public void HandlesCancellation()
{
var asyncLock = new AsyncLock();
var lockOne = asyncLock.LockAsync();
var cts = new CancellationTokenSource();
var lockTwo = asyncLock.LockAsync(cts.Token);
Assert.True(lockOne.IsCompleted);
Assert.Equal(TaskStatus.RanToCompletion, lockOne.Status);
Assert.NotNull(lockOne.Result);
Assert.False(lockTwo.IsCompleted);
cts.Cancel();
Assert.True(lockTwo.IsCompleted);
Assert.True(lockTwo.IsCanceled);
lockOne.Result.Dispose();
}
/// <summary>
/// Starts the operation queue.
/// </summary>
/// <returns>A disposable which when Disposed will stop the queue.</returns>
public IDisposable Start()
{
if (_start is not null)
{
return(_start);
}
_shouldQuit = new CancellationTokenSource();
var task = Task.Run(async() =>
{
var toProcess = new List <OperationQueueItem>();
while (!_shouldQuit.IsCancellationRequested)
{
toProcess.Clear();
IDisposable? @lock;
try
{
@lock = await _flushLock.LockAsync(_shouldQuit.Token).ConfigureAwait(false);
}
catch (OperationCanceledException)
{
break;
}
// Verify lock was acquired
if (@lock is null)
{
break;
}
using (@lock)
{
// NB: We special-case the first item because we want to
// in the empty list case, we want to wait until we have an item.
// Once we have a single item, we try to fetch as many as possible
// until we've got enough items.
OperationQueueItem?item;
try
{
item = _operationQueue.Take(_shouldQuit.Token);
}
catch (OperationCanceledException)
{
break;
}
// NB: We explicitly want to bail out *here* because we
// never want to bail out in the middle of processing
// operations, to guarantee that we won't orphan them
if (_shouldQuit.IsCancellationRequested && item is null)
{
break;
}
toProcess.Add(item);
while (toProcess.Count < Constants.OperationQueueChunkSize && _operationQueue.TryTake(out item) && item is not null)
{
toProcess.Add(item);
}
try
{
ProcessItems(CoalesceOperations(toProcess));
}
catch (SQLiteException)
{
// NB: If ProcessItems Failed, it explicitly means
// that the "BEGIN TRANSACTION" failed and that items
// have **not** been processed. We should add them back
// to the queue
foreach (var v in toProcess)
{
_operationQueue.Add(v);
}
}
}
}
});
return(_start = Disposable.Create(
() =>
{
try
{
_shouldQuit.Cancel();
task.Wait();
}
catch (OperationCanceledException)
{
}
try
{
using (_flushLock.LockAsync().Result)
{
FlushInternal();
}
}
catch (OperationCanceledException)
{
}
_start = null;
}));
}
public IDisposable Start()
{
if (start != null)
{
return(start);
}
shouldQuit = new CancellationTokenSource();
var task = new Task(async() =>
{
var toProcess = new List <OperationQueueItem>();
while (!shouldQuit.IsCancellationRequested)
{
toProcess.Clear();
using (await flushLock.LockAsync(shouldQuit.Token))
{
// NB: We special-case the first item because we want to
// in the empty list case, we want to wait until we have an item.
// Once we have a single item, we try to fetch as many as possible
// until we've got enough items.
var item = default(OperationQueueItem);
try
{
item = operationQueue.Take(shouldQuit.Token);
}
catch (OperationCanceledException)
{
break;
}
// NB: We explicitly want to bail out *here* because we
// never want to bail out in the middle of processing
// operations, to guarantee that we won't orphan them
if (shouldQuit.IsCancellationRequested && item == null)
{
break;
}
toProcess.Add(item);
while (toProcess.Count < Constants.OperationQueueChunkSize && operationQueue.TryTake(out item))
{
toProcess.Add(item);
}
try
{
ProcessItems(CoalesceOperations(toProcess));
}
catch (SQLiteException)
{
// NB: If ProcessItems Failed, it explicitly means
// that the "BEGIN TRANSACTION" failed and that items
// have **not** been processed. We should add them back
// to the queue
foreach (var v in toProcess)
{
operationQueue.Add(v);
}
}
}
}
}, TaskCreationOptions.LongRunning);
task.Start();
return(start = Disposable.Create(() =>
{
try
{
shouldQuit.Cancel();
task.Wait();
}
catch (OperationCanceledException) { }
var newQueue = new BlockingCollection <OperationQueueItem>();
ProcessItems(CoalesceOperations(Interlocked.Exchange(ref operationQueue, newQueue).ToList()));
start = null;
}));
}
