Remove roominfo cache (#2615)

* Remove roominfo cache

It's the source of a number of race conditions which are seemingly causing bugs and CI failures.

* Make the linter less sad

5 files changed, 9 insertions, 68 deletions

diff --git a/internal/caching/cache_roominfo.go b/internal/caching/cache_roominfo.go
deleted file mode 100644
index 5dfed3c8..00000000
--- a/internal/caching/cache_roominfo.go
+++ /dev/null
@@ -1,33 +0,0 @@
-package caching
-
-import (
-	"github.com/matrix-org/dendrite/roomserver/types"
-)
-
-// WARNING: This cache is mutable because it's entirely possible that
-// the IsStub or StateSnaphotNID fields can change, even though the
-// room version and room NID fields will not. This is only safe because
-// the RoomInfoCache is used ONLY within the roomserver and because it
-// will be kept up-to-date by the latest events updater. It MUST NOT be
-// used from other components as we currently have no way to invalidate
-// the cache in downstream components.
-
-// RoomInfosCache contains the subset of functions needed for
-// a room Info cache. It must only be used from the roomserver only
-// It is not safe for use from other components.
-type RoomInfoCache interface {
-	GetRoomInfo(roomID string) (roomInfo *types.RoomInfo, ok bool)
-	StoreRoomInfo(roomID string, roomInfo *types.RoomInfo)
-}
-
-// GetRoomInfo must only be called from the roomserver only. It is not
-// safe for use from other components.
-func (c Caches) GetRoomInfo(roomID string) (*types.RoomInfo, bool) {
-	return c.RoomInfos.Get(roomID)
-}
-
-// StoreRoomInfo must only be called from the roomserver only. It is not
-// safe for use from other components.
-func (c Caches) StoreRoomInfo(roomID string, roomInfo *types.RoomInfo) {
-	c.RoomInfos.Set(roomID, roomInfo)
-}
diff --git a/internal/caching/cache_roomservernids.go b/internal/caching/cache_roomservernids.go
index f27154f1..88a5b28b 100644
--- a/internal/caching/cache_roomservernids.go
+++ b/internal/caching/cache_roomservernids.go
@@ -7,7 +7,6 @@ import (
 type RoomServerCaches interface {
 	RoomServerNIDsCache
 	RoomVersionCache
-	RoomInfoCache
 	RoomServerEventsCache
 	EventStateKeyCache
 }
diff --git a/internal/caching/caches.go b/internal/caching/caches.go
index f13f743d..78c9ab7e 100644
--- a/internal/caching/caches.go
+++ b/internal/caching/caches.go
@@ -29,7 +29,6 @@ type Caches struct {
 	RoomServerRoomIDs   Cache[types.RoomNID, string]                           // room NID -> room ID
 	RoomServerEvents    Cache[int64, *gomatrixserverlib.Event]                 // event NID -> event
 	RoomServerStateKeys Cache[types.EventStateKeyNID, string]                  // event NID -> event state key
-	RoomInfos           Cache[string, *types.RoomInfo]                         // room ID -> room info
 	FederationPDUs      Cache[int64, *gomatrixserverlib.HeaderedEvent]         // queue NID -> PDU
 	FederationEDUs      Cache[int64, *gomatrixserverlib.EDU]                   // queue NID -> EDU
 	SpaceSummaryRooms   Cache[string, gomatrixserverlib.MSC2946SpacesResponse] // room ID -> space response
diff --git a/internal/caching/impl_ristretto.go b/internal/caching/impl_ristretto.go
index fdbbb4d7..fc0c8cc0 100644
--- a/internal/caching/impl_ristretto.go
+++ b/internal/caching/impl_ristretto.go
@@ -35,7 +35,6 @@ const (
 	roomNIDsCache
 	roomIDsCache
 	roomEventsCache
-	roomInfosCache
 	federationPDUsCache
 	federationEDUsCache
 	spaceSummaryRoomsCache
@@ -106,12 +105,6 @@ func NewRistrettoCache(maxCost config.DataUnit, maxAge time.Duration, enableProm
 			Prefix: eventStateKeyCache,
 			MaxAge: maxAge,
 		},
-		RoomInfos: &RistrettoCachePartition[string, *types.RoomInfo]{ // room ID -> room info
-			cache:   cache,
-			Prefix:  roomInfosCache,
-			Mutable: true,
-			MaxAge:  maxAge,
-		},
 		FederationPDUs: &RistrettoCostedCachePartition[int64, *gomatrixserverlib.HeaderedEvent]{ // queue NID -> PDU
 			&RistrettoCachePartition[int64, *gomatrixserverlib.HeaderedEvent]{
 				cache:   cache,
diff --git a/roomserver/storage/shared/storage.go b/roomserver/storage/shared/storage.go
index 9e6a4142..cbf9c8b2 100644
--- a/roomserver/storage/shared/storage.go
+++ b/roomserver/storage/shared/storage.go
@@ -156,30 +156,15 @@ func (d *Database) RoomInfo(ctx context.Context, roomID string) (*types.RoomInfo
 }
 
