More flexible caching (#1101)

16 files changed, 189 insertions, 142 deletions

diff --git a/cmd/roomserver-integration-tests/main.go b/cmd/roomserver-integration-tests/main.go
index 2433f9ff..43aca078 100644
--- a/cmd/roomserver-integration-tests/main.go
+++ b/cmd/roomserver-integration-tests/main.go
@@ -255,7 +255,7 @@ func testRoomserver(input []string, wantOutput []string, checkQueries func(api.R
 		panic(err)
 	}
 
-	cache, err := caching.NewImmutableInMemoryLRUCache()
+	cache, err := caching.NewInMemoryLRUCache()
 	if err != nil {
 		panic(err)
 	}
diff --git a/internal/basecomponent/base.go b/internal/basecomponent/base.go
index 620b12d6..3ad1e4af 100644
--- a/internal/basecomponent/base.go
+++ b/internal/basecomponent/base.go
@@ -66,7 +66,7 @@ type BaseDendrite struct {
 	UseHTTPAPIs    bool
 	httpClient     *http.Client
 	Cfg            *config.Dendrite
-	ImmutableCache caching.ImmutableCache
+	Caches         *caching.Caches
 	KafkaConsumer  sarama.Consumer
 	KafkaProducer  sarama.SyncProducer
 }
@@ -95,7 +95,7 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string, useHTTPAPIs boo
 		kafkaConsumer, kafkaProducer = setupKafka(cfg)
 	}
 
-	cache, err := caching.NewImmutableInMemoryLRUCache()
+	cache, err := caching.NewInMemoryLRUCache()
 	if err != nil {
 		logrus.WithError(err).Warnf("Failed to create cache")
 	}
@@ -126,7 +126,7 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string, useHTTPAPIs boo
 		UseHTTPAPIs:    useHTTPAPIs,
 		tracerCloser:   closer,
 		Cfg:            cfg,
-		ImmutableCache: cache,
+		Caches:         cache,
 		PublicAPIMux:   httpmux.PathPrefix(httpapis.PublicPathPrefix).Subrouter().UseEncodedPath(),
 		InternalAPIMux: httpmux.PathPrefix(httpapis.InternalPathPrefix).Subrouter().UseEncodedPath(),
 		httpClient:     &client,
@@ -151,7 +151,7 @@ func (b *BaseDendrite) AppserviceHTTPClient() appserviceAPI.AppServiceQueryAPI {
 
