Initial FIFOing of roomserver inputs

roomserver/internal/input/input.go

@@ -19,12 +19,15 @@ import (
 	"context"
 	"encoding/json"
 	"sync"
+	"time"
 
 	"github.com/Shopify/sarama"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/storage"
 	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/sirupsen/logrus"
 	log "github.com/sirupsen/logrus"
+	"go.uber.org/atomic"
 )
 
 type Inputer struct {
@@ -33,7 +36,43 @@ type Inputer struct {
 	ServerName           gomatrixserverlib.ServerName
 	OutputRoomEventTopic string
 
-	mutexes sync.Map // room ID -> *sync.Mutex, protects calls to processRoomEvent
+	workers sync.Map // room ID -> *inputWorker
+}
+
+type inputTask struct {
+	event   api.InputRoomEvent
+	wg      *sync.WaitGroup
+	eventID string // written back by worker
+	err     error  // written back by worker
+}
+
+type inputWorker struct {
+	r       *Inputer
+	running atomic.Bool
+	input   chan *inputTask
+}
+
+func (w *inputWorker) start() {
+	if !w.running.CAS(false, true) {
+		return
+	}
+	defer w.running.Store(false)
+
+	logrus.Warn("STARTING WORKER")
+	defer logrus.Warn("SHUTTING DOWN WORKER")
+
+	for {
+		select {
+		case task := <-w.input:
+			logrus.Warn("WORKER DOING TASK")
+			task.eventID, task.err = w.r.processRoomEvent(context.TODO(), task.event)
+			logrus.Warn("WORKER FINISHING TASK")
+			task.wg.Done()
+			logrus.Warn("WORKER FINISHED TASK")
+		case <-time.After(time.Second * 5):
+			return
+		}
+	}
 }
 
 // WriteOutputEvents implements OutputRoomEventWriter
@@ -74,18 +113,50 @@ func (r *Inputer) InputRoomEvents(
 	request *api.InputRoomEventsRequest,
 	response *api.InputRoomEventsResponse,
 ) (err error) {
+	wg := &sync.WaitGroup{}
+	wg.Add(len(request.InputRoomEvents))
+	tasks := make([]*inputTask, len(request.InputRoomEvents))
+	logrus.Warnf("Received %d input events", len(tasks))
+
 	for i, e := range request.InputRoomEvents {
+		// Work out if we are running per-room workers or if we're just doing
+		// it on a global basis (e.g. SQLite).
 		roomID := "global"
 		if r.DB.SupportsConcurrentRoomInputs() {
 			roomID = e.Event.RoomID()
 		}
-		mutex, _ := r.mutexes.LoadOrStore(roomID, &sync.Mutex{})
-		mutex.(*sync.Mutex).Lock()
-		if response.EventID, err = r.processRoomEvent(ctx, request.InputRoomEvents[i]); err != nil {
-			mutex.(*sync.Mutex).Unlock()
-			return err
+
+		// Look up the worker, or create it if it doesn't exist.
+		w, _ := r.workers.LoadOrStore(roomID, &inputWorker{
+			r:     r,
+			input: make(chan *inputTask),
+		})
+		worker := w.(*inputWorker)
+
+		// Create a task. This contains the input event and a reference to
+		// the wait group, so that the worker can notify us when this specific
+		// task has been finished.
+		tasks[i] = &inputTask{
+			event: e,
+			wg:    wg,
 		}
-		mutex.(*sync.Mutex).Unlock()
+
+		// Send the task to the worker.
+		go func(task *inputTask) { worker.input <- task }(tasks[i])
+		go worker.start()
 	}
+
+	logrus.Warnf("Waiting for %d task(s)", len(tasks))
+	wg.Wait()
+	logrus.Warnf("Tasks finished")
+
+	for _, task := range tasks {
+		if task.err != nil {
+			logrus.Warnf("Error: %w", task.err)
+		} else {
+			logrus.Warnf("Event ID: %s", task.eventID)
+		}
+	}
+
 	return nil
 }