Perf/background task scheduler

src/Nethermind/Nethermind.Api/IApiWithBlockchain.cs

@@ -12,6 +12,7 @@
 using Nethermind.Consensus.Processing;
 using Nethermind.Consensus.Producers;
 using Nethermind.Consensus.Rewards;
+using Nethermind.Consensus.Scheduler;
 using Nethermind.Consensus.Validators;
 using Nethermind.Core;
 using Nethermind.Evm.TransactionProcessing;
@@ -94,5 +95,6 @@ public interface IApiWithBlockchain : IApiWithStores, IBlockchainBridgeFactory
         CompositePruningTrigger PruningTrigger { get; }
 
         IBlockProductionPolicy? BlockProductionPolicy { get; set; }
+        BackgroundTaskScheduler BackgroundTaskScheduler { get; set; }
     }
 }

src/Nethermind/Nethermind.Api/IInitConfig.cs

@@ -85,6 +85,9 @@ public interface IInitConfig : IConfig
 
     [ConfigItem(Description = "[TECHNICAL] Exit when block number is reached. Useful for scripting and testing.", DefaultValue = "null", HiddenFromDocs = true)]
     long? ExitOnBlockNumber { get; set; }
+
+    [ConfigItem(Description = "[TECHNICAL] Specify concurrency limit for background task.", DefaultValue = "1", HiddenFromDocs = true)]
+    int BackgroundTaskConcurrency { get; set; }
 }
 
 public enum DiagnosticMode

src/Nethermind/Nethermind.Api/InitConfig.cs

@@ -35,6 +35,7 @@ public class InitConfig : IInitConfig
         public bool DisableGcOnNewPayload { get; set; } = true;
         public bool DisableMallocOpts { get; set; } = false;
         public long? ExitOnBlockNumber { get; set; } = null;
+        public int BackgroundTaskConcurrency { get; set; } = 1;
 
         [Obsolete("Use DiagnosticMode with MemDb instead")]
         public bool UseMemDb

src/Nethermind/Nethermind.Api/NethermindApi.cs

@@ -19,6 +19,7 @@
 using Nethermind.Consensus.Processing;
 using Nethermind.Consensus.Producers;
 using Nethermind.Consensus.Rewards;
+using Nethermind.Consensus.Scheduler;
 using Nethermind.Consensus.Validators;
 using Nethermind.Core;
 using Nethermind.Core.Authentication;
@@ -209,6 +210,7 @@ public ISealEngine SealEngine
 
         public IEthSyncingInfo? EthSyncingInfo { get; set; }
         public IBlockProductionPolicy? BlockProductionPolicy { get; set; }
+        public BackgroundTaskScheduler BackgroundTaskScheduler { get; set; } = null!;
         public IWallet? Wallet { get; set; }
         public IBlockStore? BadBlocksStore { get; set; }
         public ITransactionComparerProvider? TransactionComparerProvider { get; set; }

src/Nethermind/Nethermind.Consensus.Test/Scheduler/BackgroundTaskSchedulerTests.cs

