public When_a_commit_is_persisted()
{
Given(() =>
{
UseThe(new TransactionBuilder().WithCheckpoint(123).Build());
var eventStore = A.Fake <IPassiveEventStore>();
A.CallTo(() => eventStore.GetFrom(A <long?> .Ignored)).Returns(new[] { The <Transaction>() });
var adapter = new PollingEventStoreAdapter(eventStore, 11, pollingInterval, 100, () => DateTime.UtcNow);
WithSubject(_ => adapter.Subscribe);
});
When(() =>
{
Subject(null, new Subscriber
{
HandleTransactions = (transactions, info) =>
{
transactionHandledSource.SetResult(transactions.First());
return(Task.FromResult(0));
}
}, "someId");
});
}
public When_a_commit_is_already_projected()
{
Given(() =>
{
Transaction projectedCommit = new TransactionBuilder().WithCheckpoint(123).Build();
Transaction unprojectedCommit = new TransactionBuilder().WithCheckpoint(124).Build();
var eventStore = A.Fake <IPassiveEventStore>();
A.CallTo(() => eventStore.GetFrom(A <long?> .Ignored)).Returns(new[] { projectedCommit, unprojectedCommit });
A.CallTo(() => eventStore.GetFrom(123)).Returns(new[] { unprojectedCommit });
var adapter = new PollingEventStoreAdapter(eventStore, 11, 1.Seconds(), 100, () => DateTime.UtcNow);
WithSubject(_ => adapter.Subscribe);
});
When(() =>
{
Subject(123, new Subscriber
{
HandleTransactions = (transactions, info) =>
{
transactionHandledSource.SetResult(transactions.First());
return(Task.FromResult(0));
}
}, "someId");
});
}
public When_the_persistency_engine_is_temporarily_unavailable()
{
Given(() =>
{
UseThe(new TransactionBuilder().WithCheckpoint(123).Build());
var eventStore = A.Fake <IPassiveEventStore>();
A.CallTo(() => eventStore.GetFrom(A <long?> .Ignored)).Returns(new[] { The <Transaction>() });
A.CallTo(() => eventStore.GetFrom(A <long?> .Ignored)).Throws(new ApplicationException()).Once();
var adapter = new PollingEventStoreAdapter(eventStore, 11, pollingInterval, 100, () => DateTime.UtcNow);
WithSubject(_ => adapter.Subscribe);
});
When(() =>
{
Subject(null, new Subscriber
{
HandleTransactions = (transactions, info) =>
{
actualTransaction = transactions.First();
return(Task.FromResult(0));
}
}, "someId");
});
}
public When_requesting_a_subscription_beyond_the_highest_available_checkpoint()
{
Given(() =>
{
var eventStore = A.Fake <IPassiveEventStore>();
A.CallTo(() => eventStore.GetFrom(999)).Returns(new Transaction[0]);
var adapter = new PollingEventStoreAdapter(eventStore, 11, 1.Seconds(), 100, () => DateTime.UtcNow);
WithSubject(_ => adapter.Subscribe);
});
When(() =>
{
Subject(1000, new Subscriber
{
HandleTransactions = (transactions, info) =>
{
throw new InvalidOperationException("The adapter should not provide any events.");
},
NoSuchCheckpoint = info =>
{
noSuchCheckpointRaised.SetResult(true);
return(Task.FromResult(0));
}
}, "myIde");
});
}
When_a_subscription_starts_after_zero_checkpoint_and_another_subscription_starts_after_null_checkpoint_while_the_first_subscription_is_loading_the_first_page_from_the_event_store()
{
Given(() =>
{
IPassiveEventStore eventStore = A.Fake <IPassiveEventStore>();
A.CallTo(() => eventStore.GetFrom(A <long?> .Ignored)).ReturnsLazily(call =>
{
long checkpoint = call.GetArgument <long?>(0) ?? 0;
aSubscriptionStartedLoading.Set();
if (!secondSubscriptionCreated.Wait(TimeSpan.FromSeconds(10)))
{
throw new InvalidOperationException("The second subscription has not been created in 10 seconds.");
}
// Give the second subscription enough time to access the cache.
