Feature: Multithreaded Stress Test for List-to-Cache MergeManyChangeS…

…ets (#806)

* Fix operator and added stress test to prevent regressions

* Fix test issue

* Improvements to try and fix the stress test for List-List

* Code synchronization

src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheFixture.cs

@@ -39,9 +39,16 @@ public sealed class MergeManyChangeSetsCacheFixture : IDisposable
 
     private readonly ChangeSetAggregator<IMarket, Guid> _marketCacheResults;
 
-    private readonly Randomizer _randomizer = new (0x21123737);
+    private readonly Faker<Market> _marketFaker;
 
-    public MergeManyChangeSetsCacheFixture() => _marketCacheResults = _marketCache.Connect().AsAggregator();
+    private readonly Randomizer _randomizer;
+
+    public MergeManyChangeSetsCacheFixture()
+    {
+        _randomizer = new(0x21123737);
+        _marketFaker = Fakers.Market.WithSeed(_randomizer);
+        _marketCacheResults = _marketCache.Connect().AsAggregator();
+    }
 
     [Theory]
     [InlineData(5, 7)]
@@ -77,17 +84,13 @@ public async Task MultiThreadedStressTest(int marketCount, int priceCount)
                 });
 
         IObservable<IMarket> AddRemoveMarkets(int ownerCount, int parallel, IScheduler scheduler) =>
-            _randomizer.Interval(MaxAddTime, scheduler).Select(_ => new Market(_randomizer.Utf16String(5, 10, true)))
-                //.Parallelize(ownerCount, parallel, obs => obs.StressAddRemove(_marketCache, _ => GetRemoveTime(), scheduler))
-                .Take(ownerCount)
-                .StressAddRemove(_marketCache, _ => GetRemoveTime(), scheduler)
+            _marketFaker.IntervalGenerate(MaxAddTime, scheduler)
+                .Parallelize(ownerCount, parallel, obs => obs.StressAddRemove(_marketCache, _ => GetRemoveTime(), scheduler))
                 .Finally(_marketCache.Dispose);
 
         IObservable<MarketPrice> AddRemovePrices(Market market, int priceCount, int parallel, IScheduler scheduler) =>
             _randomizer.Interval(MaxAddTime, scheduler).Select(_ => market.CreateUniquePrice(_ => GetRandomPrice()))
-                //.Parallelize(animalCount, parallel, obs => obs.StressAddRemove(owner.Animals, _ => GetRemoveTime(), scheduler))
-                .Take(priceCount)
-                .StressAddRemove(market.PricesCache, _ => GetRemoveTime(), scheduler)
+                .Parallelize(priceCount, parallel, obs => obs.StressAddRemove(market.PricesCache, _ => GetRemoveTime(), scheduler))
                 .Finally(market.PricesCache.Dispose);
 
         var merged = _marketCache.Connect().MergeManyChangeSets(market => market.LatestPrices);

src/DynamicData.Tests/Cache/MergeManyChangeSetsListFixture.cs

@@ -29,8 +29,6 @@ public sealed class MergeManyChangeSetsListFixture : IDisposable
     const int AddRangeSize = 53;
     const int RemoveRangeSize = 37;
 #endif
-    private static readonly TimeSpan s_MaxAddTime = TimeSpan.FromSeconds(0.250);
-    private static readonly TimeSpan s_MaxRemoveTime = TimeSpan.FromSeconds(0.100);
 
     private readonly ISourceCache<AnimalOwner, Guid> _animalOwners = new SourceCache<AnimalOwner, Guid>(o => o.Id);
     private readonly ChangeSetAggregator<AnimalOwner, Guid> _animalOwnerResults;

src/DynamicData.Tests/List/MergeManyChangeSetsCacheFixture.cs

@@ -1,7 +1,12 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reactive.Concurrency;
+using System.Reactive.Disposables;
+using System.Reactive;
 using System.Reactive.Linq;
+using System.Threading.Tasks;
+using Bogus;
 using DynamicData.Kernel;
 using DynamicData.Tests.Domain;
 using DynamicData.Tests.Utilities;
@@ -28,15 +33,97 @@ public sealed class MergeManyChangeSetsCacheFixture : IDisposable
     const decimal HighestPrice = BasePrice + PriceOffset + 1.0m;
     const decimal LowestPrice = BasePrice - 1.0m;
 
