public async Task <long> GetPositionAsync(CancellationToken cancel = new CancellationToken())
{
var sw = Stopwatch.StartNew();
try
{
return(await Inner.GetPositionAsync(cancel));
}
finally
{
Trace.WriteLine("GetPositionAsync " + sw.ElapsedMilliseconds);
}
}
public Task <long> GetPositionAsync(CancellationToken cancel = new CancellationToken()) => Wrapped.GetPositionAsync(cancel);
/// <summary> Appends events to the stream. </summary>
/// <remarks>
/// The sequence number may not be before the current one.
/// You can provide an arbitrarily large number of events, which will then be
/// split into multiple writes.
/// </remarks>
public async Task WriteAsync(
IEnumerable <KeyValuePair <uint, TEvent> > events,
CancellationToken cancel = default(CancellationToken))
{
var sequence = _sequence ?? await LastWrittenAsync(cancel).ConfigureAwait(false);
var position = (long)(_position ??
(_position = await _driver.GetPositionAsync(cancel).ConfigureAwait(false)));
// If an exception is thrown before we return properly, it might leave the
// cached values (_sequence and _position) in an invalid state, so we null
// them to cause a re-load on the next call. If returning properly, we'll
// set them back to the proper values.
_sequence = null;
_position = null;
var list = new List <RawEvent>();
var otherList = new List <RawEvent>();
// Assigned the current writing task every time 'write' is called.
Task writing = Task.FromResult(0);
// Writes the events in the list to the driver
Func <IReadOnlyList <RawEvent>, Task> write = async written =>
{
if (written.Count == 0)
{
return;
}
var result = await _driver.WriteAsync(position, written, cancel)
.ConfigureAwait(false);
if (!result.Success)
{
throw new Exception(
$"Error writing events {written[0].Sequence} to {written[written.Count - 1].Sequence}");
}
position = result.NextPosition;
};
foreach (var kv in events)
{
cancel.ThrowIfCancellationRequested();
var e = kv.Value;
var seq = kv.Key;
if (seq <= sequence)
{
throw new ArgumentException($"Out-of-order sequence #{seq}", nameof(events));
}
sequence = seq;
list.Add(new RawEvent(seq, _serializer.Serialize(e)));
// Avoid runaway scheduling (having to write increasingly
// large sets of events because write is slower than enumeration
// or serialization)
//
// Also, start a new write as soon as the previous one is done.
if (writing.IsCompleted || list.Count > 1000)
{
await writing.ConfigureAwait(false);
// The created task will ALWAYS be awaited, to guarantee
// that exceptions bubble up appropriately.
writing = write(list);
// Do not overwrite the list straight away, as it will
// be used during the write process. Instead, keep two
// lists and swap them (there is only one write process
// and one serialization process running at any given
// time, so two lists are enough).
var temp = list;
list = otherList;
otherList = temp;
list.Clear();
}
}
await writing.ConfigureAwait(false);
await write(list).ConfigureAwait(false);
// Cache the values we reached.
_sequence = sequence;
_position = position;
}
/// <see cref="IStorageDriver.GetPositionAsync"/> public Task <long> GetPositionAsync(CancellationToken cancel = new CancellationToken()) => _source.GetPositionAsync(cancel);
