UA-.NETStandard/tests/Opc.Ua.Redundancy.PubSub.Tests/SharedStorePubSubLeaseStoreTests.cs

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using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Time.Testing;
using NUnit.Framework;
using Opc.Ua.Redundancy;

namespace Opc.Ua.PubSub.Redundancy.Tests
{
    /// <summary>
    /// Unit tests for the CAS-backed PubSub lease store.
    /// </summary>
    [TestFixture]
    public class SharedStorePubSubLeaseStoreTests
    {
        [Test]
        public async Task TryAcquireAsyncSucceedsWhenFreeAsync()
        {
            var time = new FakeTimeProvider();
            using var store = new InMemorySharedKeyValueStore();
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);

            PubSubLease? lease = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);

            Assert.That(lease, Is.Not.Null);
            Assert.That(lease!.Value.LeaseKey, Is.EqualTo(LeaseKey));
            Assert.That(lease.Value.OwnerId, Is.EqualTo(OwnerA));
            Assert.That(lease.Value.FencingToken, Is.EqualTo(1));
            Assert.That(lease.Value.ExpiresAt, Is.EqualTo(time.GetUtcNow() + LeaseDuration));
        }

        [Test]
        public async Task TryAcquireAsyncRejectsSecondOwnerWhileHeldAsync()
        {
            var time = new FakeTimeProvider();
            using var store = new InMemorySharedKeyValueStore();
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);

            PubSubLease? first = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);
            PubSubLease? second = await leaseStore.TryAcquireAsync(LeaseKey, OwnerB, LeaseDuration).ConfigureAwait(false);

            Assert.That(first, Is.Not.Null);
            Assert.That(second, Is.Null);
        }

        [Test]
        public async Task TryAcquireAsyncRenewsSameOwnerWithStableTokenAsync()
        {
            var time = new FakeTimeProvider();
            using var store = new InMemorySharedKeyValueStore();
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);
            PubSubLease? first = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);
            time.Advance(TimeSpan.FromSeconds(5));

            PubSubLease? renewed = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);

            Assert.That(first, Is.Not.Null);
            Assert.That(renewed, Is.Not.Null);
            Assert.That(renewed!.Value.FencingToken, Is.EqualTo(first!.Value.FencingToken));
            Assert.That(renewed.Value.ExpiresAt, Is.EqualTo(time.GetUtcNow() + LeaseDuration));
        }

        [Test]
        public async Task TryAcquireAsyncAfterExpiryLetsNewOwnerAcquireWithIncrementedTokenAsync()
        {
            var time = new FakeTimeProvider();
            using var store = new InMemorySharedKeyValueStore();
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);
            PubSubLease? first = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);
            time.Advance(LeaseDuration + TimeSpan.FromSeconds(1));

            PubSubLease? takeover = await leaseStore.TryAcquireAsync(LeaseKey, OwnerB, LeaseDuration).ConfigureAwait(false);

            Assert.That(first, Is.Not.Null);
            Assert.That(takeover, Is.Not.Null);
            Assert.That(takeover!.Value.OwnerId, Is.EqualTo(OwnerB));
            Assert.That(takeover.Value.FencingToken, Is.EqualTo(first!.Value.FencingToken + 1));
        }

        [Test]
        public async Task TryRenewAsyncFailsAfterTakeoverAsync()
        {
            var time = new FakeTimeProvider();
            using var store = new InMemorySharedKeyValueStore();
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);
            PubSubLease? first = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);
            time.Advance(LeaseDuration + TimeSpan.FromSeconds(1));
            PubSubLease? takeover = await leaseStore.TryAcquireAsync(LeaseKey, OwnerB, LeaseDuration).ConfigureAwait(false);

            PubSubLease? renewed = await leaseStore.TryRenewAsync(first!.Value, LeaseDuration).ConfigureAwait(false);

            Assert.That(takeover, Is.Not.Null);
            Assert.That(renewed, Is.Null);
        }

        [Test]
        public async Task TryRenewAsyncExtendsLeaseForCurrentOwnerAsync()
        {
            var time = new FakeTimeProvider();
            using var store = new InMemorySharedKeyValueStore();
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);
            PubSubLease? first = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);
            time.Advance(TimeSpan.FromSeconds(5));

            PubSubLease? renewed = await leaseStore.TryRenewAsync(first!.Value, LeaseDuration).ConfigureAwait(false);

