feat: timing + throughput metrics on Report (#144, #91)

src/Wolfgang.Etl.Abstractions/ExtractorBase.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using System.Threading;
@@ -22,6 +23,43 @@ public abstract class ExtractorBase<TSource, TProgress>
 {
     private int _currentItemCount;
     private int _currentSkippedItemCount;
+    private long _startTimestamp;
+    private DateTimeOffset _startedAtUtc;
+
+
+
+    /// <summary>
+    /// The UTC time at which the first item was processed (extracted or skipped), or
+    /// <c>null</c> if extraction has not produced any items yet. Captured automatically
+    /// the first time <see cref="IncrementCurrentItemCount"/> or
+    /// <see cref="IncrementCurrentSkippedItemCount"/> is called, so derived classes can
+    /// surface it on their progress report (see <see cref="Report.StartedAt"/>).
+    /// </summary>
+    protected DateTimeOffset? StartedAt =>
+        Volatile.Read(ref _startTimestamp) == 0 ? null : _startedAtUtc;
+
+
+
+    /// <summary>
+    /// The monotonic wall-clock time elapsed since the first item was processed, or
+    /// <see cref="TimeSpan.Zero"/> if extraction has not produced any items yet.
+    /// Read this when building a progress report (see <see cref="Report.Elapsed"/>) to
+    /// snapshot how long extraction has been running.
+    /// </summary>
+    protected TimeSpan Elapsed
+    {
+        get
+        {
+            var start = Volatile.Read(ref _startTimestamp);
+            if (start == 0)
+            {
+                return TimeSpan.Zero;
+            }
+
+            var ticks = Stopwatch.GetTimestamp() - start;
+            return TimeSpan.FromSeconds(ticks / (double)Stopwatch.Frequency);
+        }
+    }
 
 
 
@@ -304,6 +342,7 @@ private void ReportProgress(object? state)
         Justification = "Interlocked.Increment return value intentionally discarded; only the side-effect matters.")]
     protected void IncrementCurrentItemCount()
     {
+        EnsureStarted();
         _ = Interlocked.Increment(ref _currentItemCount);
     }
 
@@ -320,6 +359,27 @@ protected void IncrementCurrentItemCount()
         Justification = "Interlocked.Increment return value intentionally discarded; only the side-effect matters.")]
     protected void IncrementCurrentSkippedItemCount()
     {
+        EnsureStarted();
         _ = Interlocked.Increment(ref _currentSkippedItemCount);
     }
+
+
+
+    // Captures the start timestamp (monotonic) and wall-clock StartedAt the first
+    // time any item is processed. Idempotent and thread-safe: the first caller to
+    // win the CompareExchange records the start; later calls are a cheap volatile read.
+    private void EnsureStarted()
+    {
+        if (Volatile.Read(ref _startTimestamp) != 0)
+        {
+            return;
+        }
+
+        var now = DateTimeOffset.UtcNow;
+        var timestamp = Stopwatch.GetTimestamp();
+        if (Interlocked.CompareExchange(ref _startTimestamp, timestamp, 0) == 0)
+        {
+            _startedAtUtc = now;
+        }
+    }
 }

src/Wolfgang.Etl.Abstractions/IsExternalInit.cs

@@ -0,0 +1,19 @@
+#if !NET5_0_OR_GREATER
+
+using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Runtime.CompilerServices;
+
+/// <summary>
+/// Polyfill for the compiler-required <c>IsExternalInit</c> marker type, which enables
+/// <see langword="init"/>-only property setters on target frameworks (.NET Framework,
+/// .NET Standard 2.0) whose reference assemblies do not ship it. Built-in on .NET 5.0+.
+/// </summary>
+[EditorBrowsable(EditorBrowsableState.Never)]
+[ExcludeFromCodeCoverage]
+internal static class IsExternalInit
+{
+}
+
+#endif

src/Wolfgang.Etl.Abstractions/LoaderBase.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Threading;
 using System.Threading.Tasks;
@@ -22,6 +23,43 @@ public abstract class LoaderBase<TDestination, TProgress>
 {
     private int _currentItemCount;
     private int _currentSkippedItemCount;
+    private long _startTimestamp;
+    private DateTimeOffset _startedAtUtc;
+
+
+
+    /// <summary>
+    /// The UTC time at which the first item was processed (loaded or skipped), or
+    /// <c>null</c> if loading has not produced any items yet. Captured automatically
+    /// the first time <see cref="IncrementCurrentItemCount"/> or
+    /// <see cref="IncrementCurrentSkippedItemCount"/> is called, so derived classes can
+    /// surface it on their progress report (see <see cref="Report.StartedAt"/>).
+    /// </summary>
+    protected DateTimeOffset? StartedAt =>
+        Volatile.Read(ref _startTimestamp) == 0 ? null : _startedAtUtc;
+
+
+
+    /// <summary>
+    /// The monotonic wall-clock time elapsed since the first item was processed, or
+    /// <see cref="TimeSpan.Zero"/> if loading has not produced any items yet.
+    /// Read this when building a progress report (see <see cref="Report.Elapsed"/>) to
+    /// snapshot how long loading has been running.
+    /// </summary>
+    protected TimeSpan Elapsed
+    {
+        get
+        {
+            var start = Volatile.Read(ref _startTimestamp);
+            if (start == 0)
+            {
+                return TimeSpan.Zero;
+            }
+
+            var ticks = Stopwatch.GetTimestamp() - start;
+            return TimeSpan.FromSeconds(ticks / (double)Stopwatch.Frequency);
+        }
+    }
 
