dev-npgsql/npgsql: Npgsql is the .NET data provider for PostgreSQL.

test/Npgsql.Tests/TaskTimeoutAndCancellationTest.cs
156 строк6 KB
Sergiy Pavlov
Handle failed and abandoned DNS query and/or Socket connection NpgsqlConnector Tasks (#4173)
31 дек 2021, 21:53
31 дек 2021, 21:5374c7c0b
using System;
using System.Threading;
using System.Threading.Tasks;
using NUnit.Framework;
using Npgsql.Util;

namespace Npgsql.Tests;

public class TaskTimeoutAndCancellationTest : TestBase
{
    const int TestResultValue = 777;

    async Task<int> GetResultTaskAsync(int timeout, CancellationToken ct)
    {
        await Task.Delay(timeout, ct);
        return TestResultValue;
    }

    Task GetVoidTaskAsync(int timeout, CancellationToken ct) => Task.Delay(timeout, ct);

    [Test]
    public async Task SuccessfulResultTaskAsync() =>
        Assert.AreEqual(TestResultValue, await TaskTimeoutAndCancellation.ExecuteAsync(ct => GetResultTaskAsync(10, ct), NpgsqlTimeout.Infinite, CancellationToken.None));

    [Test]
    public async Task SuccessfulVoidTaskAsync() =>
        await TaskTimeoutAndCancellation.ExecuteAsync(ct => GetVoidTaskAsync(10, ct), NpgsqlTimeout.Infinite, CancellationToken.None);

    [Test]
    public void InfinitelyLongTaskTimeout() =>
        Assert.ThrowsAsync<TimeoutException>(async () =>
            await TaskTimeoutAndCancellation.ExecuteAsync(ct => GetVoidTaskAsync(Timeout.Infinite, ct), new NpgsqlTimeout(TimeSpan.FromMilliseconds(10)), CancellationToken.None));

    [Test]
    public void InfinitelyLongTaskCancellation()
    {
        using var cts = new CancellationTokenSource(10);
        Assert.ThrowsAsync<TaskCanceledException>(async () =>
            await TaskTimeoutAndCancellation.ExecuteAsync(ct => GetVoidTaskAsync(Timeout.Infinite, ct), NpgsqlTimeout.Infinite, cts.Token));
    }

    /// <summary>
    /// The test creates a delayed execution Task that is being fake-cancelled and fails subsequently and triggers 'TaskScheduler.UnobservedTaskException event'.
    /// </summary>
    /// <remarks>
    /// The test is based on timing and depends on availability of thread pool threads. Therefore it could become unstable if the environment is under pressure.
    /// </remarks>
    [Theory, IssueLink("https://github.com/npgsql/npgsql/issues/4149")]
    [TestCase("CancelAndTimeout")]
    [TestCase("CancelOnly")]
    [TestCase("TimeoutOnly")]
    [TestCase("CancelAndTimeout")]
    [TestCase("CancelOnly")]
    [TestCase("TimeoutOnly")]
    public Task DelayedFaultedTaskCancellation(string testCase) => RunDelayedFaultedTaskTestAsync(async getUnobservedTaskException =>
    {
        var cancel = true;
        var timeout = true;
        switch (testCase)
        {
            case "TimeoutOnly":
                cancel = false;
                break;
            case "CancelOnly":
                timeout = false;
                break;
        }

        var notifyDelayCompleted = new SemaphoreSlim(0, 1);

        // Invoke the method that creates a delayed execution Task that fails subsequently.
        await CreateTaskAndPreemptWithCancellationAsync(500, cancel, timeout, notifyDelayCompleted);

        // Wait enough time for the non-cancelable task to notify us that an exception is thrown.
        await notifyDelayCompleted.WaitAsync();

        // And then wait some more.
        var repeatCount = 2;
        while (getUnobservedTaskException() is null && repeatCount-- > 0)
        {
            await Task.Delay(100);

            // Run the garbage collector to collect unobserved Tasks.
            GC.Collect();
            GC.WaitForPendingFinalizers();
        }
    });

    static async Task RunDelayedFaultedTaskTestAsync(Func<Func<Exception?>, Task> test)
    {
        Exception? unobservedTaskException = null;

        // Subscribe to UnobservedTaskException event to store the Exception, if any.
        void OnUnobservedTaskException(object? source, UnobservedTaskExceptionEventArgs args)
        {
            if (!args.Observed)
            {
                args.SetObserved();
            }
            unobservedTaskException = args.Exception;
        }
        TaskScheduler.UnobservedTaskException += OnUnobservedTaskException;

        try
        {
            await test(() => unobservedTaskException);

            // Verify the unobserved Task exception event has not been received.
            Assert.IsNull(unobservedTaskException, unobservedTaskException?.Message);
        }
        finally
        {
            TaskScheduler.UnobservedTaskException -= OnUnobservedTaskException;
        }
    }

    /// <summary>
    /// Create a delayed execution, non-Cancellable Task that fails subsequently after the Task goes out of scope.
    /// </summary>
    static async Task CreateTaskAndPreemptWithCancellationAsync(int delayMs, bool cancel, bool timeout, SemaphoreSlim notifyDelayCompleted)
    {
        var nonCancellableTask = Task.Delay(delayMs, CancellationToken.None)
            .ContinueWith(
                async _ =>
                {
                    try
                    {
                        await Task.FromException(new Exception("Unobserved Task Test Exception"));
                    }
                    finally
                    {
                        notifyDelayCompleted.Release();
                    }
                })
            .Unwrap();

        var timeoutMs = delayMs / 5;
        using var cts = cancel ? new CancellationTokenSource(timeoutMs) : null;
        try
        {
            await TaskTimeoutAndCancellation.ExecuteAsync(
                _ => nonCancellableTask,
                timeout ? new NpgsqlTimeout(TimeSpan.FromMilliseconds(timeoutMs)) : NpgsqlTimeout.Infinite,
                cts?.Token ?? CancellationToken.None);
        }
        catch (TimeoutException)
        {
            // Expected due to preemptive time out.
        }
        catch (OperationCanceledException) when (cts?.IsCancellationRequested == true)
        {
            // Expected due to preemptive cancellation.
        }
        Assert.False(nonCancellableTask.IsCompleted);
    }
}