From 6e3408c7670ea05b3b990a3c22858d1aa739aa1d Mon Sep 17 00:00:00 2001
From: Alexander Entinger <cto@lxrobotics.com>
Date: Mon, 3 May 2021 07:54:25 +0200
Subject: [PATCH] Track the number of unsuccessful request-last-values. In the
 current implementation the number the board would continously attempt to
 obtain the last values from the cloud. If, however, those values never arrive
 - then the board would never move on and become operational. It's therefore
 better to count the number of failed attempts and reset the connection to
 allow a clean re-connection from the ground up.

---
 src/AIoTC_Config.h         |  1 +
 src/ArduinoIoTCloudTCP.cpp | 14 ++++++++++++++
 src/ArduinoIoTCloudTCP.h   |  1 +
 3 files changed, 16 insertions(+)

diff --git a/src/AIoTC_Config.h b/src/AIoTC_Config.h
index 7c76d4486..7c54d1751 100644
--- a/src/AIoTC_Config.h
+++ b/src/AIoTC_Config.h
@@ -141,5 +141,6 @@
 #define AIOT_CONFIG_RECONNECTION_RETRY_DELAY_ms      (1000UL)
 #define AIOT_CONFIG_MAX_RECONNECTION_RETRY_DELAY_ms (32000UL)
 #define AIOT_CONFIG_TIMEOUT_FOR_LASTVALUES_SYNC_ms  (30000UL)
+#define AIOT_CONFIG_LASTVALUES_SYNC_MAX_RETRY_CNT      (10UL)
 
 #endif /* ARDUINO_AIOTC_CONFIG_H_ */
diff --git a/src/ArduinoIoTCloudTCP.cpp b/src/ArduinoIoTCloudTCP.cpp
index 86b4bca3b..54d416596 100644
--- a/src/ArduinoIoTCloudTCP.cpp
+++ b/src/ArduinoIoTCloudTCP.cpp
@@ -71,6 +71,7 @@ ArduinoIoTCloudTCP::ArduinoIoTCloudTCP()
 , _next_connection_attempt_tick{0}
 , _last_connection_attempt_cnt{0}
 , _last_sync_request_tick{0}
+, _last_sync_request_cnt{0}
 , _mqtt_data_buf{0}
 , _mqtt_data_len{0}
 , _mqtt_data_request_retransmit{false}
@@ -424,6 +425,18 @@ ArduinoIoTCloudTCP::State ArduinoIoTCloudTCP::handle_RequestLastValues()
     DEBUG_VERBOSE("ArduinoIoTCloudTCP::%s [%d] last values requested", __FUNCTION__, now);
     requestLastValue();
     _last_sync_request_tick = now;
+    /* Track the number of times a get-last-values request was sent to the cloud.
+     * If no data is received within a certain number of retry-requests it's a better
+     * strategy to disconnect and re-establish connection from the ground up.
+     */
+    _last_sync_request_cnt++;
+    if (_last_sync_request_cnt > AIOT_CONFIG_LASTVALUES_SYNC_MAX_RETRY_CNT)
+    {
+      _last_sync_request_cnt = 0;
+      _mqttClient.stop();
+      execCloudEventCallback(ArduinoIoTCloudEvent::DISCONNECT);
+      return State::ConnectPhy;
+    }
   }
 
   return State::RequestLastValues;
@@ -517,6 +530,7 @@ void ArduinoIoTCloudTCP::handleMessage(int length)
     CBORDecoder::decode(_property_container, (uint8_t*)bytes, length, true);
     sendPropertiesToCloud();
     execCloudEventCallback(ArduinoIoTCloudEvent::SYNC);
+    _last_sync_request_cnt = 0;
     _state = State::Connected;
   }
 }
diff --git a/src/ArduinoIoTCloudTCP.h b/src/ArduinoIoTCloudTCP.h
index 364b4bf36..f29aafde7 100644
--- a/src/ArduinoIoTCloudTCP.h
+++ b/src/ArduinoIoTCloudTCP.h
@@ -99,6 +99,7 @@ class ArduinoIoTCloudTCP: public ArduinoIoTCloudClass
     unsigned long _next_connection_attempt_tick;
     unsigned int _last_connection_attempt_cnt;
     unsigned long _last_sync_request_tick;
+    unsigned int _last_sync_request_cnt;
     String _brokerAddress;
     uint16_t _brokerPort;
     uint8_t _mqtt_data_buf[MQTT_TRANSMIT_BUFFER_SIZE];