)")
+		_ = msg.Ack()
-			_ = msg.Ack()
-			return true
-		}
-
-		// only send typing events which originated from us
-		_, typingServerName, err := gomatrixserverlib.SplitID('@', ote.Event.UserID)
-		if err != nil {
-			log.WithError(err).WithField("user_id", ote.Event.UserID).Error("Failed to extract domain from typing sender")
-			_ = msg.Ack()
-			return true
-		}
-		if typingServerName != t.ServerName {
-			return true
-		}
-
-		joined, err := t.db.GetJoinedHosts(t.ctx, ote.Event.RoomID)
-		if err != nil {
-			log.WithError(err).WithField("room_id", ote.Event.RoomID).Error("failed to get joined hosts for room")
-			return false
-		}
-
-		names := make([]gomatrixserverlib.ServerName, len(joined))
-		for i := range joined {
-			names[i] = joined[i].ServerName
-		}
-
-		edu := &gomatrixserverlib.EDU{Type: ote.Event.Type}
-		if edu.Content, err = json.Marshal(map[string]interface{}{
-			"room_id": ote.Event.RoomID,
-			"user_id": ote.Event.UserID,
-			"typing":  ote.Event.Typing,
-		}); err != nil {
-			log.WithError(err).Error("failed to marshal EDU JSON")
-			return true
-		}
-
-		if err := t.queues.SendEDU(edu, t.ServerName, names); err != nil {
-			log.WithError(err).Error("failed to send EDU")
-			return false
-		}
-
 		return true
-	})
+	}
+
+	// only send typing events which originated from us
+	_, typingServerName, err := gomatrixserverlib.SplitID('@', ote.Event.UserID)
+	if err != nil {
+		log.WithError(err).WithField("user_id", ote.Event.UserID).Error("Failed to extract domain from typing sender")
+		_ = msg.Ack()
+		return true
+	}
+	if typingServerName != t.ServerName {
+		return true
+	}
+
+	joined, err := t.db.GetJoinedHosts(ctx, ote.Event.RoomID)
+	if err != nil {
+		log.WithError(err).WithField("room_id", ote.Event.RoomID).Error("failed to get joined hosts for room")
+		return false
+	}
+
+	names := make([]gomatrixserverlib.ServerName, len(joined))
+	for i := range joined {
+		names[i] = joined[i].ServerName
+	}
+
+	edu := &gomatrixserverlib.EDU{Type: ote.Event.Type}
+	if edu.Content, err = json.Marshal(map[string]interface{}{
+		"room_id": ote.Event.RoomID,
+		"user_id": ote.Event.UserID,
+		"typing":  ote.Event.Typing,
+	}); err != nil {
+		log.WithError(err).Error("failed to marshal EDU JSON")
+		return true
+	}
+
+	if err := t.queues.SendEDU(edu, t.ServerName, names); err != nil {
+		log.WithError(err).Error("failed to send EDU")
+		return false
+	}
+
+	return true
 }
 
