Ensure only one transaction is used for RS input per room (#2178)

* Ensure the input API only uses a single transaction

* Remove more of the dead query API call

* Tidy up

* Fix tests hopefully

* Don't do unnecessary work for rooms that don't exist

* Improve error, fix another case where transaction wasn't used properly

* Add a unit test for checking single transaction on RS input API

* Fix logic oops when deciding whether to use a transaction in storeEvent

roomserver/internal/input/input_test.go

@@ -0,0 +1,93 @@
+package input_test
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/matrix-org/dendrite/internal/caching"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/roomserver/internal/input"
+	"github.com/matrix-org/dendrite/roomserver/storage"
+	"github.com/matrix-org/dendrite/setup/config"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+func psqlConnectionString() config.DataSource {
+	user := os.Getenv("POSTGRES_USER")
+	if user == "" {
+		user = "dendrite"
+	}
+	dbName := os.Getenv("POSTGRES_DB")
+	if dbName == "" {
+		dbName = "dendrite"
+	}
+	connStr := fmt.Sprintf(
+		"user=%s dbname=%s sslmode=disable", user, dbName,
+	)
+	password := os.Getenv("POSTGRES_PASSWORD")
+	if password != "" {
+		connStr += fmt.Sprintf(" password=%s", password)
+	}
+	host := os.Getenv("POSTGRES_HOST")
+	if host != "" {
+		connStr += fmt.Sprintf(" host=%s", host)
+	}
+	return config.DataSource(connStr)
+}
+
+func TestSingleTransactionOnInput(t *testing.T) {
+	deadline, _ := t.Deadline()
+	if max := time.Now().Add(time.Second * 3); deadline.After(max) {
+		deadline = max
+	}
+	ctx, cancel := context.WithDeadline(context.Background(), deadline)
+	defer cancel()
+
+	event, err := gomatrixserverlib.NewEventFromTrustedJSON(
+		[]byte(`{"auth_events":[],"content":{"creator":"@neilalexander:dendrite.matrix.org","room_version":"6"},"depth":1,"hashes":{"sha256":"jqOqdNEH5r0NiN3xJtj0u5XUVmRqq9YvGbki1wxxuuM"},"origin":"dendrite.matrix.org","origin_server_ts":1644595362726,"prev_events":[],"prev_state":[],"room_id":"!jSZZRknA6GkTBXNP:dendrite.matrix.org","sender":"@neilalexander:dendrite.matrix.org","signatures":{"dendrite.matrix.org":{"ed25519:6jB2aB":"bsQXO1wketf1OSe9xlndDIWe71W9KIundc6rBw4KEZdGPW7x4Tv4zDWWvbxDsG64sS2IPWfIm+J0OOozbrWIDw"}},"state_key":"","type":"m.room.create"}`),
+		false, gomatrixserverlib.RoomVersionV6,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	in := api.InputRoomEvent{
+		Kind:  api.KindOutlier, // don't panic if we generate an output event
+		Event: event.Headered(gomatrixserverlib.RoomVersionV6),
+	}
+	cache, err := caching.NewInMemoryLRUCache(false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	db, err := storage.Open(
+		&config.DatabaseOptions{
+			ConnectionString:   psqlConnectionString(),
+			MaxOpenConnections: 1,
+			MaxIdleConnections: 1,
+		},
+		cache,
+	)
+	if err != nil {
+		t.Logf("PostgreSQL not available (%s), skipping", err)
+		t.SkipNow()
+	}
+	inputter := &input.Inputer{
+		DB: db,
+	}
+	res := &api.InputRoomEventsResponse{}
+	inputter.InputRoomEvents(
+		ctx,
+		&api.InputRoomEventsRequest{
+			InputRoomEvents: []api.InputRoomEvent{in},
+			Asynchronous:    false,
+		},
+		res,
+	)
+	// If we fail here then it's because we've hit the test deadline,
+	// so we probably deadlocked
+	if err := res.Err(); err != nil {
+		t.Fatal(err)
+	}
+}