Micro optimizations. Enhance performance investigation documentation and benchmarks for MongoDB persistence

- Updated Performance-Investigation.md to reflect current state and findings.
- Added SnapshotAssistedRebuildBenchmarks to compare full and snapshot-assisted rebuilds.
- Refined ReadFromStreamBenchmarks and StreamRevisionWindowBenchmarks for consistency.
- Adjusted benchmark job configurations for improved clarity and performance.
- Fixed minor issues in benchmark scripts and extension methods for better functionality.

Author: AGiorgetti

.github/workflows/ci.yml

@@ -88,7 +88,7 @@ jobs:
       # The test project reads NEventStore.MongoDB from the environment and expects
       # a real MongoDB server. This sidecar provides that dependency for each matrix leg.
       mongodb:
-        image: mongo:7.0
+        image: mongo:8
         ports:
           - 27017:27017
         options: >-

docs/Performance-Investigation.md

@@ -76,7 +76,7 @@ if ($LASTEXITCODE -ne 0)
     throw "Benchmark execution failed with exit code $LASTEXITCODE"
 }
 
-$reportFiles = Get-ChildItem -Path $resultsDir -Filter '*-report-github.md' -File
+$reportFiles = @(Get-ChildItem -Path $resultsDir -Filter '*-report-github.md' -File)
 if (-not $reportFiles)
 {
     throw "No benchmark report files found in $resultsDir"

scripts/benchmark-snapshot.ps1

@@ -5,7 +5,7 @@
 namespace NEventStore.Persistence.MongoDB.Benchmark.Benchmarks
 {
     [Config(typeof(AllowNonOptimized))]
-    [SimpleJob(launchCount: 3, warmupCount: 3, iterationCount: 3, invocationCount: 1)]
+    [SimpleJob(launchCount: 3, warmupCount: 3, iterationCount: 3)]
     [MemoryDiagnoser]
     [MeanColumn, StdErrorColumn, StdDevColumn, MinColumn, MaxColumn, IterationsColumn]
     public class ReadFromStreamBenchmarks

src/NEventStore.Persistence.MongoDB.Benchmark/Benchmarks/ReadFromStreamBenchmarks.cs

@@ -0,0 +1,66 @@
+using BenchmarkDotNet.Attributes;
+using NEventStore.Persistence.MongoDB;
+using NEventStore.Persistence.MongoDB.Benchmark.Support;
+using System;
+
+namespace NEventStore.Persistence.MongoDB.Benchmark.Benchmarks
+{
+    /// <summary>
+    /// Compares full aggregate rebuilds with snapshot-assisted rebuilds over the tail of a long stream.
+    /// </summary>
+    [Config(typeof(AllowNonOptimized))]
+    [SimpleJob(launchCount: 3, warmupCount: 3, iterationCount: 3)]
+    [MemoryDiagnoser]
+    [MeanColumn, StdErrorColumn, StdDevColumn, MinColumn, MaxColumn, IterationsColumn]
+    public class SnapshotAssistedRebuildBenchmarks
+    {
+        [Params(1000, 10000)]
+        public int TotalCommitsInStream { get; set; }
+
+        [Params(10, 100, 1000)]
+        public int CommitsAfterSnapshot { get; set; }
+
+        private readonly Guid _streamId = Guid.NewGuid();
+        private IStoreEvents _eventStore = null!;
+        private ISnapshot _snapshot = null!;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            var options = new MongoPersistenceOptions
+            {
+                PersistStreamHeadsOnBackgroundThread = false
+            };
+
+            _eventStore = EventStoreHelpers.WireupEventStore(options);
+            _eventStore.Advanced.Purge();
+
+            using (var stream = _eventStore.CreateStream(_streamId))
+            {
+                for (int i = 1; i <= TotalCommitsInStream; i++)
+                {
+                    stream.Add(new EventMessage { Body = new SomeDomainEvent { Value = i.ToString() } });
+                    stream.CommitChanges(Guid.NewGuid());
+                }
+            }
+
+            var snapshotRevision = Math.Max(1, TotalCommitsInStream - CommitsAfterSnapshot);
+            _snapshot = new Snapshot(_streamId.ToString(), snapshotRevision, new SomeDomainEvent { Value = snapshotRevision.ToString() });
+            _eventStore.Advanced.AddSnapshot(_snapshot);
+        }
+
+        [Benchmark(Baseline = true)]
+        public int FullRebuild()
+        {
+            using var stream = _eventStore.OpenStream(_streamId, 0, int.MaxValue);
+            return stream.CommittedEvents.Count;
+        }
+
+        [Benchmark]
+        public int SnapshotAssistedRebuild()
+        {
+            using var stream = _eventStore.OpenStream(_snapshot, int.MaxValue);
+            return stream.CommittedEvents.Count;
+        }
+    }
+}

src/NEventStore.Persistence.MongoDB.Benchmark/Benchmarks/SnapshotAssistedRebuildBenchmarks.cs