 // onReceiptEvent is called in response to a message received on the receipt
 // events topic from the EDU server.
-func (t *OutputEDUConsumer) onReceiptEvent(msg *nats.Msg) {
+func (t *OutputEDUConsumer) onReceiptEvent(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	// Extract the typing event from msg.
-		// Extract the typing event from msg.
+	var receipt api.OutputReceiptEvent
-		var receipt api.OutputReceiptEvent
+	if err := json.Unmarshal(msg.Data, &receipt); err != nil {
-		if err := json.Unmarshal(msg.Data, &receipt); err != nil {
+		// Skip this msg but continue processing messages.
-			// Skip this msg but continue processing messages.
+		log.WithError(err).Errorf("eduserver output log: message parse failed (expected receipt)")
-			log.WithError(err).Errorf("eduserver output log: message parse failed (expected receipt)")
-			return true
-		}
-
-		// only send receipt events which originated from us
-		_, receiptServerName, err := gomatrixserverlib.SplitID('@', receipt.UserID)
-		if err != nil {
-			log.WithError(err).WithField("user_id", receipt.UserID).Error("failed to extract domain from receipt sender")
-			return true
-		}
-		if receiptServerName != t.ServerName {
-			return true
-		}
-
-		joined, err := t.db.GetJoinedHosts(t.ctx, receipt.RoomID)
-		if err != nil {
-			log.WithError(err).WithField("room_id", receipt.RoomID).Error("failed to get joined hosts for room")
-			return false
-		}
-
-		names := make([]gomatrixserverlib.ServerName, len(joined))
-		for i := range joined {
-			names[i] = joined[i].ServerName
-		}
-
-		content := map[string]api.FederationReceiptMRead{}
-		content[receipt.RoomID] = api.FederationReceiptMRead{
-			User: map[string]api.FederationReceiptData{
-				receipt.UserID: {
-					Data: api.ReceiptTS{
-						TS: receipt.Timestamp,
-					},
-					EventIDs: []string{receipt.EventID},
-				},
-			},
-		}
-
-		edu := &gomatrixserverlib.EDU{
-			Type:   gomatrixserverlib.MReceipt,
-			Origin: string(t.ServerName),
-		}
-		if edu.Content, err = json.Marshal(content); err != nil {
-			log.WithError(err).Error("failed to marshal EDU JSON")
-			return true
-		}
-
-		if err := t.queues.SendEDU(edu, t.ServerName, names); err != nil {
-			log.WithError(err).Error("failed to send EDU")
-			return false
-		}
-
 		return true
-	})
+	}
+
+	// only send receipt events which originated from us
+	_, receiptServerName, err := gomatrixserverlib.SplitID('@', receipt.UserID)
+	if err != nil {
+		log.WithError(err).WithField("user_id", receipt.UserID).Error("failed to extract domain from receipt sender")
+		return true
+	}
+	if receiptServerName != t.ServerName {
+		return true
+	}
+
+	joined, err := t.db.GetJoinedHosts(ctx, receipt.RoomID)
+	if err != nil {
+		log.WithError(err).WithField("room_id", receipt.RoomID).Error("failed to get joined hosts for room")
+		return false
+	}
+
+	names := make([]gomatrixserverlib.ServerName, len(joined))
+	for i := range joined {
+		names[i] = joined[i].ServerName
+	}
+
+	content := map[string]api.FederationReceiptMRead{}
+	content[receipt.RoomID] = api.FederationReceiptMRead{
+		User: map[string]api.FederationReceiptData{
+			receipt.UserID: {
+				Data: api.ReceiptTS{
+					TS: receipt.Timestamp,
+				},
+				EventIDs: []string{receipt.EventID},
+			},
+		},
+	}
+
+	edu := &gomatrixserverlib.EDU{
+		Type:   gomatrixserverlib.MReceipt,
+		Origin: string(t.ServerName),
+	}
+	if edu.Content, err = json.Marshal(content); err != nil {
+		log.WithError(err).Error("failed to marshal EDU JSON")
+		return true
+	}
+
+	if err := t.queues.SendEDU(edu, t.ServerName, names); err != nil {
+		log.WithError(err).Error("failed to send EDU")
+		return false
+	}
+
+	return true
 }

federationapi/consumers/roomserver.go

@@ -37,7 +37,7 @@ type OutputRoomEventConsumer struct {
 	cfg       *config.FederationAPI
 	rsAPI     api.RoomserverInternalAPI
 	jetstream nats.JetStreamContext
-	durable   nats.SubOpt
+	durable   string
 	db        storage.Database
 	queues    *queue.OutgoingQueues
 	topic     string
@@ -66,74 +66,70 @@ func NewOutputRoomEventConsumer(
 
 // Start consuming from room servers
 func (s *OutputRoomEventConsumer) Start() error {
-	_, err := s.jetstream.Subscribe(
+	return jetstream.JetStreamConsumer(
-		s.topic, s.onMessage, s.durable,
+		s.ctx, s.jetstream, s.topic, s.durable, s.onMessage,
-		nats.DeliverAll(),
+		nats.DeliverAll(), nats.ManualAck(),
-		nats.ManualAck(),
 	)
-	return err
 }
 
 // onMessage is called when the federation server receives a new event from the room server output log.
 // It is unsafe to call this with messages for the same room in multiple gorountines
 // because updates it will likely fail with a types.EventIDMismatchError when it
 // realises that it cannot update the room state using the deltas.
-func (s *OutputRoomEventConsumer) onMessage(msg *nats.Msg) {
+func (s *OutputRoomEventConsumer) onMessage(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	// Parse out the event JSON
-		// Parse out the event JSON
+	var output api.OutputEvent
-		var output api.OutputEvent
+	if err := json.Unmarshal(msg.Data, &output); err != nil {
-		if err := json.Unmarshal(msg.Data, &output); err != nil {
+		// If the message was invalid, log it and move on to the next message in the stream
-			// If the message was invalid, log it and move on to the next message in the stream
+		log.WithError(err).Errorf("roomserver output log: message parse failure")
-			log.WithError(err).Errorf("roomserver output log: message parse failure")
+		return true
-			return true
+	}
-		}
 
