Add trace logging to RoomserverInternalAPI (#1120)

This is a wrapper around whatever impl we have which then logs
the function name/request/response/error.

Also tweak when we log on kafka streams: only log on the producer
side not the consumer side: we've never had issues with comms and
having 1 message rather than N would be nice.

clientapi/producers/syncapi.go

@@ -17,9 +17,9 @@ package producers
 import (
 	"encoding/json"
 
-	"github.com/matrix-org/dendrite/internal"
-
 	"github.com/Shopify/sarama"
+	"github.com/matrix-org/dendrite/internal"
+	log "github.com/sirupsen/logrus"
 )
 
 // SyncAPIProducer produces events for the sync API server to consume
@@ -44,6 +44,11 @@ func (p *SyncAPIProducer) SendData(userID string, roomID string, dataType string
 	m.Topic = string(p.Topic)
 	m.Key = sarama.StringEncoder(userID)
 	m.Value = sarama.ByteEncoder(value)
+	log.WithFields(log.Fields{
+		"user_id":   userID,
+		"room_id":   roomID,
+		"data_type": dataType,
+	}).Infof("Producing to topic '%s'", p.Topic)
 
 	_, _, err = p.Producer.SendMessage(&m)
 	return err