From 0662dbb8a132a7d5c3b6a76f4f789c916f57b07b Mon Sep 17 00:00:00 2001
From: Joachim Zobel <jz-2017@heute-morgen.de>
Date: Sun, 24 Dec 2023 15:00:04 +0100
Subject: [PATCH] MQTT client retries permanently

---
 include/mqtt.hpp |  1 +
 src/mqtt.cpp     | 45 +++++++++++++++++++++++----------------------
 2 files changed, 24 insertions(+), 22 deletions(-)

diff --git a/include/mqtt.hpp b/include/mqtt.hpp
index 784b9a0b..f206e258 100644
--- a/include/mqtt.hpp
+++ b/include/mqtt.hpp
@@ -48,6 +48,7 @@ class MqttClient {
 	std::string _id;
 	int _qos = 0;
 	bool _timestamp = false;
+	unsigned int _cntRetries;
 
 	bool _isConnected = false;
 
diff --git a/src/mqtt.cpp b/src/mqtt.cpp
index 47f79d8f..12a05a1f 100644
--- a/src/mqtt.cpp
+++ b/src/mqtt.cpp
@@ -14,6 +14,21 @@
 MqttClient *mqttClient = 0;
 volatile bool endMqttClientThread = false;
 
+/**
+ * Determines the retry time [s] from the number of previous retries.
+ */
+static inline unsigned int retryTime(unsigned int _cnt) {
+	if (_cnt <= 10) {
+		return 0;
+	}
+	else if (_cnt <= 20) {
+		return 5;
+	}
+	else {
+		return 60;
+	}
+}
+
 // class impl.
 MqttClient::MqttClient(struct json_object *option) : _enabled(false) {
 
@@ -171,28 +186,14 @@ MqttClient::MqttClient(struct json_object *option) : _enabled(false) {
 			// now connect. we use sync interface with spe. thread calling mosquitto_loop
 			res = mosquitto_connect(_mcs, _host.c_str(), _port, _keepalive);
 			if (res != MOSQ_ERR_SUCCESS) {
-				switch (res) {
-				case MOSQ_ERR_CONN_REFUSED: // mqtt might accept us later only.
-					print(log_warning, "mosquitto_connect failed (but trying anyhow): %s", "mqtt",
-						  mosquitto_strerror(res));
-					break;
-				case MOSQ_ERR_ERRNO:
-					if (errno == 111) // con refused:
-					{
-						print(log_warning, "mosquitto_connect failed (but trying anyhow): %s",
-							  "mqtt", mosquitto_strerror(res));
-					} else {
-						print(log_alert, "mosquitto_connect failed, giving up: %s", "mqtt",
-							  mosquitto_strerror(res));
-						_enabled = false;
-					}
-					break;
-				default:
-					print(log_alert, "mosquitto_connect failed, stopped: %s", "mqtt",
-						  mosquitto_strerror(res));
-					_enabled = false;
-					break;
-				}
+				// We always retry, only the frequency is reduced
+				print(log_warning, "mosquitto_connect failed (but trying anyhow): %s", "mqtt",
+					  mosquitto_strerror(res));
+			    sleep(retryTime(_cntRetries));	
+				_cntRetries++;
+			}
+			else {
+				_cntRetries = 0;
 			}
 		}
 	}