TARDA-2840 Refactor DBMDataRef for thread-safe annotation access and memory-efficient size limiting (#327)

* Thread-safe access to _annotations in DBMDataRef using lock

Signed-off-by: Johan Fitié <jfitie@gmail.com>

* Limit _annotations dictionary size to 10,000 by removing entries when exceeded

Signed-off-by: Johan Fitié <jfitie@gmail.com>

* Refactor to use constant for maximum annotations size

Signed-off-by: Johan Fitié <jfitie@gmail.com>

* Refactor _annotations to use SortedDictionary for FIFO eviction instead of random removal

Signed-off-by: Johan Fitié <jfitie@gmail.com>

* Limit line length correctly

Signed-off-by: Johan Fitié <jfitie@gmail.com>

* Update copyright year, change maximum number of annotations

Signed-off-by: Johan Fitié <jfitie@gmail.com>

---------

Signed-off-by: Johan Fitié <jfitie@gmail.com>

Author: jfitie

README.md

@@ -3,7 +3,7 @@
 # DBM
 Dynamic Bandwidth Monitor\
 Leak detection method implemented in a real-time data historian\
-Copyright (C) 2014-2024  J.H. Fitié, Vitens N.V.
+Copyright (C) 2014-2025  J.H. Fitié, Vitens N.V.
 
 ## Description
 Water company Vitens has created a demonstration site called the Vitens Innovation Playground (VIP), in which new technologies and methodologies are developed, tested, and demonstrated. The projects conducted in the demonstration site can be categorized into one of four themes: energy optimization, real-time leak detection, online water quality monitoring, and customer interaction. In the real-time leak detection theme, a method for leak detection based on statistical demand forecasting was developed.

src/DBMDataRef/DBMDataRef.vb

@@ -1,6 +1,6 @@
 ' Dynamic Bandwidth Monitor
 ' Leak detection method implemented in a real-time data historian
-' Copyright (C) 2014-2024  J.H. Fitié, Vitens N.V.
+' Copyright (C) 2014-2025  J.H. Fitié, Vitens N.V.
 '
 ' This file is part of DBM.
 '
@@ -25,6 +25,7 @@ Imports System.DateTime
 Imports System.Double
 Imports System.Math
 Imports System.Runtime.InteropServices
+Imports System.Threading
 Imports OSIsoft.AF.Asset
 Imports OSIsoft.AF.Asset.AFAttributeTrait
 Imports OSIsoft.AF.Data
@@ -83,13 +84,15 @@ Namespace Vitens.DynamicBandwidthMonitor
     '             process output.
 
 
+    Const MaxAnnotationsSize As Integer = 1000 ' Maximum number of annotations
     Const StaleDataMinutes As Integer = 10 ' Minutes until snapshot is stale
     Const CategoryNoCorrelation As String = "NoCorrelation"
     Const pValueLoHi As Double = 0.95 ' Confidence interval for Lo and Hi
     Const pValueMinMax As Double = 0.9999 ' CI for Minimum and Maximum
 
 
-    Private _annotations As New Dictionary(Of AFTime, Object)
+    Private _lock As New Object ' Object for exclusive lock on critical section.
+    Private _annotations As New SortedDictionary(Of AFTime, Object)
     Private Shared _dbm As New DBM(New DBMLoggerAFTrace)
 
 
@@ -279,20 +282,31 @@ Namespace Vitens.DynamicBandwidthMonitor
 
       If value IsNot Nothing Then ' Key
 
-        _annotations.Remove(value.Timestamp) ' Remove existing
-        value.Annotated = False
+        Monitor.Enter(_lock) ' Block
+        Try
 
-        If annotation IsNot Nothing Then ' Value
+          _annotations.Remove(value.Timestamp) ' Remove existing
+          value.Annotated = False
 
-          DBM.Logger.LogDebug(
-            "value.Timestamp " &
-            value.Timestamp.LocalTime.ToString("s") & "; " &
-            "annotation " & DirectCast(annotation, String), Attribute.GetPath)
+          If annotation IsNot Nothing Then ' Value
 
-          _annotations.Add(value.Timestamp, annotation) ' Add
-          value.Annotated = True
+            While _annotations.Count >= MaxAnnotationsSize ' Limit size
+              _annotations.Remove(_annotations.Keys.First()) ' Remove oldest
+            End While
 
-        End If
+            DBM.Logger.LogDebug(
+              "value.Timestamp " &
+              value.Timestamp.LocalTime.ToString("s") & "; " &
+              "annotation " & DirectCast(annotation, String), Attribute.GetPath)
+
+            _annotations.Add(value.Timestamp, annotation) ' Add
+            value.Annotated = True
+
+          End If
+
+        Finally
+          Monitor.Exit(_lock) ' Unblock
+        End Try
 
       End If
 
@@ -308,12 +322,22 @@ Namespace Vitens.DynamicBandwidthMonitor
       '   attributes"
 
       GetAnnotation = Nothing
-      If value IsNot Nothing AndAlso
-        _annotations.TryGetValue(value.Timestamp, GetAnnotation) Then
-        _annotations.Remove(value.Timestamp) ' Remove after get
-        Return GetAnnotation
-      Else
-        Return String.Empty ' Default
+      If value IsNot Nothing Then ' Key
+
+        Monitor.Enter(_lock) ' Block
+        Try
+
+          If _annotations.TryGetValue(value.Timestamp, GetAnnotation) Then
+            _annotations.Remove(value.Timestamp) ' Remove after get
+            Return GetAnnotation
+          Else
+            Return String.Empty ' Default
+          End If
+
+        Finally
+          Monitor.Exit(_lock) ' Unblock
+        End Try
+
       End If
 
     End Function

src/dbm/DBMManifest.vb

@@ -1,6 +1,6 @@
 ' Dynamic Bandwidth Monitor
 ' Leak detection method implemented in a real-time data historian
-' Copyright (C) 2014-2024  J.H. Fitié, Vitens N.V.
+' Copyright (C) 2014-2025  J.H. Fitié, Vitens N.V.
 '
 ' This file is part of DBM.
 '
@@ -30,6 +30,6 @@
   "Leak detection method implemented in a real-time data historian")>
 
 <assembly:System.Reflection.AssemblyCopyright(
-  "Copyright (C) 2014-2024  J.H. Fitié, Vitens N.V.")>
+  "Copyright (C) 2014-2025  J.H. Fitié, Vitens N.V.")>
 
 <assembly:System.Reflection.AssemblyCompany("Vitens N.V.")>