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
@@ -66,14 +66,15 @@ 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
 	var output api.OutputEvent
 	if err := json.Unmarshal(msg.Data, &output); err != nil {
@@ -96,7 +97,6 @@ func (s *OutputRoomEventConsumer) onMessage(msg *nats.Msg) {
 	}
 
 	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
@@ -80,9 +89,8 @@ 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
 	if err := json.Unmarshal(msg.Data, &ote); err != nil {
 		log.WithError(err).Errorf("eduserver output log: message parse failed (expected send-to-device)")
@@ -133,13 +141,11 @@ func (t *OutputEDUConsumer) onSendToDeviceEvent(msg *nats.Msg) {
 	}
 
 	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.
 	var ote api.OutputTypingEvent
 	if err := json.Unmarshal(msg.Data, &ote); err != nil {
@@ -160,7 +166,7 @@ func (t *OutputEDUConsumer) onTypingEvent(msg *nats.Msg) {
 		return true
 	}
 
-		joined, err := t.db.GetJoinedHosts(t.ctx, ote.Event.RoomID)
+	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
@@ -187,13 +193,11 @@ func (t *OutputEDUConsumer) onTypingEvent(msg *nats.Msg) {
 	}
 
 	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.
 	var receipt api.OutputReceiptEvent
 	if err := json.Unmarshal(msg.Data, &receipt); err != nil {
@@ -212,7 +216,7 @@ func (t *OutputEDUConsumer) onReceiptEvent(msg *nats.Msg) {
 		return true
 	}
 
-		joined, err := t.db.GetJoinedHosts(t.ctx, receipt.RoomID)
+	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
@@ -250,5 +254,4 @@ func (t *OutputEDUConsumer) onReceiptEvent(msg *nats.Msg) {
 	}
 
 	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
@@ -66,20 +66,17 @@ 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
 	var output api.OutputEvent
 	if err := json.Unmarshal(msg.Data, &output); err != nil {
@@ -133,7 +130,6 @@ func (s *OutputRoomEventConsumer) onMessage(msg *nats.Msg) {
 	}
 
 	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
@@ -63,15 +63,16 @@ 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
 	userID := msg.Header.Get(jetstream.UserID)
 	var output eventutil.AccountData
@@ -103,5 +104,4 @@ func (s *OutputClientDataConsumer) onMessage(msg *nats.Msg) {
 	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
@@ -64,12 +64,13 @@ 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
 	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
@@ -95,5 +96,4 @@ func (s *OutputReceiptEventConsumer) onMessage(msg *nats.Msg) {
 	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
@@ -68,12 +68,13 @@ 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
 	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
@@ -115,5 +116,4 @@ func (s *OutputSendToDeviceEventConsumer) onMessage(msg *nats.Msg) {
 	)
 
 	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
@@ -66,12 +66,13 @@ 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
 	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
@@ -102,5 +103,4 @@ func (s *OutputTypingEventConsumer) onMessage(msg *nats.Msg) {
 	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
@@ -73,19 +73,16 @@ 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
 	var err error
 	var output api.OutputEvent
@@ -131,7 +128,6 @@ func (s *OutputRoomEventConsumer) onMessage(msg *nats.Msg) {
 	}
 
 	return true
-	})
 }
 
 func (s *OutputRoomEventConsumer) onRedactEvent(