More server key updates, tests (#1129)

* More key tweaks

* Start testing stuff

* Move responsibility for generating local keys into server key API, don't register prom in caches unless needed, start tests

* Don't store our own keys in the database

* Don't store our own keys in the database

* Don't run tests for now

* Tweak caching behaviour, update tests

* Update comments, add fixes from forward-merge

* Debug logging

* Debug logging

* Perform final comparison against original set of requests

* oops

* Fetcher timeouts

* Fetcher timeouts

* missing func

* Tweaks

* Update gomatrixserverlib

* Fix Federation API test

* Break up FetchKeys

* Add comments to caching

* Add URL check in test

* Partially revert "Move responsibility for generating local keys into server key API, don't register prom in caches unless needed, start tests"

This reverts commit d7eb54c5b30b2f6a9d6514b643e32e6ad2b602f3.

* Fix federation API test

* Fix internal cache stuff again

* Fix server key API test

* Update comments

* Update comments from review

* Fix lint

2 files changed, 26 insertions, 16 deletions

diff --git a/internal/caching/cache_serverkeys.go b/internal/caching/cache_serverkeys.go
index b5e31575..4697fb4d 100644
--- a/internal/caching/cache_serverkeys.go
+++ b/internal/caching/cache_serverkeys.go
@@ -2,7 +2,6 @@ package caching
 
 import (
 	"fmt"
-	"time"
 
 	"github.com/matrix-org/gomatrixserverlib"
 )
@@ -16,22 +15,29 @@ const (
 // ServerKeyCache contains the subset of functions needed for
 // a server key cache.
 type ServerKeyCache interface {
-	GetServerKey(request gomatrixserverlib.PublicKeyLookupRequest) (response gomatrixserverlib.PublicKeyLookupResult, ok bool)
+	// request -> timestamp is emulating gomatrixserverlib.FetchKeys:
+	// https://github.com/matrix-org/gomatrixserverlib/blob/f69539c86ea55d1e2cc76fd8e944e2d82d30397c/keyring.go#L95
+	// The timestamp should be the timestamp of the event that is being
+	// verified. We will not return keys from the cache that are not valid
+	// at this timestamp.
+	GetServerKey(request gomatrixserverlib.PublicKeyLookupRequest, timestamp gomatrixserverlib.Timestamp) (response gomatrixserverlib.PublicKeyLookupResult, ok bool)
+
+	// request -> result is emulating gomatrixserverlib.StoreKeys:
+	// https://github.com/matrix-org/gomatrixserverlib/blob/f69539c86ea55d1e2cc76fd8e944e2d82d30397c/keyring.go#L112
 	StoreServerKey(request gomatrixserverlib.PublicKeyLookupRequest, response gomatrixserverlib.PublicKeyLookupResult)
 }
 
 func (c Caches) GetServerKey(
 	request gomatrixserverlib.PublicKeyLookupRequest,
+	timestamp gomatrixserverlib.Timestamp,
 ) (gomatrixserverlib.PublicKeyLookupResult, bool) {
 	key := fmt.Sprintf("%s/%s", request.ServerName, request.KeyID)
-	now := gomatrixserverlib.AsTimestamp(time.Now())
 	val, found := c.ServerKeys.Get(key)
 	if found && val != nil {
 		if keyLookupResult, ok := val.(gomatrixserverlib.PublicKeyLookupResult); ok {
-			if !keyLookupResult.WasValidAt(now, true) {
-				// We appear to be past the key validity so don't return this
-				// with the results. This ensures that the cache doesn't return
-				// values that are not useful to us.
+			if !keyLookupResult.WasValidAt(timestamp, true) {
+				// The key wasn't valid at the requested timestamp so don't
+				// return it. The caller will have to work out what to do.
 				c.ServerKeys.Unset(key)
 				return gomatrixserverlib.PublicKeyLookupResult{}, false
 			}
diff --git a/internal/caching/impl_inmemorylru.go b/internal/caching/impl_inmemorylru.go
index 158deca4..7bb791dd 100644
--- a/internal/caching/impl_inmemorylru.go
+++ b/internal/caching/impl_inmemorylru.go
@@ -8,11 +8,12 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
-func NewInMemoryLRUCache() (*Caches, error) {
+func NewInMemoryLRUCache(enablePrometheus bool) (*Caches, error) {
 	roomVersions, err := NewInMemoryLRUCachePartition(
 		RoomVersionCacheName,
 		RoomVersionCacheMutable,
 		RoomVersionCacheMaxEntries,
+		enablePrometheus,
 	)
 	if err != nil {
 		return nil, err
@@ -21,6 +22,7 @@ func NewInMemoryLRUCache() (*Caches, error) {
 		ServerKeyCacheName,
 		ServerKeyCacheMutable,
 		ServerKeyCacheMaxEntries,
+		enablePrometheus,
 	)
 	if err != nil {
 		return nil, err
@@ -38,7 +40,7 @@ type InMemoryLRUCachePartition struct {
 	lru        *lru.Cache
 }
 
-func NewInMemoryLRUCachePartition(name string, mutable bool, maxEntries int) (*InMemoryLRUCachePartition, error) {
+func NewInMemoryLRUCachePartition(name string, mutable bool, maxEntries int, enablePrometheus bool) (*InMemoryLRUCachePartition, error) {
 	var err error
 	cache := InMemoryLRUCachePartition{
 		name:       name,
@@ -49,13 +51,15 @@ func NewInMemoryLRUCachePartition(name string, mutable bool, maxEntries int) (*I
 	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())
-	})
+	if enablePrometheus {
+		promauto.NewGaugeFunc(prometheus.GaugeOpts{
+			Namespace: "dendrite",
+			Subsystem: "caching_in_memory_lru",
+			Name:      name,
+		}, func() float64 {
+			return float64(cache.lru.Len())
+		})
+	}
 	return &cache, nil
 }