-    private static readonly Random Random = new (0x03251976);
-
-    private static decimal GetRandomPrice() => MarketPrice.RandomPrice(Random, BasePrice, PriceOffset);
-
     private readonly ISourceList<IMarket> _marketList = new SourceList<IMarket>();
 
     private readonly ChangeSetAggregator<IMarket> _marketListResults;
 
-    public MergeManyChangeSetsCacheFixture() => _marketListResults = _marketList.Connect().AsAggregator();
+    private readonly Faker<Market> _marketFaker;
+
+    private readonly Randomizer _randomizer;
+
+    public MergeManyChangeSetsCacheFixture()
+    {
+        _randomizer = new(0x03251976);
+        _marketFaker = Fakers.Market.WithSeed(_randomizer);
+        _marketListResults = _marketList.Connect().AsAggregator();
+    }
+
+
+    [Theory]
+    [InlineData(5, 7)]
+    [InlineData(10, 50)]
+    [InlineData(5, 100)]
+    [InlineData(200, 500)]
+    [InlineData(100, 5)]
+    public async Task MultiThreadedStressTest(int marketCount, int priceCount)
+    {
+        var MaxAddTime = TimeSpan.FromSeconds(0.250);
+        var MaxRemoveTime = TimeSpan.FromSeconds(0.100);
+
+        TimeSpan? GetRemoveTime() => _randomizer.Bool() ? _randomizer.TimeSpan(MaxRemoveTime) : null;
+
+        IObservable<Unit> AddRemoveStress(int marketCount, int priceCount, int parallel, IScheduler scheduler) =>
+            Observable.Create<Unit>(observer => new CompositeDisposable
+                {
+                    AddRemoveMarkets(marketCount, parallel, scheduler)
+                            .Subscribe(
+                                onNext: _ => { },
+                                onError: ex => observer.OnError(ex)),
+
+                    _marketList.Connect()
+                            .MergeMany(market => AddRemovePrices((Market)market, priceCount, parallel, scheduler))
+                            .Subscribe(
+                                onNext: _ => { },
+                                onError: ex => observer.OnError(ex),
+                                onCompleted: () =>
+                                    {
+                                        observer.OnNext(Unit.Default);
+                                        observer.OnCompleted();
+                                    })
+                });
+
+        IObservable<IMarket> AddRemoveMarkets(int ownerCount, int parallel, IScheduler scheduler) =>
+            _marketFaker.IntervalGenerate(MaxAddTime, scheduler)
+                .Parallelize(ownerCount, parallel, obs => obs.StressAddRemove(_marketList, _ => GetRemoveTime(), scheduler))
+                .Finally(_marketList.Dispose);
+
+        IObservable<MarketPrice> AddRemovePrices(Market market, int priceCount, int parallel, IScheduler scheduler) =>
+            _randomizer.Interval(MaxAddTime, scheduler).Select(_ => market.CreateUniquePrice(_ => GetRandomPrice()))
+                .Parallelize(priceCount, parallel, obs => obs.StressAddRemove(market.PricesCache, _ => GetRemoveTime(), scheduler))
+                .Finally(market.PricesCache.Dispose);
+
+        var merged = _marketList.Connect().MergeManyChangeSets(market => market.LatestPrices);
+        using var priceResults = merged.AsAggregator();
+
+        var adding = true;
+
+        // Start asynchrononously modifying the parent list and the child lists
+        using var addingSub = AddRemoveStress(marketCount, priceCount, Environment.ProcessorCount, TaskPoolScheduler.Default)
+            .Finally(() => adding = false)
+            .Subscribe();
+
+        // Subscribe / unsubscribe over and over while the collections are being modified
+        do
+        {
+            // Ensure items are being added asynchronously before subscribing to changes
+            await Task.Yield();
+
+            {
+                // Subscribe
+                var mergedSub = merged.Subscribe();
+
+                // Let other threads run
+                await Task.Yield();
+
+                // Unsubscribe
+                mergedSub.Dispose();
+            }
+        }
+        while (adding);
+
+        // Verify the results
+        CheckResultContents(_marketListResults, priceResults);
+    }
 