-		switch output.Type {
+	switch output.Type {
-		case api.OutputTypeNewRoomEvent:
+	case api.OutputTypeNewRoomEvent:
-			ev := output.NewRoomEvent.Event
+		ev := output.NewRoomEvent.Event
 
-			if output.NewRoomEvent.RewritesState {
+		if output.NewRoomEvent.RewritesState {
-				if err := s.db.PurgeRoomState(s.ctx, ev.RoomID()); err != nil {
+			if err := s.db.PurgeRoomState(s.ctx, ev.RoomID()); err != nil {
-					log.WithError(err).Errorf("roomserver output log: purge room state failure")
+				log.WithError(err).Errorf("roomserver output log: purge room state failure")
-					return false
-				}
-			}
-
-			if err := s.processMessage(*output.NewRoomEvent); err != nil {
-				switch err.(type) {
-				case *queue.ErrorFederationDisabled:
-					log.WithField("error", output.Type).Info(
-						err.Error(),
-					)
-				default:
-					// panic rather than continue with an inconsistent database
-					log.WithFields(log.Fields{
-						"event_id":   ev.EventID(),
-						"event":      string(ev.JSON()),
-						"add":        output.NewRoomEvent.AddsStateEventIDs,
-						"del":        output.NewRoomEvent.RemovesStateEventIDs,
-						log.ErrorKey: err,
-					}).Panicf("roomserver output log: write room event failure")
-				}
-			}
-
-		case api.OutputTypeNewInboundPeek:
-			if err := s.processInboundPeek(*output.NewInboundPeek); err != nil {
-				log.WithFields(log.Fields{
-					"event":      output.NewInboundPeek,
-					log.ErrorKey: err,
-				}).Panicf("roomserver output log: remote peek event failure")
 				return false
 			}
-
-		default:
-			log.WithField("type", output.Type).Debug(
-				"roomserver output log: ignoring unknown output type",
-			)
 		}
 
-		return true
+		if err := s.processMessage(*output.NewRoomEvent); err != nil {
-	})
+			switch err.(type) {
+			case *queue.ErrorFederationDisabled:
+				log.WithField("error", output.Type).Info(
+					err.Error(),
+				)
+			default:
+				// panic rather than continue with an inconsistent database
+				log.WithFields(log.Fields{
+					"event_id":   ev.EventID(),
+					"event":      string(ev.JSON()),
+					"add":        output.NewRoomEvent.AddsStateEventIDs,
+					"del":        output.NewRoomEvent.RemovesStateEventIDs,
+					log.ErrorKey: err,
+				}).Panicf("roomserver output log: write room event failure")
+			}
+		}
+
+	case api.OutputTypeNewInboundPeek:
+		if err := s.processInboundPeek(*output.NewInboundPeek); err != nil {
+			log.WithFields(log.Fields{
+				"event":      output.NewInboundPeek,
+				log.ErrorKey: err,
+			}).Panicf("roomserver output log: remote peek event failure")
+			return false
+		}
+
+	default:
+		log.WithField("type", output.Type).Debug(
+			"roomserver output log: ignoring unknown output type",
+		)
+	}
+
+	return true
 }
 
 // processInboundPeek starts tracking a new federated inbound peek (replacing the existing one if any)

roomserver/internal/api.go

@@ -41,7 +41,7 @@ type RoomserverInternalAPI struct {
 	fsAPI                  fsAPI.FederationInternalAPI
 	asAPI                  asAPI.AppServiceQueryAPI
 	JetStream              nats.JetStreamContext
-	Durable                nats.SubOpt
+	Durable                string
 	InputRoomEventTopic    string // JetStream topic for new input room events
 	OutputRoomEventTopic   string // JetStream topic for new output room events
 	PerspectiveServerNames []gomatrixserverlib.ServerName
@@ -87,7 +87,7 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.FederationInternalA
 		InputRoomEventTopic:  r.InputRoomEventTopic,
 		OutputRoomEventTopic: r.OutputRoomEventTopic,
 		JetStream:            r.JetStream,
-		Durable:              r.Durable,
+		Durable:              nats.Durable(r.Durable),
 		ServerName:           r.Cfg.Matrix.ServerName,
 		FSAPI:                fsAPI,
 		KeyRing:              keyRing,

setup/config/config_jetstream.go

@@ -2,8 +2,6 @@ package config
 
 import (
 	"fmt"
-
-	"github.com/nats-io/nats.go"
 )
 
 type JetStream struct {
@@ -25,8 +23,8 @@ func (c *JetStream) TopicFor(name string) string {
 	return fmt.Sprintf("%s%s", c.TopicPrefix, name)
 }
 
