Fix backfilling (#2926)

This should fix #2923

Author: S7evinK

Diff for: go.mod

@@ -22,7 +22,7 @@ require (
 	github.com/matrix-org/dugong v0.0.0-20210921133753-66e6b1c67e2e
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20220419092513-28aa791a1c91
 	github.com/matrix-org/gomatrix v0.0.0-20220926102614-ceba4d9f7530
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20221129095800-8835f6db16b8
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20230105074811-965b10ae73ab
 	github.com/matrix-org/pinecone v0.0.0-20221118192051-fef26631b847
 	github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4
 	github.com/mattn/go-sqlite3 v1.14.15

Diff for: go.sum

@@ -348,8 +348,8 @@ github.com/matrix-org/go-sqlite3-js v0.0.0-20220419092513-28aa791a1c91 h1:s7fexw
 github.com/matrix-org/go-sqlite3-js v0.0.0-20220419092513-28aa791a1c91/go.mod h1:e+cg2q7C7yE5QnAXgzo512tgFh1RbQLC0+jozuegKgo=
 github.com/matrix-org/gomatrix v0.0.0-20220926102614-ceba4d9f7530 h1:kHKxCOLcHH8r4Fzarl4+Y3K5hjothkVW5z7T1dUM11U=
 github.com/matrix-org/gomatrix v0.0.0-20220926102614-ceba4d9f7530/go.mod h1:/gBX06Kw0exX1HrwmoBibFA98yBk/jxKpGVeyQbff+s=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20221129095800-8835f6db16b8 h1:jVvlCGs6OosCdvw9MkfiVnTVnIt7vKMHg/F6th9BtSo=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20221129095800-8835f6db16b8/go.mod h1:Mtifyr8q8htcBeugvlDnkBcNUy5LO8OzUoplAf1+mb4=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20230105074811-965b10ae73ab h1:ChaQdT2mpxMm3GRXNOZzLDQ/wOnlKZ8o60LmZGOjdj8=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20230105074811-965b10ae73ab/go.mod h1:Mtifyr8q8htcBeugvlDnkBcNUy5LO8OzUoplAf1+mb4=
 github.com/matrix-org/pinecone v0.0.0-20221118192051-fef26631b847 h1:auIBCi7gfZuvztD0aPr1G/J5Ya5vWr79M/+TJqwD/JM=
 github.com/matrix-org/pinecone v0.0.0-20221118192051-fef26631b847/go.mod h1:F3GHppRuHCTDeoOmmgjZMeJdbql91+RSGGsATWfC7oc=
 github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4 h1:eCEHXWDv9Rm335MSuB49mFUK44bwZPFSDde3ORE3syk=

Diff for: roomserver/internal/perform/perform_backfill.go

@@ -122,11 +122,14 @@ func (r *Backfiller) backfillViaFederation(ctx context.Context, req *api.Perform
 		ctx, req.VirtualHost, requester,
 		r.KeyRing, req.RoomID, info.RoomVersion, req.PrevEventIDs(), 100,
 	)
-	if err != nil {
+	// Only return an error if we really couldn't get any events.
+	if err != nil && len(events) == 0 {
 		logrus.WithError(err).Errorf("gomatrixserverlib.RequestBackfill failed")
 		return err
 	}
-	logrus.WithField("room_id", req.RoomID).Infof("backfilled %d events", len(events))
+	// If we got an error but still got events, that's fine, because a server might have returned a 404 (or something)
+	// but other servers could provide the missing event.
+	logrus.WithError(err).WithField("room_id", req.RoomID).Infof("backfilled %d events", len(events))
 
 	// persist these new events - auth checks have already been done
 	roomNID, backfilledEventMap := persistEvents(ctx, r.DB, events)
@@ -319,6 +322,7 @@ FederationHit:
 			FedClient:          b.fsAPI,
 			RememberAuthEvents: false,
 			Server:             srv,
+			Origin:             b.virtualHost,
 		}
 		res, err := c.StateIDsBeforeEvent(ctx, targetEvent)
 		if err != nil {
@@ -394,6 +398,7 @@ func (b *backfillRequester) StateBeforeEvent(ctx context.Context, roomVer gomatr
 			FedClient:          b.fsAPI,
 			RememberAuthEvents: false,
 			Server:             srv,
+			Origin:             b.virtualHost,
 		}
 		result, err := c.StateBeforeEvent(ctx, roomVer, event, eventIDs)
 		if err != nil {