/// <summary>
/// Parallel task that checks if the transaction has been aborted internally
/// If so, cause the waiting dequeuer to throw InvalidOperationException
/// </summary>
private async Task PollTransactionStateAsync(
Transaction txn,
TaskCompletionSource <ConditionalValue <IListElement <T> > > tcs,
CancellationToken cancellationToken)
{
while (true)
{
// Ignore the exception thrown by this call
// As this polls every 4 secs, The cancellationTokenSource could have been disposed and set to null
// causing Task.Delay to throw ObjectDisposedException.
// The token would be honoured by the StartTimerAsync task and the tcs would be set to the TaskCanceledException.
await Task.Delay(this.DefaultTransactionStatePollingTimeout, cancellationToken).ConfigureAwait(false);
if (tcs.Task.IsCompleted)
{
// If the tcs was already set, no need to wait check the transaction state.
// End transaction polling task
return;
}
switch (txn.State)
{
case TransactionState.Active:
case TransactionState.Reading:
// Do nothing, the transaction is still active, go back to sleep
break;
case TransactionState.Aborted:
case TransactionState.Aborting:
case TransactionState.Faulted:
tcs.TrySetException(
new InvalidOperationException(
string.Format("DataStore.PollTransactionStateAsync : The transaction was aborted or faulted, dispose the transaction and try again, Txn : {0}", txn)));
return;
case TransactionState.Committed:
case TransactionState.Committing:
var exc =
new InvalidOperationException(
string.Format(
"DataStore.PollTransactionStateAsync : The transaction was commited but DequeueAsync did not finish. Make sure DequeueAsync was awaited. Txn : {0}",
txn));
if (tcs.TrySetException(exc))
{
// If we were able to set the result, then DequeueAsync was not awaited.
// Do not Assert as this is something that the user is doing incorrectly.
// Do not throw as the exception would be thrown by the tcs.
FabricEvents.Events.ReliableConcurrentQueue_ExceptionWarning(this.traceType, exc.ToString());
}
return;
default:
// Unknown transaction state : Assert
TestableAssertHelper.FailInvalidOperation(this.traceType, "DataStore.PollTransactionStateAsync", "Unknown transaction state");
return;
}
}
}
/// <summary>
/// The prepare for remove async.
/// </summary>
/// <param name="transaction">
/// The transaction.
/// </param>
/// <param name="timeout">
/// The timeout.
/// </param>
/// <param name="cancellationToken">
/// The cancellation token.
/// </param>
/// <returns>
/// The <see cref="Task"/>.
/// </returns>
Task IStateProvider2.PrepareForRemoveAsync(
Transaction transaction,
TimeSpan timeout,
CancellationToken cancellationToken)
{
Trace.TraceInformation("[" + this.partitionId + "] " + "PrepareForRemoveAsync()");
return(Task.FromResult(0));
}
/// <summary>
/// Try and dequeue from the DataStore.
/// If there are dequeuers waiting or there is no element to dequeue, this dequeueur would be added to the waiting queue.
/// Else, the result would be set for the <paramref name="tcs"/>
/// Caller must await on tcs.Task
/// </summary>
public void TryDequeue(
Transaction txn,
TaskCompletionSource <ConditionalValue <IListElement <T> > > tcs,
TimeSpan timeout,
CancellationToken cancellationToken)
{
lock (this.updateLatch)
{
switch (this.dequeuersState)
{
case DequeuerState.Aborting:
case DequeuerState.Closing:
tcs.TrySetException(
new FabricObjectClosedException(
string.Format("Queue is closed. Please dispose the current transaction and retry the operation with a new transaction, Cause : {0}", this.dequeuersState)));
return;
case DequeuerState.None:
case DequeuerState.ChangeRoleFromPrimary:
tcs.TrySetException(
new FabricNotPrimaryException(
string.Format("Current role not Primary. Please dispose the current transaction and retry the operation with a new transaction, Cause : {0}", this.dequeuersState)));
return;
case DequeuerState.OnPrimary:
// In the expected state, continue DataStore.TryDequeue
break;
default:
TestableAssertHelper.FailInvalidOperation(
this.traceType,
"TryDequeue",
"DataStore.TryDequeue : Trying to add a dequeuer in an invalid state. Current DequeuerState = {0}",
this.dequeuersState);
break; // unreachable
}
var res = this.TryUnlinkHead();
if (res.HasValue)
{
// There is something to unlink and no waiting dequeuer
if (!tcs.TrySetResult(res))
{
TestableAssertHelper.FailInvalidOperation(
this.traceType,
"TryDequeue",
"Could not set the tcs result after unlinking from the DataStore. TCS {0}",
res);
}
}
else
{
this.AddDequeuer(txn, tcs, timeout, cancellationToken);
}
}
}
/// <summary>
/// Start a timer and add the <paramref name="tcs"/> to the dequeuerQueue
/// Should be called under the updateLatch
/// </summary>
private void AddDequeuer(
Transaction txn,
TaskCompletionSource <ConditionalValue <IListElement <T> > > tcs,
TimeSpan timeSpan,
CancellationToken cancellationToken)
{
this.dequeuerQueue.Enqueue(tcs);
// Fire the timer task
var t1 = this.StartDequeueTimerAsync(tcs, timeSpan, cancellationToken);
var t2 = this.PollTransactionStateAsync(txn, tcs, cancellationToken).IgnoreException();
}