@@ -0,0 +1,136 @@
+// SPDX-FileCopyrightText: 2024 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Nethermind.Consensus.Processing;
+using Nethermind.Consensus.Scheduler;
+using Nethermind.Core.Extensions;
+using Nethermind.Logging;
+using NSubstitute;
+using NUnit.Framework;
+using TaskCompletionSource = DotNetty.Common.Concurrency.TaskCompletionSource;
+
+namespace Nethermind.Consensus.Test.Scheduler;
+
+public class BackgroundTaskSchedulerTests
+{
+    private IBlockProcessor _blockProcessor;
+
+    [SetUp]
+    public void Setup()
+    {
+        _blockProcessor = Substitute.For<IBlockProcessor>();
+    }
+
+    [Test]
+    public async Task Test_task_will_execute()
+    {
+        TaskCompletionSource tcs = new TaskCompletionSource();
+        await using BackgroundTaskScheduler scheduler = new BackgroundTaskScheduler(_blockProcessor, 1, LimboLogs.Instance);
+
+        scheduler.ScheduleTask(1, (_, token) =>
+        {
+            tcs.SetResult(1);
+            return Task.CompletedTask;
+        });
+
+        await tcs.Task;
+    }
+
+    [Test]
+    public async Task Test_task_will_execute_concurrently_when_configured_so()
+    {
+        await using BackgroundTaskScheduler scheduler = new BackgroundTaskScheduler(_blockProcessor, 2, LimboLogs.Instance);
+
+        int counter = 0;
+
+        ManualResetEvent waitSignal = new ManualResetEvent(false);
+        scheduler.ScheduleTask(1, async (_, token) =>
+        {
+            counter++;
+            await waitSignal.WaitOneAsync(token);
+            counter--;
+        });
+        scheduler.ScheduleTask(1, async (_, token) =>
+        {
+            counter++;
+            await waitSignal.WaitOneAsync(token);
+            counter--;
+        });
+
+        Assert.That(() => counter, Is.EqualTo(2).After(10, 1));
+        waitSignal.Set();
+    }
+
+    [Test]
+    public async Task Test_task_will_cancel_on_block_processing()
+    {
+        await using BackgroundTaskScheduler scheduler = new BackgroundTaskScheduler(_blockProcessor, 2, LimboLogs.Instance);
+
+        bool wasCancelled = false;
+
+        ManualResetEvent waitSignal = new ManualResetEvent(false);
+        scheduler.ScheduleTask(1, async (_, token) =>
+        {
+            waitSignal.Set();
+            try
+            {
+                await Task.Delay(100000, token);
+            }
+            catch (OperationCanceledException)
+            {
+                wasCancelled = true;
+            }
+        });
+
+        await waitSignal.WaitOneAsync(CancellationToken.None);
+        _blockProcessor.BlocksProcessing += Raise.EventWith(new BlocksProcessingEventArgs(null));
+        Assert.That(() => wasCancelled, Is.EqualTo(true).After(10, 1));
+    }
+
+    [Test]
+    public async Task Test_task_that_is_scheduled_during_block_processing_will_continue_after()
+    {
+        await using BackgroundTaskScheduler scheduler = new BackgroundTaskScheduler(_blockProcessor, 2, LimboLogs.Instance);
+        _blockProcessor.BlocksProcessing += Raise.EventWith(new BlocksProcessingEventArgs(null));
+
+        int executionCount = 0;
+        for (int i = 0; i < 5; i++)
+        {
+            scheduler.ScheduleTask(1, (_, token) =>
+            {
+                executionCount++;
+                return Task.CompletedTask;
+            });
+        }
+
+        await Task.Delay(10);
+        executionCount.Should().Be(0);
+
+        _blockProcessor.BlockProcessed += Raise.EventWith(new BlockProcessedEventArgs(null, null));
+        Assert.That(() => executionCount, Is.EqualTo(5).After(10, 1));
+    }
+
+    [Test]
+    public async Task Test_task_that_is_scheduled_during_block_processing_but_deadlined_will_get_called_and_cancelled()
+    {
+        await using BackgroundTaskScheduler scheduler = new BackgroundTaskScheduler(_blockProcessor, 2, LimboLogs.Instance);
+        _blockProcessor.BlocksProcessing += Raise.EventWith(new BlocksProcessingEventArgs(null));
+
+        bool wasCancelled = false;
+        ManualResetEvent waitSignal = new ManualResetEvent(false);
+        scheduler.ScheduleTask(1, (_, token) =>
+        {
+            wasCancelled = token.IsCancellationRequested;
+            waitSignal.Set();
+            return Task.CompletedTask;
+        }, TimeSpan.FromMilliseconds(1));
+
+        (await waitSignal.WaitOneAsync(CancellationToken.None)).Should().BeTrue();
+
+        wasCancelled.Should().BeTrue();
+    }
+}