 // RoomserverHTTPClient returns RoomserverInternalAPI for hitting the roomserver over HTTP.
 func (b *BaseDendrite) RoomserverHTTPClient() roomserverAPI.RoomserverInternalAPI {
-	rsAPI, err := rsinthttp.NewRoomserverClient(b.Cfg.RoomServerURL(), b.httpClient, b.ImmutableCache)
+	rsAPI, err := rsinthttp.NewRoomserverClient(b.Cfg.RoomServerURL(), b.httpClient, b.Caches)
 	if err != nil {
 		logrus.WithError(err).Panic("RoomserverHTTPClient failed", b.httpClient)
 	}
@@ -182,7 +182,7 @@ func (b *BaseDendrite) ServerKeyAPIClient() serverKeyAPI.ServerKeyInternalAPI {
 	f, err := skinthttp.NewServerKeyClient(
 		b.Cfg.ServerKeyAPIURL(),
 		b.httpClient,
-		b.ImmutableCache,
+		b.Caches,
 	)
 	if err != nil {
 		logrus.WithError(err).Panic("NewServerKeyInternalAPIHTTP failed", b.httpClient)
diff --git a/internal/caching/cache_roomversions.go b/internal/caching/cache_roomversions.go
new file mode 100644
index 00000000..0b46d3d4
--- /dev/null
+++ b/internal/caching/cache_roomversions.go
@@ -0,0 +1,30 @@
+package caching
+
+import "github.com/matrix-org/gomatrixserverlib"
+
+const (
+	RoomVersionCacheName       = "room_versions"
+	RoomVersionCacheMaxEntries = 1024
+	RoomVersionCacheMutable    = false
+)
+
+// RoomVersionsCache contains the subset of functions needed for
+// a room version cache.
+type RoomVersionCache interface {
+	GetRoomVersion(roomID string) (roomVersion gomatrixserverlib.RoomVersion, ok bool)
+	StoreRoomVersion(roomID string, roomVersion gomatrixserverlib.RoomVersion)
+}
+
+func (c Caches) GetRoomVersion(roomID string) (gomatrixserverlib.RoomVersion, bool) {
+	val, found := c.RoomVersions.Get(roomID)
+	if found && val != nil {
+		if roomVersion, ok := val.(gomatrixserverlib.RoomVersion); ok {
+			return roomVersion, true
+		}
+	}
+	return "", false
+}
+
+func (c Caches) StoreRoomVersion(roomID string, roomVersion gomatrixserverlib.RoomVersion) {
+	c.RoomVersions.Set(roomID, roomVersion)
+}
diff --git a/internal/caching/cache_serverkeys.go b/internal/caching/cache_serverkeys.go
new file mode 100644
index 00000000..8c71ffbd
--- /dev/null
+++ b/internal/caching/cache_serverkeys.go
@@ -0,0 +1,41 @@
+package caching
+
+import (
+	"fmt"
+
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const (
+	ServerKeyCacheName       = "server_key"
+	ServerKeyCacheMaxEntries = 4096
+	ServerKeyCacheMutable    = true
+)
+
+// ServerKeyCache contains the subset of functions needed for
+// a server key cache.
+type ServerKeyCache interface {
+	GetServerKey(request gomatrixserverlib.PublicKeyLookupRequest) (response gomatrixserverlib.PublicKeyLookupResult, ok bool)
+	StoreServerKey(request gomatrixserverlib.PublicKeyLookupRequest, response gomatrixserverlib.PublicKeyLookupResult)
+}
+
+func (c Caches) GetServerKey(
+	request gomatrixserverlib.PublicKeyLookupRequest,
+) (gomatrixserverlib.PublicKeyLookupResult, bool) {
+	key := fmt.Sprintf("%s/%s", request.ServerName, request.KeyID)
+	val, found := c.ServerKeys.Get(key)
+	if found && val != nil {
+		if keyLookupResult, ok := val.(gomatrixserverlib.PublicKeyLookupResult); ok {
+			return keyLookupResult, true
+		}
+	}
+	return gomatrixserverlib.PublicKeyLookupResult{}, false
+}
+
+func (c Caches) StoreServerKey(
+	request gomatrixserverlib.PublicKeyLookupRequest,
+	response gomatrixserverlib.PublicKeyLookupResult,
+) {
+	key := fmt.Sprintf("%s/%s", request.ServerName, request.KeyID)
+	c.ServerKeys.Set(key, response)
+}
diff --git a/internal/caching/caches.go b/internal/caching/caches.go
new file mode 100644
index 00000000..70f380ba
--- /dev/null
+++ b/internal/caching/caches.go
@@ -0,0 +1,15 @@
+package caching
+
+// Caches contains a set of references to caches. They may be
+// different implementations as long as they satisfy the Cache
+// interface.
+type Caches struct {
+	RoomVersions Cache // implements RoomVersionCache