 
 
@@ -307,6 +345,7 @@ private void ReportProgress(object? state)
         Justification = "Interlocked.Increment return value intentionally discarded; only the side-effect matters.")]
     protected void IncrementCurrentItemCount()
     {
+        EnsureStarted();
         _ = Interlocked.Increment(ref _currentItemCount);
     }
 
@@ -323,6 +362,27 @@ protected void IncrementCurrentItemCount()
         Justification = "Interlocked.Increment return value intentionally discarded; only the side-effect matters.")]
     protected void IncrementCurrentSkippedItemCount()
     {
+        EnsureStarted();
         _ = Interlocked.Increment(ref _currentSkippedItemCount);
     }
+
+
+
+    // Captures the start timestamp (monotonic) and wall-clock StartedAt the first
+    // time any item is processed. Idempotent and thread-safe: the first caller to
+    // win the CompareExchange records the start; later calls are a cheap volatile read.
+    private void EnsureStarted()
+    {
+        if (Volatile.Read(ref _startTimestamp) != 0)
+        {
+            return;
+        }
+
+        var now = DateTimeOffset.UtcNow;
+        var timestamp = Stopwatch.GetTimestamp();
+        if (Interlocked.CompareExchange(ref _startTimestamp, timestamp, 0) == 0)
+        {
+            _startedAtUtc = now;
+        }
+    }
 }

src/Wolfgang.Etl.Abstractions/PublicAPI.Shipped.txt

@@ -2,6 +2,7 @@
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.CurrentItemCount.get -> int
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.CurrentSkippedItemCount.get -> int
+Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.Elapsed.get -> System.TimeSpan
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.ExtractorBase() -> void
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.IncrementCurrentItemCount() -> void
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.IncrementCurrentSkippedItemCount() -> void
@@ -11,6 +12,7 @@ Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.ReportingInterval.ge
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.ReportingInterval.set -> void
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.SkipItemCount.get -> int
 Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.SkipItemCount.set -> void
+Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.StartedAt.get -> System.DateTimeOffset?
 Wolfgang.Etl.Abstractions.IExtractAsync<TSource>
 Wolfgang.Etl.Abstractions.IExtractAsync<TSource>.ExtractAsync() -> System.Collections.Generic.IAsyncEnumerable<TSource>!
 Wolfgang.Etl.Abstractions.IExtractStage<TSource>
@@ -71,6 +73,7 @@ Wolfgang.Etl.Abstractions.ITransformWithProgressAsync<TSource, TDestination, TPr
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.CurrentItemCount.get -> int
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.CurrentSkippedItemCount.get -> int
+Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.Elapsed.get -> System.TimeSpan
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.IncrementCurrentItemCount() -> void
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.IncrementCurrentSkippedItemCount() -> void
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.LoaderBase() -> void
@@ -80,13 +83,24 @@ Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.ReportingInterval.
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.ReportingInterval.set -> void
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.SkipItemCount.get -> int
 Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.SkipItemCount.set -> void
+Wolfgang.Etl.Abstractions.LoaderBase<TDestination, TProgress>.StartedAt.get -> System.DateTimeOffset?
 Wolfgang.Etl.Abstractions.Pipeline
 Wolfgang.Etl.Abstractions.Report
 Wolfgang.Etl.Abstractions.Report.CurrentItemCount.get -> int
+Wolfgang.Etl.Abstractions.Report.Elapsed.get -> System.TimeSpan
+Wolfgang.Etl.Abstractions.Report.Elapsed.init -> void
+Wolfgang.Etl.Abstractions.Report.EstimatedRemaining.get -> System.TimeSpan?
+Wolfgang.Etl.Abstractions.Report.ItemsPerSecond.get -> double
+Wolfgang.Etl.Abstractions.Report.PercentComplete.get -> double?
 Wolfgang.Etl.Abstractions.Report.Report(int currentItemCount) -> void
+Wolfgang.Etl.Abstractions.Report.StartedAt.get -> System.DateTimeOffset?
+Wolfgang.Etl.Abstractions.Report.StartedAt.init -> void
+Wolfgang.Etl.Abstractions.Report.TotalItemCount.get -> int?
+Wolfgang.Etl.Abstractions.Report.TotalItemCount.init -> void
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.CurrentItemCount.get -> int
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.CurrentSkippedItemCount.get -> int
+Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.Elapsed.get -> System.TimeSpan
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.IncrementCurrentItemCount() -> void
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.IncrementCurrentSkippedItemCount() -> void
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.MaximumItemCount.get -> int
@@ -95,6 +109,7 @@ Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.Repo
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.ReportingInterval.set -> void
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.SkipItemCount.get -> int
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.SkipItemCount.set -> void
+Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.StartedAt.get -> System.DateTimeOffset?
 Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>.TransformerBase() -> void
 abstract Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.CreateProgressReport() -> TProgress
 abstract Wolfgang.Etl.Abstractions.ExtractorBase<TSource, TProgress>.ExtractWorkerAsync(System.Threading.CancellationToken token) -> System.Collections.Generic.IAsyncEnumerable<TSource>!