src/Nethermind/Nethermind.Consensus/Scheduler/BackgroundTaskScheduler.cs

@@ -0,0 +1,173 @@
+// SPDX-FileCopyrightText: 2024 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using System;
+using System.Threading;
+using System.Threading.Channels;
+using System.Threading.Tasks;
+using Nethermind.Consensus.Processing;
+using Nethermind.Core.Extensions;
+using Nethermind.Logging;
+
+namespace Nethermind.Consensus.Scheduler;
+
+/// <summary>
+/// Provide a way to orchestrate task to run in background.
+/// - Task will be run in a separate thread.. well it depends on the threadpool, but there is a concurrency limit.
+/// - Task closure will have CancellationToken which will be cancelled if block processing happens while the task is running.
+/// - Task have a default timeout, which is counted from the time it is queued. If timedout because too many other background
+///    task before it for example, the cancellation token passed to it will be cancelled.
+/// - Task will still run when block processing is happening and its timedout this is so that it can handle its cancellation.
+/// - Task will not run if block processing is happening and it still have some time left.
+///   It is up to the task to determine what happen if cancelled, maybe it will reschedule for later, or resume later, but
+///   preferably, stop execution immediately. Don't hang BTW. Other background task need to cancel too.
+///
+/// Note: Yes, I know there is a built in TaskScheduler that can do some magical stuff that stop execution on async
+/// and stuff, but that is complicated and I don't wanna explain why you need `async Task.Yield()` in the middle of a loop,
+/// or explicitly specify it to run on this task scheduler and such. Maybe some other time ok?
+/// </summary>
+public class BackgroundTaskScheduler : IBackgroundTaskScheduler, IAsyncDisposable
+{
+    private static readonly TimeSpan DefaultTimeout = TimeSpan.FromSeconds(2);
+
+    private readonly CancellationTokenSource _mainCancellationTokenSource;
+    private CancellationTokenSource _blockProcessorCancellationTokenSource;
+    private readonly Channel<IActivity> _taskQueue;
+    private readonly ILogger _logger;
+    private readonly IBlockProcessor _blockProcessor;
+    private readonly ManualResetEvent _restartQueueSignal;
+
+    public BackgroundTaskScheduler(IBlockProcessor blockProcessor, int concurrency, ILogManager logManager)
+    {
+        if (concurrency < 1) throw new ArgumentException("concurrency must be at least 1");
+
+        _mainCancellationTokenSource = new CancellationTokenSource();
+        _blockProcessorCancellationTokenSource = new CancellationTokenSource();
+        _taskQueue = Channel.CreateUnbounded<IActivity>();
+        _logger = logManager.GetClassLogger();
+        _blockProcessor = blockProcessor;
+        _restartQueueSignal = new ManualResetEvent(true);
+
+        _blockProcessor.BlocksProcessing += BlockProcessorOnBlocksProcessing;
+        _blockProcessor.BlockProcessed += BlockProcessorOnBlockProcessed;
+
+        for (int i = 0; i < concurrency; i++)
+        {
+            Task.Factory.StartNew(StartChannel, TaskCreationOptions.LongRunning);
+        }
+    }
+
+    private void BlockProcessorOnBlocksProcessing(object? sender, BlocksProcessingEventArgs e)
+    {
+        // On block processing, we cancel the block process cts, causing current task to get cancelled.
+        _blockProcessorCancellationTokenSource.Cancel();
+        // We also reset queue signal, causing it to wait
+        _restartQueueSignal.Reset();
+    }
+
+    private void BlockProcessorOnBlockProcessed(object? sender, BlockProcessedEventArgs e)
+    {
+        // Once block is processed, we replace it with the
+        CancellationTokenSource oldTokenSource = Interlocked.Exchange(ref _blockProcessorCancellationTokenSource, new CancellationTokenSource());
+        oldTokenSource.Dispose();
+        // We also set queue signal causing it to continue queue.
+        _restartQueueSignal.Set();
+    }
+
+
+    private async Task StartChannel()
+    {
+        await foreach (IActivity activity in _taskQueue.Reader.ReadAllAsync(_mainCancellationTokenSource.Token))
+        {
+            if (_blockProcessorCancellationTokenSource.IsCancellationRequested)
+            {
+                // In case of task that is suppose to run when a block is being processed, if there is some time left
