Send fleet status update on MQTT reconnect (#587)

iotcored/src/mqtt.c

@@ -15,6 +15,9 @@
 #include <core_mqtt_config.h>
 #include <core_mqtt_serializer.h>
 #include <ggl/backoff.h>
+#include <ggl/bump_alloc.h>
+#include <ggl/core_bus/client.h>
+#include <ggl/object.h>
 #include <pthread.h>
 #include <string.h>
 #include <sys/time.h>
@@ -127,6 +130,7 @@ static GglError establish_connection(void *ctx) {
 }
 
 noreturn static void *mqtt_recv_thread_fn(void *arg) {
+    bool reconnect = false;
     while (true) {
         // Connect to IoT core with backoff between 10ms->10s.
         GglError err
@@ -143,6 +147,32 @@ noreturn static void *mqtt_recv_thread_fn(void *arg) {
             _Exit(1);
         }
 
+        // Send a fleet status update on reconnection
+        if (reconnect) {
+            static uint8_t buffer[10 * sizeof(GglObject)] = { 0 };
+            GglMap args = GGL_MAP({ GGL_STR("trigger"),
+                                    GGL_OBJ_BUF(GGL_STR("RECONNECT")) });
+            GglBumpAlloc alloc = ggl_bump_alloc_init(GGL_BUF(buffer));
+            GglObject result;
+
+            GglError ret = ggl_call(
+                GGL_STR("/aws/ggl/gg-fleet-statusd"),
+                GGL_STR("send_fleet_status_update"),
+                args,
+                NULL,
+                &alloc.alloc,
+                &result
+            );
+
+            if (ret != 0) {
+                GGL_LOGE(
+                    "Failed to call send_fleet_status_update on MQTT "
+                    "reconnection: %d.",
+                    ret
+                );
+            }
+        }
+
         MQTTStatus_t mqtt_ret;
         MQTTContext_t *ctx = arg;
         do {
@@ -159,6 +189,10 @@ noreturn static void *mqtt_recv_thread_fn(void *arg) {
         // Remove all subscriptions. This will force the callers to
         // resubscribe.
         iotcored_unregister_all_subs();
+
+        // Set reconnect flag. Future connections will send a fleet status
+        // update
+        reconnect = true;
     }
 }