Avoid unneeded JSON operations (#2698)

We were `json.Unmarshal`ing the EDU and `json.Marshal`ing right before
sending the EDU to the stream. Those are now removed and the consumer
does `json.Unmarshal` once.

federationapi/producers/syncapi.go

@@ -167,15 +167,11 @@ func (p *SyncAPIProducer) SendPresence(
 }
 
 func (p *SyncAPIProducer) SendDeviceListUpdate(
-	ctx context.Context, deviceListUpdate *gomatrixserverlib.DeviceListUpdateEvent,
+	ctx context.Context, deviceListUpdate gomatrixserverlib.RawJSON, origin string,
 ) (err error) {
 	m := nats.NewMsg(p.TopicDeviceListUpdate)
-	m.Header.Set(jetstream.UserID, deviceListUpdate.UserID)
-	m.Data, err = json.Marshal(deviceListUpdate)
-	if err != nil {
-		return fmt.Errorf("json.Marshal: %w", err)
-	}
-
+	m.Header.Set("origin", origin)
+	m.Data = deviceListUpdate
 	log.Debugf("Sending device list update: %+v", m.Header)
 	_, err = p.JetStream.PublishMsg(m, nats.Context(ctx))
 	return err

federationapi/routing/send.go

@@ -359,7 +359,9 @@ func (t *txnReq) processEDUs(ctx context.Context) {
 				}
 			}
 		case gomatrixserverlib.MDeviceListUpdate:
-			t.processDeviceListUpdate(ctx, e)
+			if err := t.producer.SendDeviceListUpdate(ctx, e.Content, e.Origin); err != nil {
+				util.GetLogger(ctx).WithError(err).Error("failed to InputDeviceListUpdate")
+			}
 		case gomatrixserverlib.MReceipt:
 			// https://matrix.org/docs/spec/server_server/r0.1.4#receipts
 			payload := map[string]types.FederationReceiptMRead{}
@@ -454,21 +456,3 @@ func (t *txnReq) processReceiptEvent(ctx context.Context,
 
 	return nil
 }
-
-func (t *txnReq) processDeviceListUpdate(ctx context.Context, e gomatrixserverlib.EDU) {
-	var payload gomatrixserverlib.DeviceListUpdateEvent
-	if err := json.Unmarshal(e.Content, &payload); err != nil {
-		util.GetLogger(ctx).WithError(err).Error("Failed to unmarshal device list update event")
-		return
-	}
-	if _, serverName, err := gomatrixserverlib.SplitID('@', payload.UserID); err != nil {
-		return
-	} else if serverName == t.ourServerName {
-		return
-	} else if serverName != t.Origin {
-		return
-	}
-	if err := t.producer.SendDeviceListUpdate(ctx, &payload); err != nil {
-		util.GetLogger(ctx).WithError(err).WithField("user_id", payload.UserID).Error("failed to InputDeviceListUpdate")
-	}
-}

keyserver/consumers/devicelistupdate.go

@@ -18,22 +18,24 @@ import (
 	"context"
 	"encoding/json"
 
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/nats-io/nats.go"
+	"github.com/sirupsen/logrus"
+
 	"github.com/matrix-org/dendrite/keyserver/internal"
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/dendrite/setup/jetstream"
 	"github.com/matrix-org/dendrite/setup/process"
-	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/nats-io/nats.go"
-	"github.com/sirupsen/logrus"
 )
 
 // DeviceListUpdateConsumer consumes device list updates that came in over federation.
 type DeviceListUpdateConsumer struct {
-	ctx       context.Context
-	jetstream nats.JetStreamContext
-	durable   string
-	topic     string
-	updater   *internal.DeviceListUpdater
+	ctx        context.Context
+	jetstream  nats.JetStreamContext
+	durable    string
+	topic      string
+	updater    *internal.DeviceListUpdater
+	serverName gomatrixserverlib.ServerName
 }
 
 // NewDeviceListUpdateConsumer creates a new DeviceListConsumer. Call Start() to begin consuming from key servers.
@@ -44,11 +46,12 @@ func NewDeviceListUpdateConsumer(
 	updater *internal.DeviceListUpdater,
 ) *DeviceListUpdateConsumer {
 	return &DeviceListUpdateConsumer{
-		ctx:       process.Context(),
-		jetstream: js,
-		durable:   cfg.Matrix.JetStream.Prefixed("KeyServerInputDeviceListConsumer"),
-		topic:     cfg.Matrix.JetStream.Prefixed(jetstream.InputDeviceListUpdate),
-		updater:   updater,
+		ctx:        process.Context(),
+		jetstream:  js,
+		durable:    cfg.Matrix.JetStream.Prefixed("KeyServerInputDeviceListConsumer"),
+		topic:      cfg.Matrix.JetStream.Prefixed(jetstream.InputDeviceListUpdate),
+		updater:    updater,
+		serverName: cfg.Matrix.ServerName,
 	}
 }
 
@@ -69,6 +72,15 @@ func (t *DeviceListUpdateConsumer) onMessage(ctx context.Context, msgs []*nats.M
 		logrus.WithError(err).Errorf("Failed to read from device list update input topic")
 		return true
 	}
+	origin := gomatrixserverlib.ServerName(msg.Header.Get("origin"))
+	if _, serverName, err := gomatrixserverlib.SplitID('@', m.UserID); err != nil {
+		return true
+	} else if serverName == t.serverName {
+		return true
+	} else if serverName != origin {
+		return true
+	}
+
 	err := t.updater.Update(ctx, m)
 	if err != nil {
 		logrus.WithFields(logrus.Fields{