-func (c *JetStream) Durable(name string) nats.SubOpt {
+func (c *JetStream) Durable(name string) string {
-	return nats.Durable(c.TopicFor(name))
+	return c.TopicFor(name)
 }
 
 func (c *JetStream) Defaults(generate bool) {

setup/jetstream/helpers.go

@@ -1,12 +1,81 @@
 package jetstream
 
-import "github.com/nats-io/nats.go"
+import (
+	"context"
+	"fmt"
 
-func WithJetStreamMessage(msg *nats.Msg, f func(msg *nats.Msg) bool) {
+	"github.com/nats-io/nats.go"
-	_ = msg.InProgress()
+	"github.com/sirupsen/logrus"
-	if f(msg) {
+)
-		_ = msg.Ack()
+
-	} else {
+func JetStreamConsumer(
-		_ = msg.Nak()
+	ctx context.Context, js nats.JetStreamContext, subj, durable string,
+	f func(ctx context.Context, msg *nats.Msg) bool,
+	opts ...nats.SubOpt,
+) error {
+	defer func() {
+		// If there are existing consumers from before they were pull
+		// consumers, we need to clean up the old push consumers. However,
+		// in order to not affect the interest-based policies, we need to
+		// do this *after* creating the new pull consumers, which have
+		// "Pull" suffixed to their name.
+		if _, err := js.ConsumerInfo(subj, durable); err == nil {
+			if err := js.DeleteConsumer(subj, durable); err != nil {
+				logrus.WithContext(ctx).Warnf("Failed to clean up old consumer %q", durable)
+			}
+		}
+	}()
+
+	name := durable + "Pull"
+	sub, err := js.PullSubscribe(subj, name, opts...)
+	if err != nil {
+		return fmt.Errorf("nats.SubscribeSync: %w", err)
 	}
+	go func() {
+		for {
+			// The context behaviour here is surprising — we supply a context
+			// so that we can interrupt the fetch if we want, but NATS will still
+			// enforce its own deadline (roughly 5 seconds by default). Therefore
+			// it is our responsibility to check whether our context expired or
+			// not when a context error is returned. Footguns. Footguns everywhere.
+			msgs, err := sub.Fetch(1, nats.Context(ctx))
+			if err != nil {
+				if err == context.Canceled || err == context.DeadlineExceeded {
+					// Work out whether it was the JetStream context that expired
+					// or whether it was our supplied context.
+					select {
+					case <-ctx.Done():
+						// The supplied context expired, so we want to stop the
+						// consumer altogether.
+						return
+					default:
+						// The JetStream context expired, so the fetch probably
+						// just timed out and we should try again.
+						continue
+					}
+				} else {
+					// Something else went wrong, so we'll panic.
+					logrus.WithContext(ctx).WithField("subject", subj).Fatal(err)
+				}
+			}
+			if len(msgs) < 1 {
+				continue
+			}
+			msg := msgs[0]
+			if err = msg.InProgress(); err != nil {
+				logrus.WithContext(ctx).WithField("subject", subj).Warn(fmt.Errorf("msg.InProgress: %w", err))
+				continue
+			}
+			if f(ctx, msg) {
+				if err = msg.Ack(); err != nil {
+					logrus.WithContext(ctx).WithField("subject", subj).Warn(fmt.Errorf("msg.Ack: %w", err))
+				}
+			} else {
+				if err = msg.Nak(); err != nil {
+					logrus.WithContext(ctx).WithField("subject", subj).Warn(fmt.Errorf("msg.Nak: %w", err))
+				}
+			}
+		}
+	}()
+	return nil
 }

syncapi/consumers/clientapi.go

@@ -34,7 +34,7 @@ import (
 type OutputClientDataConsumer struct {
 	ctx       context.Context
 	jetstream nats.JetStreamContext
-	durable   nats.SubOpt
+	durable   string
 	topic     string
 	db        storage.Database
 	stream    types.StreamProvider
@@ -63,45 +63,45 @@ func NewOutputClientDataConsumer(
 
 // Start consuming from room servers
 func (s *OutputClientDataConsumer) Start() error {
-	_, err := s.jetstream.Subscribe(s.topic, s.onMessage, s.durable)
+	return jetstream.JetStreamConsumer(
-	return err
+		s.ctx, s.jetstream, s.topic, s.durable, s.onMessage,
+		nats.DeliverAll(), nats.ManualAck(),
+	)
 }
 
