Don't prematurely stop trying to join using servers (#1041)

* Don't prematurely stop trying to join using servers

* Factor out performJoinUsingServer

federationsender/internal/perform.go

@@ -52,13 +52,46 @@ func (r *FederationSenderInternalAPI) PerformJoin(
 	// Try each server that we were provided until we land on one that
 	// successfully completes the make-join send-join dance.
 	for _, serverName := range request.ServerNames {
+		if err := r.performJoinUsingServer(
+			ctx,
+			request.RoomID,
+			request.UserID,
+			request.Content,
+			serverName,
+			supportedVersions,
+		); err != nil {
+			logrus.WithError(err).WithFields(logrus.Fields{
+				"server_name": serverName,
+				"room_id":     request.RoomID,
+			}).Warnf("Failed to join room through server")
+			continue
+		}
+
+		// We're all good.
+		return nil
+	}
+
+	// If we reach here then we didn't complete a join for some reason.
+	return fmt.Errorf(
+		"failed to join user %q to room %q through %d server(s)",
+		request.UserID, request.RoomID, len(request.ServerNames),
+	)
+}
+
+func (r *FederationSenderInternalAPI) performJoinUsingServer(
+	ctx context.Context,
+	roomID, userID string,
+	content map[string]interface{},
+	serverName gomatrixserverlib.ServerName,
+	supportedVersions []gomatrixserverlib.RoomVersion,
+) error {
 	// Try to perform a make_join using the information supplied in the
 	// request.
 	respMakeJoin, err := r.federation.MakeJoin(
 		ctx,
 		serverName,
-			request.RoomID,
+		roomID,
-			request.UserID,
+		userID,
 		supportedVersions,
 	)
 	if err != nil {
@@ -66,19 +99,20 @@ func (r *FederationSenderInternalAPI) PerformJoin(
 		r.statistics.ForServer(serverName).Failure()
 		return fmt.Errorf("r.federation.MakeJoin: %w", err)
 	}
+	r.statistics.ForServer(serverName).Success()
 
 	// Set all the fields to be what they should be, this should be a no-op
 	// but it's possible that the remote server returned us something "odd"
 	respMakeJoin.JoinEvent.Type = gomatrixserverlib.MRoomMember
-		respMakeJoin.JoinEvent.Sender = request.UserID
+	respMakeJoin.JoinEvent.Sender = userID
-		respMakeJoin.JoinEvent.StateKey = &request.UserID
+	respMakeJoin.JoinEvent.StateKey = &userID
-		respMakeJoin.JoinEvent.RoomID = request.RoomID
+	respMakeJoin.JoinEvent.RoomID = roomID
 	respMakeJoin.JoinEvent.Redacts = ""
-		if request.Content == nil {
+	if content == nil {
-			request.Content = map[string]interface{}{}
+		content = map[string]interface{}{}
 	}
-		request.Content["membership"] = "join"
+	content["membership"] = "join"
-		if err = respMakeJoin.JoinEvent.SetContent(request.Content); err != nil {
+	if err = respMakeJoin.JoinEvent.SetContent(content); err != nil {
 		return fmt.Errorf("respMakeJoin.JoinEvent.SetContent: %w", err)
 	}
 	if err = respMakeJoin.JoinEvent.SetUnsigned(struct{}{}); err != nil {
@@ -114,18 +148,17 @@ func (r *FederationSenderInternalAPI) PerformJoin(
 		respMakeJoin.RoomVersion,
 	)
 	if err != nil {
-			logrus.WithError(err).Warnf("r.federation.SendJoin failed")
 		r.statistics.ForServer(serverName).Failure()
-			continue
+		return fmt.Errorf("r.federation.SendJoin: %w", err)
 	}
+	r.statistics.ForServer(serverName).Success()
 
 	// Check that the send_join response was valid.
 	joinCtx := perform.JoinContext(r.federation, r.keyRing)
 	if err = joinCtx.CheckSendJoinResponse(
 		ctx, event, serverName, respMakeJoin, respSendJoin,
 	); err != nil {
-			logrus.WithError(err).Warnf("joinCtx.CheckSendJoinResponse failed")
+		return fmt.Errorf("joinCtx.CheckSendJoinResponse: %w", err)
-			continue
 	}
 
 	// If we successfully performed a send_join above then the other
@@ -136,22 +169,12 @@ func (r *FederationSenderInternalAPI) PerformJoin(
 		respSendJoin.ToRespState(),
 		event.Headered(respMakeJoin.RoomVersion),
 	); err != nil {
-			logrus.WithError(err).Warnf("r.producer.SendEventWithState failed")
+		return fmt.Errorf("r.producer.SendEventWithState: %w", err)
-			continue
 	}
 
-		// We're all good.
-		r.statistics.ForServer(serverName).Success()
 	return nil
 }
 
-	// If we reach here then we didn't complete a join for some reason.
-	return fmt.Errorf(
-		"failed to join user %q to room %q through %d server(s)",
-		request.UserID, request.RoomID, len(request.ServerNames),
-	)
-}
-
 // PerformLeaveRequest implements api.FederationSenderInternalAPI
 func (r *FederationSenderInternalAPI) PerformLeave(
 	ctx context.Context,