[IMPROVED] Only enable JetStream account updates in clustered mode. (#…

…4233)

If we know we are in stand alone mode we do not need to run the updates
for JetStream account resources updates.

Signed-off-by: Derek Collison <derek@nats.io>

Resolves #4227 (Partial)

server/jetstream.go

@@ -1020,9 +1020,9 @@ func (a *Account) EnableJetStream(limits map[string]JetStreamAccountLimits) erro
 		return fmt.Errorf("jetstream can not be enabled on the system account")
 	}
 
-	s.mu.Lock()
+	s.mu.RLock()
 	sendq := s.sys.sendq
-	s.mu.Unlock()
+	s.mu.RUnlock()
 
 	// No limits means we dynamically set up limits.
 	// We also place limits here so we know that the account is configured for JetStream.
@@ -1054,12 +1054,15 @@ func (a *Account) EnableJetStream(limits map[string]JetStreamAccountLimits) erro
 	jsa := &jsAccount{js: js, account: a, limits: limits, streams: make(map[string]*stream), sendq: sendq, usage: make(map[string]*jsaStorage)}
 	jsa.storeDir = filepath.Join(js.config.StoreDir, a.Name)
 
-	jsa.usageMu.Lock()
-	jsa.utimer = time.AfterFunc(usageTick, jsa.sendClusterUsageUpdateTimer)
-	// Cluster mode updates to resource usage, but we always will turn on. System internal prevents echos.
-	jsa.updatesPub = fmt.Sprintf(jsaUpdatesPubT, a.Name, sysNode)
-	jsa.updatesSub, _ = s.sysSubscribe(fmt.Sprintf(jsaUpdatesSubT, a.Name), jsa.remoteUpdateUsage)
-	jsa.usageMu.Unlock()
+	// A single server does not need to do the account updates at this point.
+	if js.cluster != nil || !s.standAloneMode() {
+		jsa.usageMu.Lock()
+		jsa.utimer = time.AfterFunc(usageTick, jsa.sendClusterUsageUpdateTimer)
+		// Cluster mode updates to resource usage. System internal prevents echos.
+		jsa.updatesPub = fmt.Sprintf(jsaUpdatesPubT, a.Name, sysNode)
+		jsa.updatesSub, _ = s.sysSubscribe(fmt.Sprintf(jsaUpdatesSubT, a.Name), jsa.remoteUpdateUsage)
+		jsa.usageMu.Unlock()
+	}
 
 	js.accounts[a.Name] = jsa
 	js.mu.Unlock()