src/Wolfgang.Etl.Abstractions/Report.cs

@@ -3,11 +3,23 @@
 namespace Wolfgang.Etl.Abstractions;
 
 /// <summary>
-/// Provides a report of the current item count in an ETL process.
+/// Provides a point-in-time snapshot of the progress of an ETL process — how many
+/// items have been processed, how long it has been running, and (when the total is
+/// known) how far along it is and how much longer it is expected to take.
 /// </summary>
 /// <remarks>
+/// <para>
 /// This class can be used as a base class for other progress reports and expanded
-/// with additional information such as total count, count remaining, etc.
+/// with additional information specific to a particular extractor, transformer, or loader.
+/// </para>
+/// <para>
+/// All values are <em>snapshot</em> values captured at the moment the report is
+/// constructed. <see cref="Elapsed"/> does not advance after construction, mirroring
+/// <see cref="CurrentItemCount"/>. The throughput and completion estimates
+/// (<see cref="ItemsPerSecond"/>, <see cref="PercentComplete"/>,
+/// <see cref="EstimatedRemaining"/>) are derived from those snapshot values, so a
+/// given report is internally consistent.
+/// </para>
 /// </remarks>
 public record Report
 {
@@ -32,4 +44,107 @@ public Report(int currentItemCount)
     /// The number of items that have been processed so far in the ETL process.
     /// </summary>
     public int CurrentItemCount { get; }
+
+
+
+    /// <summary>
+    /// The wall-clock time (UTC) at which processing started, or <c>null</c> if it
+    /// has not started yet (no items processed) or the producer does not track it.
+    /// </summary>
+    public DateTimeOffset? StartedAt { get; init; }
+
+
+
+    /// <summary>
+    /// The wall-clock time that had elapsed since processing started, captured at the
+    /// moment this report was constructed. <see cref="TimeSpan.Zero"/> when timing is
+    /// not tracked or processing has not started.
+    /// </summary>
+    public TimeSpan Elapsed { get; init; }
+
+
+
+    /// <summary>
+    /// The total number of items expected to be processed, when known (for example a
+    /// file line count or a SQL <c>COUNT(*)</c>). <c>null</c> for unknown-size or
+    /// infinite sources. Must be greater than or equal to 0 when set.
+    /// </summary>
+    /// <exception cref="ArgumentOutOfRangeException">The specified value is less than 0.</exception>
+    public int? TotalItemCount
+    {
+        get;
+        init
+        {
+            if (value is < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(value), "Total item count cannot be less than 0.");
+            }
+
+            field = value;
+        }
+    }
+
+
+
+    /// <summary>
+    /// The processing throughput, in items per second, derived from
+    /// <see cref="CurrentItemCount"/> and <see cref="Elapsed"/>. Returns 0 until at
+    /// least some time has elapsed.
+    /// </summary>
+    public double ItemsPerSecond =>
+        Elapsed.TotalSeconds > 0
+            ? CurrentItemCount / Elapsed.TotalSeconds
+            : 0d;
+
+
+
+    /// <summary>
+    /// The fraction of work completed, as a percentage in the range [0, 100], when
+    /// <see cref="TotalItemCount"/> is known; otherwise <c>null</c>. Clamped to 100
+    /// if <see cref="CurrentItemCount"/> exceeds <see cref="TotalItemCount"/>.
+    /// </summary>
+    public double? PercentComplete
+    {
+        get
+        {
+            if (TotalItemCount is not { } total)
+            {
+                return null;
+            }
+
+            return total == 0
+                ? 100d
+                : Math.Min(100d, 100d * CurrentItemCount / total);
+        }
+    }
+
+
+
+    /// <summary>
+    /// The estimated time remaining until completion, when both
+    /// <see cref="TotalItemCount"/> is known and throughput can be measured;
+    /// otherwise <c>null</c>. Returns <see cref="TimeSpan.Zero"/> once the current
+    /// count has reached the total.
+    /// </summary>
+    public TimeSpan? EstimatedRemaining
+    {
+        get
+        {
+            if (TotalItemCount is not { } total)
+            {
+                return null;
+            }
+
+            var remaining = total - CurrentItemCount;
+            if (remaining <= 0)
+            {
+                return TimeSpan.Zero;
+            }
+
+            var rate = ItemsPerSecond;
+            return rate > 0
+                ? TimeSpan.FromSeconds(remaining / rate)
+                : (TimeSpan?)null;
+        }
+    }
 }