+	ServerKeys   Cache // implements ServerKeyCache
+}
+
+// Cache is the interface that an implementation must satisfy.
+type Cache interface {
+	Get(key string) (value interface{}, ok bool)
+	Set(key string, value interface{})
+}
diff --git a/internal/caching/immutablecache.go b/internal/caching/immutablecache.go
deleted file mode 100644
index fea05dd1..00000000
--- a/internal/caching/immutablecache.go
+++ /dev/null
@@ -1,17 +0,0 @@
-package caching
-
-import (
-	"github.com/matrix-org/gomatrixserverlib"
-)
-
-const (
-	RoomVersionMaxCacheEntries = 1024
-	ServerKeysMaxCacheEntries  = 1024
-)
-
-type ImmutableCache interface {
-	GetRoomVersion(roomId string) (gomatrixserverlib.RoomVersion, bool)
-	StoreRoomVersion(roomId string, roomVersion gomatrixserverlib.RoomVersion)
-	GetServerKey(request gomatrixserverlib.PublicKeyLookupRequest) (gomatrixserverlib.PublicKeyLookupResult, bool)
-	StoreServerKey(request gomatrixserverlib.PublicKeyLookupRequest, response gomatrixserverlib.PublicKeyLookupResult)
-}
diff --git a/internal/caching/immutableinmemorylru.go b/internal/caching/immutableinmemorylru.go
deleted file mode 100644
index 36cd56dc..00000000
--- a/internal/caching/immutableinmemorylru.go
+++ /dev/null
@@ -1,95 +0,0 @@
-package caching
-
-import (
-	"fmt"
-
-	lru "github.com/hashicorp/golang-lru"
-	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
-)
-
-type ImmutableInMemoryLRUCache struct {
-	roomVersions *lru.Cache
-	serverKeys   *lru.Cache
-}
-
-func NewImmutableInMemoryLRUCache() (*ImmutableInMemoryLRUCache, error) {
-	roomVersionCache, rvErr := lru.New(RoomVersionMaxCacheEntries)
-	if rvErr != nil {
-		return nil, rvErr
-	}
-	serverKeysCache, rvErr := lru.New(ServerKeysMaxCacheEntries)
-	if rvErr != nil {
-		return nil, rvErr
-	}
-	cache := &ImmutableInMemoryLRUCache{
-		roomVersions: roomVersionCache,
-		serverKeys:   serverKeysCache,
-	}
-	cache.configureMetrics()
-	return cache, nil
-}
-
-func (c *ImmutableInMemoryLRUCache) configureMetrics() {
-	promauto.NewGaugeFunc(prometheus.GaugeOpts{
-		Namespace: "dendrite",
-		Subsystem: "caching",
-		Name:      "number_room_version_entries",
-		Help:      "The number of room version entries cached.",
-	}, func() float64 {
-		return float64(c.roomVersions.Len())
-	})
-
-	promauto.NewGaugeFunc(prometheus.GaugeOpts{
-		Namespace: "dendrite",
-		Subsystem: "caching",
-		Name:      "number_server_key_entries",
-		Help:      "The number of server key entries cached.",
-	}, func() float64 {
-		return float64(c.serverKeys.Len())
-	})
-}
-
-func checkForInvalidMutation(cache *lru.Cache, key string, value interface{}) {
-	if peek, ok := cache.Peek(key); ok && peek != value {
-		panic(fmt.Sprintf("invalid use of immutable cache tries to mutate existing value of %q", key))
-	}
-}
-
-func (c *ImmutableInMemoryLRUCache) GetRoomVersion(roomID string) (gomatrixserverlib.RoomVersion, bool) {
-	val, found := c.roomVersions.Get(roomID)
-	if found && val != nil {
-		if roomVersion, ok := val.(gomatrixserverlib.RoomVersion); ok {
-			return roomVersion, true
-		}
-	}
-	return "", false
-}
-
-func (c *ImmutableInMemoryLRUCache) StoreRoomVersion(roomID string, roomVersion gomatrixserverlib.RoomVersion) {
-	checkForInvalidMutation(c.roomVersions, roomID, roomVersion)
-	c.roomVersions.Add(roomID, roomVersion)
-}
-
-func (c *ImmutableInMemoryLRUCache) GetServerKey(
-	request gomatrixserverlib.PublicKeyLookupRequest,
-) (gomatrixserverlib.PublicKeyLookupResult, bool) {
-	key := fmt.Sprintf("%s/%s", request.ServerName, request.KeyID)
-	val, found := c.serverKeys.Get(key)
-	if found && val != nil {
-		if keyLookupResult, ok := val.(gomatrixserverlib.PublicKeyLookupResult); ok {
-			return keyLookupResult, true
-		}
-	}
-	return gomatrixserverlib.PublicKeyLookupResult{}, false
-}
-
-func (c *ImmutableInMemoryLRUCache) StoreServerKey(
