From e6b2615693feb6e00e79f63c0f9eb6288fd2a464 Mon Sep 17 00:00:00 2001
From: Shreyas Zare <shreyas@technitium.com>
Date: Sun, 20 Feb 2022 17:54:39 +0530
Subject: [PATCH] StatsManager: Updated DoMaintenance() to unload not required
 minute stats from cached hourly stats data for objects older than 1 hour to
 free memory.

---
 DnsServerCore/Dns/StatsManager.cs | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/DnsServerCore/Dns/StatsManager.cs b/DnsServerCore/Dns/StatsManager.cs
index 716adf47..b3b6ec95 100644
--- a/DnsServerCore/Dns/StatsManager.cs
+++ b/DnsServerCore/Dns/StatsManager.cs
@@ -1,6 +1,6 @@
 /*
 Technitium DNS Server
-Copyright (C) 2021  Shreyas Zare (shreyas@technitium.com)
+Copyright (C) 2022  Shreyas Zare (shreyas@technitium.com)
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -58,7 +58,7 @@ namespace DnsServerCore.Dns
 
         readonly Timer _maintenanceTimer;
         const int MAINTENANCE_TIMER_INITIAL_INTERVAL = 10000;
-        const int MAINTENANCE_TIMER_INTERVAL = 10000;
+        const int MAINTENANCE_TIMER_PERIODIC_INTERVAL = 10000;
 
         readonly BlockingCollection<StatsQueueItem> _queue = new BlockingCollection<StatsQueueItem>();
         readonly Thread _consumerThread;
@@ -99,7 +99,7 @@ namespace DnsServerCore.Dns
                     if (log != null)
                         log.Write(ex);
                 }
-            }, null, MAINTENANCE_TIMER_INITIAL_INTERVAL, MAINTENANCE_TIMER_INTERVAL);
+            }, null, MAINTENANCE_TIMER_INITIAL_INTERVAL, MAINTENANCE_TIMER_PERIODIC_INTERVAL);
 
             //stats consumer thread
             _consumerThread = new Thread(delegate ()
@@ -350,6 +350,18 @@ namespace DnsServerCore.Dns
                     _hourlyStatsCache.TryRemove(key, out _);
             }
 
+            //unload minute stats data from hourly stats cache for data older than last hour
+            {
+                DateTime lastHourThreshold = DateTime.UtcNow.AddHours(-1);
+                lastHourThreshold = new DateTime(lastHourThreshold.Year, lastHourThreshold.Month, lastHourThreshold.Day, lastHourThreshold.Hour, 0, 0, DateTimeKind.Utc);
+
+                foreach (KeyValuePair<DateTime, HourlyStats> item in _hourlyStatsCache)
+                {
+                    if (item.Key < lastHourThreshold)
+                        item.Value.UnloadMinuteStats();
+                }
+            }
+
             //remove old data from daily stats cache
             {
                 DateTime threshold = DateTime.UtcNow.AddMonths(-12);
@@ -1159,7 +1171,7 @@ namespace DnsServerCore.Dns
             #region variables
 
             readonly StatCounter _hourStat; //calculated value
-            readonly StatCounter[] _minuteStats = new StatCounter[60];
+            StatCounter[] _minuteStats = new StatCounter[60];
 
             #endregion
 
@@ -1209,6 +1221,11 @@ namespace DnsServerCore.Dns
                 _minuteStats[dateTime.Minute] = minuteStat;
             }
 
+            public void UnloadMinuteStats()
+            {
+                _minuteStats = null;
+            }
+
             public void WriteTo(BinaryWriter bW)
             {
                 bW.Write(Encoding.ASCII.GetBytes("HS")); //format