fix: v2 migration process report is always 0 when having many monitors / dates (#6516)

Signed-off-by: Shengqi Chen <i@harrychen.xyz>
Co-authored-by: Frank Elsinga <frank@elsinga.de>

server/database.js

@@ -826,9 +826,7 @@ class Database {
         await Settings.set("migrateAggregateTableState", "migrating");
 
         let progressPercent = 0;
-        let part = 100 / monitors.length;
-        let i = 1;
-        for (let monitor of monitors) {
+        for (const [ i, monitor ] of monitors.entries()) {
             // Get a list of unique dates from the heartbeat table, using raw sql
             let dates = await R.getAll(`
                 SELECT DISTINCT DATE(time) AS date
@@ -839,7 +837,7 @@ class Database {
                 monitor.monitor_id
             ]);
 
-            for (let date of dates) {
+            for (const [ dateIndex, date ] of dates.entries()) {
                 // New Uptime Calculator
                 let calculator = new UptimeCalculator();
                 calculator.monitorID = monitor.monitor_id;
@@ -855,7 +853,7 @@ class Database {
                 `, [ monitor.monitor_id, date.date ]);
 
                 if (heartbeats.length > 0) {
-                    msg = `[DON'T STOP] Migrating monitor data ${monitor.monitor_id} - ${date.date} [${progressPercent.toFixed(2)}%][${i}/${monitors.length}]`;
+                    msg = `[DON'T STOP] Migrating monitor ${monitor.monitor_id}s' (${i + 1} of ${monitors.length} total) data - ${date.date} - total migration progress ${progressPercent.toFixed(2)}%`;
                     log.info("db", msg);
                     migrationServer?.update(msg);
                 }
@@ -864,15 +862,14 @@ class Database {
                     await calculator.update(heartbeat.status, parseFloat(heartbeat.ping), dayjs(heartbeat.time));
                 }
 
-                progressPercent += (Math.round(part / dates.length * 100) / 100);
+                // Calculate progress: (current_monitor_index + relative_date_progress) / total_monitors
+                progressPercent = (i + (dateIndex + 1) / dates.length) / monitors.length * 100;
 
                 // Lazy to fix the floating point issue, it is acceptable since it is just a progress bar
                 if (progressPercent > 100) {
                     progressPercent = 100;
                 }
             }
-
-            i++;
         }
 
         msg = "Clearing non-important heartbeats";