-	request gomatrixserverlib.PublicKeyLookupRequest,
-	response gomatrixserverlib.PublicKeyLookupResult,
-) {
-	key := fmt.Sprintf("%s/%s", request.ServerName, request.KeyID)
-	checkForInvalidMutation(c.roomVersions, key, response)
-	c.serverKeys.Add(request, response)
-}
diff --git a/internal/caching/impl_inmemorylru.go b/internal/caching/impl_inmemorylru.go
new file mode 100644
index 00000000..f7901d2e
--- /dev/null
+++ b/internal/caching/impl_inmemorylru.go
@@ -0,0 +1,73 @@
+package caching
+
+import (
+	"fmt"
+
+	lru "github.com/hashicorp/golang-lru"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+func NewInMemoryLRUCache() (*Caches, error) {
+	roomVersions, err := NewInMemoryLRUCachePartition(
+		RoomVersionCacheName,
+		RoomVersionCacheMutable,
+		RoomVersionCacheMaxEntries,
+	)
+	if err != nil {
+		return nil, err
+	}
+	serverKeys, err := NewInMemoryLRUCachePartition(
+		ServerKeyCacheName,
+		ServerKeyCacheMutable,
+		ServerKeyCacheMaxEntries,
+	)
+	if err != nil {
+		return nil, err
+	}
+	return &Caches{
+		RoomVersions: roomVersions,
+		ServerKeys:   serverKeys,
+	}, nil
+}
+
+type InMemoryLRUCachePartition struct {
+	name       string
+	mutable    bool
+	maxEntries int
+	lru        *lru.Cache
+}
+
+func NewInMemoryLRUCachePartition(name string, mutable bool, maxEntries int) (*InMemoryLRUCachePartition, error) {
+	var err error
+	cache := InMemoryLRUCachePartition{
+		name:       name,
+		mutable:    mutable,
+		maxEntries: maxEntries,
+	}
+	cache.lru, err = lru.New(maxEntries)
+	if err != nil {
+		return nil, err
+	}
+	promauto.NewGaugeFunc(prometheus.GaugeOpts{
+		Namespace: "dendrite",
+		Subsystem: "caching_in_memory_lru",
+		Name:      name,
+	}, func() float64 {
+		return float64(cache.lru.Len())
+	})
+	return &cache, nil
+}
+
+func (c *InMemoryLRUCachePartition) Set(key string, value interface{}) {
+	if !c.mutable {
+		if peek, ok := c.lru.Peek(key); ok && peek != value {
+			panic(fmt.Sprintf("invalid use of immutable cache tries to mutate existing value of %q", key))
+		}
+	}
+	c.lru.Add(key, value)
+}
+
+func (c *InMemoryLRUCachePartition) Get(key string) (value interface{}, ok bool) {
+	return c.lru.Get(key)
+}
diff --git a/roomserver/internal/api.go b/roomserver/internal/api.go
index 3a7b0d76..37a8a39b 100644
--- a/roomserver/internal/api.go
+++ b/roomserver/internal/api.go
@@ -16,7 +16,7 @@ type RoomserverInternalAPI struct {
 	DB                   storage.Database
 	Cfg                  *config.Dendrite
 	Producer             sarama.SyncProducer
-	ImmutableCache       caching.ImmutableCache
+	Cache                caching.RoomVersionCache
 	ServerName           gomatrixserverlib.ServerName
 	KeyRing              gomatrixserverlib.JSONVerifier
 	FedClient            *gomatrixserverlib.FederationClient
diff --git a/roomserver/internal/query.go b/roomserver/internal/query.go
index fce2ae90..9fb67e7e 100644
--- a/roomserver/internal/query.go
+++ b/roomserver/internal/query.go
@@ -951,7 +951,7 @@ func (r *RoomserverInternalAPI) QueryRoomVersionForRoom(
 	request *api.QueryRoomVersionForRoomRequest,
 	response *api.QueryRoomVersionForRoomResponse,
 ) error {
-	if roomVersion, ok := r.ImmutableCache.GetRoomVersion(request.RoomID); ok {
+	if roomVersion, ok := r.Cache.GetRoomVersion(request.RoomID); ok {
 		response.RoomVersion = roomVersion
 		return nil
 	}
@@ -961,6 +961,6 @@ func (r *RoomserverInternalAPI) QueryRoomVersionForRoom(
 		return err
 	}
 	response.RoomVersion = roomVersion
-	r.ImmutableCache.StoreRoomVersion(request.RoomID, response.RoomVersion)
+	r.Cache.StoreRoomVersion(request.RoomID, response.RoomVersion)
 	return nil
 }
diff --git a/roomserver/inthttp/client.go b/roomserver/inthttp/client.go
index 99db9e1e..5cc2537e 100644
--- a/roomserver/inthttp/client.go
+++ b/roomserver/inthttp/client.go
@@ -43,9 +43,9 @@ const (
 )
 