            Assert.That(renewed, Is.Not.Null);
            Assert.That(renewed!.Value.OwnerId, Is.EqualTo(OwnerA));
            Assert.That(renewed.Value.FencingToken, Is.EqualTo(first!.Value.FencingToken));
            Assert.That(renewed.Value.ExpiresAt, Is.EqualTo(time.GetUtcNow() + LeaseDuration));
        }

        [Test]
        public async Task ReleaseAsyncLetsAnotherOwnerAcquireImmediatelyAsync()
        {
            var time = new FakeTimeProvider();
            using var store = new InMemorySharedKeyValueStore();
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);
            PubSubLease? first = await leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).ConfigureAwait(false);

            await leaseStore.ReleaseAsync(first!.Value).ConfigureAwait(false);
            PubSubLease? next = await leaseStore.TryAcquireAsync(LeaseKey, OwnerB, LeaseDuration).ConfigureAwait(false);

            Assert.That(next, Is.Not.Null);
            Assert.That(next!.Value.OwnerId, Is.EqualTo(OwnerB));
            Assert.That(next.Value.FencingToken, Is.EqualTo(first.Value.FencingToken + 1));
        }

        [Test]
        public async Task TryAcquireAsyncRetriesAfterContendedCompareAndSwapAsync()
        {
            var time = new FakeTimeProvider();
            using var innerStore = new InMemorySharedKeyValueStore();
            using var store = new CoordinatedReadSharedKeyValueStore(
                innerStore,
                PubSubRedundancyStoreKeys.LeasePrefix + LeaseKey);
            var leaseStore = new SharedStorePubSubLeaseStore(store, time);

            Task<PubSubLease?> firstAcquire = leaseStore.TryAcquireAsync(LeaseKey, OwnerA, LeaseDuration).AsTask();
            Task<PubSubLease?> secondAcquire = leaseStore.TryAcquireAsync(LeaseKey, OwnerB, LeaseDuration).AsTask();
            PubSubLease?[] results = await Task.WhenAll(firstAcquire, secondAcquire).ConfigureAwait(false);

            Assert.That(results, Has.Exactly(1).Not.Null);
            Assert.That(results, Has.Exactly(1).Null);
        }

        private const string LeaseKey = "writer-group";
        private const string OwnerA = "owner-a";
        private const string OwnerB = "owner-b";
        private static readonly TimeSpan LeaseDuration = TimeSpan.FromSeconds(30);

        private sealed class CoordinatedReadSharedKeyValueStore : ISharedKeyValueStore, IDisposable
        {
            public CoordinatedReadSharedKeyValueStore(ISharedKeyValueStore innerStore, string coordinatedKey)
            {
                m_innerStore = innerStore;
                m_coordinatedKey = coordinatedKey;
            }

            public async ValueTask<(bool Found, ByteString Value)> TryGetAsync(
                string key,
                CancellationToken ct = default)
            {
                if (string.Equals(key, m_coordinatedKey, StringComparison.Ordinal))
                {
                    int count = Interlocked.Increment(ref m_coordinatedReads);
                    if (count == 2)
                    {
                        m_secondReadArrived.TrySetResult(true);
                    }

                    await m_secondReadArrived.Task.WaitAsync(ct).ConfigureAwait(false);
                }

                return await m_innerStore.TryGetAsync(key, ct).ConfigureAwait(false);
            }

            public ValueTask SetAsync(string key, ByteString value, CancellationToken ct = default)
            {
                return m_innerStore.SetAsync(key, value, ct);
            }

            public ValueTask<bool> CompareAndSwapAsync(
                string key,
                ByteString expected,
                ByteString value,
                CancellationToken ct = default)
            {
                return m_innerStore.CompareAndSwapAsync(key, expected, value, ct);
            }

            public ValueTask<bool> DeleteAsync(string key, CancellationToken ct = default)
            {
                return m_innerStore.DeleteAsync(key, ct);
            }

            public IAsyncEnumerable<KeyValuePair<string, ByteString>> ScanAsync(
                string keyPrefix,
                CancellationToken ct = default)
            {
                return m_innerStore.ScanAsync(keyPrefix, ct);
            }

            public IAsyncEnumerable<KeyValueChange> WatchAsync(
                string keyPrefix,
                CancellationToken ct = default)
            {
                return m_innerStore.WatchAsync(keyPrefix, ct);
            }

            public void Dispose()
            {
                m_secondReadArrived.TrySetCanceled();
            }

            private readonly ISharedKeyValueStore m_innerStore;
            private readonly string m_coordinatedKey;

            private readonly TaskCompletionSource<bool> m_secondReadArrived =
                new(TaskCreationOptions.RunContinuationsAsynchronously);

            private int m_coordinatedReads;
        }
    }
}