From 1daa25d0f954cb09f86ae22f7e8957cf5097237b Mon Sep 17 00:00:00 2001
From: Wei Zhao <zhaowms@live.com>
Date: Wed, 23 Oct 2024 14:17:04 +0800
Subject: [PATCH] Issues #2091 Improve the performance of RetainedMessages
 without subscribing to RetainedMessageChangedEvent.

---
 .../MQTTnet.Server/Internal/MqttRetainedMessagesManager.cs   | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Source/MQTTnet.Server/Internal/MqttRetainedMessagesManager.cs b/Source/MQTTnet.Server/Internal/MqttRetainedMessagesManager.cs
index 8995b35f..6d2e288f 100644
--- a/Source/MQTTnet.Server/Internal/MqttRetainedMessagesManager.cs
+++ b/Source/MQTTnet.Server/Internal/MqttRetainedMessagesManager.cs
@@ -62,6 +62,7 @@ public async Task UpdateMessage(string clientId, MqttApplicationMessage applicat
             {
                 List<MqttApplicationMessage> messagesForSave = null;
                 var saveIsRequired = false;
+                var hasHandlers = _eventContainer.RetainedMessageChangedEvent.HasHandlers;
 
                 lock (_messages)
                 {
@@ -93,13 +94,13 @@ public async Task UpdateMessage(string clientId, MqttApplicationMessage applicat
                         _logger.Verbose("Client '{0}' set retained message for topic '{1}'.", clientId, applicationMessage.Topic);
                     }
 
-                    if (saveIsRequired)
+                    if (saveIsRequired && hasHandlers)
                     {
                         messagesForSave = new List<MqttApplicationMessage>(_messages.Values);
                     }
                 }
 
-                if (saveIsRequired)
+                if (saveIsRequired && hasHandlers)
                 {
                     using (await _storageAccessLock.EnterAsync().ConfigureAwait(false))
                     {