     [Fact]
     public void NullChecks()
@@ -449,7 +536,7 @@ public void ComparerOnlyAddsBetterValuesOnSourceReplace()
         lowPriceResults.Data.Count.Should().Be(PricesPerMarket);
         lowPriceResults.Summary.Overall.Adds.Should().Be(PricesPerMarket);
         lowPriceResults.Summary.Overall.Removes.Should().Be(0);
-        lowPriceResults.Summary.Overall.Updates.Should().Be(PricesPerMarket * 3);
+        lowPriceResults.Summary.Overall.Updates.Should().Be(PricesPerMarket * 2);
         lowPriceResults.Data.Items.Select(cp => cp.MarketId).ForEach(guid => guid.Should().Be(marketLowLow.Id));
         highPriceResults.Data.Count.Should().Be(PricesPerMarket);
         highPriceResults.Summary.Overall.Adds.Should().Be(PricesPerMarket);
@@ -739,10 +826,28 @@ public void Dispose()
         DisposeMarkets();
     }
 
+    private void AddUniquePrices(Market[] markets) => markets.ForEach(m => m.AddUniquePrices(PricesPerMarket, _ => GetRandomPrice()));
+
+    private void CheckResultContents(ChangeSetAggregator<IMarket> marketResults, ChangeSetAggregator<MarketPrice, int> priceResults)
+    {
+        var expectedMarkets = _marketList.Items.ToList();
+        var expectedPrices = expectedMarkets.SelectMany(market => ((Market)market).PricesCache.Items).ToList();
+
+        // These should be subsets of each other
+        expectedMarkets.Should().BeSubsetOf(marketResults.Data.Items);
+        marketResults.Data.Items.Count().Should().Be(expectedMarkets.Count);
+
+        // These should be subsets of each other
+        expectedPrices.Should().BeSubsetOf(priceResults.Data.Items);
+        priceResults.Data.Items.Count().Should().Be(expectedPrices.Count);
+    }
+
     private void DisposeMarkets()
     {
         _marketList.Items.ForEach(m => (m as IDisposable)?.Dispose());
         _marketList.Dispose();
         _marketList.Clear();
     }
+
+    private decimal GetRandomPrice() => MarketPrice.RandomPrice(_randomizer, BasePrice, PriceOffset);
 }

src/DynamicData/Cache/Internal/MergeManyCacheChangeSets.cs

@@ -29,6 +29,7 @@ internal sealed class MergeManyCacheChangeSets<TObject, TKey, TDestination, TDes
                 // This is manages all of the changes
                 var changeTracker = new ChangeSetMergeTracker<TDestination, TDestinationKey>(() => sourceCacheOfCaches.Items, comparer, equalityComparer);
 
+                // Share a connection to the source cache
                 var shared = sourceCacheOfCaches.Connect().Publish();
 
                 // Merge the child changeset changes together and apply to the tracker

src/DynamicData/Cache/Internal/MergeManyCacheChangeSetsSourceCompare.cs

@@ -34,7 +34,7 @@ internal sealed class MergeManyCacheChangeSetsSourceCompare<TObject, TKey, TDest
                                             .AsObservableCache();
 
                 // Share a single connection to the cache
-                var shared = sourceCacheOfCaches.Connect().Publish();
+                var shared = sourceCacheOfCaches.Connect().Synchronize(locker).Publish();
 
                 // This is manages all of the changes
                 var changeTracker = new ChangeSetMergeTracker<ParentChildEntry, TDestinationKey>(() => sourceCacheOfCaches.Items, _comparer, _equalityComparer);
@@ -48,7 +48,6 @@ internal sealed class MergeManyCacheChangeSetsSourceCompare<TObject, TKey, TDest
 
                 // When a source item is removed, all of its sub-items need to be removed
                 var removedItems = shared
-                    .Synchronize(locker)
                     .OnItemRemoved(mc => changeTracker.RemoveItems(mc.Cache.KeyValues, observer))
                     .OnItemUpdated((_, prev) => changeTracker.RemoveItems(prev.Cache.KeyValues, observer))
                     .Subscribe();
@@ -57,7 +56,6 @@ internal sealed class MergeManyCacheChangeSetsSourceCompare<TObject, TKey, TDest
                 // Because the comparison is based on the parent, which has just been refreshed.
                 var refreshItems = reevalOnRefresh
                     ? shared
-                        .Synchronize(locker)
                         .OnItemRefreshed(mc => changeTracker.RefreshItems(mc.Cache.Keys, observer))
                         .Subscribe()
                     : Disposable.Empty;

src/DynamicData/List/Internal/MergeManyCacheChangeSets.cs

@@ -24,28 +24,30 @@ internal sealed class MergeManyCacheChangeSets<TObject, TDestination, TDestinati
 
