From 40cb5afbad6ee7a0ce6a66b1344290f3cd754ed9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Jastrz=C4=99bski?= <pj@napcode.eu>
Date: Fri, 23 Apr 2021 19:15:13 +0200
Subject: [PATCH] Skip heartbeat if there is no response

Fix xhr callbacks
---
 .../templates/analytics/scripts/page.js        | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/shynet/analytics/templates/analytics/scripts/page.js b/shynet/analytics/templates/analytics/scripts/page.js
index 89c4f0a..f2c96c1 100644
--- a/shynet/analytics/templates/analytics/scripts/page.js
+++ b/shynet/analytics/templates/analytics/scripts/page.js
@@ -8,11 +8,18 @@
 var Shynet = {
   idempotency: null,
   heartbeatTaskId: null,
+  skipHeartbeat: false,
   sendHeartbeat: function () {
     try {
       if (document.hidden) {
         return;
       }
+      if (Shynet.skipHeartbeat) {
+        console.warn("Heartbeat skipped due to lack of server response");
+        return;
+      }
+
+      Shynet.skipHeartbeat = true;
       var xhr = new XMLHttpRequest();
       xhr.open(
         "POST",
@@ -20,6 +27,12 @@ var Shynet = {
         true
       );
       xhr.setRequestHeader("Content-Type", "application/json");
+      xhr.onload = function () { 
+        Shynet.skipHeartbeat = false;
+      };
+      xhr.onerror = function () { 
+        Shynet.skipHeartbeat = false;
+      };
       xhr.send(
         JSON.stringify({
           idempotency: Shynet.idempotency,
@@ -30,13 +43,14 @@ var Shynet = {
             window.performance.timing.navigationStart,
         })
       );
-    } catch (e) { }
+    } catch (e) {}
   },
   newPageLoad: function () {
     if (Shynet.heartbeatTaskId != null) {
       clearInterval(Shynet.heartbeatTaskId);
     }
     Shynet.idempotency = Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15);
+    Shynet.skipHeartbeat = false;
     Shynet.heartbeatTaskId = setInterval(Shynet.sendHeartbeat, parseInt("{{heartbeat_frequency}}"));
     Shynet.sendHeartbeat();
   }
@@ -51,4 +65,4 @@ window.addEventListener("load", Shynet.newPageLoad);
 // -- START --
 {{script_inject|safe}}
 // -- END --
-{% endif %}
\ No newline at end of file
+{% endif %}