 type httpRoomserverInternalAPI struct {
-	roomserverURL  string
-	httpClient     *http.Client
-	immutableCache caching.ImmutableCache
+	roomserverURL string
+	httpClient    *http.Client
+	cache         caching.RoomVersionCache
 }
 
 // NewRoomserverClient creates a RoomserverInputAPI implemented by talking to a HTTP POST API.
@@ -53,15 +53,15 @@ type httpRoomserverInternalAPI struct {
 func NewRoomserverClient(
 	roomserverURL string,
 	httpClient *http.Client,
-	immutableCache caching.ImmutableCache,
+	cache caching.RoomVersionCache,
 ) (api.RoomserverInternalAPI, error) {
 	if httpClient == nil {
 		return nil, errors.New("NewRoomserverInternalAPIHTTP: httpClient is <nil>")
 	}
 	return &httpRoomserverInternalAPI{
-		roomserverURL:  roomserverURL,
-		httpClient:     httpClient,
-		immutableCache: immutableCache,
+		roomserverURL: roomserverURL,
+		httpClient:    httpClient,
+		cache:         cache,
 	}, nil
 }
 
@@ -320,7 +320,7 @@ func (h *httpRoomserverInternalAPI) QueryRoomVersionForRoom(
 	request *api.QueryRoomVersionForRoomRequest,
 	response *api.QueryRoomVersionForRoomResponse,
 ) error {
-	if roomVersion, ok := h.immutableCache.GetRoomVersion(request.RoomID); ok {
+	if roomVersion, ok := h.cache.GetRoomVersion(request.RoomID); ok {
 		response.RoomVersion = roomVersion
 		return nil
 	}
@@ -331,7 +331,7 @@ func (h *httpRoomserverInternalAPI) QueryRoomVersionForRoom(
 	apiURL := h.roomserverURL + RoomserverQueryRoomVersionForRoomPath
 	err := internalHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
 	if err == nil {
-		h.immutableCache.StoreRoomVersion(request.RoomID, response.RoomVersion)
+		h.cache.StoreRoomVersion(request.RoomID, response.RoomVersion)
 	}
 	return err
 }
diff --git a/roomserver/roomserver.go b/roomserver/roomserver.go
index ae0b0794..a55b20be 100644
--- a/roomserver/roomserver.go
+++ b/roomserver/roomserver.go
@@ -44,7 +44,7 @@ func SetupRoomServerComponent(
 		Cfg:                  base.Cfg,
 		Producer:             base.KafkaProducer,
 		OutputRoomEventTopic: string(base.Cfg.Kafka.Topics.OutputRoomEvent),
-		ImmutableCache:       base.ImmutableCache,
+		Cache:                base.Caches,
 		ServerName:           base.Cfg.Matrix.ServerName,
 		FedClient:            fedClient,
 		KeyRing:              keyRing,
diff --git a/serverkeyapi/inthttp/client.go b/serverkeyapi/inthttp/client.go
index f986634b..f22b0e31 100644
--- a/serverkeyapi/inthttp/client.go
+++ b/serverkeyapi/inthttp/client.go
@@ -24,7 +24,7 @@ const (
 func NewServerKeyClient(
 	serverKeyAPIURL string,
 	httpClient *http.Client,
-	immutableCache caching.ImmutableCache,
+	cache caching.ServerKeyCache,
 ) (api.ServerKeyInternalAPI, error) {
 	if httpClient == nil {
 		return nil, errors.New("NewRoomserverInternalAPIHTTP: httpClient is <nil>")
@@ -32,14 +32,14 @@ func NewServerKeyClient(
 	return &httpServerKeyInternalAPI{
 		serverKeyAPIURL: serverKeyAPIURL,
 		httpClient:      httpClient,
-		immutableCache:  immutableCache,
+		cache:           cache,
 	}, nil
 }
 
 type httpServerKeyInternalAPI struct {
 	serverKeyAPIURL string
 	httpClient      *http.Client
-	immutableCache  caching.ImmutableCache
+	cache           caching.ServerKeyCache
 }
 