 // onMessage is called when the sync server receives a new event from the client API server output log.
 // It is not safe for this function to be called from multiple goroutines, or else the
 // sync stream position may race and be incorrectly calculated.
-func (s *OutputClientDataConsumer) onMessage(msg *nats.Msg) {
+func (s *OutputClientDataConsumer) onMessage(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	// Parse out the event JSON
-		// Parse out the event JSON
+	userID := msg.Header.Get(jetstream.UserID)
-		userID := msg.Header.Get(jetstream.UserID)
+	var output eventutil.AccountData
-		var output eventutil.AccountData
+	if err := json.Unmarshal(msg.Data, &output); err != nil {
-		if err := json.Unmarshal(msg.Data, &output); err != nil {
+		// If the message was invalid, log it and move on to the next message in the stream
-			// If the message was invalid, log it and move on to the next message in the stream
+		log.WithError(err).Errorf("client API server output log: message parse failure")
-			log.WithError(err).Errorf("client API server output log: message parse failure")
+		sentry.CaptureException(err)
-			sentry.CaptureException(err)
-			return true
-		}
-
-		log.WithFields(log.Fields{
-			"type":    output.Type,
-			"room_id": output.RoomID,
-		}).Debug("Received data from client API server")
-
-		streamPos, err := s.db.UpsertAccountData(
-			s.ctx, userID, output.RoomID, output.Type,
-		)
-		if err != nil {
-			sentry.CaptureException(err)
-			log.WithFields(log.Fields{
-				"type":       output.Type,
-				"room_id":    output.RoomID,
-				log.ErrorKey: err,
-			}).Panicf("could not save account data")
-		}
-
-		s.stream.Advance(streamPos)
-		s.notifier.OnNewAccountData(userID, types.StreamingToken{AccountDataPosition: streamPos})
-
 		return true
-	})
+	}
+
+	log.WithFields(log.Fields{
+		"type":    output.Type,
+		"room_id": output.RoomID,
+	}).Debug("Received data from client API server")
+
+	streamPos, err := s.db.UpsertAccountData(
+		s.ctx, userID, output.RoomID, output.Type,
+	)
+	if err != nil {
+		sentry.CaptureException(err)
+		log.WithFields(log.Fields{
+			"type":       output.Type,
+			"room_id":    output.RoomID,
+			log.ErrorKey: err,
+		}).Panicf("could not save account data")
+	}
+
+	s.stream.Advance(streamPos)
+	s.notifier.OnNewAccountData(userID, types.StreamingToken{AccountDataPosition: streamPos})
+
+	return true
 }

syncapi/consumers/eduserver_receipts.go

@@ -34,7 +34,7 @@ import (
 type OutputReceiptEventConsumer struct {
 	ctx       context.Context
 	jetstream nats.JetStreamContext
-	durable   nats.SubOpt
+	durable   string
 	topic     string
 	db        storage.Database
 	stream    types.StreamProvider
@@ -64,36 +64,36 @@ func NewOutputReceiptEventConsumer(
 
 // Start consuming from EDU api
 func (s *OutputReceiptEventConsumer) Start() error {
-	_, err := s.jetstream.Subscribe(s.topic, s.onMessage, s.durable)
+	return jetstream.JetStreamConsumer(
-	return err
+		s.ctx, s.jetstream, s.topic, s.durable, s.onMessage,
+		nats.DeliverAll(), nats.ManualAck(),
+	)
 }
 
-func (s *OutputReceiptEventConsumer) onMessage(msg *nats.Msg) {
+func (s *OutputReceiptEventConsumer) onMessage(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	var output api.OutputReceiptEvent
-		var output api.OutputReceiptEvent
+	if err := json.Unmarshal(msg.Data, &output); err != nil {
-		if err := json.Unmarshal(msg.Data, &output); err != nil {
+		// If the message was invalid, log it and move on to the next message in the stream
-			// If the message was invalid, log it and move on to the next message in the stream
+		log.WithError(err).Errorf("EDU server output log: message parse failure")
-			log.WithError(err).Errorf("EDU server output log: message parse failure")
+		sentry.CaptureException(err)
-			sentry.CaptureException(err)
-			return true
-		}
-
-		streamPos, err := s.db.StoreReceipt(
-			s.ctx,
-			output.RoomID,
-			output.Type,
-			output.UserID,
-			output.EventID,
-			output.Timestamp,
-		)
-		if err != nil {
-			sentry.CaptureException(err)
-			return true
-		}
-
-		s.stream.Advance(streamPos)
-		s.notifier.OnNewReceipt(output.RoomID, types.StreamingToken{ReceiptPosition: streamPos})
-
 		return true
-	})
+	}
+
+	streamPos, err := s.db.StoreReceipt(
+		s.ctx,
+		output.RoomID,
+		output.Type,
+		output.UserID,
+		output.EventID,
+		output.Timestamp,
+	)
+	if err != nil {
+		sentry.CaptureException(err)
+		return true
+	}
+
+	s.stream.Advance(streamPos)
+	s.notifier.OnNewReceipt(output.RoomID, types.StreamingToken{ReceiptPosition: streamPos})
+
+	return true
 }