Thread.Sleep(TimeSpan.FromSeconds(1));
return(checkpoint > 0
? new Transaction[0]
: new[] { new TransactionBuilder().WithCheckpoint(1).Build() });
});
var adapter = new PollingEventStoreAdapter(eventStore, 11, pollingInterval, 100, () => DateTime.UtcNow);
WithSubject(_ => adapter.Subscribe);
});
When(() =>
{
Subject(0, new Subscriber
{
HandleTransactions = (transactions, info) => Task.FromResult(0)
}, "firstId");
if (!aSubscriptionStartedLoading.Wait(TimeSpan.FromSeconds(10)))
{
throw new InvalidOperationException("The first subscription has not started loading in 10 seconds.");
}
Subject(null, new Subscriber
{
HandleTransactions = (transactions, info) =>
{
secondSubscriptionReceivedTheTransaction.Set();
return(Task.FromResult(0));
}
}, "secondId");
secondSubscriptionCreated.Set();
});
}
public When_there_are_no_more_commits()
{
Given(() =>
{
var eventStore = A.Fake <IPassiveEventStore>();
A.CallTo(() => eventStore.GetFrom(A <long?> .Ignored)).ReturnsLazily <IEnumerable <Transaction>, long?>(
checkpoint =>
{
pollingTimeStamps.Add(new PollingCall(checkpoint, DateTime.UtcNow));
if (pollingTimeStamps.Count == 4)
{
pollingCompleted.SetResult(true);
}
long checkPoint = checkpoint ?? 0;
long offsetToDetectAheadSubscriber = 1;
if (checkPoint <= (subscriptionCheckpoint - offsetToDetectAheadSubscriber))
{
return(new TransactionBuilder().WithCheckpoint(checkPoint + 1).BuildAsEnumerable());
}
else
{
return(new Transaction[0]);
}
});
var adapter = new PollingEventStoreAdapter(eventStore, 0, pollingInterval, 100, () => DateTime.UtcNow);
WithSubject(_ => adapter.Subscribe);
});
When(() =>
{
return(Subject(subscriptionCheckpoint, new Subscriber
{
HandleTransactions = (transactions, info) => Task.FromResult(0)
}, "someId"));
});
}
static void Main(string[] args)
{
var stopWatch = new Stopwatch();
stopWatch.Start();
// var adapter = new PollingEventStoreAdapter(new PassiveEventStore(), 50000, 5.Seconds(), 1000, () => DateTime.UtcNow, messageFunc => Console.WriteLine(messageFunc()));
var adapter = new PollingEventStoreAdapter(new PassiveEventStore(), 50000, TimeSpan.FromSeconds(5), 1000, () => DateTime.UtcNow);
int maxSubscribers = 50;
for (int id = 0; id < maxSubscribers; id++)
{
int localId = id;
adapter.Subscribe(0, new Subscriber
{
HandleTransactions = (transactions, info) =>
{
Console.WriteLine(
$"{stopWatch.Elapsed}: Subscriber {info.Id} received transactions {transactions.First().Checkpoint} to {transactions.Last().Checkpoint} on thead {Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(new Random().Next(100, 500));
return(Task.FromResult(0));
},
NoSuchCheckpoint = info => Task.FromResult(0)
}, id.ToString());
Console.WriteLine($"{stopWatch.Elapsed}: Started subscriber {localId}");
Thread.Sleep(1000);
}
Console.WriteLine("Press a key to shutdown");
Console.ReadLine();
adapter.Dispose();
}
/// <summary>
/// Creates an adapter that observes an implementation of <see cref="IPersistStreams"/> and efficiently handles
/// multiple subscribers.
/// </summary>
/// <param name="eventStore">
/// The persistency implementation that the NEventStore is configured with.
/// </param>
/// <param name="cacheSize">
/// The size of the LRU cache that will hold transactions already loaded from the event store. The larger the cache,
/// the higher the chance multiple subscribers can reuse the same transactions without hitting the underlying event store.
/// Set to <c>0</c> to disable the cache alltogether.
/// </param>
/// <param name="pollInterval">
/// The amount of time to wait before polling again after the event store has not yielded any transactions anymore.
/// </param>
/// <param name="maxPageSize">
/// The size of the page of transactions the adapter should load from the event store for every query.
/// </param>
/// <param name="getUtcNow">
/// Provides the current date and time in UTC.
/// </param>
public NEventStoreAdapter(IPersistStreams eventStore, int cacheSize, TimeSpan pollInterval, int maxPageSize,
Func <DateTime> getUtcNow)
{
pollingAdapter = new PollingEventStoreAdapter(new StreamPersisterAdapter(eventStore), cacheSize, pollInterval, maxPageSize, getUtcNow);
}