 func (s *httpServerKeyInternalAPI) KeyRing() *gomatrixserverlib.KeyRing {
@@ -71,7 +71,7 @@ func (s *httpServerKeyInternalAPI) StoreKeys(
 	response := api.InputPublicKeysResponse{}
 	for req, res := range results {
 		request.Keys[req] = res
-		s.immutableCache.StoreServerKey(req, res)
+		s.cache.StoreServerKey(req, res)
 	}
 	return s.InputPublicKeys(ctx, &request, &response)
 }
@@ -92,7 +92,7 @@ func (s *httpServerKeyInternalAPI) FetchKeys(
 	}
 	now := gomatrixserverlib.AsTimestamp(time.Now())
 	for req, ts := range requests {
-		if res, ok := s.immutableCache.GetServerKey(req); ok {
+		if res, ok := s.cache.GetServerKey(req); ok {
 			if now > res.ValidUntilTS && res.ExpiredTS == gomatrixserverlib.PublicKeyNotExpired {
 				continue
 			}
@@ -107,7 +107,7 @@ func (s *httpServerKeyInternalAPI) FetchKeys(
 	}
 	for req, res := range response.Results {
 		result[req] = res
-		s.immutableCache.StoreServerKey(req, res)
+		s.cache.StoreServerKey(req, res)
 	}
 	return result, nil
 }
diff --git a/serverkeyapi/inthttp/server.go b/serverkeyapi/inthttp/server.go
index d5517e14..9efe7d9d 100644
--- a/serverkeyapi/inthttp/server.go
+++ b/serverkeyapi/inthttp/server.go
@@ -12,7 +12,7 @@ import (
 	"github.com/matrix-org/util"
 )
 
-func AddRoutes(s api.ServerKeyInternalAPI, internalAPIMux *mux.Router, cache caching.ImmutableCache) {
+func AddRoutes(s api.ServerKeyInternalAPI, internalAPIMux *mux.Router, cache caching.ServerKeyCache) {
 	internalAPIMux.Handle(ServerKeyQueryPublicKeyPath,
 		internal.MakeInternalAPI("queryPublicKeys", func(req *http.Request) util.JSONResponse {
 			request := api.QueryPublicKeysRequest{}
diff --git a/serverkeyapi/serverkeyapi.go b/serverkeyapi/serverkeyapi.go
index 5bf8f67d..ad885270 100644
--- a/serverkeyapi/serverkeyapi.go
+++ b/serverkeyapi/serverkeyapi.go
@@ -29,7 +29,7 @@ func SetupServerKeyAPIComponent(
 		logrus.WithError(err).Panicf("failed to connect to server key database")
 	}
 
-	serverKeyDB, err := cache.NewKeyDatabase(innerDB, base.ImmutableCache)
+	serverKeyDB, err := cache.NewKeyDatabase(innerDB, base.Caches)
 	if err != nil {
 		logrus.WithError(err).Panicf("failed to set up caching wrapper for server key database")
 	}
@@ -77,7 +77,7 @@ func SetupServerKeyAPIComponent(
 		}).Info("Enabled perspective key fetcher")
 	}
 
-	inthttp.AddRoutes(&internalAPI, base.InternalAPIMux, base.ImmutableCache)
+	inthttp.AddRoutes(&internalAPI, base.InternalAPIMux, base.Caches)
 
 	return &internalAPI
 }
diff --git a/serverkeyapi/storage/cache/keydb.go b/serverkeyapi/storage/cache/keydb.go
index a0cdb900..b662e4fd 100644
--- a/serverkeyapi/storage/cache/keydb.go
+++ b/serverkeyapi/storage/cache/keydb.go
@@ -12,10 +12,10 @@ import (
 // the public keys for other matrix servers.
 type KeyDatabase struct {
 	inner gomatrixserverlib.KeyDatabase
-	cache caching.ImmutableCache
+	cache caching.ServerKeyCache
 }
 
-func NewKeyDatabase(inner gomatrixserverlib.KeyDatabase, cache caching.ImmutableCache) (*KeyDatabase, error) {
+func NewKeyDatabase(inner gomatrixserverlib.KeyDatabase, cache caching.ServerKeyCache) (*KeyDatabase, error) {
 	if inner == nil {
 		return nil, errors.New("inner database can't be nil")
 	}