syncapi/consumers/eduserver_sendtodevice.go

@@ -36,7 +36,7 @@ import (
 type OutputSendToDeviceEventConsumer struct {
 	ctx        context.Context
 	jetstream  nats.JetStreamContext
-	durable    nats.SubOpt
+	durable    string
 	topic      string
 	db         storage.Database
 	serverName gomatrixserverlib.ServerName // our server name
@@ -68,52 +68,52 @@ func NewOutputSendToDeviceEventConsumer(
 
 // Start consuming from EDU api
 func (s *OutputSendToDeviceEventConsumer) Start() error {
-	_, err := s.jetstream.Subscribe(s.topic, s.onMessage, s.durable)
+	return jetstream.JetStreamConsumer(
-	return err
+		s.ctx, s.jetstream, s.topic, s.durable, s.onMessage,
+		nats.DeliverAll(), nats.ManualAck(),
+	)
 }
 
-func (s *OutputSendToDeviceEventConsumer) onMessage(msg *nats.Msg) {
+func (s *OutputSendToDeviceEventConsumer) onMessage(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	var output api.OutputSendToDeviceEvent
-		var output api.OutputSendToDeviceEvent
+	if err := json.Unmarshal(msg.Data, &output); err != nil {
-		if err := json.Unmarshal(msg.Data, &output); err != nil {
+		// If the message was invalid, log it and move on to the next message in the stream
-			// If the message was invalid, log it and move on to the next message in the stream
+		log.WithError(err).Errorf("EDU server output log: message parse failure")
-			log.WithError(err).Errorf("EDU server output log: message parse failure")
+		sentry.CaptureException(err)
-			sentry.CaptureException(err)
-			return true
-		}
-
-		_, domain, err := gomatrixserverlib.SplitID('@', output.UserID)
-		if err != nil {
-			sentry.CaptureException(err)
-			return true
-		}
-		if domain != s.serverName {
-			return true
-		}
-
-		util.GetLogger(context.TODO()).WithFields(log.Fields{
-			"sender":     output.Sender,
-			"user_id":    output.UserID,
-			"device_id":  output.DeviceID,
-			"event_type": output.Type,
-		}).Info("sync API received send-to-device event from EDU server")
-
-		streamPos, err := s.db.StoreNewSendForDeviceMessage(
-			s.ctx, output.UserID, output.DeviceID, output.SendToDeviceEvent,
-		)
-		if err != nil {
-			sentry.CaptureException(err)
-			log.WithError(err).Errorf("failed to store send-to-device message")
-			return false
-		}
-
-		s.stream.Advance(streamPos)
-		s.notifier.OnNewSendToDevice(
-			output.UserID,
-			[]string{output.DeviceID},
-			types.StreamingToken{SendToDevicePosition: streamPos},
-		)
-
 		return true
-	})
+	}
+
+	_, domain, err := gomatrixserverlib.SplitID('@', output.UserID)
+	if err != nil {
+		sentry.CaptureException(err)
+		return true
+	}
+	if domain != s.serverName {
+		return true
+	}
+
+	util.GetLogger(context.TODO()).WithFields(log.Fields{
+		"sender":     output.Sender,
+		"user_id":    output.UserID,
+		"device_id":  output.DeviceID,
+		"event_type": output.Type,
+	}).Info("sync API received send-to-device event from EDU server")
+
+	streamPos, err := s.db.StoreNewSendForDeviceMessage(
+		s.ctx, output.UserID, output.DeviceID, output.SendToDeviceEvent,
+	)
+	if err != nil {
+		sentry.CaptureException(err)
+		log.WithError(err).Errorf("failed to store send-to-device message")
+		return false
+	}
+
+	s.stream.Advance(streamPos)
+	s.notifier.OnNewSendToDevice(
+		output.UserID,
+		[]string{output.DeviceID},
+		types.StreamingToken{SendToDevicePosition: streamPos},
+	)
+
+	return true
 }

syncapi/consumers/eduserver_typing.go

@@ -35,7 +35,7 @@ import (
 type OutputTypingEventConsumer struct {
 	ctx       context.Context
 	jetstream nats.JetStreamContext
-	durable   nats.SubOpt
+	durable   string
 	topic     string
 	eduCache  *cache.EDUCache
 	stream    types.StreamProvider
@@ -66,41 +66,41 @@ func NewOutputTypingEventConsumer(
 
