fix(mqtt): mark configuration as dirty on setter calls and optimize config application during connect and reconnect

Update the PsychicMqttClient to set a _config_dirty flag whenever a configuration setter is called. This ensures that the MQTT configuration is only applied when changes are made, optimizing the connect and reconnect processes. Added logging to indicate whether the configuration was updated or unchanged.

lib/PsychicMqttClient/src/PsychicMqttClient.cpp

@@ -44,6 +44,7 @@ PsychicMqttClient &PsychicMqttClient::setKeepAlive(int keepAlive)
 #else
     _mqtt_cfg.keepalive = keepAlive;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -54,6 +55,7 @@ PsychicMqttClient &PsychicMqttClient::setAutoReconnect(bool reconnect)
 #else
     _mqtt_cfg.disable_auto_reconnect = !reconnect;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -64,6 +66,7 @@ PsychicMqttClient &PsychicMqttClient::setClientId(const char *clientId)
 #else
     _mqtt_cfg.client_id = clientId;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -74,6 +77,7 @@ PsychicMqttClient &PsychicMqttClient::setCleanSession(bool cleanSession)
 #else
     _mqtt_cfg.disable_clean_session = !cleanSession;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -84,6 +88,7 @@ PsychicMqttClient &PsychicMqttClient::setBufferSize(int bufferSize)
 #else
     _mqtt_cfg.buffer_size = bufferSize;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -96,6 +101,7 @@ PsychicMqttClient &PsychicMqttClient::setTaskStackAndPriority(int stackSize, int
     _mqtt_cfg.task_stack = stackSize;
     _mqtt_cfg.task_prio = priority;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -108,6 +114,7 @@ PsychicMqttClient &PsychicMqttClient::setCACert(const char *rootCA, size_t rootC
     _mqtt_cfg.cert_pem = rootCA;
     _mqtt_cfg.cert_len = rootCALen;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -136,6 +143,7 @@ PsychicMqttClient &PsychicMqttClient::setCACertBundle(const uint8_t *bundle, siz
         _mqtt_cfg.crt_bundle_attach = NULL;
     }
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -152,6 +160,7 @@ PsychicMqttClient &PsychicMqttClient::attachArduinoCACertBundle(bool attach)
     else
         _mqtt_cfg.crt_bundle_attach = NULL;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -166,6 +175,7 @@ PsychicMqttClient &PsychicMqttClient::setCredentials(const char *username, const
     if (password != nullptr)
         _mqtt_cfg.password = password;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -183,6 +193,7 @@ PsychicMqttClient &PsychicMqttClient::setClientCertificate(const char *clientCer
     _mqtt_cfg.client_cert_len = clientCertLen;
     _mqtt_cfg.client_key_len = clientKeyLen;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -201,6 +212,7 @@ PsychicMqttClient &PsychicMqttClient::setWill(const char *topic, uint8_t qos, bo
     _mqtt_cfg.lwt_msg_len = length;
     _mqtt_cfg.lwt_msg = payload;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -211,6 +223,7 @@ PsychicMqttClient &PsychicMqttClient::setServer(const char *uri)
 #else
     _mqtt_cfg.uri = uri;
 #endif
+    _config_dirty = true;
     return *this;
 }
 
@@ -374,10 +387,28 @@ void PsychicMqttClient::connect()
         // Register event handler only once when client is first created
         // to avoid memory leak from repeated registrations
         esp_mqtt_client_register_event(_client, MQTT_EVENT_ANY, _onMqttEventStatic, this);
+        _config_dirty = false;
     }
     else
     {
-        ESP_ERROR_CHECK_WITHOUT_ABORT(esp_mqtt_set_config(_client, &_mqtt_cfg));
+        if (_config_dirty)
+        {
+            esp_err_t cfg_result = esp_mqtt_set_config(_client, &_mqtt_cfg);
+            ESP_ERROR_CHECK_WITHOUT_ABORT(cfg_result);
+            if (cfg_result == ESP_OK)
+            {
+                _config_dirty = false;
+                ESP_LOGD(TAG, "connect(): applied mqtt config update");
+            }
+            else
+            {
+                ESP_LOGW(TAG, "connect(): failed to apply mqtt config, will retry");
+            }
+        }
+        else
+        {
+            ESP_LOGD(TAG, "connect(): mqtt config unchanged, skipping set_config");
+        }
     }
 
     ESP_ERROR_CHECK_WITHOUT_ABORT(esp_mqtt_client_start(_client));
@@ -391,8 +422,25 @@ void PsychicMqttClient::reconnect()
         ESP_LOGW(TAG, "MQTT client not initialized, cannot reconnect.");
         return;
     }
-    // Update config in case credentials changed (e.g., refreshed JWT token)
-    ESP_ERROR_CHECK_WITHOUT_ABORT(esp_mqtt_set_config(_client, &_mqtt_cfg));
+    if (_config_dirty)
+    {
+        // Apply config only when mutating setters changed _mqtt_cfg.
+        esp_err_t cfg_result = esp_mqtt_set_config(_client, &_mqtt_cfg);
+        ESP_ERROR_CHECK_WITHOUT_ABORT(cfg_result);
+        if (cfg_result == ESP_OK)
+        {
+            _config_dirty = false;
+            ESP_LOGD(TAG, "reconnect(): applied mqtt config update");
+        }
+        else
+        {
+            ESP_LOGW(TAG, "reconnect(): failed to apply mqtt config, reconnecting with previous config");
+        }
+    }
+    else
+    {
+        ESP_LOGD(TAG, "reconnect(): mqtt config unchanged, skipping set_config");
+    }
     ESP_ERROR_CHECK_WITHOUT_ABORT(esp_mqtt_client_reconnect(_client));
     ESP_LOGI(TAG, "MQTT client reconnect requested.");
 }

lib/PsychicMqttClient/src/PsychicMqttClient.h

@@ -405,6 +405,7 @@ private:
     esp_mqtt_error_codes_t _lastError;
     bool _connected = false;
     bool _stopMqttClient = false;
+    bool _config_dirty = true;
 
     // Multipart message reassembly. _buffer is lazily allocated at connect() time
     // to match the configured buffer size, then reused for the client's lifetime.