From 3ca36e1319bfe05739e732099a33010ea26e409a Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Wed, 22 Apr 2020 11:01:42 +0100
Subject: [PATCH] Use hashicorp implementation which mutexes for us

---
 common/basecomponent/base.go  |  7 ++++++-
 common/caching/inmemorylru.go | 21 +++++++++------------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/common/basecomponent/base.go b/common/basecomponent/base.go
index c3df6c50a..743e034fa 100644
--- a/common/basecomponent/base.go
+++ b/common/basecomponent/base.go
@@ -85,11 +85,16 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string) *BaseDendrite {
 		kafkaConsumer, kafkaProducer = setupKafka(cfg)
 	}
 
+	cache, err := caching.NewInMemoryLRUCache()
+	if err != nil {
+		logrus.WithError(err).Warnf("Failed to create cache")
+	}
+
 	return &BaseDendrite{
 		componentName: componentName,
 		tracerCloser:  closer,
 		Cfg:           cfg,
-		Cache:         caching.NewInMemoryLRUCache(), // TODO: make configurable
+		Cache:         cache,
 		APIMux:        mux.NewRouter().UseEncodedPath(),
 		httpClient:    &http.Client{Timeout: HTTPClientTimeout},
 		KafkaConsumer: kafkaConsumer,
diff --git a/common/caching/inmemorylru.go b/common/caching/inmemorylru.go
index 774b70b2c..df9295ba2 100644
--- a/common/caching/inmemorylru.go
+++ b/common/caching/inmemorylru.go
@@ -1,30 +1,29 @@
 package caching
 
 import (
-	"sync"
-
-	"github.com/golang/groupcache/lru"
+	lru "github.com/hashicorp/golang-lru"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
 type InMemoryLRUCache struct {
-	roomVersions      *lru.Cache
-	roomVersionsMutex sync.RWMutex
+	roomVersions *lru.Cache
 }
 
-func NewInMemoryLRUCache() *InMemoryLRUCache {
-	return &InMemoryLRUCache{
-		roomVersions: lru.New(128),
+func NewInMemoryLRUCache() (*InMemoryLRUCache, error) {
+	roomVersionCache, rvErr := lru.New(128)
+	if rvErr != nil {
+		return nil, rvErr
 	}
+	return &InMemoryLRUCache{
+		roomVersions: roomVersionCache,
+	}, nil
 }
 
 func (c *InMemoryLRUCache) GetRoomVersion(roomID string) (gomatrixserverlib.RoomVersion, bool) {
 	if c == nil {
 		return "", false
 	}
-	c.roomVersionsMutex.RLock()
 	val, found := c.roomVersions.Get(roomID)
-	c.roomVersionsMutex.RUnlock()
 	if found && val != nil {
 		if roomVersion, ok := val.(gomatrixserverlib.RoomVersion); ok {
 			return roomVersion, true
@@ -37,7 +36,5 @@ func (c *InMemoryLRUCache) StoreRoomVersion(roomID string, roomVersion gomatrixs
 	if c == nil {
 		return
 	}
-	c.roomVersionsMutex.Lock()
-	defer c.roomVersionsMutex.Unlock()
 	c.roomVersions.Add(roomID, roomVersion)
 }