 // Start consuming from EDU api
 func (s *OutputTypingEventConsumer) Start() error {
-	_, err := s.jetstream.Subscribe(s.topic, s.onMessage, s.durable)
+	return jetstream.JetStreamConsumer(
-	return err
+		s.ctx, s.jetstream, s.topic, s.durable, s.onMessage,
+		nats.DeliverAll(), nats.ManualAck(),
+	)
 }
 
-func (s *OutputTypingEventConsumer) onMessage(msg *nats.Msg) {
+func (s *OutputTypingEventConsumer) onMessage(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	var output api.OutputTypingEvent
-		var output api.OutputTypingEvent
+	if err := json.Unmarshal(msg.Data, &output); err != nil {
-		if err := json.Unmarshal(msg.Data, &output); err != nil {
+		// If the message was invalid, log it and move on to the next message in the stream
-			// If the message was invalid, log it and move on to the next message in the stream
+		log.WithError(err).Errorf("EDU server output log: message parse failure")
-			log.WithError(err).Errorf("EDU server output log: message parse failure")
+		sentry.CaptureException(err)
-			sentry.CaptureException(err)
-			return true
-		}
-
-		log.WithFields(log.Fields{
-			"room_id": output.Event.RoomID,
-			"user_id": output.Event.UserID,
-			"typing":  output.Event.Typing,
-		}).Debug("received data from EDU server")
-
-		var typingPos types.StreamPosition
-		typingEvent := output.Event
-		if typingEvent.Typing {
-			typingPos = types.StreamPosition(
-				s.eduCache.AddTypingUser(typingEvent.UserID, typingEvent.RoomID, output.ExpireTime),
-			)
-		} else {
-			typingPos = types.StreamPosition(
-				s.eduCache.RemoveUser(typingEvent.UserID, typingEvent.RoomID),
-			)
-		}
-
-		s.stream.Advance(typingPos)
-		s.notifier.OnNewTyping(output.Event.RoomID, types.StreamingToken{TypingPosition: typingPos})
-
 		return true
-	})
+	}
+
+	log.WithFields(log.Fields{
+		"room_id": output.Event.RoomID,
+		"user_id": output.Event.UserID,
+		"typing":  output.Event.Typing,
+	}).Debug("received data from EDU server")
+
+	var typingPos types.StreamPosition
+	typingEvent := output.Event
+	if typingEvent.Typing {
+		typingPos = types.StreamPosition(
+			s.eduCache.AddTypingUser(typingEvent.UserID, typingEvent.RoomID, output.ExpireTime),
+		)
+	} else {
+		typingPos = types.StreamPosition(
+			s.eduCache.RemoveUser(typingEvent.UserID, typingEvent.RoomID),
+		)
+	}
+
+	s.stream.Advance(typingPos)
+	s.notifier.OnNewTyping(output.Event.RoomID, types.StreamingToken{TypingPosition: typingPos})
+
+	return true
 }

syncapi/consumers/roomserver.go

@@ -38,7 +38,7 @@ type OutputRoomEventConsumer struct {
 	cfg          *config.SyncAPI
 	rsAPI        api.RoomserverInternalAPI
 	jetstream    nats.JetStreamContext
-	durable      nats.SubOpt
+	durable      string
 	topic        string
 	db           storage.Database
 	pduStream    types.StreamProvider
@@ -73,65 +73,61 @@ func NewOutputRoomEventConsumer(
 
 // Start consuming from room servers
 func (s *OutputRoomEventConsumer) Start() error {
-	_, err := s.jetstream.Subscribe(
+	return jetstream.JetStreamConsumer(
-		s.topic, s.onMessage, s.durable,
+		s.ctx, s.jetstream, s.topic, s.durable, s.onMessage,
-		nats.DeliverAll(),
+		nats.DeliverAll(), nats.ManualAck(),
-		nats.ManualAck(),
 	)
-	return err
 }
 