 func (d *Database) roomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error) {
-	roomInfo, ok := d.Cache.GetRoomInfo(roomID)
-	if ok && roomInfo != nil && !roomInfo.IsStub() {
-		// The data that's in the cache is not stubby, so return it.
-		return roomInfo, nil
-	}
-	// At this point we either don't have an entry in the cache, or
-	// it is stubby, so let's check the roomserver_rooms table again.
-	roomInfoFromDB, err := d.RoomsTable.SelectRoomInfo(ctx, txn, roomID)
+	roomInfo, err := d.RoomsTable.SelectRoomInfo(ctx, txn, roomID)
 	if err != nil {
 		return nil, err
 	}
-	// If we have a stubby cache entry already, update it and return
-	// the reference to the cache entry.
 	if roomInfo != nil {
-		roomInfo.CopyFrom(roomInfoFromDB)
-		return roomInfo, nil
+		d.Cache.StoreRoomServerRoomID(roomInfo.RoomNID, roomID)
+		d.Cache.StoreRoomVersion(roomID, roomInfo.RoomVersion)
 	}
-	// Otherwise, try to admit the data into the cache and return the
-	// new reference from the database.
-	if roomInfoFromDB != nil {
-		d.Cache.StoreRoomServerRoomID(roomInfoFromDB.RoomNID, roomID)
-		d.Cache.StoreRoomInfo(roomID, roomInfoFromDB)
-	}
-	return roomInfoFromDB, err
+	return roomInfo, err
 }
 
 func (d *Database) AddState(
@@ -504,8 +489,8 @@ func (d *Database) events(
 	fetchNIDList := make([]types.RoomNID, 0, len(uniqueRoomNIDs))
 	for n := range uniqueRoomNIDs {
 		if roomID, ok := d.Cache.GetRoomServerRoomID(n); ok {
-			if roomInfo, ok := d.Cache.GetRoomInfo(roomID); ok {
-				roomVersions[n] = roomInfo.RoomVersion
+			if roomVersion, ok := d.Cache.GetRoomVersion(roomID); ok {
+				roomVersions[n] = roomVersion
 				continue
 			}
 		}
@@ -762,9 +747,6 @@ func (d *Database) MissingAuthPrevEvents(
 func (d *Database) assignRoomNID(
 	ctx context.Context, roomID string, roomVersion gomatrixserverlib.RoomVersion,
 ) (types.RoomNID, error) {
-	if roomInfo, ok := d.Cache.GetRoomInfo(roomID); ok {
-		return roomInfo.RoomNID, nil
-	}
 	// Check if we already have a numeric ID in the database.
 	roomNID, err := d.RoomsTable.SelectRoomNID(ctx, nil, roomID)
 	if err == sql.ErrNoRows {
@@ -837,8 +819,9 @@ func extractRoomVersionFromCreateEvent(event *gomatrixserverlib.Event) (
 // "servers should not apply or send redactions to clients until both the redaction event and original event have been seen, and are valid."
 // https://matrix.org/docs/spec/rooms/v3#authorization-rules-for-events
 // These cases are:
-//  - This is a redaction event, redact the event it references if we know about it.
-//  - This is a normal event which may have been previously redacted.
+//   - This is a redaction event, redact the event it references if we know about it.
+//   - This is a normal event which may have been previously redacted.
+//
 // In the first case, check if we have the referenced event then apply the redaction, else store it
 // in the redactions table with validated=FALSE. In the second case, check if there is a redaction for it:
 // if there is then apply the redactions and set validated=TRUE.