+                // from its deadline, we re-queue it. We do this in case there are some task in the queue that already
+                // reached deadline during block processing in which case, it will need to execute in order to handle
+                // its cancellation.
+                if (DateTimeOffset.Now < activity.Deadline)
+                {
+                    await _taskQueue.Writer.WriteAsync(activity, _mainCancellationTokenSource.Token);
+                    // Throttle deque to prevent infinite loop.
+                    await _restartQueueSignal.WaitOneAsync(TimeSpan.FromMilliseconds(1), _mainCancellationTokenSource.Token);
+                    continue;
+                }
+            }
+
+            try
+            {
+                using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(
+                    _blockProcessorCancellationTokenSource.Token,
+                    _mainCancellationTokenSource.Token
+                );
+                await activity.Do(cts.Token);
+            }
+            catch (OperationCanceledException)
+            {
+            }
+            catch (Exception e)
+            {
+                if (_logger.IsDebug) _logger.Debug($"Error processing background task {e}.");
+            }
+        }
+    }
+
+    public void ScheduleTask<TReq>(TReq request, Func<TReq, CancellationToken, Task> fulfillFunc, TimeSpan? timeout = null)
+    {
+        timeout ??= DefaultTimeout;
+        DateTimeOffset deadline = DateTimeOffset.Now + timeout.Value;
+
+        IActivity activity = new Activity<TReq>()
+        {
+            Deadline = deadline,
+            Request = request,
+            FulfillFunc = fulfillFunc,
+        };
+
+        if (!_taskQueue.Writer.TryWrite(activity))
+        {
+            // This should never happen unless something goes very wrong.
+            throw new InvalidOperationException("Unable to write to background task queue.");
+        }
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        _blockProcessor.BlocksProcessing += BlockProcessorOnBlocksProcessing;
+        _blockProcessor.BlockProcessed += BlockProcessorOnBlockProcessed;
+
+        _taskQueue.Writer.Complete();
+        await _mainCancellationTokenSource.CancelAsync();
+    }
+
+    private readonly struct Activity<TReq> : IActivity
+    {
+        public DateTimeOffset Deadline { get; init; }
+        public TReq Request { get; init; }
+        public Func<TReq, CancellationToken, Task> FulfillFunc { get; init; }
+
+        public async Task Do(CancellationToken cancellationToken)
+        {
+            using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+            DateTimeOffset now = DateTimeOffset.Now;
+            TimeSpan timeToComplete = Deadline - now;
+            if (timeToComplete <= TimeSpan.Zero)
+            {
+                // Cancel immediately. Got no time left.
+                await cts.CancelAsync();
+            }
+            else
+            {
+                cts.CancelAfter(timeToComplete);
+            }
+
+            await FulfillFunc.Invoke(Request, cts.Token);
+        }
+    }
+
+    private interface IActivity
+    {
+        DateTimeOffset Deadline { get; }
+        Task Do(CancellationToken cancellationToken);
+    }
+}

src/Nethermind/Nethermind.Consensus/Scheduler/IBackgroundTaskScheduler.cs

@@ -0,0 +1,13 @@
+// SPDX-FileCopyrightText: 2024 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Nethermind.Consensus.Scheduler;
+
+public interface IBackgroundTaskScheduler
+{
+    void ScheduleTask<TReq>(TReq request, Func<TReq, CancellationToken, Task> fulfillFunc, TimeSpan? timeout = null);
+}

src/Nethermind/Nethermind.Core.Test/RunImmediatelyScheduler.cs

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2024 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Nethermind.Consensus.Scheduler;
+
+namespace Nethermind.Core.Test;
+
+public class RunImmediatelyScheduler : IBackgroundTaskScheduler
+{
+    public static RunImmediatelyScheduler Instance = new RunImmediatelyScheduler();
+
+    private RunImmediatelyScheduler()
+    {
+    }
+
+    public void ScheduleTask<TReq>(TReq request, Func<TReq, CancellationToken, Task> fulfillFunc, TimeSpan? timeout = null)
+    {
+        fulfillFunc(request, CancellationToken.None);
+    }
+}