From 1da4b89a4a84380e2cbf69e306ca93ef89f0fd21 Mon Sep 17 00:00:00 2001
From: Gerard Krupa <github@krupa.me.uk>
Date: Wed, 13 Jul 2022 20:29:10 +0100
Subject: [PATCH 1/2] Log the reason for MQTT server disconnection

---
 src/submitters/mqtt_submitter.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/submitters/mqtt_submitter.cpp b/src/submitters/mqtt_submitter.cpp
index ff955ee..2f20b6c 100644
--- a/src/submitters/mqtt_submitter.cpp
+++ b/src/submitters/mqtt_submitter.cpp
@@ -55,7 +55,7 @@ void MQTTSubmitter::onConnect(bool sessionPresent)
 
 void MQTTSubmitter::onDisconnect(AsyncMqttClientDisconnectReason reason)
 {
-    logln("MQTT is down");
+    logfmt("MQTT is down because %d\n", reason);
     disconnected = true;
 }
 

From 2577b3da16d6f33195b81b1418b007c13e658378 Mon Sep 17 00:00:00 2001
From: Gerard Krupa <github@krupa.me.uk>
Date: Wed, 13 Jul 2022 21:04:15 +0100
Subject: [PATCH 2/2] Try to reconnect on MQTT disconnection while waiting for
 ready

---
 src/submitters/mqtt_submitter.cpp | 78 ++++++++++++++++++++++---------
 src/submitters/mqtt_submitter.h   |  1 +
 2 files changed, 56 insertions(+), 23 deletions(-)

diff --git a/src/submitters/mqtt_submitter.cpp b/src/submitters/mqtt_submitter.cpp
index 2f20b6c..524e5e6 100644
--- a/src/submitters/mqtt_submitter.cpp
+++ b/src/submitters/mqtt_submitter.cpp
@@ -11,6 +11,7 @@ MQTTSubmitter::MQTTSubmitter(String location, const char* host, int port) :
     port(port),
     started(false),
     disconnected(false),
+    failure(false),
     pendingAcks(),
     client(new AsyncMqttClient())
 {
@@ -40,12 +41,22 @@ void MQTTSubmitter::initialise()
 
 bool MQTTSubmitter::ready()
 {
-    return client->connected();
+    if (disconnected)
+    {
+        logln("MQTT was disconnected, trying to reconnect");
+        disconnected = false;
+        client->connect();
+        return false;
+    }
+    else
+    {
+        return client->connected();
+    }
 }
 
 bool MQTTSubmitter::failed()
 {
-    return disconnected;
+    return failure;
 }
 
 void MQTTSubmitter::onConnect(bool sessionPresent)
@@ -56,7 +67,14 @@ void MQTTSubmitter::onConnect(bool sessionPresent)
 void MQTTSubmitter::onDisconnect(AsyncMqttClientDisconnectReason reason)
 {
     logfmt("MQTT is down because %d\n", reason);
-    disconnected = true;
+    if (reason == AsyncMqttClientDisconnectReason::TCP_DISCONNECTED)
+    {
+        disconnected = true;
+    }
+    else
+    {
+        failure = true;
+    }
 }
 
 void MQTTSubmitter::onPublishAck(uint16_t packetId)
@@ -66,30 +84,44 @@ void MQTTSubmitter::onPublishAck(uint16_t packetId)
 
 void MQTTSubmitter::sendReading(String name, double value)
 {
-    String topic = "environment/";
-    topic.concat(location);
-    topic.concat("/");
-    topic.concat(name);
-
-    String valueString = String(value);
-
-    logfmt("MQTT <- %s = %f\n", topic.c_str(), value);
-
-    uint16_t msgId = client->publish(topic.c_str(), 1, true, valueString.c_str(), valueString.length());
-    pendingAcks.insert(msgId);
+    if (disconnected)
+    {
+        logln("Attempting to send data to disconnected MQTT server");
+    }
+    else
+    {
+        String topic = "environment/";
+        topic.concat(location);
+        topic.concat("/");
+        topic.concat(name);
+
+        String valueString = String(value);
+
+        logfmt("MQTT <- %s = %f\n", topic.c_str(), value);
+
+        uint16_t msgId = client->publish(topic.c_str(), 1, true, valueString.c_str(), valueString.length());
+        pendingAcks.insert(msgId);
+    }
 }
 
 void MQTTSubmitter::sendReading(String name, String value)
 {
-    String topic = "environment/";
-    topic.concat(location);
-    topic.concat("/");
-    topic.concat(name);
-
-    logfmt("MQTT <- %s = %s\n", topic.c_str(), value.c_str());
-
-    uint16_t msgId = client->publish(topic.c_str(), 1, true, value.c_str(), value.length());
-    pendingAcks.insert(msgId);
+    if (disconnected)
+    {
+        logln("Attempting to send data to disconnected MQTT server");
+    }
+    else
+    {
+        String topic = "environment/";
+        topic.concat(location);
+        topic.concat("/");
+        topic.concat(name);
+
+        logfmt("MQTT <- %s = %s\n", topic.c_str(), value.c_str());
+
+        uint16_t msgId = client->publish(topic.c_str(), 1, true, value.c_str(), value.length());
+        pendingAcks.insert(msgId);
+    }
 }
 
 bool MQTTSubmitter::complete()
diff --git a/src/submitters/mqtt_submitter.h b/src/submitters/mqtt_submitter.h
index 23e3268..7782a05 100644
--- a/src/submitters/mqtt_submitter.h
+++ b/src/submitters/mqtt_submitter.h
@@ -12,6 +12,7 @@ class MQTTSubmitter: public ReadingSubmitter {
     int port;
     bool started;
     volatile bool disconnected;
+    volatile bool failure;
     AsyncMqttClient *client;
     std::set<uint16_t> pendingAcks;