                 // Transform to an observable list of merge containers.
                 var sourceListOfCaches = source
-                                            .Transform(obj => new ChangeSetCache<TDestination, TDestinationKey>(changeSetSelector(obj)))
-                                            .Synchronize(locker)
-                                            .AsObservableList();
-
-                var shared = sourceListOfCaches.Connect().Publish();
+                    .Transform(obj => new ChangeSetCache<TDestination, TDestinationKey>(changeSetSelector(obj).Synchronize(locker)))
+                    .AsObservableList();
 
                 // This is manages all of the changes
                 var changeTracker = new ChangeSetMergeTracker<TDestination, TDestinationKey>(() => sourceListOfCaches.Items.ToArray(), comparer, equalityComparer);
 
+                // Share a connection to the source list
+                var shared = sourceListOfCaches.Connect().Publish();
+
+                // Merge the child changeset changes together and apply to the tracker
+                var allChanges = shared
+                    .Synchronize(locker)
+                    .MergeMany(mc => mc.Source)
+                    .Subscribe(
+                        changes => changeTracker.ProcessChangeSet(changes, observer),
+                        observer.OnError,
+                        observer.OnCompleted);
+
                 // When a source item is removed, all of its sub-items need to be removed
                 var removedItems = shared
+                    .Synchronize(locker)
                     .OnItemRemoved(mc => changeTracker.RemoveItems(mc.Cache.KeyValues, observer))
                     .Subscribe();
 
-                // Merge the items back together
-                var allChanges = shared.MergeMany(mc => mc.Source)
-                                                 .Synchronize(locker)
-                                                 .Subscribe(
-                                                        changes => changeTracker.ProcessChangeSet(changes, observer),
-                                                        observer.OnError,
-                                                        observer.OnCompleted);
-
                 return new CompositeDisposable(sourceListOfCaches, allChanges, removedItems, shared.Connect());
             });
 }

src/DynamicData/List/Internal/MergeManyListChangeSets.cs

@@ -20,27 +20,32 @@ internal sealed class MergeManyListChangeSets<TObject, TDestination>(IObservable
             {
                 var locker = new object();
 
+                // Transform to a changeset of Cloned Child Lists and then Share
+                var sourceListOfLists = source
+                                            .Transform(obj => new ClonedListChangeSet<TDestination>(selector(obj).Synchronize(locker), equalityComparer))
+                                            .AsObservableList();
+
                 // This is manages all of the changes
                 var changeTracker = new ChangeSetMergeTracker<TDestination>();
 
-                // Transform to a changeset of Cloned Child Lists and then Share
-                var shared = source
-                                            .Transform(obj => new ClonedListChangeSet<TDestination>(selector(obj).Synchronize(locker), equalityComparer))
-                                            .Publish();
+                // Share a connection to the source cache
+                var shared = sourceListOfLists.Connect().Publish();
 
                 // Merge the items back together
-                var allChanges = shared.MergeMany(clonedList => clonedList.Source.RemoveIndex())
-                                                 .Subscribe(
-                                                        changes => changeTracker.ProcessChangeSet(changes, observer),
-                                                        observer.OnError,
-                                                        observer.OnCompleted);
+                var allChanges = shared
+                    .Synchronize(locker)
+                    .MergeMany(clonedList => clonedList.Source.RemoveIndex())
+                    .Subscribe(
+                        changes => changeTracker.ProcessChangeSet(changes, observer),
+                        observer.OnError,
+                        observer.OnCompleted);
 
                 // When a source item is removed, all of its sub-items need to be removed
                 var removedItems = shared
                     .Synchronize(locker)
                     .OnItemRemoved(mc => changeTracker.RemoveItems(mc.List, observer), invokeOnUnsubscribe: false)
                     .Subscribe();
 
-                return new CompositeDisposable(allChanges, removedItems, shared.Connect());
+                return new CompositeDisposable(sourceListOfLists, allChanges, removedItems, shared.Connect());
             });
 }