 // onMessage is called when the sync server receives a new event from the room server output log.
 // It is not safe for this function to be called from multiple goroutines, or else the
 // sync stream position may race and be incorrectly calculated.
-func (s *OutputRoomEventConsumer) onMessage(msg *nats.Msg) {
+func (s *OutputRoomEventConsumer) onMessage(ctx context.Context, msg *nats.Msg) bool {
-	jetstream.WithJetStreamMessage(msg, func(msg *nats.Msg) bool {
+	// Parse out the event JSON
-		// Parse out the event JSON
+	var err error
-		var err error
+	var output api.OutputEvent
-		var output api.OutputEvent
+	if err = json.Unmarshal(msg.Data, &output); err != nil {
-		if err = json.Unmarshal(msg.Data, &output); err != nil {
+		// If the message was invalid, log it and move on to the next message in the stream
-			// If the message was invalid, log it and move on to the next message in the stream
+		log.WithError(err).Errorf("roomserver output log: message parse failure")
-			log.WithError(err).Errorf("roomserver output log: message parse failure")
-			return true
-		}
-
-		switch output.Type {
-		case api.OutputTypeNewRoomEvent:
-			// Ignore redaction events. We will add them to the database when they are
-			// validated (when we receive OutputTypeRedactedEvent)
-			event := output.NewRoomEvent.Event
-			if event.Type() == gomatrixserverlib.MRoomRedaction && event.StateKey() == nil {
-				// in the special case where the event redacts itself, just pass the message through because
-				// we will never see the other part of the pair
-				if event.Redacts() != event.EventID() {
-					return true
-				}
-			}
-			err = s.onNewRoomEvent(s.ctx, *output.NewRoomEvent)
-		case api.OutputTypeOldRoomEvent:
-			err = s.onOldRoomEvent(s.ctx, *output.OldRoomEvent)
-		case api.OutputTypeNewInviteEvent:
-			s.onNewInviteEvent(s.ctx, *output.NewInviteEvent)
-		case api.OutputTypeRetireInviteEvent:
-			s.onRetireInviteEvent(s.ctx, *output.RetireInviteEvent)
-		case api.OutputTypeNewPeek:
-			s.onNewPeek(s.ctx, *output.NewPeek)
-		case api.OutputTypeRetirePeek:
-			s.onRetirePeek(s.ctx, *output.RetirePeek)
-		case api.OutputTypeRedactedEvent:
-			err = s.onRedactEvent(s.ctx, *output.RedactedEvent)
-		default:
-			log.WithField("type", output.Type).Debug(
-				"roomserver output log: ignoring unknown output type",
-			)
-		}
-		if err != nil {
-			log.WithError(err).Error("roomserver output log: failed to process event")
-			return false
-		}
-
 		return true
-	})
+	}
+
+	switch output.Type {
+	case api.OutputTypeNewRoomEvent:
+		// Ignore redaction events. We will add them to the database when they are
+		// validated (when we receive OutputTypeRedactedEvent)
+		event := output.NewRoomEvent.Event
+		if event.Type() == gomatrixserverlib.MRoomRedaction && event.StateKey() == nil {
+			// in the special case where the event redacts itself, just pass the message through because
+			// we will never see the other part of the pair
+			if event.Redacts() != event.EventID() {
+				return true
+			}
+		}
+		err = s.onNewRoomEvent(s.ctx, *output.NewRoomEvent)
+	case api.OutputTypeOldRoomEvent:
+		err = s.onOldRoomEvent(s.ctx, *output.OldRoomEvent)
+	case api.OutputTypeNewInviteEvent:
+		s.onNewInviteEvent(s.ctx, *output.NewInviteEvent)
+	case api.OutputTypeRetireInviteEvent:
+		s.onRetireInviteEvent(s.ctx, *output.RetireInviteEvent)
+	case api.OutputTypeNewPeek:
+		s.onNewPeek(s.ctx, *output.NewPeek)
+	case api.OutputTypeRetirePeek:
+		s.onRetirePeek(s.ctx, *output.RetirePeek)
+	case api.OutputTypeRedactedEvent:
+		err = s.onRedactEvent(s.ctx, *output.RedactedEvent)
+	default:
+		log.WithField("type", output.Type).Debug(
+			"roomserver output log: ignoring unknown output type",
+		)
+	}
+	if err != nil {
+		log.WithError(err).Error("roomserver output log: failed to process event")
+		return false
+	}
+
+	return true
 }
 
 func (s *OutputRoomEventConsumer) onRedactEvent(