@@ -8,9 +8,9 @@ namespace NEventStore.Persistence.MongoDB.Benchmark.Benchmarks
     /// <summary>
     /// Measures per-stream reads over focused revision windows.
     /// </summary>
-    [Config(typeof(AllowNonOptimized))]
-    [SimpleJob(launchCount: 3, warmupCount: 3, iterationCount: 3, invocationCount: 1)]
-    [MemoryDiagnoser]
+    [Config(typeof(AllowNonOptimized))]
+    [SimpleJob(launchCount: 3, warmupCount: 3, iterationCount: 3)]
+    [MemoryDiagnoser]
     [MeanColumn, StdErrorColumn, StdDevColumn, MinColumn, MaxColumn, IterationsColumn]
     public class StreamRevisionWindowBenchmarks
     {
@@ -20,35 +20,44 @@ public class StreamRevisionWindowBenchmarks
         [Params(10, 100, 1000)]
         public int RevisionWindowSize { get; set; }
 
-        private static readonly Guid StreamId = Guid.NewGuid();
-        private readonly IStoreEvents _eventStore;
-        private readonly IPersistStreams _persistence;
-
-        public StreamRevisionWindowBenchmarks()
-        {
-            _eventStore = EventStoreHelpers.WireupEventStore();
-            _persistence = (IPersistStreams)_eventStore.Advanced;
-        }
+        private readonly string _streamId = Guid.NewGuid().ToString();
+        private readonly IPersistStreams _persistence;
+
+        public StreamRevisionWindowBenchmarks()
+        {
+            _persistence = (IPersistStreams)EventStoreHelpers.WireupEventStore().Advanced;
+        }
 
         [GlobalSetup]
         public void Setup()
         {
             _persistence.Purge();
 
-            using var stream = _eventStore.CreateStream(StreamId);
-            for (int i = 0; i < TotalCommitsInStream; i++)
-            {
-                stream.Add(new EventMessage { Body = new SomeDomainEvent { Value = i.ToString() } });
-                stream.CommitChanges(Guid.NewGuid());
-            }
-        }
+            for (int i = 1; i <= TotalCommitsInStream; i++)
+            {
+                var attempt = new CommitAttempt(
+                    bucketId: Bucket.Default,
+                    streamId: _streamId,
+                    streamRevision: i,
+                    commitId: Guid.NewGuid(),
+                    commitSequence: i,
+                    commitStamp: DateTime.UtcNow,
+                    headers: null,
+                    events:
+                    [
+                        new EventMessage { Body = new SomeDomainEvent { Value = i.ToString() } }
+                    ]);
+
+                _persistence.Commit(attempt);
+            }
+        }
 
         [Benchmark]
         public int ReadTailRevisionWindow()
         {
-            var minRevision = Math.Max(1, TotalCommitsInStream - RevisionWindowSize + 1);
-            var maxRevision = TotalCommitsInStream;
-            return _persistence.GetFrom(Bucket.Default, StreamId.ToString(), minRevision, maxRevision).Count();
-        }
-    }
-}
+            var minRevision = Math.Max(1, TotalCommitsInStream - RevisionWindowSize + 1);
+            var maxRevision = TotalCommitsInStream;
+            return _persistence.GetFrom(Bucket.Default, _streamId, minRevision, maxRevision).Count();
+        }
+    }
+}

src/NEventStore.Persistence.MongoDB.Benchmark/Benchmarks/StreamRevisionWindowBenchmarks.cs

@@ -85,7 +85,7 @@ public static ICommit ToCommit(this BsonDocument doc, IDocumentSerializer serial
             {
                 BsonValue payload = mc.Events[i][MongoCommitFields.Payload];
                 events[i] = payload.IsBsonDocument
-                    ? BsonSerializer.Deserialize<EventMessage>(payload.ToBsonDocument())!
+                    ? BsonSerializer.Deserialize<EventMessage>(payload.AsBsonDocument)
                     : serializer.Deserialize<EventMessage>(payload.AsByteArray)!; // ByteStreamDocumentSerializer ?!?! doesn't work this way!
             }
 

src/NEventStore.Persistence.MongoDB/ExtensionMethods.cs

@@ -2,9 +2,9 @@
 #pragma warning disable CA2254 // Template should be a static expression
 
 using System.Globalization;
+using Microsoft.Extensions.Logging;
 using MongoDB.Bson;
 using MongoDB.Driver;
-using Microsoft.Extensions.Logging;
 using NEventStore.Logging;
 using NEventStore.Persistence.MongoDB.Support;
 using NEventStore.Serialization;
@@ -559,9 +559,8 @@ public virtual IEnumerable<IStreamHead> GetStreamsToSnapshot(string bucketId, in
                     .Find(query)
                     .Sort(SortByDescendingSnapshotRevision)
                     .Limit(1)
-                    .ToEnumerable()
-                    .Select(mc => mc.ToSnapshot(_serializer))
-                    .FirstOrDefault();
+                    .FirstOrDefault()
+                    ?.ToSnapshot(_serializer);
             });
         }