improve uptime calculation

server/model/monitor.js

@@ -158,7 +158,9 @@ class Monitor extends BeanModel {
         ]);
 
         let downtime = 0;
+        let uptime = 0;
 
+        if (downtimeList.length === 0) {
             for (let row of downtimeList) {
                 let value = parseInt(row.duration)
                 let time = row.time
@@ -179,11 +181,32 @@ class Monitor extends BeanModel {
                 }
             }
 
-        let uptime = (sec - downtime) / sec;
+            uptime = (sec - downtime) / sec;
 
             if (uptime < 0) {
                 uptime = 0;
             }
+        } else {
+            // This case for someone who are not running UptimeKuma 24x7.
+            // If there is no heartbeat in this time range, use last heartbeat as reference
+            // If is down, uptime = 0
+            // If is up, uptime = 1
+
+            let lastHeartbeat = await R.findOne("heartbeat", " monitor_id = ? ORDER BY time DESC", [
+                monitorID
+            ]);
+
+            if (lastHeartbeat) {
+                if (lastHeartbeat.status === 1) {
+                    uptime = 1;
+                } else {
+                    uptime = 0;
+                }
+            } else {
+                // No heartbeat is found, assume 100%
+                uptime = 1;
+            }
+        }
 
         io.to(userID).emit("uptime", monitorID, duration, uptime);
     }